| 1. |
- Agostinelli, Marta, et al.
(författare)
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Mycobiome of Fraxinus excelsior With Different Phenotypic Susceptibility to Ash Dieback
- 2021
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Ingår i: Frontiers in Forests and Global Change. - : Frontiers Media S.A.. - 2624-893X. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- For the last two decades, large-scale population decline of European ash (Fraxinus excelsior) has occurred in Europe because of the introduction of the alien fungal pathogen, Hymenoscyphus fraxineus, from East Asia. Since European ash is a keystone species having critical importance for biodiversity, and only a small percentage of the ash population appears to show some tolerance against the pathogen, the loss of ash trees means that other associated organisms, especially those with high or obligate associations to ash, are at risk of further species declines. In this study, we used high throughput DNA sequencing and multivariate analysis to characterize: (i) the mycobiome in aerial tissues (i.e., leaf, bark, and xylem) of ash trees showing different phenotypic response to ash dieback, (ii) the temporal variation in fungal communities across the growing season, and (iii) the similarity in fungal community structure between ash and other common trees species that may serve as an ecological niche substitute for ash microfungi. Results showed that fungal communities differed among the three tissue types, susceptibility classes, in time and between sites. Trophic analysis of functional groups using the FUNGuild tool indicated a higher presence of pathotrophic fungi in leaves than in bark and xylem. The share of pathotrophic fungi increased along a gradient of low to high disease susceptibility in both bark and xylem tissue, while the proportion of symbiotrophic fungi correspondingly decreased in both tissue types. Neighboring, alternative host trees did not share all the fungal species found in ash, however, most microfungi uniquely associated to ash in this study are generalists and not strictly host specific. The progressive disappearance of ash trees on the landscape imposes a high risk for extinction of Red-listed macrofungal species, and breeding for resistance against ash dieback should help sustain important biodiversity associated to ash. Microfungal diversity though may be less prone to such demise since most ash-associated endophytes appear to occur on a broad range of host species.
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| 2. |
- Angelstam, Per
(författare)
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Natural Disturbance-Based Forest Management: Moving Beyond Retention and Continuous-Cover Forestry
- 2021
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Ingår i: Frontiers in forests and global change. - : Frontiers Media SA. - 2624-893X. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Global forest area is declining rapidly, along with degradation of the ecological condition of remaining forests. Hence it is necessary to adopt forest management approaches that can achieve a balance between (1) human management designs based on homogenization of forest structure to efficiently deliver economic values and (2) naturally emerging self-organized ecosystem dynamics that foster heterogeneity, biodiversity, resilience and adaptive capacity. Natural disturbance-based management is suggested to provide such an approach. It is grounded on the premise that disturbance is a key process maintaining diversity of ecosystem structures, species and functions, and adaptive and evolutionary potential, which functionally link to sustainability of ecosystem services supporting human well-being. We review the development, ecological and evolutionary foundations and applications of natural disturbance-based forest management. With emphasis on boreal forests, we compare this approach with two mainstream approaches to sustainable forest management, retention and continuous-cover forestry. Compared with these approaches, natural disturbance-based management provides a more comprehensive framework, which is compatible with current understanding of multiple-scale ecological processes and structures, which underlie biodiversity, resilience and adaptive potential of forest ecosystems. We conclude that natural disturbance-based management provides a comprehensive ecosystem-based framework for managing forests for human needs of commodity production and immaterial values, while maintaining forest health in the rapidly changing global environment.
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| 3. |
- Bastos Lima, Mairon G., 1984, et al.
