| 1. |
- Bradshaw, Richard H. W., et al.
(författare)
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Long-term succession in a Danish temperate deciduous forest
- 2005
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Ingår i: Ecography. - : John Wiley & Sons. - 0906-7590 .- 1600-0587. ; 28:2, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- Forest successional trajectories covering the last 2000 yr from a mixed deciduous forest in Denmark show a gradual shift in dominance from Tilia cordata to Fagus sylvatica and a recent increase in total forest basal area since direct management ceased in 1948. The successions are reconstructed by combining a fifty-year record of direct tree observations with local pollen diagrams from Draved Forest, Denmark. Five of the seven successions record a heathland phase of Viking Age dating from 830 AD. The anthropogenic influence is considerable throughout the period of study even though Draved contains some of the most pristine forest stands in Denmark. Anthropogenic influence including felling masks the underlying natural dynamics, with the least disturbed sites showing the smallest compositional change. Some effects of former management, such as loss of Tilia cordata dominance, are irreversible. Artificial disturbance, particularly drainage, has accelerated and amplified the shift towards Fagus dominance that would have occurred on a smaller scale and at a slower rate in the absence of human intervention. Copyright © Ecography 2005.
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| 2. |
- Didion, M., et al.
(författare)
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Ungulate herbivory modifies the effects of climate change on mountain forests
- 2011
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Ingår i: Climatic Change. - : Springer. - 0165-0009 .- 1573-1480. ; 109:3-4, s. 647-669
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Tidskriftsartikel (refereegranskat)abstract
- Recent temperature observations suggest a general warming trend that may be causing the range of tree species to shift to higher latitudes and altitudes. Since biotic interactions such as herbivory can change tree species composition, it is important to understand their contribution to vegetation changes triggered by climate change. To investigate the response of forests to climate change and herbivory by wild ungulates, we used the forest gap model ForClim v2. 9. 6 and simulated forest development in three climatically different valleys in the Swiss Alps. We used altitudinal transects on contrasting slopes covering a wide range of forest types from the cold (upper) to the dry (lower) treeline. This allowed us to investigate (1) altitudinal range shifts in response to climate change, (2) the consequences for tree species composition, and (3) the combined effect of climate change and ungulate herbivory. We found that ungulate herbivory changed species composition and that both basal area and stem numbers decreased with increasing herbivory intensity. Tree species responded differently to the change in climate, and their ranges did not change concurrently, thus causing a succession to new stand types. While climate change partially compensated for the reductions in basal area caused by ungulate herbivory, the combined effect of these two agents on the mix of the dominant species and forest type was non-compensatory, as browsing selectively excluded species from establishing or reaching dominance and altered competition patterns, particularly for light. We conclude that there is an urgent need for adaptive forest management strategies that address the joint effects of climate change and ungulate herbivory.
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| 3. |
- Gimmi, Urs, et al.
(författare)
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Quantifying disturbance effects on vegetation carbon pools in mountain forests based on historical data
- 2009
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Ingår i: Regional Environmental Change. - : Springer Science and Business Media LLC. - 1436-3798 .- 1436-378X. ; 9:2, s. 121-130
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Tidskriftsartikel (refereegranskat)abstract
- Although the terrestrial carbon budget is of key importance for atmospheric CO(2) concentrations, little is known on the effects of management and natural disturbances on historical carbon stocks at the regional scale. We reconstruct the dynamics of vegetation carbon stocks and flows in forests across the past 100 years for a valley in the eastern Swiss Prealps using quantitative and qualitative information from forest management plans. The excellent quality of the historical information makes it possible to link dynamics in growing stocks with high-resolution time series for natural and anthropogenic disturbances. The results of the historical reconstruction are compared with modelled potential natural vegetation. Forest carbon stock at the beginning of the twentieth century was substantially reduced compared to natural conditions as a result of large scale clearcutting lasting until the late nineteenth century. Recovery of the forests from this unsustainable exploitation and systematic forest management were the main drivers of a strong carbon accumulation during almost the entire twentieth century. In the 1990s two major storm events and subsequent bark beetle infestations significantly reduced stocks back to the levels of the mid-twentieth century. The future potential for further carbon accumulation was found to be strongly limited, as the potential for further forest expansion in this valley is low and forest properties seem to approach equilibrium with the natural disturbance regime. We conclude that consistent long-term observations of carbon stocks and their changes provide rich information on the historical range of variability of forest ecosystems. Such historical information improves our ability to assess future changes in carbon stocks. Further, the information is vital for better parameterization and initialization of dynamic regional scale vegetation models and it provides important background for appropriate management decisions.
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| 4. |
- Gimmi, Urs, et al.
