| 1. |
- Stroud, J.T., et al.
(författare)
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Priority effects transcend scales and disciplines in biology
- 2024
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Ingår i: Trends in Ecology & Evolution. - : Elsevier. - 0169-5347 .- 1872-8383.
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Forskningsöversikt (refereegranskat)abstract
- Although primarily studied through the lens of community ecology, phenomena consistent with priority effects appear to be widespread across many different scenarios spanning a broad range of spatial, temporal, and biological scales. However, communication between these research fields is inconsistent and has resulted in a fragmented co-citation landscape, likely due to the diversity of terms used to refer to priority effects across these fields. We review these related terms, and the biological contexts in which they are used, to facilitate greater cross-disciplinary cohesion in research on priority effects. In breaking down these semantic barriers, we aim to provide a framework to better understand the conditions and mechanisms of priority effects, and their consequences across spatial and temporal scales.
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| 2. |
- Sarneel, Judith M., et al.
(författare)
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Reading tea leaves worldwide : decoupled drivers of initial litter decomposition mass-loss rate and stabilization
- 2024
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Ingår i: Ecology Letters. - : John Wiley & Sons. - 1461-023X .- 1461-0248. ; 27:5
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Tidskriftsartikel (refereegranskat)abstract
- The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models.
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| 3. |
- Lembrechts, Jonas J., et al.
(författare)
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Global maps of soil temperature
- 2022
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 28:9, s. 3110-3144
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Tidskriftsartikel (refereegranskat)abstract
- Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean=3.0±2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6±2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7±2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.
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| 4. |
- Ludewig, Kristin, et al.
(författare)
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Phenology and morphology of the invasive legume Lupinus polyphyllus along a latitudinal gradient in Europe
- 2022
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Ingår i: NeoBiota. - : Pensoft Publishers. - 1619-0033 .- 1314-2488. ; 78
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Tidskriftsartikel (refereegranskat)abstract
- Plant phenology, i. e. the timing of life cycle events, is related to individual fitness and species distributionranges. Temperature is one of the most important drivers of plant phenology together with day length.The adaptation of their phenology may be important for the success of invasive plant species. The presentstudy aims at understanding how the performance and the phenology of the invasive legume Lupinuspolyphyllus vary with latitude. We sampled data across a >2000 km latitudinal gradient from Centralto Northern Europe. We quantified variation in phenology of flowering and fruiting of L. polyphyllususing >1600 digital photos of inflorescences from 220 individual plants observed weekly at 22 sites. Theday of the year at which different phenological phases were reached, increased 1.3–1.8 days per degreelatitude, whereas the growing degree days (gdd) required for these phenological phases decreased 5–16 gddper degree latitude. However, this difference disappeared, when the day length of each day included inthe calculation of gdd was considered. The day of the year of the earliest and the latest climatic zone toreach any of the three studied phenological phases differed by 23–30 days and temperature requirementsto reach these stages differed between 62 and 236 gdd. Probably, the invasion of this species will furtherincrease in the northern part of Europe over the next decades due to climate warming. For invasive speciescontrol, our results suggest that in countries with a large latitudinal extent, the mowing date should shiftby ca. one week per 500 km at sites with similar elevations.
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| 5. |
- Ludewig, Kristin, et al.
(författare)
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Phenology of Lupinus polyphyllus from Central to Northern Europe
- 2022
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Annan publikationabstract
- Plant phenology, i. e. the timing of life cycle events, is related to individual fitness and species distribution ranges. Among the environmental factors, phenology is mostly driven by temperature and day length. Rapid adaptation of their phenology may also be important for the success of invasive plant species. Our main aim was to understand how the performance, timing, and temperature dependence of the phenology of the invasive legume Lupinus polyphyllus varies with latitude. L. polyphyllus is one of the most frequent invasive species in Europe, and the gained information may help to make management more effective by adjustments to latitude and phenology.Methods:We quantified variation in phenology across a >2000 km latitudinal gradient from Central to Northern Europe. We sampled data of flowering and fruiting of L. polyphyllus using >1600 digital photos of inflorescences from 220 individual plants observed weekly at 22 locations. We calculated the accumulated growing degree days for each observation date at each site from the temperature data of the meteorological stations, which are listed in the metadata of the dataset.