(författare)
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Commodity-Centric Landscape Governance as a Double-Edged Sword: The Case of Soy and the Cerrado Working Group in Brazil
- 2020
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Ingår i: Frontiers in Forests and Global Change. - : Frontiers Media SA. - 2624-893X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Persistent ecological and socio-economic impacts from the expansion of industrial monocultures in the tropics have raised land use sustainability to the top of the environmental policy agenda. As major crops such as soy continue to experience growing market demand and threaten both natural ecosystems and traditional populations, a number of multi-stakeholder governance initiatives have been established around agricultural commodity chains or key landscapes. Effectiveness in curbing unsustainable land use, however, remains limited. In this context, innovative initiatives have blurred the lines to combine both supply chain and landscape governance. We analyze such arrangements-here conceptualized as commodity-centric landscape governance (CCLG)-with an in-depth case study of the Cerrado Working Group, a multi-stakeholder initiative led by civil society and the soy agribusiness to address land use change in that savanna landscape in Brazil. The paper examines how that initiative has come about, its agenda, as well as usually underexposed political dimensions using agenda-setting theory. The research is based on extensive fieldwork in Brazil, with data collected through document analysis and 56 key-informant interviews. The findings suggest that a sustainable development agenda for the Cerrado has been substantially narrowed to become mostly one of conversion-free soy supply, serving more the interests of that agroindustry and its consumers than those of the landscape's most vulnerable stakeholders, such as local communities. While the Cerrado Working Group has importantly broadened the policy scope beyond commodity certification, its limited inclusiveness and a skewed agenda have led to instruments that target only soy farmers as beneficiaries. We conclude that, although effective for targeting conversion drivers, CCLG can crystallize and reinforce existing land use patterns by granting disproportionate power to dominant stakeholders, thus limiting the agenda to incremental changes. As a consequence, distant demand-side actors may exert greater governance authority than the landscape's own population. If embodying norms of inclusiveness and equitable participation, CCLG may serve as an entry point, but it does not per se replace inclusive land-use planning and integrated landscape governance.
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| 4. |
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| 5. |
- Braun, Sabine, et al.
(författare)
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Nitrogen deposition in forests: Statistical modeling of total deposition from throughfall loads
- 2022
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Ingår i: Frontiers in Forests and Global Change. - : IVL Svenska Miljöinstitutet. - 2624-893X. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Nitrogen (N) gradient studies in some cases use N deposition inthroughfall as measure of N deposition to forests.For evaluating critical loadsof N, however, information on total N deposition is required, i.e., the sum ofestimates of dry, wet and occult deposition.Methods: The present paper collects a number of studies in Europe wherethroughfall and total N deposition were compared in different forest types.From this dataset a function was derived which allows to estimate total Ndeposition from throughfall N deposition.Results: At low throughfall N deposition values, the proportion of canopyuptake is high and thus the underestimation of total deposition by throughfallN needs to be corrected.At throughfall N deposition values > 20 kg Nha?1 yr?1 canopy uptake is getting less important.Conclusion: This work shows that throughfall clearly underestimates totaldeposition of nitrogen. With the present data set covering large parts of Europe it is possible to derive a critical load estimate from gradient studiesusing throughfall data.
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| 6. |
- Churchland, Carolyn, et al.
(författare)
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Dispersed Variable-Retention Harvesting Mitigates N Losses on Harvested Sites in Conjunction With Changes in Soil Microbial Community Structure
- 2021
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Ingår i: Frontiers in Forests and Global Change. - : Frontiers Media SA. - 2624-893X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- As an alternative to clear-cutting, variable-retention harvesting is now standard forest management practice on the coast of British Columbia and in temperate forests globally, due to the benefits associated with maintaining mature forest species and forest structural diversity. Although there is some evidence that variable-retention harvesting, particularly single-tree (dispersed) retention will mitigate the impacts of clear-cutting on soil microbial communities and nutrient cycling, findings have been inconsistent. We examined microbial community structure (phospholipid-fatty acid), and nutrient availability (PRSTM probes) in a large (aggregated) retention patch and over three harvesting treatments: dispersed retention, clear-cut and clear-cut edge 2 years after harvest. Unlike previous studies, we did not observe elevated nitrate in the harvested areas, instead ammonium was elevated. Availability of N and other nutrients were surprisingly similar between the dispersed-retention treatment and the retention patch. The microbial community, however, was different in the clear-cut and dispersed-retention treatments, mostly due to significantly lower abundance of fungi combined with an increase in bacteria, specifically Gram-negative bacteria. This was accompanied by lower δ13CPDB value of the Gram-negative PLFA's in these treatments, suggesting the decline in mycorrhizal fungal abundance may have allowed the dominant Gram-negative bacteria to access more of the recently photosynthesized C. This shift in the microbial community composition in the dispersed-retention treatment did not appear to have a major impact on microbial functioning and nutrient availability, indicating that this harvesting practice is more effective at maintaining generic microbial functions/processes. However, as Mn levels were twice as high in the retention patch compared to the harvested treatments, indicating the other “narrow” processes (i.e., those performed by a small number of specialized microorganisms), such as lignin degradation, catalyzed by Mn peroxidase, which concomitantly removes Mn from solution, may be more sensitive to harvesting regimes. The effect of harvesting on such narrow nutrient cycling processes requires further investigation.