(författare)
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Soil carbon pools in Swiss forests show legacy effects from historic forest litter raking
- 2013
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Ingår i: Landscape Ecology. - 3311 GZ DORDRECHT, NETHERLANDS : Springer. - 0921-2973 .- 1572-9761. ; 28:5, s. 835-846
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Tidskriftsartikel (refereegranskat)abstract
- Globally, forest soils contain twice as much carbon as forest vegetation. Consequently, natural and anthropogenic disturbances affecting carbon accumulation in forest soils can alter regional to global carbon balance. In this study, we evaluate the effects of historic litter raking on soil carbon stocks, a former forest use which used to be widespread throughout Europe for centuries. We estimate, for Switzerland, the carbon sink potential in current forest soils due to recovery from past litter raking ('legacy effect'). The year 1650 was chosen as starting year for litter raking, with three different end years (1875/1925/1960) implemented for this forest use in the biogeochemical model LPJ-GUESS. The model was run for different agricultural and climatic zones separately. Number of cattle, grain production and the area of wet meadow have an impact on the specific demand for forest litter. The demand was consequently calculated based on historical statistical data on these factors. The results show soil carbon pools to be reduced by an average of 17 % after 310 years of litter raking and legacy effects were still visible 130 years after abandonment of this forest use (2 % average reduction). We estimate the remaining carbon sink potential in Swiss forest due to legacy effects from past litter raking to amount to 158,000 tC. Integrating historical data into biogeochemical models provides insight into the relevance of past land-use practices. Our study underlines the importance of considering potentially long-lasting effects of such land use practices for carbon accounting.
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| 5. |
- Göttel, Holger, et al.
(författare)
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Influence of changed vegetations fields on regional climate simulations in the Barents Sea Region
- 2008
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Ingår i: Climatic Change. - : Springer. - 0165-0009 .- 1573-1480. ; 87:1-2, s. 35-50
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Tidskriftsartikel (refereegranskat)abstract
- In the context of the EU-Project BALANCE (http://balance-eu.info) the regional climate model REMO was used for extensive calculations of the Barents Sea climate to investigate the vulnerability of this region to climate change. The regional climate model REMO simulated the climate change of the Barents Sea Region between 1961 and 2100 (Control and Climate Change run, CCC-Run). REMO on similar to 50 km horizontal resolution was driven by the transient ECHAM4/OPYC3 IPCC SRES B2 scenario. The output of the CCC-Run was applied to drive the dynamic vegetation model LPJ-GUESS. The results of the vegetation model were used to repeat the CCC-Run with dynamic vegetation fields. The feedback effect of the modified vegetation on the climate change signal is investigated and discussed with focus on precipitation, temperature and snow cover. The effect of the offline coupled vegetation feedback run is much lower than the greenhouse gas effect.
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| 6. |
- Heiri, C., et al.
(författare)
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Forty years of natural dynamics in Swiss beech forests : Structure, composition, and the influence of former management
- 2009
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Ingår i: Ecological Applications. - : John Wiley & Sons. - 1051-0761 .- 1939-5582. ; 19:7, s. 1920-1934
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Tidskriftsartikel (refereegranskat)abstract
- We investigated forest development after the cessation of management based on inventory data from six beech forest reserves in Switzerland covering nearly 40 years, using observed changes to assess the textbook understanding of natural beech forest dynamics. Specifically, we evaluated the importance of light as a driver of tree species composition, and we aimed to disentangle the role of site characteristics and past management regimes for shaping today’s forest properties. Forest dynamics in the reserves showed a clear trend toward a broadening of the diameter distribution, an increase in basal area and standing dead wood, an increase in beech dominance, and a reduction of tree species diversity over time, conforming to expectations. However, the expected development of specific structural features, such as significant amounts of large living trees and snags or a small-scale mosaic of various developmental phases, appears to take longer than the time elapsed since the cessation of management. The observed loss in species richness can be attributed to decreasing light availability, as almost all species that disappeared were shade intolerant. Additionally, the shade-intolerant tree species had a characteristic bell-shaped diameter distribution in all reserves, indicating a lack of recruits, whereas shade-tolerant species had an irregular to monotonically decreasing diameter distribution, demonstrating sustained regeneration. Along the environmental gradient covered by the six reserves, abiotic factors are sufficient to explain tree species distribution, with management history not contributing additional information. This suggests that at larger scales, tree species composition is determined by abiotic factors, but historical management strategies were obviously adapted well to the species’ autecological requirements. Analyses such as ours provide the foundation for refining forest management systems as well as for developing effective and target-oriented conservation strategies. © 2009 by the Ecological Society of America beech forests;.
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| 7. |
- Heiri, Caroline, et al.
(författare)
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Successional pathways in Swiss mountain forest reserves
- 2012
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Ingår i: European Journal of Forest Research. - : Springer. - 1612-4669 .- 1612-4677. ; 131:2, s. 503-518
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge on the natural dynamics of Norway spruce-European silver fir forests is scarce, but is of high importance for the sustainable management of these ecosystems. Using a unique data set from five forest reserves in the Swiss Alps that covers up to 35 years, we elucidated communalities and differences in stand structure and species composition across the reserves and over time and investigated the role of site conditions versus intrinsic forest dynamics. For the early and late successional phases, we found a clear relationship between stand structure (diameter distributions) and species composition. Two pathways of early succession were evident as a function of the disturbance regime. Thus, the spatial extent of disturbances in spruce-fir forests strongly determines the pathway in early succession. Contrary to earlier descriptions of clearly distinguishable optima phases, our data did not reveal a relationship between stand structure and species composition for the early, mid-, and late optimum phases. Although the reserves investigated here are characterized by highly different climatic and soil conditions, their temporal development was found to fit well into a single successional scheme, suggesting that in spruce-fir mountain forests, the life-history strategies of the tree species may have a stronger influence on successional trajectories than site conditions per se.