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| 6. |
- Ochoa-Hueso, Raúl, et al.
(författare)
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Microbial processing of plant remains is co-limited by multiple nutrients in global grasslands
- 2020
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 26:8, s. 4572-4582
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Tidskriftsartikel (refereegranskat)abstract
- Microbial processing of aggregate-unprotected organic matter inputs is key for soil fertility, long-term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro- and micro-nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak-season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains.
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| 7. |
- Alsafran, Mohammed H.S.A., et al.
(författare)
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Variation in plant litter decomposition rates across extreme dry environments in Qatar
- 2017
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Ingår i: Arab World Geographer. - : The University of Akron Press. - 1480-6800. ; 20:2-3, s. 252-261
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Forskningsöversikt (refereegranskat)abstract
- Decomposition of plant litter is a key process for transfer of carbon and nutrients in ecosystems. Carbon contained in decaying biomass is released to the atmosphere as respired CO2, a greenhouse gas that contributes to global warming. To our knowledge, there have been no studies on litter decomposition in terrestrial ecosystems in the Arabian peninsula. Here we used commercial teabags (green tea, rooibos tea) as standard substrates to study decomposition rates across contrasting ecosystems in Qatar. Teabags were buried under and beside Acacia tortilis trees, in depressions with abundant grass vegetation, in saltmarsh without and with vegetation, under Zygophyllum qatarense in drylands, in natural mangrove and in planted mangrove. There were significant site effects across ecosystems on decomposition rate (k), litter stabilisation factor (S), final weight of green tea and final weight of rooibos tea. Mangrove and depressions with grassland had the smallest amounts of remaining green and rooibos tea after the incubation period (69-82 days), while teabags buried under A. tortilis and in saltmarsh without vegetation had the largest amounts. Thus decomposition rates differ among ecosystems in the desert environment. Further multi-year and site studies are needed to identify factors that influence decomposition rates across sites in extreme environments.
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| 8. |
- Beltman, B., et al.
(författare)
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Phosphate Release Upon Long- and Short -Term Flooding of Fen Meadows Depends on Land Use History and Soil pH
- 2014
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Ingår i: Wetlands (Wilmington, N.C.). - : Springer Netherlands. - 0277-5212 .- 1943-6246. ; 34:5, s. 989-1001
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Tidskriftsartikel (refereegranskat)abstract
- Flooding of acidified and desiccated fen meadows is a management approach for mitigating loss of plant species as well as a short-term measure to prevent flooding in urban areas. Studies have shown that flooding events can cause extreme P release from soils. We questioned whether the occurrence of this 'internal eutrophication' from flooding depended on fertilization history and soil pH. A greenhouse experiment with soil cores from Ireland (turloughs) and from the Netherlands, exposed to flooding for 216 days (long-term) showed a substantial P release for sites with a history of fertilizer use only. Short-term flooding (20-25 days) caused little P release in all soils. There was no correlation between P release and initial soil pH (range 4.1-7.1). All flooded soils showed a significant decline in sulfate and increased iron in the pore water upon flooding. Field trials applying short term flooding to sites differing in soil pH, average soil moisture and history of fertilizer application showed there was no overall effect of flooding on phosphate, nitrate, ammonium, iron concentrations and pH of pore water. Sulfate concentrations significantlyincreased. Hence, problematic phosphate release is only induced by long term flooding of fen meadows with a history of fertilization.
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| 9. |
- Keuskamp, Joost A., et al.
