| 1. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Changes in nitrogen cycling in riparian zones along a chronosequence of restored streams in northern Sweden
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding how stream restoration affects nitrogen (N) cycling in riparian zones is crucial for setting realistic performance criteria for restored streams. Most streams in northern Sweden were channelized for timber floating, and many streams have now been restored. Channelization disconnected streams from the riparian zone, and reduced the flooding that creates anoxic conditions necessary for many N-cycling reactions. We used a space-for-time substitution consisting of stream reaches restored 2 to 25 years ago, unrestored channelized and natural reference reaches to determine how N-cycling in riparian zones changes with time after restoration. Using stable isotopes of N (δ15N), we found that restoration caused more enriched foliar and root δ15N in recently restored sites, suggesting more gaseous losses of N in younger sites. This enrichment in foliar and root δ15N decreased over the 25-year chronosequence suggesting that the N-cycle becomes tighter and loses less N as it ages. Although the [N] in foliage, roots, and soils did not change over time, understory biomass decreased over time, suggesting that more N was available to plants in younger compared to older sites. Changes in the mechanism of N acquisition (i.e., mycorrhizal colonization, as shown by Δδ15N), plant species richness, and cover of deciduous trees (carbon source), were the most important factors explaining variation in δ15N along with time after restoration. It is clear that the restoration of these streams causes a large and rapid change in nitrogen processing in the riparian zone and this alteration persists for at least 25 years.
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| 2. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Management of non-native annual plants to support recovery of an endangered perennial forb, Ambrosia pumila
- 2013
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Ingår i: Restoration Ecology. - 1061-2971 .- 1526-100X. ; 21:2, s. 224-231
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Tidskriftsartikel (refereegranskat)abstract
- Invasive non-native plants pose a ubiquitous threat to native plant communities and have been blamed for the decline of many endangered species. Endangered species legislation provides legal instruments for protection, but identifying a general method for protecting endangered species by managing non-natives is confounded by multiple factors. We compared non-native management methods aimed at increasing populations of an endangered forb, Ambrosia pumila, and associated native plants. We compared the effects of a grass-specific herbicide (Fusilade II), hand-pulling, and mowing in two degraded coastal sage scrub sites in southern California, U.S.A. At both sites, hand-pulling had the greatest effect on non-native cover, and correspondingly resulted in the greatest increase in A. pumila stems. Fusilade II application also led to an increase in A. pumila, but was not as effective in controlling non-native plants as hand-pulling and its effect varied with the dominant non-native species. Mowing was not effective at promoting A. pumila, and its effect on non-native cover seemed to be related to rainfall patterns. Although some methods increased A. pumila, none of our treatments simultaneously increased cover of other native plants. Hand-pulling, the most effective treatment, is labor intensive and thus only feasible at small spatial scales. At larger scales, managers should take an experimental approach to identifying the most appropriate method because this can vary depending on the specific management objective (endangered species or whole native community), the dominant non-natives, yearly variation in weather, and the timing of treatment application.
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| 3. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Recovery of nitrogen cycling in riparian zones after stream restoration using delta N-15 along a 25-year chronosequence in northern Sweden
- 2017
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 410:1-2, s. 423-436
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Tidskriftsartikel (refereegranskat)abstract
- Swedish boreal streams were modified to transport timber by pushing boulders to stream sides, creating levees that disconnected streams from riparian areas. Many streams have since been restored and our goal was to understand how this affects riparian nitrogen (N) cycling. We compared the natural abundance of delta N-15 isotopes in foliage and roots of Filipendula ulmaria plus soils and litter along streams restored 2-25 years ago. We measured sources of N, potential immobilization of N, namely plant diversity and biomass, and the amount and sources of carbon (C) to determine if these were important for describing riparian N cycling. The delta N-15 of F. ulmaria foliage changed dramatically just after restoration compared to the channelized, disconnected state and then converged over the next 25 years with the steady-state reference. The disturbance and reconnection of the stream with the riparian zone during restoration created a short-term pulse of N availability and gaseous losses of N as a result of enhanced microbial processing of N. With increasing time since restoration, N availability appears to have decreased, and N sources changed to those derived from mycorrhizae, amino acids, or the humus layer, or there was enhanced N-use efficiency by older, more diverse plant communities.
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| 4. |
- Kozii, Nataliia, et al.
(författare)
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Partitioning growing season water balance within a forested boreal catchment using sap flux, eddy covariance, and a process-based model
- 2020
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 24, s. 2999-3014
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Tidskriftsartikel (refereegranskat)abstract
- Although it is well known that evapotranspiration (ET) represents an important water flux at local to global scales, few studies have quantified the magnitude and relative importance of ET and its individual flux components in high-latitude forests. In this study, we combined empirical sapflux, throughfall, and eddy-covariance measurements with estimates from a process-based model to partition the water balance in a northern boreal forested catchment. This study was conducted within the Krycklan catchment, which has a rich history of hydrological measurements, thereby providing us with the unique opportunity to compare the absolute and relative magnitudes of ET and its flux components to other water balance components. During the growing season, ET represented ca. 85 % of the incoming precipitation. Both empirical results and model estimates suggested that tree transpiration (T) and evaporation of intercepted water from the tree canopy (I-C) represented 43 % and 31 % of ET, respectively, and together were equal to ca. 70 % of incoming precipitation during the growing season. Understory evapotranspiration (ETu) was less important than T and I-C during most of the study period, except for late autumn, when ETu was the largest ET flux component. Overall, our study high-lights the importance of trees in regulating the water cycle of boreal catchments, implying that forest management impacts on stand structure as well as climate change effects on tree growth are likely to have large cascading effects on the way water moves through these forested landscapes.
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| 5. |
- Laudon, Hjalmar, et al.
(författare)
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Northern landscapes in transition : Evidence, approach and ways forward using the Krycklan Catchment Study
- 2021
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Ingår i: Hydrological Processes. - : John Wiley & Sons. - 0885-6087 .- 1099-1085. ; 35:4
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Tidskriftsartikel (refereegranskat)abstract
- Improving our ability to detect changes in terrestrial and aquatic systems is a grand challenge in the environmental sciences. In a world experiencing increasingly rapid rates of climate change and ecosystem transformation, our ability to understand and predict how, when, where, and why changes occur is essential for adapting and mitigating human behaviours. In this context, long-term field research infrastructures have a fundamentally important role to play. For northern boreal landscapes, the Krycklan Catchment Study (KCS) has supported monitoring and research aimed at revealing these changes since it was initiated in 1980. Early studies focused on forest regeneration and microclimatic conditions, nutrient balances and forest hydrology, which included monitoring climate variables, water balance components, and stream water chemistry. The research infrastructure has expanded over the years to encompass a 6790 ha catchment, which currently includes 11 gauged streams, ca. 1000 soil lysimeters, 150 groundwater wells, >500 permanent forest inventory plots, and a 150 m tall tower (a combined ecosystem-atmosphere station of the ICOS, Integrated Carbon Observation System) for measurements of atmospheric gas concentrations and biosphere-atmosphere exchanges of carbon, water, and energy. In addition, the KCS has also been the focus of numerous high resolution multi-spectral LiDAR measurements and large scale experiments. This large collection of equipment and data generation supports a range of disciplinary studies, but more importantly fosters multi-, trans-, and interdisciplinary research opportunities. The KCS attracts a broad collection of scientists, including biogeochemists, ecologists, foresters, geologists, hydrologists, limnologists, soil scientists, and social scientists, all of whom bring their knowledge and experience to the site. The combination of long-term monitoring, shorter-term research projects, and large-scale experiments, including manipulations of climate and various forest management practices, has contributed much to our understanding of boreal landscape functioning, while also supporting the development of models and guidelines for research, policy, and management.