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| 8. |
- Leuzinger, Sebastian, et al.
(författare)
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A sink-limited growth model improves biomass estimation along boreal and alpine tree lines
- 2013
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Ingår i: Global Ecology and Biogeography. - HOBOKEN 07030-5774, NJ USA : John Wiley & Sons. - 1466-822X .- 1466-8238. ; 22:8, s. 924-932
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Tidskriftsartikel (refereegranskat)abstract
- Aim Despite increasing evidence for plant growth often being limited by sink (meristem) activity rather than source (photosynthesis) activity, all currently available dynamic global vegetation models (DGVMs) simulate plant growth via source-limited processes. For a given climatic region, this may lead to an overestimation of carbon stock per unit surface area, particularly if a model fails to correctly predict forest cover. Our aim is to improve the Lund-Potsdam-Jena (LPJ) DGVM by replacing the source-limited (SoL) tree growth algorithm by a sink-limited (SiL) one. Location Our analysis focuses on the cold tree line at high latitudes and altitudes. We study two altitudinal transects in the Swiss Alps and the northern tree line. Methods We limit annual net primary productivity of the LPJ DGVM by an algorithm based on the annual sum of growing degree-days (GDD), assuming that maximum plant growth is reached asymptotically with increasing GDD. Results Comparing simulation results with observational data, we show that the locations of both the northern and the alpine tree line are estimated more accurately when using a SiL algorithm than when using the commonly employed SoL algorithm. Also, simulated carbon stocks decrease in a more realistic manner towards the tree line when the SiL algorithm is used. This has far-reaching implications for estimating and projecting present and future carbon stocks in temperature-limited ecosystems. Main conclusions In the range of 60-80 degrees N over Europe and Asia, carbon stored in vegetation is estimated to be c. 50% higher in the LPJ standard version (LPJ-SoL) compared with LPJ-SiL, resulting in a global difference in estimated biomass of 25 Pg (c. 5% of the global terrestrial standing biomass). Similarly, the simulated elevation of the upper tree line in the European Alps differs by c. 400 m between the two model versions, thus implying an additional overestimation of carbon stored in mountain forests around the world.
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| 9. |
- Leuzinger, Sebastian, et al.
(författare)
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Poor methodology for predicting large-scale tree die-off
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:38
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Manusch, Corina, et al.
(författare)
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Sensitivity of simulated productivity to soil characteristics and plant water uptake along drought gradients in the Swiss Alps
- 2014
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Ingår i: Ecological Modelling. - : Elsevier. - 0304-3800 .- 1872-7026. ; 282, s. 25-34
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Tidskriftsartikel (refereegranskat)abstract
- Future climate scenarios indicate a change in precipitation patterns, i.e. in frequency and intensity, and thus a change of water availability for plants. The consequences for ecosystems can be evaluated using dynamic vegetation models (DVMs), but the description of soil properties and assumptions about root distribution and functionality are rather simplistic in many DVMs. We use the LPJ-GUESS model to evaluate (i) the usage of high-quality data sources for describing soil properties and (ii) the assumptions regarding roots. Specifically, we compare simulated carbon uptake when applying the frequently used FAO global soil map vs. soil measurements from 98 sites in the driest regions of Switzerland. The multilayer soil data were used either as observed (non-aggregated) or aggregated into two layers. At sites with low water holding capacities (whc < 100 mm) and a low precipitation sum that does not compensate for small whc, the FAO data led to a higher annual net primary productivity (ANPP) than when using observed soil data. In contrast under wetter conditions, the description of soil data did not make much difference. A comparison of different rooting strategies revealed a higher importance of vertical root distribution per soil layer than variable rooting depths due to the overriding effect of the hydrological assumptions in the model. We conclude that it is pivotal to use high-quality soil data and possibly to refine the hydrological assumptions in DVMs when attempting to study drought impacts on ecosystems. (C) 2014 Elsevier B.V. All rights reserved.
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| 11. |
- Manusch, Corina, et al.