(författare)
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Tea Bag Index : a novel approach to collect uniform decomposition data across ecosystems
- 2013
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Ingår i: Methods in Ecology and Evolution. - : Wiley-Blackwell. - 2041-210X. ; 4:11, s. 1070-1075
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Tidskriftsartikel (refereegranskat)abstract
- 1. Changes in the balance between soil carbon storage and release can significantly amplify or attenuate global warming. Although a lot of progress has been made in determining potential drivers of carbon release through large-scale decomposition experiments, climate predictions are still hampered by data limitation at a global scale as a result of high effort and measurement costs of comparative litter decomposition studies.2. We introduce an innovative, cost-effective, well-standardised method to gather data on decomposition rate and litter stabilisation using commercially available tea bags as standardised test kits. By using two tea types with contrasting decomposability, we can construct a decomposition curve using a single measurement in time. The acquired Tea Bag Index (TBI) consists of two parameters describing decomposition rate (k) and litter stabilisation factor (S).3. The method was tested for its sensitivity and robustness in contrasting ecosystems and biomes, confirming that the TBI is sensitive enough to discriminate between these systems. Within an ecosystem, TBI is responsive to differences in abiotic circumstances such as soil temperature and moisture content. The collected k and S values are in accordance with expectations based on decomposition process literature. They are therefore interpretable within the current knowledge framework.4. Tea Bag Index is a unique, multifunctional method requiring few resources and minimal prior knowledge. The standardisation and simplicity of the method make it possible to collect comparable, globally distributed data through crowdsourcing. TBI can further provide an excellent decomposition reference and has the potential to increase reliability of soil carbon flux estimates based on extrapolations of decomposition data.
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| 10. |
- Sarneel, Judith M., et al.
(författare)
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Alternative transient states and slow plant community responses after changed flooding regimes
- 2019
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 25:4, s. 1358-1367
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Tidskriftsartikel (refereegranskat)abstract
- Climate change will have large consequences for flooding frequencies in freshwater systems. In interaction with anthropogenic activities (flow regulation, channel restoration and catchment land-use) this will both increase flooding and drought across the world. Like in many other ecosystems facing changed environmental conditions, it remains difficult to predict the rate and trajectory of vegetation responses to changed conditions. Given that critical ecosystem services (e.g. bank stabilization, carbon subsidies to aquatic communities or water purification) depend on riparian vegetation composition, it is important to understand how and how fast riparian vegetation responds to changing flooding regimes. We studied vegetation changes over 19 growing seasons in turfs that were transplanted in a full-factorial design between three riparian elevations with different flooding frequencies. We found that (a) some transplanted communities may have developed into an alternative stable state and were still different from the target community, and (b) pathways of vegetation change were highly directional but alternative trajectories did occur, (c) changes were rather linear but faster when flooding frequencies increased than when they decreased, and (d) we observed fastest changes in turfs when proxies for mortality and colonization were highest. These results provide rare examples of alternative transient trajectories and stable states under field conditions, which is an important step towards understanding their drivers and their frequency in a changing world.
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| 11. |
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| 12. |
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| 13. |
- Sarneel, Judith M., et al.
(författare)
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Species traits interact with stress level to determine intraspecific facilitation and competition
- 2022
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Ingår i: Journal of Vegetation Science. - : John Wiley & Sons. - 1100-9233 .- 1654-1103. ; 33:5
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Tidskriftsartikel (refereegranskat)abstract
- Questions: Flooding and drought stress are expected to increase significantly across the world and plant responses to these abiotic changes may be mediated by plant–plant interactions. Stress tolerance and recovery often require a biomass investment that may have consequences for these plant–plant interactions. Therefore, we questioned whether phenotypic plasticity in response to flooding and drought affected the balance between competition and facilitation for species with specific adaptations to drought or flooding.Location: Utrecht University. Methods: Stem elongation, root porosity, root:shoot ratio and biomass production were measured for six species during drought, well-drained and submerged conditions when grown alone or together with conspecifics. We quantified competition and facilitation as the ‘neighbour intensity effect’ directly after the 10-day treatment and again after a seven-day recovery period in well-drained conditions.Results: Water stress, planting density and species identity interactively affected standardized stem elongation in a way that could lead to facilitation during submergence for species that preferably grow in wet soils. Root porosity was affected by the interaction between neighbour presence and time-step. Plant traits were only slightly affected during drought. The calculated neighbour interaction effect indicated facilitation for wetland species during submerged conditions and, after a period to recover from flooding, for species that prefer dry habitats.Conclusions: Our results imply that changing plant–plant interactions in response to submergence and to a lesser extent to drought should be considered when predicting vegetation dynamics due to changing hydroclimatic regimes. Moreover, facilitation during a recovery period may enable species maladapted to flooding to persist.