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| 6. |
- Eklöf, Karin, et al.
(författare)
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Effekter av dikesrensning och våtmarksrestaurering på kvicksilver i vatten
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Dikning av våtmark i svenska skogsområden under de senaste 120 åren har bidragit till ökad skogsproduktion men också orsakat genomgripande förändringar i skogarnas omsättning och lagring av vatten. Med tiden ansamlas sediment och vegetation i dikena, och dikesrensning kan behövas för att upprätthålla en hög skogsproduktion. Åtgärden kan dock påverka markegenskaper och -processer, vattenkvalitet och kolbalans. Ökad avrinning av total-kvicksilver (THg) och biotillgängligt metylkvicksilver (MeHg) har pekats ut som en potentiell risk vid dikesrensning. En alternativ åtgärd för dikade områden är restaurering till mer naturliga våtmarksförhållanden. Från politiskt håll uppmuntras restaurering som en åtgärd mot översvämningar och torka, för att minska emission av växthusgaser och för att öka den biologiska mångfalden. Åtgärden, som i regel blötlägger torv, riskerar dock att öka den mikrobiella bildningen av MeHg. Mer ytliga flödesvägar i restaurerade våtmarker riskerar också att mobilisera kvicksilver (Hg) från markens övre lager. I ett experimentellt fältförsök med sex avrinningsområden och tre referensområden studerades effekter på THg och MeHg i dikesvatten, efter både dikesrensning och våtmarksrestaurering, upp till ca två år efter åtgärderna. Fältförsöket kompletterades med provtagning av THg och MeHg i rensade (n = 25; 1–4 år efter rensning) och orensade (n = 25) diken i en rumslig studie med en stor geografisk spridning. Dessutom utvärderades 15 sedimentationsdammar belägna nedströms dikesrensade områden med avseende på bildning av MeHg i dammarna. Slutligen i en litteraturstudie sammanställdes effekter av dikesrensning på skogsproduktion med syftet att väga dessa effekter mot effekter på THg och MeHg i vatten. Resultaten visar att dikesrensning inte ledde till några ökningar av THg och MeHg i avrinnande vatten. Tvärt om, minskade koncentrationen och exporten av THg och MeHg i vissa områden. Dikesrensning ledde inte heller till några tydliga ökningar av partikelbundet THg och MeHg. Risken att dikesrensning i avverkade områden kan leda till ökad mobilisering av MeHg från de avverkade områdena kunde inte påvisas genom hydrologisk modellering. Sedimentationsdammar, merparten relativt små, nedströms dikesrensade områden orsakade inga förhöjda halter av MeHg, varken i bottensediment eller i dikesvatten nedströms dammarna. Våtmarksrestaurering ledde till ökade koncentration och export av THg och MeHg i ett av de två restaurerade områdena. Sammanfattningsvis visar studierna i projektet att dikesrensning kan minska, och våtmarksrestaurering kan öka THg och MeHg i avrinnande vatten, men att det kan variera mellan områden. Det gäller åtminstone under de första åren efter åtgärderna som studierna avser. Dessa förändringar drivs troligtvis av en kombination av i) ändrade flödesvägar för vattnet och ii) förändrade redox-förhållanden i marken då grundvattenytan sänks (vid dikesrensning) respektive höjs (vid våtmarksrestaurering).
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| 7. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Contrasting effects of geomorphic complexity on diversity of three aquatic organism groups after stream restoration
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Ecological theory states that greater habitat heterogeneity should support higher biodiversity. Many stream restoration projects aim to increase geomorphic complexity, assuming that this increases habitat heterogeneity and, thus, biodiversity. However, little evidence has been published that supports this theory, especially with respect to stream restoration and aquatic organisms.Previous assessments of stream habitat restoration have suffered from four major limitations: (1) incomplete quantification of habitat complexity metrics, (2) assessment of the responses of only one organism group, most often macroinvertebrates, (3) mismatch between scale of restoration and scale of disturbance, and (4) limited number of restoration measures applied.We used 12 metrics of geomorphic complexity spanning five dimensions of complexity (sediment grain size distribution, longitudinal profile, cross section, planform, and instream wood) to evaluate if the diversity, abundance and community composition of three aquatic organism groups (benthic macroinvertebrates, diatoms and macrophytes) relate positively to complexity along near-natural, restored and channelised stream reaches in rural northern Sweden where disturbance to the streams has been primarily reach-scale channelisation to facilitate timber floating.We found that the variation in biodiversity and abundance within each of the three organism groups could be described by multiple regression models that included only geomorphic complexity metrics, but the variation within an organism group could rarely be described by only one metric of complexity in isolation. Rather, three metrics were needed on average to describe the variation in biodiversity and abundance, and rarely did all metrics relate positively to diversity. Sediment grain size distribution metrics were most often significant as explanatory variables, but were inconsistent in the direction of influence. The other four dimensions of complexity were less consistently significant but were nearly all positively related to our diversity metrics.Most of the variation in these metrics was driven by advanced restoration techniques and to a lesser extent older best practice techniques. Three complexity metrics were most often included in multiple regression models as well as described community composition in ordinations: a metric quantifying heterogeneity of small sediment sizes, a metric that represents the variation in stream depth along the longitudinal profile, and instream wood metrics. Therefore, specifically these metrics could be targets for future restoration. The organism groups were not concordant in their patterns of diversity, abundance, or community composition; thus, none can be used as a surrogate in monitoring biodiversity of these sites.Synthesis and applications. Geomorphic complexity should be measured in multiple dimensions, and ideally in all five dimensions, to understand the full breadth of restoration impacts to which organisms could be responding. More than one organism group should be used in monitoring to ensure biodiversity goals are met. Finally, even though the scale of the restorations matched the scale of the disturbance at the reach scale, the older best practice methods of restoration rarely restored the large-scale features necessary to bring the sites up to their potential levels of complexity as these elements (large boulders, bedrock, log jams) had been destroyed or removed from the system. Although the advanced restoration sites were the youngest, advanced restoration techniques that added big boulders, coarse gravel and instream wood increased complexity to a level that elicited a biological response. Finally, the complexity level needed to elicit a biological response could be difficult to understand for a given system, so we suggest doing restoration work in an experimental way in collaboration with geomorphologists to determine what level of complexity is needed.
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| 8. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Contrasting Responses among Aquatic Organism Groups to Changes in Geomorphic Complexity Along a Gradient of Stream Habitat Restoration : Implications for Restoration Planning and Assessment
- 2018
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Ingår i: Water. - : MDPI. - 2073-4441. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Many stream restoration projects aim to increase geomorphic complexity, assuming that this increases habitat heterogeneity and, thus, biodiversity. However, empirical data supporting these linkages remain scant. Previous assessments of stream restoration suffer from incomplete quantification of habitat complexity, or a narrow focus on only one organism group and/or one restoration measure, limiting learning. Based on a comprehensive quantification of geomorphic complexity in 20 stream reaches in northern Sweden, ranging from streams channelized for timber floating to restored and reference reaches, we investigated responses of macroinvertebrates, diatoms, and macrophytes to multiple geomorphic metrics. Sediment size heterogeneity, which was generally improved in restored sites, favored macroinvertebrate and diatom diversity and macroinvertebrate abundance. In contrast, macrophyte diversity responded to increased variation along the longitudinal stream profile (e.g., step-pools), which was not consistently improved by the restoration. Our analyses highlight the value of learning across multiple restoration projects, both in identifying which aspects of restoration have succeeded, and pinpointing other measures that might be targeted during adaptive management or future restoration. Given our results, a combination of restoration measures targeting not only sediment size heterogeneity, but also features such as step-pools and instream wood, is most likely to benefit benthic biota in streams.