(författare)
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The impact of climate change and its uncertainty on carbon storage in Switzerland
- 2014
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Ingår i: Regional Environmental Change. - : Springer. - 1436-3798 .- 1436-378X. ; 14:4, s. 1437-1450
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Tidskriftsartikel (refereegranskat)abstract
- Projected future climate change will alter carbon storage in forests, which is of pivotal importance for the national carbon balance of most countries. Yet, national-scale assessments are largely lacking. We evaluated climate impacts on vegetation and soil carbon storage for Swiss forests using a dynamic vegetation model. We considered three novel climate scenarios, each featuring a quantification of the inherent uncertainty of the underlying climate models. We evaluated which regions of Switzerland would benefit or lose in terms of carbon storage under different climates, and which abiotic factors determine these patterns. The simulation results showed that the prospective carbon storage ability of forests depends on the current climate, the severity of the change, and the time required for new species to establish. Regions already prone to drought and heat waves under current climate will likely experience a decrease in carbon stocks under prospective 'extreme' climate change, while carbon storage in forests close to the upper treeline will increase markedly. Interestingly, when climate change is severe, species shifts can result in increases in carbon stocks, but when there is only slight climate change, climate conditions may reduce growth of extant species while not allowing for species shifts, thus leading to decreases in carbon stocks.
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| 12. |
- Manusch, Corina, et al.
(författare)
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Tree mortality in dynamic vegetation models - A key feature for accurately simulating forest properties
- 2012
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Ingår i: Ecological Modelling. - 1000 AE AMSTERDAM, NETHERLANDS : Elsevier. - 0304-3800 .- 1872-7026. ; 243, s. 101-111
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic vegetation models are important tools in ecological research, but not all processes of vegetation dynamics are captured adequately. Tree mortality is often modeled as a function of growth efficiency and maximum age. However, empirical studies have shown for different species that slow-growing trees may become older than fast-growing trees, implying a correlation of mortality with growth rate and size rather than age. We used the ecosystem model LPJ-GUESS to compare the standard age-dependent mortality with two size-dependent mortality approaches. We found that all mortality approaches, when calibrated, yield a realistic pattern of growing stock and Plant Functional Type (PFT) distribution at five study sites in Switzerland. However, only the size-dependent approaches match a third pattern, i.e. the observed negative relationship between growth rate and longevity. As a consequence, trees are simulated to get older at higher than at lower altitudes/latitudes. In contrast, maximum tree ages do not change along these climatic gradients when the standard age-dependent mortality is used. As tree age and size determine forest structure, our more realistic mortality assumptions improved forest biomass estimation, but indicate a potential decline of carbon storage under climate change. We conclude that tree mortality should be modeled as a function of size rather than age. (C) 2012 Elsevier B.V. All rights reserved.
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| 13. |
- Matthes, Heidrun, et al.
(författare)
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Sensitivity of high-resolution Arctic regional climate model projections to different implementations of land surface processes
- 2012
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Ingår i: Climatic Change. - : Springer Science and Business Media LLC. - 0165-0009 .- 1573-1480. ; 111:2, s. 197-214
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the effects of vegetation cover and soil parameters on the climate change projections of a regional climate model over the Arctic domain. Different setups of the land surface model of the regional climate model HIRHAM were realized to analyze differences in the atmospheric circulation caused by (1) the incorporation of freezing/thawing of soil moisture, (2) the consideration of top organic soil horizons typical for the Arctic and (3) a vegetation shift due to a changing climate. The largest direct thermal effect in 2 m air temperature was found for the vegetation shift, which ranged between −1.5 K and 3 K. The inclusion of a freeze/thaw scheme for soil moisture shows equally large sensitivities in spring over cool areas with high soil moisture content. Although the sensitivity signal in 2 m air temperature for the experiments differs in amplitude, all experiments show changes in mean sea level pressure (mslp) and geopotential height (z) throughout the troposphere of similar magnitude (mslp: −2 hPa to 1.5 hPa, z: −15 gpm to 5 gpm). This points to the importance of dynamical feedbacks within the atmosphere-land system. Land and soil processes have a distinct remote influence on large scale atmospheric circulation patterns in addition to their direct, regional effects. The assessment of induced uncertainties due to the changed implementations of land surface processes discussed in this study demonstrates the need to take all those processes for future Arctic climate projections into account, and demonstrates a clear need to include similar implementations in regional and global climate models.
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| 14. |
- Pappas, Christoforos, et al.
(författare)
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Sensitivity analysis of a process-based ecosystem model : Pinpointing parameterization and structural issues
- 2013
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union. - 2169-8953 .- 2169-8961. ; 118:2, s. 505-528
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic vegetation models have been widely used for analyzing ecosystem dynamics and their interactions with climate. Their performance has been tested extensively against observations and by model intercomparison studies. In the present analysis, Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS), a state-of-the-art ecosystem model, was evaluated by performing a global sensitivity analysis. The study aims at examining potential model limitations, particularly with regard to long-term applications. A detailed sensitivity analysis based on variance decomposition is presented to investigate structural model assumptions and to highlight processes and parameters that cause the highest variability in the output. First- and total-order sensitivity indices were calculated for selected parameters using Sobol's methodology. In order to elucidate the role of climate on model sensitivity, different climate forcings were used based on observations from Switzerland. The results clearly indicate a very high sensitivity of LPJ-GUESS to photosynthetic parameters. Intrinsic quantum efficiency alone is able to explain about 60% of the variability in vegetation carbon fluxes and pools for a wide range of climate forcings. Processes related to light harvesting were also found to be important together with parameters affecting forest structure (growth, establishment, and mortality). The model shows minor sensitivity to hydrological and soil texture parameters, questioning its skills in representing spatial vegetation heterogeneity at regional or watershed scales. In the light of these results, we discuss the deficiencies of LPJ-GUESS and possibly that of other, structurally similar, dynamic vegetation models and we highlight potential directions for further model improvements.