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| 14. |
- Sarneel, Judith M., et al.
(författare)
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Windows of opportunity for germination of riparian species after restoring water level fluctuations : a field experiment with controlled seed banks
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51:4, s. 1006-1014
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Tidskriftsartikel (refereegranskat)abstract
- 1. Restoration activities aiming at increasing vegetation diversity often try to stimulate both dispersal and germination. In wetlands, dispersal and germination are coupled as water and water level fluctuations (WLF) simultaneously influence seed transport and germination conditions (soil moisture). Water regime shifts have been shown to affect vegetation composition. However, the interactions between WLF, dispersal and subsequent germination as drivers of such changes are still poorly understood, especially within the complexity of a field situation.2. We tested the effect of soil moisture on ten riparian species in the greenhouse and sowed these species on 135 field locations in nine wetlands with recently restored WLF. We used quantile regressions to test the effects of WLF on the window of opportunity for germination from sown seeds and other seeds naturally dispersed to our plots, as well as on community diversity.3. Soil moisture significantly affected germination both in the greenhouse and in the field. In the complexity of a field situation, a flooding depth just below the soil level, an intermediate flooding duration and a high flooding frequency provided the best opportunities for maximal germination. This was because these conditions enhanced germination from the seed bank as well as increasing germination from dispersed seeds. Seedling diversity showed identical patterns.4. Other known (i.e., light conditions) and unknown factors played a role as we found low and variable germination, even under optimal conditions. We found evidence that WLF can affect vegetation zonation as flooded seedling communities contained more species with high moisture affinity.5. Synthesis and applications. Water level fluctuations provide clear windows of opportunity for germination both from the seed bank and from dispersed seeds. Water regime changes are therefore likely to strongly affect recruitment opportunities and subsequent community assembly in riparian ecosystems, for instance through climate change or management. Water level fluctuations can be used as management tool to stimulate plant recruitment and seedling diversity in riparian wetlands.
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| 15. |
- Althuizen, Inge H. J., et al.
(författare)
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Long-Term climate regime modulates the impact of short-term climate variability on decomposition in alpine grassland soils
- 2018
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Ingår i: Ecosystems (New York. Print). - : Springer. - 1432-9840 .- 1435-0629. ; 21:8, s. 1580-1592
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Tidskriftsartikel (refereegranskat)abstract
- Decomposition of plant litter is an important process in the terrestrial carbon cycle and makes up approximately 70% of the global carbon flux from soils to the atmosphere. Climate change is expected to have significant direct and indirect effects on the litter decomposition processes at various timescales. Using the TeaBag Index, we investigated the impact on decomposition of short-term direct effects of temperature and precipitation by comparing temporal variability over years, versus long-term climate impacts that incorporate indirect effects mediated through environmental changes by comparing sites along climatic gradients. We measured the initial decomposition rate (k) and the stabilization factor (S; amount of labile litter stabilizing) across a climate grid combining three levels of summer temperature (6.5-10.5 degrees C) with four levels of annual precipitation (600-2700 mm) in three summers with varying temperature and precipitation. Several (a)biotic factors were measured to characterize environmental differences between sites. Increased temperatures enhanced k, whereas increased precipitation decreased k across years and climatic regimes. In contrast, S showed diverse responses to annual changes in temperature and precipitation between climate regimes. Stabilization of labile litter fractions increased with temperature only in boreal and sub-alpine sites, while it decreased with increasing precipitation only in sub-alpine and alpine sites. Environmental factors such as soil pH, soil C/N, litter C/N, and plant diversity that are associated with long-term climate variation modulate the response of k and S. This highlights the importance of long-term climate in shaping the environmental conditions that influences the response of decomposition processes to climate change.