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| 9. |
- Hasselquist, Eliza Maher, 1977-
(författare)
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Gradients of time and complexity : understanding how riparian and instream ecosystems recover after stream restoration
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Why evaluations of the ecological outcomes of stream and river restoration have largely reported inconclusive or negative results has been the subject of much debate over the last decade or more. Understanding the reasons behind the lack of positive results is important for bettering future restoration efforts and setting realistic expectations for restoration outcomes. This thesis explores possible explanations for why researchers have failed to find clear and predictable biotic responses to stream restoration: recovery time has been too short, that restoration of habitat complexity is not clearly linked to instream biodiversity, that one monitored organism group is not representative of the entire community, that restoration effort was not intense enough to restore the potential habitat complexity of a system, and that reach-scale restoration done in the presence of catchment-scale degradation obscures restoration results. The overarching goal of this thesis is to study the holistic effect of reach-scale restoration of historic reach-scale simplification, due to timber floating in northern Swedish streams, thus avoiding the added pressure of catchment-scale degradation typically found at most restoration sites (e.g., non-point-source pollution and impervious cover). Using this model system, I was able to show that it took 25 years for riparian plant species richness at restored sites to increase above that of channelized sites. Furthermore, it was clear that restoration of these streams caused a large and rapid change in N-processing in the riparian zone and this alteration persists for at least 25 years. Additionally, multiple metrics of geomorphic complexity were needed to explain some of the more subtle responses of organism groups. Macroinvertebrates, diatoms, and macrophytes did not respond concordantly and cannot serve as surrogates or indicators for each other. I found that older best practice methods of restoration rarely restored the large-scale features needed to bring the sites up to their potential complexity because these elements were destroyed or removed from the system. Advanced restoration techniques used in more recent restorations added big boulders and instream wood and increased complexity to a level that elicited a biological response. By combining surveys of multiple metrics of structure, diversity of multiple organism groups, and process in this thesis I was able to get a holistic view of the effects of restoration of streams after timber floating. We now know that it takes at least 25 years for riparian plants and N-cycling to recover, we understand that multiple metrics of geomorphic complexity should be measured to be able to explain biotic responses, and that restored complexity should better match the potential complexity of the site in order to elicit a biological response. Finally, we know that multiple organism groups need to be assessed when evaluating the response of biodiversity to restoration.
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| 10. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Microsite differentiation among conifer species during seedling establishment at alpine treeline
- 2006
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Ingår i: Ecoscience. - : Presses de L`Université Laval. - 1195-6860. ; 13:3, s. 334-341
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Tidskriftsartikel (refereegranskat)abstract
- Tree establishment is a potentially important factor affecting tree populations in alpine-treeline ecotones. Patterns of seedling establishment of Abies lasiocarpa, Pinus albicaulis, and Picea engelmannii were evaluated relative to neighbouring trees and herbs over two years and three treelines of the Rocky Mountains, USA. The greatest mortality rates were observed in seedlings that had just emerged from seed and were in their first year of growth and in seedlings that had the least amount of cover provided by trees or other landscape features that block exposure to the sky. Although herb cover promoted survivorship in microsites that were not near trees, no seedlings were detected at or above the upper limit of the treeline ecotone. Microsite tree cover was greatest for A. lasiocarpa and least for P. albicaulis seedlings, which matches predictions based on their relative photosynthetic tolerances to the bright sunlight and frequent frost that occur in exposed microsites. Interspecific differences in seedling requirements for neighbouring plant cover likely contribute to the apparent coexistence and possible interdependency of these conifers along a continuum of colonization and succession within treelines.
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| 11. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Moving towards multi-layered, mixed-species forests in riparian buffers will enhance their long-term function in boreal landscapes
- 2021
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Ingår i: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 493
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Tidskriftsartikel (refereegranskat)abstract
- Riparian buffers are the primary tool in forest management for protecting the habitat structure and function of streams. They help protect against biogeochemical perturbation, filter sediments and nutrients, prevent erosion, contribute food to aquatic organisms, regulate light and hence water temperature, contribute deadwood, and preserve biodiversity. However, in production forests of Sweden and Finland, many headwater streams have been straightened, ditched, and/or channelized, resulting in altered hydrology and reduced natural disturbance by floods, which in turn affects important riparian functions. Furthermore, in even-aged management systems as practiced in much of Fennoscandia, understory trees have usually been cleared right up to the stream’s edge during thinning operations, especially around small, headwater streams. Fire suppression has further favored succession towards shade tolerant species. In the regions within Fennoscandia that have experienced this combination of intensive management and lack of natural disturbance, riparian zones are now dominated by single-storied, native Norway spruce. When the adjacent forest is cut, thin (5 - 15m) conifer-dominated riparian buffers are typically left. These buffers do not provide the protection and subsidies, in terms of leaf litter quality, needed to maintain water quality or support riparian or aquatic biodiversity. Based on a literature review, we found compelling evidence that the ecological benefits of multi-layered, mixed-species riparian forest with a large component of broadleaved species are higher than what is now commonly found in the managed stands of Fennoscandia. To improve the functionality of riparian zones, and hence the protection of streams in managed forest landscapes, we present some basic principles that could be used to enhance the ecological function of these interfaces. These management actions should be prioritized on streams and streamside stands that have been affected by simplification either through forest management or hydrological modification. Key to these principles is the planning and managing of buffer zones as early as possible in the rotation to ensure improved function throughout the rotation cycle and not only at final felling. This is well in line with EU and national legislation which can be interpreted as requiring landscape planning at all forest ages to meet biodiversity and other environmental goals. However, it is still rare that planning for conservation is done other than at the final felling stage. Implementing this new strategy is likely to have long-term positive effects and improve the protection of surface waters from negative forestry effects and a history of fire suppression. By following these suggested management principles, there will be a longer time period with high function and greater future management flexibility in addition to the benefits provided by leaving riparian buffers at the final felling stage.
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| 12. |
- Hasselquist, Eliza Maher, et al.
(författare)
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The role of riparian buffer width on sediment connectivity through windthrow in a boreal headwater stream
- 2024
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Ingår i: Geomorphology. - : Elsevier. - 0169-555X .- 1872-695X. ; 461
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Tidskriftsartikel (refereegranskat)abstract
- Riparian buffers are commonly used to mitigate the negative effects of forestry operations near water, particularly sediment transport to streams. In Sweden, current practices typically involve 5-7 m wide riparian buffers along small streams. Historical forest management, which favored conifers up to the channel edge, has resulted in these narrow buffers having a simplified tree species composition and structure, making them prone to windthrow. While windthrow can contribute large wood (LW) to streams, windthrow also risks increasing sediment inputs if rootwads are exposed near stream edges. This disturbance affects sediment connectivity, or the movement of particles through the fluvial system, but the interaction between LW dynamics and sediment connectivity in small boreal streams is not well understood. We investigated sediment connectivity at the Trollberget Experimental Area in northern Sweden, where six 100 m stream reaches had either 5 m or 15 m wide riparian buffers. Pre-harvest and one-year post-harvest data on windthrow, hydrology, and sediment yields were collected. Forest harvesting increased sediment connectivity in the streams regardless of buffer width, indicating that buffers wider than 15 m are necessary to reduce sediment input impacts in small headwater streams. Windthrow affecting stream channels was more common in the 5 m buffers, leading to significantly higher deposition of very fine sediments (<250 μm) compared to the 15 m buffers. Coarse (>1 mm) and fine sediments (250 μm – 1 mm) were also higher in the 5 m buffers. We found that sediment connectivity in streams was closely linked to LW dynamics, negatively before harvest but positively after harvest. Before harvest, LW trapped sediment and prevented downstream transport, but after harvest, the increased sediment input overwhelmed this function. Our results highlight a trade-off between the recruitment of LW and minimizing sediment connectivity, two key objectives in riparian buffer management.