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| 7. |
- Covey, Kristofer, et al.
(författare)
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Carbon and Beyond : The Biogeochemistry of Climate in a Rapidly Changing Amazon
- 2021
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Ingår i: Frontiers in Forests and Gobal Change. - : Frontiers Media S.A.. - 2624-893X. ; 4
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Forskningsöversikt (refereegranskat)abstract
- The Amazon Basin is at the center of an intensifying discourse about deforestation, land-use, and global change. To date, climate research in the Basin has overwhelmingly focused on the cycling and storage of carbon (C) and its implications for global climate. Missing, however, is a more comprehensive consideration of other significant biophysical climate feedbacks [i.e., CH4, N2O, black carbon, biogenic volatile organic compounds (BV0Cs), aerosols, evapotranspiration, and albedo] and their dynamic responses to both localized (fire, land-use change, infrastructure development, and storms) and global (warming, drying, and some related to El Nino or to warming in the tropical Atlantic) changes. Here, we synthesize the current understanding of (1) sources and fluxes of all major forcing agents, (2) the demonstrated or expected impact of global and local changes on each agent, and (3) the nature, extent, and drivers of anthropogenic change in the Basin. We highlight the large uncertainty in flux magnitude and responses, and their corresponding direct and indirect effects on the regional and global climate system. Despite uncertainty in their responses to change, we conclude that current warming from non-CO2 agents (especially CH4 and N2O) in the Amazon Basin largely offsets- and most likely exceeds-the climate service provided by atmospheric CO2 uptake. We also find that the majority of anthropogenic impacts act to increase the radiative forcing potential of the Basin. Given the large contribution of less-recognized agents (e.g., Amazonian trees alone emit similar to 3.5% of all global CH4), a continuing focus on a single metric (i.e., C uptake and storage) is incompatible with genuine efforts to understand and manage the biogeochemistry of climate in a rapidly changing Amazon Basin.
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| 8. |
- Cusack, Daniela Francis, et al.
(författare)
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Tradeoffs and Synergies in Tropical Forest Root Traits and Dynamics for Nutrient and Water Acquisition : Field and Modeling Advances
- 2021
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Ingår i: Frontiers in Forests and Global Change. - : Frontiers Media S.A.. - 2624-893X. ; 4
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Forskningsöversikt (refereegranskat)abstract
- Vegetation processes are fundamentally limited by nutrient and water availability, the uptake of which is mediated by plant roots in terrestrial ecosystems. While tropical forests play a central role in global water, carbon, and nutrient cycling, we know very little about tradeoffs and synergies in root traits that respond to resource scarcity. Tropical trees face a unique set of resource limitations, with rock-derived nutrients and moisture seasonality governing many ecosystem functions, and nutrient versus water availability often separated spatially and temporally. Root traits that characterize biomass, depth distributions, production and phenology, morphology, physiology, chemistry, and symbiotic relationships can be predictive of plants’ capacities to access and acquire nutrients and water, with links to aboveground processes like transpiration, wood productivity, and leaf phenology. In this review, we identify an emerging trend in the literature that tropical fine root biomass and production in surface soils are greatest in infertile or sufficiently moist soils. We also identify interesting paradoxes in tropical forest root responses to changing resources that merit further exploration. For example, specific root length, which typically increases under resource scarcity to expand the volume of soil explored, instead can increase with greater base cation availability, both across natural tropical forest gradients and in fertilization experiments. Also, nutrient additions, rather than reducing mycorrhizal colonization of fine roots as might be expected, increased colonization rates under scenarios of water scarcity in some forests. Efforts to include fine root traits and functions in vegetation models have grown more sophisticated over time, yet there is a disconnect between the emphasis in models characterizing nutrient and water uptake rates and carbon costs versus the emphasis in field experiments on measuring root biomass, production, and morphology in response to changes in resource availability. Closer integration of field and modeling efforts could connect mechanistic investigation of fine-root dynamics to ecosystem-scale understanding of nutrient and water cycling, allowing us to better predict tropical forest-climate feedbacks.