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| 16. |
- Bakker, Elisabeth S., et al.
(författare)
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High grazing pressure of geese threatens conservation and restoration of reed belts
- 2018
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Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Reed (Phragmites australis (Cav.) Trin. ex Steud.) beds are important habitat for marsh birds, but are declining throughout Europe. Increasing numbers of the native marsh bird, the Greylag goose (Anser anser L.), are hypothesized to cause reed bed decline and inhibit restoration of reed beds, but data are largely lacking. In this study, we experimentally tested the effect of grazing by Greylag geese on the growth and expansion of reed growing in belts along lake shorelines. After 5 years of protecting reed from-grazing with exclosures, reed stems were over 4-fold denser and taller than in the grazed plots. Grazing pressure was intense with 50-100% of the stems being grazed among years in the control plots open to grazing. After 5 years of protection we opened half of the exclosures and the geese immediately grazed almost 100% of the reed stems. Whereas this did not affect the reed stem density, the stem height was strongly reduced and similar to permanently grazed reed. The next year geese were actively chased away by management from mid-March to mid-June, which changed the maximum amount of geese from over 2300 to less than 50. As a result, reed stem density and height increased and the reed belt had recovered over the full 6 m length of the experimental plots. Lastly, we introduced reed plants in an adjacent lake where no reed was growing and geese did visit this area. After two years, the density of the planted reed was six to nine-fold higher and significantly taller in exclosures compared to control plots where geese had access to the reed plants. We conclude that there is a conservation dilemma regarding how to preserve and restore reed belts in the presence of high densities of Greylag geese as conservation of both reed belts and high goose numbers seems infeasible. We suggest that there are three possible solutions for this dilemma: (1) effects of the geese can be mediated by goose population management, (2) the robustness of the reed marshes can be increased, and (3) at the landscape level, spatial planning can be used to configure landscapes with large reed bed reserves surrounded by unmown, unfertilized meadows.
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| 17. |
- Baladrón, Alejandro, et al.
(författare)
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Trapped between drowning and desiccation : riverine plants under hydropeaking
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 829
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Tidskriftsartikel (refereegranskat)abstract
- Hydropeaking is part of hydropower production. The discontinuous release of turbined water during hydropeaking generates sudden rise and falls of the water levels, as well as extended droughts. These artificial flow fluctuations impose challenging growing conditions for riverine vegetation. In order to identify vulnerable/resistant plant species to hydropeaking and to evaluate the impact of contrasting hydropeaking scenarios (simplified (i.e., sudden deep floods, frequent soil saturation and drought) and real-life, power plant-induced scenarios), we measured germination, survival, and morphological and physiological attributes of a selection of 14 plant species commonly found along riparian areas. Species were subject to different hydropeaking scenarios during three months (vegetative period) in the field and in a greenhouse. Half of the species performed worse under hydropeaking in comparison to the control (e.g., less germination and biomass, lower growth rates, reduced stem and root length, physiological stress) but none of the tested hydropeaking scenarios was clearly more disruptive than others. Betula pubescens, Alnus incana and Filipendula ulmifolia showed the largest vulnerability to hydropeaking, while other species (e.g., Carex acuta) were resistant to it. Both in the field and in the greenhouse, plants in perturbed scenarios accumulated more 13C than in the control scenario indicating limited capacity to perform 13C isotope discrimination and evidencing plant physiological stress. The highest 13C abundances were found under drought or flooding conditions in the greenhouse, and under the highest hydropeaking intensities in the field (e.g., Betula pubescens). Our results suggest that any hydropeaking scheme can be equally detrimental in terms of plant performance. Hydropeaking schemes that combine periods of severe drought with long and frequent flooding episodes may create a hostile environment for riverine species. Further research on "hydropeaking-tolerant" plant traits is key to draw the boundaries beyond which riverine species can germinate, grow and complete their life cycle under hydropeaking.