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| 13. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Time for recovery of riparian plants in restored northern Swedish streams : A chronosequence study
- 2015
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Ingår i: Ecological Applications. - : Wiley. - 1051-0761 .- 1939-5582. ; 25:5, s. 1373-1389
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Tidskriftsartikel (refereegranskat)abstract
- A lack of ecological responses in stream restoration projects has been prevalent throughout recent literature with many studies reporting insufficient time for recovery. We assessed the relative importance of time, site variables, and landscape setting for understanding how plant species richness and understory productivity recover over time in riparian zones of northern Swedish streams. We used a space-for-time substitution consisting of 13 stream reaches restored 5-25 years ago, as well as five unrestored channelized reference reaches. We inventoried the riparian zone for all vascular plant species along 60-m study reaches and quantified cover and biomass in plots. We found that while species richness increased with time, understory biomass decreased. Forbs made up the majority of the species added, while the biomass of graminoids decreased the most over time, suggesting that the reduced dominance of graminoids favored less productive forbs. Species richness and density patterns could be attributed to dispersal limitation, with anemochorous species being more associated with time after restoration than hydrochorous, zoochorous, or vegetatively reproducing species. Using multiple linear regression, we found that time along with riparian slope and riparian buffer width (e.g., distance to logging activities) explained the most variability in species richness, but that variability in total understory biomass was explained primarily by time. The plant community composition of restored reaches differed from that of channelized references, but the difference did not increase over time. Rather, different time categories had different successional trajectories that seemed to converge on a unique climax community for that time period. Given our results, timelines for achieving species richness objectives should be extended to 25 years or longer if recovery is defined as a saturation of the accumulation of species over time. Other recommendations include making riparian slopes as gentle as possible given the landscape context and expanding riparian buffer width for restoration to have as much impact as possible.
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| 14. |
- Jørgensen, Dolly, et al.
(författare)
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Policy Language in Restoration Ecology
- 2014
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Ingår i: Restoration Ecology. - : Wiley-Blackwell. - 1061-2971 .- 1526-100X. ; 22:1, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- Relating restoration ecology to policy is one of the aims of the Society for Ecological Restoration and its journal Restoration Ecology. As an interdisciplinary team of researchers in both ecological science and political science, we have struggled with how policy-relevant language is and could be deployed in restoration ecology. Using language in scientific publications that resonates with overarching policy questions may facilitate linkages between researcher investigations and decision-makers' concerns on all levels. Climate change is the most important environmental problem of our time and to provide policymakers with new relevant knowledge on this problem is of outmost importance. To determine whether or not policy-specific language was being included in restoration ecology science, we surveyed the field of restoration ecology from 2008 to 2010, identifying 1,029 articles, which we further examined for the inclusion of climate change as a key element of the research. We found that of the 58 articles with climate change or global warming in the abstract, only 3 identified specific policies relevant to the research results. We believe that restoration ecologists are failing to include themselves in policy formation and implementation of issues such as climate change within journals focused on restoration ecology. We suggest that more explicit reference to policies and terminology recognizable to policymakers might enhance the impact of restoration ecology on decision-making processes.
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| 15. |
- Kritzberg, Emma S., et al.
(författare)
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Browning of freshwaters : Consequences to ecosystem services, underlying drivers, and potential mitigation measures
- 2020
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Ingår i: Ambio: a Journal of the Human Environment. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 49:2, s. 375-390
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Forskningsöversikt (refereegranskat)abstract
- Browning of surface waters, as a result of increasing dissolved organic carbon and iron concentrations, is a widespread phenomenon with implications to the structure and function of aquatic ecosystems. In this article, we provide an overview of the consequences of browning in relation to ecosystem services, outline what the underlying drivers and mechanisms of browning are, and specifically focus on exploring potential mitigation measures to locally counteract browning. These topical concepts are discussed with a focus on Scandinavia, but are of relevance also to other regions. Browning is of environmental concern as it leads to, e.g., increasing costs and risks for drinking water production, and reduced fish production in lakes by limiting light penetration. While climate change, recovery from acidification, and land-use change are all likely factors contributing to the observed browning, managing the land use in the hydrologically connected parts of the landscape may be the most feasible way to counteract browning of natural waters.
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| 16. |
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| 17. |
- Kuglerova, Lenka, et al.
(författare)
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Multiple stressors in small streams in the forestry context of Fennoscandia : The effects in time and space
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 756
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe how forest management practices in Fennoscandian countries, namely Sweden and Finland, expose streams to multiple stressors over space and time. In this region, forestry includes several different management actions and we explore how these may successively disturb the same location over 60-100 year long rotation periods. Of these actions, final harvest and associated road construction, soil scarification, and/or ditch network maintenance are the most obvious sources of stressors to aquatic ecosystems. Yet, more subtle actions such as planting, thinning of competing saplings and trees, and removing logging residues also represent disturbances around waterways in these landscapes. We review literature about how these different forestry practices may introduce a combination of physicochemical stressors, including hydrological change, increased sediment transport, altered thermal and light regimes, and water quality deterioration. We further elaborate on how the single stressors may combine and interact and we consequently hypothesise how these interactions may affect aquatic communities and processes. Because production forestry is practiced on a large area in both countries, the various stressors appear multiple times during the rotation cycles and potentially affect the majority of the stream network length within most catchments. We concluded that forestry practices have traditionally not been the focus of multiple stressor studies and should be investigated further in both observational and experimental fashion. Stressors accumulate across time and space in forestry dominated landscapes, and may interact in unpredictable ways, limiting our current understanding of what forested stream networks are exposed to and how we can design and apply best management practices.
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| 18. |
- Kuglerova, Lenka, et al.
(författare)
-
Too much, too soon? Two Swedish case studies of short-term deadwood recruitment in riparian buffers
- 2023
-
Ingår i: AMBIO: A Journal of the Human Environment. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 52, s. 440-452
-
Tidskriftsartikel (refereegranskat)abstract
- Forested riparian buffers are retained along streams during forest harvest to maintain a number of ecological functions. In this paper, we examine how recently established riparian buffers along northern Swedish streams provide deadwood, a key objective for riparian buffer management in Sweden. We used observational and experimental data to show that the investigated buffers provided large volumes of deadwood to streams and riparian zones shortly after their establishment, likely jeopardizing continued recruitment over the long term. Deadwood volume decreased with increasing buffer width, and the narrowest buffers tended to blow down completely. Wider buffers (similar to 15 m) provided similar volumes of deadwood as narrow buffers due to blowdowns but were, overall, more resistant to wind-felling. It is clear from our study, that wider buffers are currently a safer strategy for riparian management that aims to sustain provision of deadwood and other ecological objectives continuously on the long term.
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| 19. |
- Laudon, Hjalmar, et al.