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| 9. |
- Eckdahl, Johan A., et al.
(författare)
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Climate and forest properties explain wildfire impact on microbial community and nutrient mobilization in boreal soil
- 2023
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Ingår i: Frontiers in Forests and Global Change. - : Frontiers Media S.A.. - 2624-893X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The boreal landscape stores an estimated 40% of the earth's carbon (C) found in terrestrial vegetation and soils, with a large portion collected in thick organic soil layers. These ground stores are subject to substantial removals due to the centurial return of wildfire, which has strong impacts on the soil microbial community and nutrient cycling, which in turn can control ecosystem recovery patterns and process rates, such as C turnover. Currently, predictive knowledge used in assessing fire impacts is largely focused on ecosystems that experience only superficial burning and few robust observations exist regarding the effect that smoldering combustion in deeper active soil layers has on post-fire soil activity. This study provided a highly replicated and regionally extensive survey of wildfire impact on microbial community structure (using fatty acid biomarkers) and nutrient cycling (using in situ ionic resin capsules) across broad gradients of climate, forest properties and fire conditions within 50 separate burn scars and 50 additional matched unburnt boreal forest soils. The results suggest a strong metabolic shift in burnt soils due to heat impact on their structure and a decoupling from aboveground processes, releasing ecosystem N limitation and increasing mobilization of N, P, K, and S as excess in conjunction with an altered, C-starved microbial community structure and reduced root uptake due to vegetation mortality. An additional observed climatic control over burnt soil properties has implications for altered boreal forest function in future climate and fire regimes deserving of further attention.
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| 10. |
- Ekström, Magnus, 1966-, et al.
(författare)
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A Comparison of Model-Assisted Estimators, With and Without Data-Driven Transformations of Auxiliary Variables, With Application to Forest Inventory
- 2021
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Ingår i: Frontiers in Forests and Global Change. - : Frontiers Media S.A.. - 2624-893X. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Forest information is requested at many levels and for many purposes. Samplingbasednational forest inventories (NFIs) can provide reliable estimates on national andregional levels. By combining expensive field plot data with different sources of remotelysensed information, from airplanes and/or satellite platforms, the precision in estimatorsof forest variables can be improved. This paper focuses on the design-based modelassistedapproach to using NFI data together with remotely sensed data to estimateforest variables for small areas, where the variables studied are total growing stockvolume, volume of Norway spruce (Picea abies), and volume of broad-leaved trees.Remote sensing variables may be highly correlated with one another and some mayhave poor predictive ability for target forest variables, and therefore model selectionand/or coefficient shrinkage may be appropriate to improve the efficiency of modelassistedestimators of forest variables. For this purpose, one can use modern shrinkageestimators based on lasso, ridge, and elastic net regression methods. In a simulationstudy using real NFI data, Sentinel 2 remote-sensing data, and a national airborne laserscanning (ALS) campaign, we show that shrinkage estimators offer advantages overthe (weighted) ordinary least-squares (OLS) estimator in a model-assisted setting. Forexample, for a sample size n of about 900 and with 72 auxiliary variables, the RMSE wasup to 41% larger when based on OLS. We propose a data-driven method for findingsuitable transformations of auxiliary variables, and show that it can improve estimatorsof forest variables. For example, when estimating volume of Norway spruce, using asmaller expert selection of auxiliary variables, transformations reduced the RMSE byup to 10%. The overall best results in terms of RMSE were obtained using shrinkageestimators and a larger set of 72 auxiliary variables. However, for this larger set ofvariables, the use of transformations yielded at most small improvements of RMSE,and at worst large increases of RMSE, except in combination with ridge and elasticnet regression.
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