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| 18. |
- Bejarano, Maria D., et al.
(författare)
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Shifts in Riparian Plant Life Forms Following Flow Regulation
- 2020
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Ingår i: Forests. - : MDPI. - 1999-4907. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- Flow regulation affects bordering riparian plant communities worldwide, but how different plant life forms are affected by river regulation still needs further research. In northern Sweden, we selected 10 rivers ranging from free-flowing to low, moderately, and highly regulated ones. In 94 reaches across those rivers, we evaluated the relative abundance of woody and herbaceous (i.e., graminoids and forbs) life forms, their species richness, and their relative presence. We also explored which, and to what extent, hydrological variables drove species assembly within each life form. The relative abundance and species richness of each life form decreased across river categories with increasing levels of regulation. This was particularly apparent in herbaceous life forms, and the most drastic decreases were observed in all life forms in moderately or highly regulated reaches. Additionally, when river regulation increased, the relative presence of many species from all life forms decreased. Unlike woody species, only a few new herbaceous species appeared in regulated reaches. A canonical correspondence analyses (CCA) revealed that a wide range of hydrological variables explained the occurrence of woody species, while fewer variables explained variation in the graminoid and forb life forms. We conclude that flow regulation and its intensity result into clear shifts in the relative abundance of different life forms, as well as in changes of within-group species richness and composition. Consequently, the modification of certain flow attributes in flow regulation schemes, as well as the intensity of these modifications, may alter the ratio between herbaceous and woody species, ultimately impacting the functions and benefits derived from each life form.
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| 19. |
- Fanin, Nicolas, et al.
(författare)
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Relative Importance of Climate, Soil and Plant Functional Traits During the Early Decomposition Stage of Standardized Litter
- 2020
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Ingår i: Ecosystems (New York. Print). - : Springer. - 1432-9840 .- 1435-0629. ; 23:5, s. 1004-1018
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Tidskriftsartikel (refereegranskat)abstract
- Climatic factors have long been considered predominant in controlling decomposition rates at large spatial scales. However, recent research suggests that edaphic factors and plant functional traits may play a more important role than previously expected. In this study, we investigated how biotic and abiotic factors interacted with litter quality by analyzing decomposition rates for two forms of standardized litter substitutes: green tea (high-quality litter) and red tea (low-quality litter). We placed 1188 teabags at two different positions (forest floor and 8 cm deep) across 99 forest sites in France and measured 46 potential drivers at each site. We found that high-quality litter decomposition was strongly related to climatic factors, whereas low-quality litter decomposition was strongly related to edaphic factors and the identity of the dominant tree species in the stand. This indicates that the relative importance of climate, soil and plant functional traits in the litter decomposition process depends on litter quality, which was the predominant factor controlling decomposition rate in this experiment. We also found that burying litter increased decomposition rates, and that this effect was more important for green tea in drier environments. This suggests that changes in position (surface vs. buried) at the plot scale may be as important as the role of macroclimate on decomposition rates because of varying water availability along the soil profile. Acknowledging that the effect of climate on decomposition depends on litter quality and that the macroclimate is not necessarily the predominant factor at large spatial scales is the first step toward identifying the factors regulating decomposition rates from the local scale to the global scale.
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| 20. |
- Herberg, Erik R., et al.