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| 15. |
- Portner, H., et al.
(författare)
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Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes
- 2010
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Ingår i: Biogeosciences. - : Nicolaus Copernicus University Press. - 1726-4170 .- 1726-4189. ; 7:11, s. 3669-3684
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Tidskriftsartikel (refereegranskat)abstract
- Models of carbon cycling in terrestrial ecosystems contain formulations for the dependence of respiration on temperature, but the sensitivity of predicted carbon pools and fluxes to these formulations and their parameterization is not well understood. Thus, we performed an uncertainty analysis of soil organic matter decomposition with respect to its temperature dependency using the ecosystem model LPJ-GUESS. We used five temperature response functions (Exponential, Arrhenius, Lloyd-Taylor, Gaussian, Van’t Hoff). We determined the parameter confidence ranges of the formulations by nonlinear regression analysis based on eight experimental datasets from Northern Hemisphere ecosystems. We sampled over the confidence ranges of the parameters and ran simulations for each pair of temperature response function and calibration site. We analyzed both the long-term and the short-term heterotrophic soil carbon dynamics over a virtual elevation gradient in southern Switzerland. The temperature relationship of Lloyd-Taylor fitted the overall data set best as the other functions either resulted in poor fits (Exponential, Arrhenius) or were not applicable for all datasets (Gaussian, Van’t Hoff). There were two main sources of uncertainty for model simulations: (1) the lack of confidence in the parameter estimates of the temperature response, which increased with increasing temperature, and (2) the size of the simulated soil carbon pools, which increased with elevation, as slower turn-over times lead to higher carbon stocks and higher associated uncertainties. Our results therefore indicate that such projections are more uncertain for higher elevations and hence also higher latitudes, which are of key importance for the global terrestrial carbon budget.
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| 16. |
- Reyer, Christopher P. O., et al.
(författare)
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A plant's perspective of extremes : terrestrial plant responses to changing climatic variability
- 2013
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Ingår i: Global Change Biology. - HOBOKEN 07030-5774, NJ USA : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 19:1, s. 75-89
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Forskningsöversikt (refereegranskat)abstract
- We review observational, experimental, and model results on how plants respond to extreme climatic conditions induced by changing climatic variability. Distinguishing between impacts of changing mean climatic conditions and changing climatic variability on terrestrial ecosystems is generally underrated in current studies. The goals of our review are thus (1) to identify plant processes that are vulnerable to changes in the variability of climatic variables rather than to changes in their mean, and (2) to depict/evaluate available study designs to quantify responses of plants to changing climatic variability. We find that phenology is largely affected by changing mean climate but also that impacts of climatic variability are much less studied, although potentially damaging. We note that plant water relations seem to be very vulnerable to extremes driven by changes in temperature and precipitation and that heatwaves and flooding have stronger impacts on physiological processes than changing mean climate. Moreover, interacting phenological and physiological processes are likely to further complicate plant responses to changing climatic variability. Phenological and physiological processes and their interactions culminate in even more sophisticated responses to changing mean climate and climatic variability at the species and community level. Generally, observational studies are well suited to study plant responses to changing mean climate, but less suitable to gain a mechanistic understanding of plant responses to climatic variability. Experiments seem best suited to simulate extreme events. In models, temporal resolution and model structure are crucial to capture plant responses to changing climatic variability. We highlight that a combination of experimental, observational, and/or modeling studies have the potential to overcome important caveats of the respective individual approaches.
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| 17. |
- Rice, Stephen, et al.
(författare)
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Disturbance regimes at the interface of geomorphology and ecology
- 2012
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Ingår i: Earth Surface Processes and Landforms. - : John Wiley & Sons. - 0197-9337 .- 1096-9837. ; 37:15, s. 1678-1682
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Tidskriftsartikel (refereegranskat)abstract
- Geomorphological processes are an integral part of ecosystem functioning and ecosystem functioning affects geomorphological processes. Increasingly widespread acknowledgement of this simple idea is manifest in a vigorous research community engaged with questions that address the two-way interaction between biota and geomorphology, at a range of scales and in a variety of terrestrial and aquatic environments. Geomorphological disturbances are a core element of biogeomorphological interest, and although the disciplines of geomorphology and ecology have each developed languages and theories that help to explore, model and understand disturbance events, little attempt has been made to draw together these approaches. Following a brief review of these issues, we introduce thirteen papers that investigate the interactions and feedbacks between geomorphological disturbance regimes and ecosystem functions. These papers reveal the singularity of wildfire impacts, the importance of landsliding for carbon budgeting and of vegetation accumulation for landsliding, the zoogeomorphic role of iconic and Cinderella animals in fluvial geomorphology, biophysical interactions in aeolian, fluvial and torrential environments and the utility of living ecosystems as archives of geomorphic events. Most of these papers were first presented in a conference session at the European Geoscience Union General Assembly in 2010 and several others are from recent volumes of Earth Surface Processes and Landforms.