(författare)
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Applying continuous-cover forestry on drained boreal peatlands; water regulation, biodiversity, climate benefits and remaining uncertainties
- 2023
-
Ingår i: Trees, Forests and People. - : Elsevier BV. - 2666-7193. ; 11
-
Forskningsöversikt (refereegranskat)abstract
- Continuous-cover forestry (CCF) is increasingly argued as an alternative to clear-cut harvesting in managed boreal forests to improve water quality and quantity, biodiversity, and carbon sequestration. We review the empirical evidence for the potential benefits of CCF on drained forested peatlands in boreal ecosystems as an alternative to conventional clear-cut harvesting. We also discuss possible risks and uncertainties that need further consideration and highlight unanswered questions that need to be resolved before large-scale implementation. In general, we found that the ability to maintain forest production on drained forested peatlands pri-marily depends on water regulation of the groundwater (GW) table. Currently, the problem with high GW is typically solved using ditch cleaning, but if CCF is adopted, it could be an alternative approach to manage GW without the need of disturbing this already extensive artificial channel network. Implementation of CCF could lower the risk of extreme flooding and droughts, in addition to maintaining water quality and potentially enhancing the carbon sequestration conditions. Furthermore, it could provide a compromise between industrialized forestry and peatland restoration to better meet these targets. However, several important uncertainties remain regarding the potential for natural regeneration in northern latitudes, the net effect of different types of soil damage due to repeated use of heavy machinery, and consequences of climate change that could result in enhanced storm felling. We primarily focus on Swedish conditions, but also evaluate implications in an international context and propose ways to close remaining knowledge gaps.
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| 20. |
- Laudon, Hjalmar, et al.
(författare)
-
Consequences of rewetting and ditch cleaning on hydrology, water quality and greenhouse gas balance in a drained northern landscape
- 2023
-
Ingår i: Scientific Reports. - 2045-2322. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Drainage for forestry has created ~ 1 million km of artificial waterways in Sweden, making it one of the largest human-induced environmental disturbances in the country. These extensive modifications of both peatland and mineral soil dominated landscapes still carry largely unknown, but potentially enormous environmental legacy effects. However, the consequences of contemporary ditch management strategies, such as hydrological restoration via ditch blocking or enhancing forest drainage to promote biomass production via ditch cleaning, on water resources and greenhouse gas (GHG) fluxes are unclear. To close the gap between science and management, we have developed a unique field research platform to experimentally evaluate key environmental strategies for drained northern landscapes with the aim to avoid further environmental degeneration. The Trollberget Experimental Area (TEA) includes replicated and controlled treatments applied at the catchment scale based on a BACI approach (before-after and control-impact). The treatments represent the dominant ecosystem types impacted by ditching in Sweden and the boreal zone: (1) rewetting of a drained peatland, (2) ditch cleaning in productive upland forests and (3) leaving these ditches unmanaged. Here we describe the TEA platform, report initial results, suggest ways forward for how to best manage this historical large-scale alteration of the boreal landscape, as well as warn against applying these treatments broadly before more long-term results are reported.
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| 21. |
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| 22. |
- Lind, Lovisa, et al.
(författare)
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Towards ecologically functional riparian zones : A meta-analysis to develop guidelines for protecting ecosystem functions and biodiversity in agricultural landscapes
- 2019
-
Ingår i: Journal of Environmental Management. - London : Academic Press. - 0301-4797 .- 1095-8630. ; 249, s. 1-8
-
Tidskriftsartikel (refereegranskat)abstract
- Riparian zones contribute with biodiversity and ecosystem functions of fundamental importance for regulating flow and nutrient transport in waterways. However, agricultural land-use and physical changes made to improve crop productivity and yield have resulted in modified hydrology and displaced natural vegetation. The modification to the hydrology and natural vegetation have affected the biodiversity and many ecosystem functions provided by riparian zones. Here we review the literature to provide state-of-the-art recommendations for riparian zones in agricultural landscapes. We analysed all available publications since 1984 that have quantified services provided by riparian zones and use this information to recommend minimum buffer widths. We also analysed publications that gave buffer width recommendations to sustain different groups of organisms. We found that drainage size matters for nutrient and sediment removal, but also that a 3 m wide buffer zone acts as a basic nutrient filter. However, to maintain a high floral diversity, a 24 m buffer zone is required, while a 144 m buffer is needed to preserve bird diversity. Based on the analysis, we developed the concept of “Ecologically Functional Riparian Zones” (ERZ) and provide a step-by-step framework that managers can use to balance agricultural needs and environmental protection of waterways from negative impacts. By applying ERZ in already existing agricultural areas, we can better meet small targets and move towards the long-term goal of achieving a more functional land management and better environmental status of waterways.
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| 23. |
- Maher, Eliza L., et al.
(författare)
-
Interactive effects of tree and herb cover on survivorship, physiology, and microclimate of conifer seedlings at the alpine tree-line ecotone
- 2005
-
Ingår i: Canadian Journal of Forest Research. - 0045-5067 .- 1208-6037. ; 35:3, s. 567-574
-
Tidskriftsartikel (refereegranskat)abstract
- Factors affecting the establishment of trees in subalpine meadows are important to population dynamics of trees in the alpine tree- line ecotone ( ATE). Interactive effects of tree and herb cover on conifer seedlings were investigated in the ATE of the Snowy Range, Wyoming, USA. Microclimate, physiology, and survivorship of first-year conifer seedlings of Pinus albicaulis Engelm., Picea engelmannii Parry, and Abies lasiocarpa Hook. were measured in response to manipulations of surrounding herb and tree cover, as well as water availability. Tree and herb cover had nearly additive effects on survivorship and photosynthesis of conifer seedlings, except under alleviated water stress. In P. albicaulis, photosynthesis was greater near compared with away from trees and herbs, and photosynthetic efficiency ( F-v/ F-m) increased under herb cover. Tree cover led to greater nighttime temperatures, soil water contents, and, like herb cover, shade from solar radiation for seedlings. We did not detect any negative responses of conifer seedlings to surrounding vegetation. Furthermore, the effect of surrounding vegetation on conifer establishment appeared dependent on the type of surrounding vegetation, the species of conifer, and microsite stress level. These factors may lead to variation in the way conifer seedlings interact with surrounding vegetation and could explain changes in the relative abundances of tree species during forest succession in ATEs.
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| 24. |
- Maher Hasselquist, Eliza, et al.
(författare)
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Identifying and assessing the potential hydrological function of past artificial forest drainage
- 2018
-
Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 47:5, s. 546-556
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Tidskriftsartikel (refereegranskat)abstract
- Drainage of forested wetlands for increased timber production has profoundly altered the hydrology and water quality of their downstream waterways. Some ditches need network maintenance (DNM), but potential positive effects on tree productivity must be balanced against environmental impacts. Currently, no clear guidelines exist for DNM that strike this balance. Our study helps begin to prioritise DNM by: (1) quantifying ditches by soil type in the 68 km(2) Krycklan Catchment Study in northern Sweden and (2) using upslope catchment area algorithms on new high-resolution digital elevation models to determine their likelihood to drain water. Ditches nearly doubled the size of the stream network (178-327 km) and 17% of ditches occurred on well-draining sedimentary soils, presumably making DNM unwarranted. Modelling results suggest that 25-50% of ditches may never support flow. With new laser scanning technology, simple mapping and modelling methods can locate ditches and model their function, facilitating efforts to balance DNM with environmental impacts.
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| 25. |
- Maher Hasselquist, Eliza
(författare)
-
Long-Term Nitrogen and Phosphorus Dynamics in Waters Discharging from Forestry-Drained and Undrained Boreal Peatlands
- 2021
-
Ingår i: Water, Air, and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 232
-
Tidskriftsartikel (refereegranskat)abstract
- Contradictory results for the long-term evolution of nitrogen and phosphorus concentrations in waters discharging from drained peatland forests need reconciliation. We gathered long-term (10-29 years) water quality data from 29 forested catchments, 18 forestry-drained and 11 undrained peatlands. Trend analysis of the nitrogen and phosphorus concentration data indicated variable trends from clearly decreasing to considerably increasing temporal trends. While the variations in phosphorus concentration trends over time did not correlate with any of our explanatory factors, trends in nitrogen concentrations correlated positively with tree stand volume in the catchments and temperature sum. A positive correlation of increasing nitrogen concentrations with temperature sum raises concerns of the future evolution of nitrogen dynamics under a warming climate. Furthermore, the correlation with tree stand volume is troublesome due to the generally accepted policy to tackle the climate crisis by enhancing tree growth. However, future research is still needed to assess which are the actual processes related to stand volume and temperature sum that contribute to increasing TN concentrations.