(författare)
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Recruitment of riparian plants after restoration of geomorphic complexity in northern Sweden
- 2017
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Ingår i: Applied Vegetation Science. - : John Wiley & Sons. - 1402-2001 .- 1654-109X. ; 20:3, s. 435-445
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Tidskriftsartikel (refereegranskat)abstract
- Question: Restoration of channelized streams increases geomorphic complexity but it remains unclear how this interacts with processes that drive future vegetation changes (dispersal, germination and establishment). This study asks if increased geomorphic complexity increases recruitment conditions of sown seeds or affects post-dispersal natural seedling densities. Location: Vindel River catchment, northern Sweden. Methods: We selected seven study streams with paired reaches that differed in the degree to which geomorphic complexity was restored. Basic reaches used simple restoration methods while enhanced reaches additionally added large boulders and woody debris. We sowed seeds of six species at ten locations in each reach in 2014 and counted the number of seedlings after 8wk and the number of naturally occurring seedlings in a plot adjacent to the sowing locations in 2013 and 2014. Using factor analysis based on 34 complexity measurements, overall geomorphic complexity was quantified for eight of the 14 reaches. Results: Total numbers of sown (2014) and natural seedlings (2013 and 2014) summed per reach did not differ between restoration types when tested pair-wise. Enhanced restoration did not always significantly increase geomorphic complexity, which differed considerably between the streams. More complex reaches were steeper, had larger size sediment and more nutrient-poor soils. Total recruitment of sown species significantly decreased with increasing complexity. Numbers of natural seedlings differed considerably from 2013 to 2014, but were not related to complexity. In 2014, a potential parent plant of the same species occurred within the same plot for 71.8% of the natural seedlings that could be identified. Conclusions: The recruitment of sown seeds was affected by overall geomorphic complexity rather than by the enhanced restoration. The absence of a correlation between geomorphic complexity and natural seedlings could indicate that natural seedling dynamics are not solely determined by recruitment conditions, but also by dispersal.
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| 21. |
- Hidding, Bert, et al.
(författare)
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Flooding tolerance and horizontal expansion of wetland plants : facilitation by floating mats?
- 2014
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Ingår i: Aquatic Botany. - : Elsevier BV. - 0304-3770 .- 1879-1522. ; 113, s. 83-89
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Tidskriftsartikel (refereegranskat)abstract
- Water level fluctuations (WLF) can be important disturbances promoting the diversity of riparian plant communities, but are currently absent from many managed aquatic ecosystems. A lack of WLF is thought to reduce plant diversity and hamper hydrosere succession. However, a positive impact of WLF on plant diversity may crucially depend on nutrient availability and the presence of a potential ecosystem engineer, the floating plant Strati otes abides, that may provide structural support to riparian plants. We tested the interactive effects of 40 cm flooding, presence of S. abides and sediment nutrient availability (N and P) on growth and horizontal expansion of eight wetland plant species in a 10 week experiment. Seven out of eight species showed a significant elongation response to flooding. Compared to stagnant water levels, flooding in combination with high nutrient availability decreased horizontal expansion in two short species and increased it in two tall species, whereas flooding decreased horizontal expansion in two other short species under both nutrient levels. In this 10 week experiment, we observed no effect of S. abides on the measured plant parameters. This experiment shows short-term negative effects of flooding on most of the short species. On the long-term, we hypothesize that improvements in water quality and seedling recruitment due to drawdown may result in net positive effects of WLF in the riparian zone, but as the species that were rare in the field happened to be short, care should be taken to maintain rare species when allowing more WLF.(C) 2013 Elsevier B.V. All rights reserved.
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| 22. |
- Hunter, William Ross, et al.