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| 18. |
- Roderfeld, Hedwig, et al.
(författare)
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Potential impact of climate change on ecosystems of the Barents Sea Region
- 2008
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Ingår i: Climatic Change. - : Springer. - 0165-0009 .- 1573-1480. ; 87:1-2, s. 283-303
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Tidskriftsartikel (refereegranskat)abstract
- The EU project BALANCE (Global Change Vulnerabilities in the Barents region: Linking Arctic Natural Resources, Climate Change and Economies) aims to assess vulnerability to climate change in the Barents Sea Region. As a prerequisite the potential impact of climate change on selected ecosystems of the study area has to be quantified, which is the subject of the present paper. A set of ecosystem models was run to generate baseline and future scenarios for 1990, 2020, 2050 and 2080. The models are based on data from the Regional Climate Model (REMO), driven by a GCM which in turn is forced by the IPCC-B2 scenario. The climate change is documented by means of the Koppen climate classification. Since the multitude of models requires the effect of climate change on individual terrestrial and marine systems to be integrated, the paper concentrates on a standardised visualisation of potential impacts by use of a Geographical Information System for the timeslices 2050 and 2080. The resulting maps show that both terrestrial and marine ecosystems of the Barents region will undergo significant changes until both 2050 and 2080.
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| 19. |
- Sitch, Stephen, et al.
(författare)
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Assessing the carbon balance of circumpolar Arctic tundra using remote sensing and process modeling
- 2007
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Ingår i: Ecological Applications. - : John Wiley & Sons. - 1051-0761 .- 1939-5582. ; 17:1, s. 213-234
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the current status of using remote sensing and process-based modeling approaches to assess the contemporary and future circumpolar carbon balance of Arctic tundra, including the exchange of both carbon dioxide and methane with the atmosphere. Analyses based on remote sensing approaches that use a 20-year data record of satellite data indicate that tundra is greening in the Arctic, suggesting an increase in photosynthetic activity and net primary production. Modeling studies generally simulate a small net carbon sink for the distribution of Arctic tundra, a result that is within the uncertainty range of field-based estimates of net carbon exchange. Applications of processbased approaches for scenarios of future climate change generally indicate net carbon sequestration in Arctic tundra as enhanced vegetation production exceeds simulated increases in decomposition. However, methane emissions are likely to increase dramatically, in response to rising soil temperatures, over the next century. Key uncertainties in the response of Arctic ecosystems to climate change include uncertainties in future fire regimes and uncertainties relating to changes in the soil environment. These include the response of soil decomposition and respiration to warming and deepening of the soil active layer, uncertainties in precipitation and potential soil drying, and distribution of wetlands. While there are numerous uncertainties in the projections of process-based models, they generally indicate that Arctic tundra will be a small sink for carbon over the next century and that methane emissions will increase considerably, which implies that exchange of greenhouse gases between the atmosphere and Arctic tundra ecosystems is likely to contribute to climate warming.
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| 20. |
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| 21. |
- Turesson, Håkan, et al.
(författare)
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Satiation effects in piscivore prey size selection
- 2006
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Ingår i: Ecology of Freshwater Fish. - : John Wiley & Sons. - 0906-6691 .- 1600-0633. ; 15:1, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- We present a functional response model that primarily evaluates effects of satiation in piscivore prey-size selection. The model also includes other passive processes, such as prey-size-dependent encounter rate and prey-size-dependent capture success, where capture success decreases and encounter rate increases with prey size. The model generates a wide variety of outcomes, where small, intermediate or large prey is positively selected for. These very different selectivity patterns are generated without any active prey choice included in the model. The results stress the importance of controlling for satiation and other passive processes in empirical studies on prey-size selection, especially if the aim is to test active prey choice in piscivores. © 2005 The Authors Journal compilation 2005 Blackwell Munksgaard.
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| 22. |
- Wolf, Annett
(författare)
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Determining the rate of change in a mixed deciduous forest monitored for 50 years
- 2011
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Ingår i: Annals of Forest Science. - PARIS, 75002, FRANCE : Springer. - 1286-4560 .- 1297-966X. ; 68:3, s. 485-495
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Tidskriftsartikel (refereegranskat)abstract
- Trees in two compartments of the mixed deciduous forest Draved Forest have been monitored regularly for 50 years. This data set was used to study the rate of change in forest structure and composition applying the Kolmogorov-Smirnov statistics, chi-square test for the goodness of fit, and principal component analysis. We also correlated the specific test statistics with other forest properties to elucidate the importance of various factors for the observed changes in forest structure. After 50 years, the still significant changes in the forest structure and species composition indicate that the compartments have not reached the state of an old growth forest. Although some measures indicated that the compartments were approaching this stage, other showed the opposite response and even an increasing rate of change. As the three statistical methods contributed in different ways, we recommend the combination of several statistical methods to assess changes in the forest structure.