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| 26. |
- Maher Hasselquist, Eliza, et al.
(författare)
-
Peatland drainage - a missing link behind increasing TOC concentrations in waters from high latitude forest catchments?
- 2021
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 774
-
Tidskriftsartikel (refereegranskat)abstract
- Total Organic Carbon (TOC) concentrations in stream waters from peat-covered catchments have increased over the last 15–25 years, resulting in large-scale brownification of lakes and rivers in high latitudes. While this increase has primarily been attributed to decreased acid deposition and climatic warming in most regions, we studied whether peatland drainage in forested catchments has contributed to the increasing TOC concentrations. We analysed the spatial variability of average TOC concentrations from a total of 133 peatland dominated catchments in Sweden and Finland, of which 62 were pristine and 71 were drained during the last century. In addition, we performed a trend analysis on 37 catchments for which long-term data were available. We found about 14 mg l−1 higher TOC concentrations in streams discharging from drained than undrained sites in southern latitudes, and about 8 mg l−1 higher concentrations from drained sites in northern latitudes. Trend analysis did not indicate significant differences in TOC concentration trends between drained and undrained catchments but indicated that tree stand volume correlated with increasing trends. This supports earlier findings in that the general increase in forest cover and biomass that has occurred in high latitudes during the last decades is another factor that has contributed to brownification.
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| 27. |
- Maher Hasselquist, Eliza, et al.
(författare)
-
Policy change implications for forest water protection in Sweden over the last 50 years
- 2020
-
Ingår i: Ambio. - : Springer. - 0044-7447 .- 1654-7209. ; 49:7, s. 1341-1351
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Tidskriftsartikel (refereegranskat)abstract
- Improving water quality has become an important environmental issue, spurred in part by the Water Framework Directive. However, the relationship of policy change with forest water protection measures is relatively unknown. We analyzed how policy and practice have developed in Sweden using 50 years of historic data from the Krycklan Catchment Study, ocusing on riparian buffers. Corresponding to legislation, education and voluntary measures mphasizing stream protection, two step changes occurred; between the 1970s–1980s, buffers increased by 67%, then by 100% between 1990s and 2000s. By 2013, just 50% of the stream length affected by forestry was protected and the application has varied by stream size; small streams lacked a buffer approximately 65% of the time, while 90% of large streams had buffers. The doubling of buffer implementation from the 1990s–2000s corresponded to the adoption of a number of environmental protection policies in the 1990s that all came into effect during this period.
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| 28. |
- Maher Hasselquist, Eliza, et al.
(författare)
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Post-drainage stand growth and peat mineralization impair water quality from forested peatlands
- 2022
-
Ingår i: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 51, s. 1211-1221
-
Tidskriftsartikel (refereegranskat)abstract
- Many recent studies have indicated upward trends in carbon and nutrient concentrations from drained peatland forests over time since their initial drainage, but the mechanisms behind these trends are still poorly understood. We gathered data on nitrogen and phosphorus concentrations discharged from 37 drained boreal peatland forests where we also had data on peat and tree stand characteristics. We found that tree stand volume and peat bulk density were positively correlated with the nitrogen and phosphorus concentrations discharged from particularly the deep-peated sites. We interpret these results to indicate that a plausible reason for the reported upward trends in nutrient concentrations is the maturing and growing of the tree stands over time since initial drainage and the consequent increasing evapotranspiration capacity, which results in lowered soil water levels and enhanced aerobic peat mineralization. We discuss how our results should be considered in the management of drained peatland forests.
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| 29. |
- Maher Hasselquist, Eliza, et al.
(författare)
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Time for recovery of riparian plants in restored northern Swedish streams : a chronosequence study
- 2015
-
Ingår i: Ecological Applications. - : Ecological Society of America. - 1051-0761 .- 1939-5582. ; 25:5, s. 1373-1389
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Tidskriftsartikel (refereegranskat)abstract
- A lack of ecological responses in stream restoration projects has been prevalent throughout recent literature with many studies reporting insufficient time for recovery. We assessed the relative importance of time, site variables, and landscape setting for understanding how plant species richness and understory productivity recover over time in riparian zones of northern Swedish streams. We used a space-for-time substitution consisting of 13 stream reaches restored 5-25 years ago, as well as five unrestored channelized reference reaches. We inventoried the riparian zone for all vascular plant species along 60-m study reaches and quantified cover and biomass in plots. We found that while species richness increased with time, understory biomass decreased. Forbs made up the majority of the species added, while the biomass of graminoids decreased the most over time, suggesting that the reduced dominance of graminoids favored less productive forbs. Species richness and density patterns could be attributed to dispersal limitation, with anemochorous species being more associated with time after restoration than hydrochorous, zoochorous, or vegetatively reproducing species. Using multiple linear regression, we found that time along with riparian slope and riparian buffer width (e.g., distance to logging activities) explained the most variability in species richness, but that variability in total understory biomass was explained primarily by time. The plant community composition of restored reaches differed from that of channelized references, but the difference did not increase over time. Rather, different time categories had different successional trajectories that seemed to converge on a unique climax community for that time period. Given our results, timelines for achieving species richness objectives should be extended to 25 years or longer if recovery is defined as a saturation of the accumulation of species over time. Other recommendations include making riparian slopes as gentle as possible given the landscape context and expanding riparian buffer width for restoration to have as much impact as possible.
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| 30. |
- Mosquera, Virginia, et al.
(författare)
-
Biochar as a potential tool to mitigate nutrient exports from managed boreal forest: A laboratory and field experiment
- 2024
-
Ingår i: GCB Bioenergy. - 1757-1693 .- 1757-1707. ; 16
-
Tidskriftsartikel (refereegranskat)abstract
- Forest management in drained forested peatlands can negatively affect water quality due to the increase in exports of organic matter and nutrients. Therefore, new methods to alleviate this impact are needed. In laboratory conditions, biochar has been shown to be a strong sorbent of organic and inorganic nutrients due to its high surface area and ion-exchange capacity. However, evidence of the adsorption capacity in field conditions is lacking. Here, we studied the water purification performance of two different biochar feedstocks (wood- and garden residue-based) in a 10-day laboratory experiment where we incubated biochar with runoff water collected from drainage ditches in clear-cut peatland forests. We measured changes in pH and concentrations of inorganic phosphorus (PO4), total dissolved nitrogen (TDN), and dissolved organic carbon (DOC). The biochar with the best adsorbent capacity in the laboratory experiment was then tested in field conditions in a replicated catchment-scale experiment, where both clear-cutting and ditch cleaning were performed. We determined the nutrient concentration of water at the inlet and outlet of biochar filters placed in outflow ditches of four catchments. We found that under laboratory conditions wood-based biochar efficiently adsorbed TDN and DOC, however, it released PO4. Furthermore, we found that the biochar filters reduced TDN and DOC concentration in field conditions. However, the percentage decrease in concentration was dependent on the initial concentrations of nutrients in the water and could be considered low. Moreover, we found that the biochar in the filters increased in TN content over the course of the experiment. This suggests that a wood-based biochar filter has the potential to be a water protection tool for reducing the export of nutrients from catchments with high nutrient concentration. And that the biochar from the ditches could be applied back to the regenerating forest catchment as a potential soil amendment, closing the nutrient cycle.
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| 31. |
- Mosquera, Virginia, et al.