(författare)
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Using the Tea Bag Index to determine how two human pharmaceuticals affect litter decomposition by aquatic microorganisms
- 2021
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Ingår i: Ecotoxicology. - : Springer. - 0963-9292 .- 1573-3017. ; 30:6, s. 1272-1278
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Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates that independent additive effects of two human pharmaceuticals, the antibiotic trimethoprim and the artificial estrogen 17a-Ethinylestradiol (EE2), inhibit plant litter decomposition by aquatic microorganisms. The constant release of pharmaceuticals, such as these, has the potential to affect aquatic microbial metabolism and alter biogeochemical cycling of carbon and nutrients. Here we advance the Tea Bag Index (TBI) for decomposition by using it in a series of contaminant exposure experiments testing how interactions between trimethoprim and EE2 affect aquatic microbial activity. The TBI is a citizen science tool used to test microbial activity by measuring the differential degradation of green and rooibos tea as proxies for respectively labile and recalcitrant litter decomposition. Exposure to either trimethoprim or EE2 decreased decomposition of green tea, suggesting additive effects upon microbial activity. Exposure to EE2 alone decreased rooibos tea decomposition. Consequently, trimethoprim and EE2 stabilized labile organic matter against microbial degradation and restricted decomposition. We propose that the method outlined could provide a powerful tool for testing the impacts of multiple interacting pollutants upon microbial activity, at a range of scales, across aquatic systems and over ecologically relevant time scales.
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| 23. |
- Nilsson, Christer, et al.
(författare)
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Ecological Restoration as a Means of Managing Inland Flood Hazards
- 2018
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Ingår i: BioScience. - : Oxford University Press. - 0006-3568 .- 1525-3244. ; 68:2, s. 89-99
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Tidskriftsartikel (refereegranskat)abstract
- Many streams and rivers experience major floods. Historically, human societies have responded to such floods by moving away from them or by abating them, the latter with large negative impacts on stream and river ecology. Societies are currently implementing a strategy of "living with floods,"which may involve ecological restoration. It further involves flood mapping, forecasting, and warning systems. We evaluate 14 different stream-and river-restoration measures, which differ in their capacity to modify water retention and runoff. We discuss these restoration measures in the light of predicted changes in climate and flooding and discuss future restoration needs. We focus on the Nordic countries, where substantial changes in the water cycle are foreseen. We conclude that sustainable solutions require researchers to monitor the effect of flood management and study the relative importance of individual restoration measures, as well as the side effects of flood attenuation.
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| 24. |
- Nilsson, Christer, et al.
(författare)
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How do biota respond to additional physical restoration of restored streams?
- 2017
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Ingår i: Ecosystems (New York. Print). - : Springer. - 1432-9840 .- 1435-0629. ; 20:1, s. 144-162
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Tidskriftsartikel (refereegranskat)abstract
- Restoration of channelized streams by returning coarse sediment from stream edges to the wetted channel has become a common practice in Sweden. Yet, restoration activities do not always result in the return of desired biota. This study evaluated a restoration project in the Vindel River in northern Sweden in which practitioners further increased channel complexity of previously restored stream reaches by placing very large boulders (> 1 m), trees (> 8 m), and salmonid spawning gravel from adjacent upland areas into the channels. One reach restored with basic methods and another with enhanced methods were selected in each of ten different tributaries to the main channel. Geomorphic and hydraulic complexity was enhanced but the chemical composition of riparian soils and the communities of riparian plants and fish did not exhibit any clear responses to the enhanced restoration measures during the first 5 years compared to reaches restored with basic restoration methods. The variation in the collected data was among streams instead of between types of restored reaches. We conclude that restoration is a disturbance in itself, that immigration potential varies across landscapes, and that biotic recovery processes in boreal river systems are slow. We suggest that enhanced restoration has to apply a catchment-scale approach accounting for connectivity and availability of source populations, and that low-intensity monitoring has to be performed over several decades to evaluate restoration outcomes.
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| 25. |
- Nilsson, Christer, et al.
(författare)
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Riparian and in-stream restoration of boreal streams and rivers : success or failure?
- 2015
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Ingår i: Ecohydrology. - : Wiley-Blackwell. - 1936-0584 .- 1936-0592. ; 8:5, s. 753-764
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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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