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| 23. |
- Wolf, Annett
(författare)
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Determining the rate of change in a mixed deciduous forest monitored for 50 years
- 2011
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Ingår i: Annals of Forest Science. - : BioMed Central (BMC). - 1286-4560 .- 1297-966X. ; 68:3, s. 485-495
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Trees in two compartments of the mixed deciduous forest Draved Forest have been monitored regularly for 50 years.Materials and methods: This data set was used to study the rate of change in forest structure and composition applying the Kolmogorov–Smirnov statistics, chi-square test for the goodness of fit, and principal component analysis. We also correlated the specific test statistics with other forest properties to elucidate the importance of various factors for the observed changes in forest structure.Results: After 50 years, the still significant changes in the forest structure and species composition indicate that the compartments have not reached the state of an old growth forest. Although some measures indicated that the compartments were approaching this stage, other showed the opposite response and even an increasing rate of change.Conclusion: As the three statistical methods contributed in different ways, we recommend the combination of several statistical methods to assess changes in the forest structure.
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| 24. |
- Wolf, Annett
(författare)
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Estimating the potential impact of vegetation on the water cycle requires accurate soil water parameter estimation
- 2011
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Ingår i: Ecological Modelling. - : Elsevier. - 0304-3800 .- 1872-7026. ; 222:15, s. 2595-2605
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that vegetation dynamics at the catchment scale depends on the prevailing weather and soil moisture conditions. Soil moisture, however, is not equally distributed in space due to differences in topography, weather patterns, soil properties and the type and amount of vegetation cover. To elucidate the complex interaction between vegetation and soil moisture, the dynamic vegetation model LPJ-GUESS (Smith et al., 2001), which provides estimations of vegetation dynamics, but does not consider lateral water fluxes was coupled with the hydrological TOPMODEL (cf. Beven, 2001) in order to be able to evaluate the importance of these lateral fluxes. The new model LG-TM was calibrated and validated in two climatically different mountain catchments. The estimations of runoff were good, when monthly and weekly time scales were considered, although the low flow periods at winter time were somewhat underestimated. The uncertainty in the climate induced change vegetation carbon storage caused by the uncertainty in soil parameters was up to 3–5 kg C m−2 (depending on elevation and catchment), compared to the total change in vegetation carbon storage of 5–9 kg C m−2. Therefore accurate estimates of the parameters influencing the water holding capacity of the soil, for example depth and porosity, are necessary when estimating future changes in vegetation carbon storage. Similarly, changes in plant transpiration due to climatic changes could be almost double as high (88 mm m−2) in the not calibrated model compared to the new model version (ca 50 mm m−2 transpiration change). The uncertainties in these soil properties were found to be more important than the lateral water exchange between grid cells, even in steep topography at least for the temporal and spatial resolution used here.
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| 25. |
- Wolf, Annett
(författare)
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Fifty year record of change in tree spatial patterns within a mixed deciduous forest
- 2005
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Ingår i: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 215:1-3, s. 212-223
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Tidskriftsartikel (refereegranskat)abstract
- Ripley's K-function was used to investigate the changes in spatial pattern among trees in a semi-natural mixed deciduous forest in Denmark over 50 years, from 1948 to 2001. Trees larger than 10 cm diameter in breast height (dbh) were mapped at 10-year intervals in 16 blocks within two former compartments. At the start of the observation, trees were found to be regularly distributed at distances less than 10 m. This pattern changed with time in different ways, depending on tree density at the beginning of the recording. Tree density has a greater influence on the number of recruits than on the number of dead trees. New recruits were significantly aggregated and positively correlated with dead trees, which suggests that regeneration occurred in canopy gaps. Compartments with many new recruits therefore showed a change in pattern towards more random distribution or even towards aggregation. In blocks with high basal area and few recruits, the pattern changed only slightly. Past management was found to be important in generating the patterns of tree distribution.
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| 26. |
- Wolf, Annett, et al.