(författare)
-
Co-occurrence of browning and oligotrophication in a boreal stream network
- 2022
-
Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 67:10, s. 2325-2339
-
Tidskriftsartikel (refereegranskat)abstract
- The relative supply of carbon (C), nitrogen (N), and phosphorus (P) to freshwater ecosystems is of fundamental importance to aquatic productivity, nutrient cycling, and food web dynamics. In northern landscapes, ongoing climate change, as well as legacies from atmospheric deposition, have the potential to drive changes in how these elements are recycled on land and exported to streams. While it is well established that dissolved organic carbon (DOC) concentrations have increased in many high latitude streams, the simultaneous trends for N and P and the ratios among these resources, are not well documented. We used data from 13 sites in a boreal stream network to analyze decadal-scale changes in dissolved inorganic N (DIN), dissolved organic N (DON), and dissolved inorganic P (DIP) concentrations and partition these trends seasonally. We observed widespread declines for DIP and DIN in streams, regardless of catchment characteristics. DIN decline was strongest during the growing season, and together with increases in DOC/DON at several sites, suggests increasing N retention by plants and soil microbes across this landscape. By contrast, declines for DIP occurred primarily during late autumn and winter, indicating that key biogeochemical changes are also occurring during non-growing season. Linking these trends to increases in DOC concentration in streams revealed changes in the ratio of energy to nutrient supply for the majority of sites, becoming richer in carbon and poorer in limiting nutrients over time. Overall, our observations from this stream network point to ongoing oligotrophication, with possible consequences for aquatic ecosystems in boreal landscapes.
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| 32. |
- Mosquera, Virginia, et al.
(författare)
-
Concentration-discharge patterns reveal catchment controls over the stoichiometry of carbon and nutrient supply to boreal streams
- 2023
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 128:8
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon (C), nitrogen (N), and phosphorus (P) export from catchments is strongly regulated by interactions between hydrological flowpaths and their terrestrial use/storage. While concentration-discharge (c-Q) relationships have been widely used to understand this interplay for C, N, and P individually, how flow regulates the relative supply of these resources across spatial and temporal scales is not well documented. Here, we analyze c-Q relationships from 12 years of data to test how seasonal flow regulates the concentrations of inorganic N (Dissolved inorganic nitrogen [DIN]) and P (Dissolved inorganic phosphorus [DIP]), dissolved organic N (DON) and C (dissolved organic carbon [DOC]) and their respective ratios across 12 streams in a boreal landscape. We observed opposing c-Q relationships between organic and inorganic solutes. DOC and DON tended toward transport limitation with little year-to-year change, whereas ammonium (NH4) and DIP were increasingly source limited over time. These different c-Q relationships translated into large (up to three-fold) shifts in resource ratios (e.g., DOC:DIN) in response to changes in flow. Our results also highlight strong influences of catchment structure on c-Q patterns, regardless of solute, season, and longer-term directional changes. Here, the organic solute c-Q responses became less transport limited over time; while inorganic solute responses became less source limited with increasing mire/decreasing forest cover. Overall, differences in timing of catchment exports for C, N, and P, create dynamic variation in solute concentrations in streams with subsequent impacts on resource stoichiometry that is central to aquatic ecological processes.
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| 33. |
- Nilsson, Christer, et al.
(författare)
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Riparian and in-stream restoration of boreal streams and rivers : success or failure?
- 2015
-
Ingår i: Ecohydrology. - : Wiley-Blackwell. - 1936-0584 .- 1936-0592. ; 8:5, s. 753-764
-
Tidskriftsartikel (refereegranskat)abstract
- We reviewed follow-up studies from Finnish and Swedish streams that have been restored after timber floating to assess the abiotic and biotic responses to restoration. More specifically, from a review of 18 case studies (16 published and 2 unpublished), we determined whether different taxonomic groups react differently or require different periods of time to respond to the same type of restoration. Restoration entailed returning coarse sediment (cobbles and boulders) and sometimes large wood to previously channelized turbulent reaches, primarily with the objective of meeting habitat requirements of naturally reproducing salmonid fish. The restored streams showed a consistent increase in channel complexity and retention capacity, but the biotic responses were weak or absent in most species groups. Aquatic mosses growing on boulders were drastically reduced shortly after restoration, but in most studies, they recovered after a few years. Riparian plants, macroinvertebrates and fish did not show any consistent trends in response. We discuss seven alternative explanations to these inconsistent results and conclude that two decades is probably too short a time for most organisms to recover. We recommend long-term monitoring using standardized methods, a landscape-scale perspective and a wider range of organisms to improve the basis for judging to what extent restoration in boreal streams has achieved its goal of reducing the impacts from timber floating.
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| 34. |
- Norstedt, Gudrun, 1965-, et al.
(författare)
-
From Haymaking to Wood Production : Past Use of Mires in Northern Sweden Affect Current Ecosystem Services and Function
- 2021
-
Ingår i: Rural Landscapes. - : Stockholm University Press. - 2002-0104. ; 8:1, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- Mires form a large part of the boreal Swedish landscape and are important for biodiversity and natural ecosystem processes. Historically, mires also played a key role for the expansion of agricultural practices, and later to create new forest land, but knowledge is limited on how the land use has affected the current ecosystem services and functions of mires. In this case study from northern Sweden, we have combined historical maps with remote-sensing data to analyze the use of mires over time. Here, 22% of the mire area has been used for hay harvesting, an activity that peaked in the late 1800s. Later, about 3% was reclaimed for intensive agriculture. Drainage to enhance wood production followed in the 1940s, and about 40% of the original mire area is currently forested. The most productive mires have been relatively more affected by human measures. We suggest that this past land use has legacy effects on several ecosystem services. Haymaking likely had positive effects on biodiversity, but may have negatively influenced carbon sequestration. Reclamation led to habitat loss and likely less carbon sequestration. Drainage to promote forest growth generally lowered the ground water level, which in turn enhanced peat decomposition and subsequently released CO2. However, if tree growth outpaces peat decomposition, drainage could increase carbon sequestration. The overall carbon balance is hence influenced by past management regimes, which implies that past human use must be taken into account when considering the role of mires in providing ecosystem services.
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| 35. |
- Paul, Siddhartho Shekhar, et al.
(författare)
-
Virtual landscape-scale restoration of altered channels helps us understand the extent of impacts to guide future ecosystem management
- 2023
-
Ingår i: Ambio. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 52:1, s. 182-194
-
Tidskriftsartikel (refereegranskat)abstract
- Human modification of hydrological connectivity of landscapes has had significant consequences on ecosystem functioning. Artificial drainage practices have fundamentally altered northern landscapes, yet these man made channels are rarely considered in ecosystem management. To better understand the effects of drainage ditches, we conducted a landscape-scale analysis across eleven selected study regions in Sweden. We implemented a unique approach by backfilling ditches in the current digital elevation model to recreate the prehistoric landscape, thus quantifying and characterizing the channel networks of prehistoric (natural) and current (drained) landscapes. Our analysis detected that 58% of the prehistoric natural channels had been converted to ditches. Even more striking was that the average channel density increased from 1.33 km km(-2) in the prehistoric landscape to 4.66 km km(-2) in the current landscape, indicating the extent of ditching activities in the northern regions. These results highlight that man-made ditches should be accurately mapped across northern landscapes to enable more informed decisions in ecosystem management.
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| 36. |
- Polvi, Lina E., et al.
(författare)
-
Potential and actual geomorphic complexity of restored headwater streams in northern Sweden
- 2014
-
Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X .- 1872-695X. ; 210, s. 98-118
-
Tidskriftsartikel (refereegranskat)abstract
- Stream restoration usually relies on ecological theories presuming that increased habitat heterogeneity leads to higher biodiversity. However, to test this hypothesis a quantitative metric of overall geomorphic complexity is needed. We quantified geomorphic complexity using 29 metrics over five dimensions (sediment distribution, longitudinal profile, cross section, planform, and instream wood) of headwater streams in northern Sweden. We examined reaches with four different restoration statuses after a century of timber floating (channelized, restored, demonstration restored, and unimpacted) to determine (1) whether restoration increases complexity in all dimensions, (2) whether a complexity gradient can be quantified and which metrics can serve as proxies for the gradient, and (3) levels of potential complexity based on large-scale controls (drainage area, glacial legacy sediment, valley slope, valley confinement old-growth forest/buffer zone, and beaver activity). We found a significantly higher complexity in unimpacted and demonstration restoration sites than in channelized sites in all five dimensions except the cross section (based on the two metrics quantifying variability in the cross section). Multivariate analyses were able to elucidate an apparent complexity gradient driven by three complexity metrics: longitudinal roughness, sediment sorting, and cross section chain and tape ratio. The large-scale factors of valley and channel gradient as well as median grain size, along with restoration status, drive differences in complexity composition. Restoring a reach to its potential complexity is beneficial in regions without reference systems or sufficient data to model flow and sediment processes. Unimpacted and demonstration restoration reaches displayed not only more intrareach variability than channelized reaches but also greater interreach heterogeneity in complexity composition, which supports a focus on reach-scale controls on potential complexity and a landscape-scale view on restoration. (C) 2014 Elsevier B.V. All rights reserved.
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| 37. |
- Zannella, Alberto, et al.
(författare)
-
Metabolic processes control carbon dioxide dynamics in a boreal forest ditch affected by clear-cut forestry
- 2023
-
Ingår i: Frontiers in Water. - 2624-9375. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Boreal watercourses are large emitters of carbon dioxide (CO2) to the atmosphere. For forestry intensive areas of the Nordic and Baltic countries, a high share of these watercourses are man-made ditches, created to improve drainage and increase forest productivity. Previous studies have suggested that terrestrial sources sustain the CO2 in these ditches and variability in hydrology is the main temporal control. However, few studies have explored ditch CO2 dynamics and its associated controls in catchments being exposed to forest harvest. An altered hydrology, increased nutrient export and light availability following forest harvest are all factors that potentially can change both levels, dynamics, and source controls of ditch CO2. Here, high-frequency (30 min) CO2 concentration dynamics together with other hydrochemical variables were studied in a forest ditch draining a fully harvested catchment in the Trollberget Experimental Area, northern Sweden. We collected data during the snow-free season from May to October. Ditch CO2 concentrations displayed a clear seasonal pattern with higher CO2 concentrations during summer than in spring and autumn. Concentrations ranged from 1.8 to 3.5 mg C L−1 (median: 2.4 mg C L−1 , IQR = 0.5 mg C L−1 ). Strong diel cycles in CO2 developed during early summer, with daily amplitudes in CO2 reaching up to 1.1 mg C L−1 . These pronounced daily cycles in CO2 were closely related to the daily sum of shortwave radiation and water temperature. Variations in hydrology had generally a low impact on the CO2 dynamics but did vary among seasons and between individual hydrological events. It was evident from our study that growing season CO2 concentrations in a forest ditch aected by clearcut harvest were highly variable and mainly controlled by light and temperature induced metabolism. These high dynamics and the associated controls need to be considered when scaling up ditch CO2 emissions across boreal landscapes aected by intensive forest
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| 38. |
- Ågren, Anneli, et al.
(författare)
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Delineating the distribution of mineral and peat soils at the landscape scale in northern boreal regions
- 2022
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Ingår i: Soil. - : Copernicus GmbH. - 2199-3971 .- 2199-398X. ; 8, s. 733-749
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Tidskriftsartikel (refereegranskat)abstract
- To meet the sustainable development goals and enable sustainable management and protection of peatlands, there is a strong need for improving the mapping of peatlands. Here we present a novel approach to identify peat soils based on a high-resolution digital soil moisture map that was produced by combining airborne laser scanning-derived terrain indices and machine learning to model soil moisture at 2 m spatial resolution across the Swedish landscape. As soil moisture is a key factor in peat formation, we fitted an empirical relationship between the thickness of the organic layer (measured at 5479 soil plots across the country) and the continuous SLU (Swedish University of Agricultural Science) soil moisture map (R2= 0.66, p < 0.001). We generated categorical maps of peat occurrence using three different definitions of peat (30, 40, and 50 cm thickness of the organic layer) and a continuous map of organic layer thickness. The predicted peat maps had a higher overall quality (MCC = 0.69–0.73) compared to traditional Quaternary deposits maps (MCC = 0.65) and topographical maps (MCC = 0.61) and captured the peatlands with a recall of ca. 80 % compared to 50 %–70 % on the traditional maps. The predicted peat maps identified more peatland area than previous maps, and the areal coverage estimates fell within the same order as upscaling estimates from national field surveys. Our method was able to identify smaller peatlands resulting in more accurate maps of peat soils, which was not restricted to only large peatlands that can be visually detected from aerial imagery – the historical approach of mapping. We also provided a continuous map of the organic layer, which ranged 6–88 cm organic layer thickness, with an R2 of 0.67 and RMSE (root mean square error) of 19 cm. The continuous map exhibits a smooth transition of organic layers from mineral soil to peat soils and likely provides a more natural representation of the distribution of soils. The continuous map also provides an intuitive uncertainty estimate in the delineation of peat soils, critically useful for sustainable spatial planning, e.g., greenhouse gas or biodiversity inventories and landscape ecological research.
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- Ågren, Anneli, et al.
(författare)
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Ditches show systematic impacts on soil and vegetation properties across the Swedish forest landscape
- 2024
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Ingår i: Forest Ecology and Management. - 0378-1127 .- 1872-7042. ; 555
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Tidskriftsartikel (refereegranskat)abstract
- Novel mapping methods using AI have led to improved mapping of the extent of drainage systems, but the full scope of the effects of drainage on ecosystems has yet to be understood. By combining ditches mapped with remote sensing and AI methods with soil data from the Swedish Forest Soil Inventory, and vegetation data from the National Forest Inventory we identified 4 126 survey plots within 100 m of a ditch. The inventory data span across three biomes; the northern boreal zone, the hemiboreal zone, and the temperate zone. We explored if soils and vegetation close to ditches were indeed different from the surrounding landscape. The large number of plots spread widely across the Swedish forest landscape spanning different physiographic regions, climates, topography, soils, and vegetation made it possible to identify the general effect of drainage on soil properties, tree productivity, and plant species composition. We found a surprisingly large amount of ditches on mineral soils (50-70%, depending on the definition of peatlands). Forest growth was affected, with higher growth rates of trees closer to ditches, particularly Norway spruce. Sphagnum mosses - a key indicator of wet soils - were less common near ditches, where they were replaced by feather mosses. The soil bulk density was higher closer to ditches, as was the concentration of metals that are typically associated with organic matter (Al), while concentrations of metals with a lower affinity for organic material decreased toward ditches (Na, K, Mg). The results from mineral soils and peat soils often differed. For example, N and tree volume increased toward ditches, but on different levels for peat and mineral soils, while the thickness of the humus layer and Pleurozium schreberi cover showed opposite patterns for the different soils. Clearly, ditches have affected the entire Swedish forest landscape, driving it towards a drier, more spruce-dominated productive forested ecosystem and away from wetland ecosystems like mires and littoral areas along streams. Furthermore, the biogeochemistry of the soils and understory species cover near ditches have changed, potentially irreversibly, at least within human time frames, and have implications for restoration goals and the future of forestry.
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