(författare)
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Future changes in vegetation and ecosystem function of the Barents Region
- 2008
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Ingår i: Climatic Change. - : Springer. - 0165-0009 .- 1573-1480. ; 87:1-2, s. 51-73
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic vegetation model (LPJ-GUESS) is used to project transient impacts of changes in climate on vegetation of the Barents Region. We incorporate additional plant functional types, i.e. shrubs and defined different types of open ground vegetation, to improve the representation of arctic vegetation in the global model. We use future climate projections as well as control climate data for 1981-2000 from a regional climate model (REMO) that assumes a development of atmospheric CO(2)-concentration according to the B2-SRES scenario [IPCC, Climate Change 2001: The scientific basis. Contribution working group I to the Third assessment report of the IPCC. Cambridge University Press, Cambridge (2001)]. The model showed a generally good fit with observed data, both qualitatively when model outputs were compared to vegetation maps and quantitatively when compared with observations of biomass, NPP and LAI. The main discrepancy between the model output and observed vegetation is the overestimation of forest abundance for the northern parts of the Kola Peninsula that cannot be explained by climatic factors alone. Over the next hundred years, the model predicted an increase in boreal needle leaved evergreen forest, as extensions northwards and upwards in mountain areas, and as an increase in biomass, NPP and LAI. The model also projected that shade-intolerant broadleaved summergreen trees will be found further north and higher up in the mountain areas. Surprisingly, shrublands will decrease in extent as they are replaced by forest at their southern margins and restricted to areas high up in the mountains and to areas in northern Russia. Open ground vegetation will largely disappear in the Scandinavian mountains. Also counter-intuitively, tundra will increase in abundance due to the occupation of previously unvegetated areas in the northern part of the Barents Region. Spring greening will occur earlier and LAI will increase. Consequently, albedo will decrease both in summer and winter time, particularly in the Scandinavian mountains (by up to 18%). Although this positive feedback to climate could be offset to some extent by increased CO(2) drawdown from vegetation, increasing soil respiration results in NEE close to zero, so we cannot conclude to what extent or whether the Barents Region will become a source or a sink of CO(2).
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| 27. |
- Wolf, Annett, et al.
(författare)
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Impact of non-outbreak insect damage on vegetation in northern Europe will be greater than expected during a changing climate
- 2008
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Ingår i: Climatic Change. - : Springer. - 0165-0009 .- 1573-1480. ; 87:1-2, s. 91-106
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Tidskriftsartikel (refereegranskat)abstract
- Background insect herbivory, in addition to insect outbreaks, can have an important long term influence on the performance of tree species. Since a projected warmer climate may favour insect herbivores, we use a dynamic ecosystem model to investigate the impacts of background herbivory on vegetation growth and productivity, as well as distribution and associated changes in terrestrial ecosystems of northern Europe. We used the GUESS ecosystem modelling framework and a simple linear model for including the leaf area loss of Betula pubescens in relation to mean July temperature. We tested the sensitivity of the responses of the simulated ecosystems to different, but realistic, degrees of insect damage. Predicted temperature increases are likely to enhance the potential insect impacts on vegetation. The impacts are strongest in the eastern areas, where potential insect damage to B. pubescens can increase by 4-5%. The increase in insect damage to B. pubescens results in a reduction of total birch leaf area (LAI), total birch biomass and birch productivity (Net Primary Production). This effect is stronger than the insect damage to leaf area alone would suggest, due to its second order effect on the competition between tree species. The model’s demonstration that background herbivory may cause changes in vegetation structure suggests that insect damage, generally neglected by vegetation models, can change predictions of future forest composition. Carbon fluxes and albedo are only slightly influenced by background insect herbivory, indicating that background insect damage is of minor importance for estimating the feedback of terrestrial ecosystems to climate change.
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| 28. |
- Wolf, Annett, et al.
(författare)
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Process-based estimates of terrestrial ecosystem isoprene emissions : incorporating the effects of a direct CO2-isoprene interaction
- 2007
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 7:1, s. 31-53
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Tidskriftsartikel (refereegranskat)abstract
- In recent years evidence has emerged that the amount of isoprene emitted from a leaf is affected by the CO2 growth environment. Many - though not all - laboratory experiments indicate that emissions increase significantly at below-ambient CO2 concentrations and decrease when concentrations are raised to above-ambient. A small number of process-based leaf isoprene emission models can reproduce this CO2 stimulation and inhibition. These models are briefly reviewed, and their performance in standard conditions compared with each other and to an empirical algorithm. One of the models was judged particularly useful for incorporation into a dynamic vegetation model framework, LPJ-GUESS, yielding a tool that allows the interactive effects of climate and increasing CO2 concentration on vegetation distribution, productivity, and leaf and ecosystem isoprene emissions to be explored. The coupled vegetation dynamics-isoprene model is described and used here in a mode particularly suited for the ecosystem scale, but it can be employed at the global level as well. Annual and/or daily isoprene emissions simulated by the model were evaluated against flux measurements ( or model estimates that had previously been evaluated with flux data) from a wide range of environments, and agreement between modelled and simulated values was generally good. By using a dynamic vegetation model, effects of canopy composition, disturbance history, or trends in CO2 concentration can be assessed. We show here for five model test sites that the suggested CO2-inhibition of leaf-isoprene metabolism can be large enough to offset increases in emissions due to CO2-stimulation of vegetation productivity and leaf area growth. When effects of climate change are considered atop the effects of atmospheric composition the interactions between the relevant processes will become even more complex. The CO2-isoprene inhibition may have the potential to significantly dampen the expected steep increase of ecosystem isoprene emission in a future, warmer atmosphere with higher CO2 levels; this effect raises important questions for projections of future atmospheric chemistry, and its connection to the terrestrial vegetation and carbon cycle.
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| 29. |
- Wolf, Annett, et al.
(författare)
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Sensitivity of an ecosystem model to hydrology and temperature
- 2008
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Ingår i: Climatic Change. - : Springer. - 0165-0009 .- 1573-1480. ; 87:1-2, s. 75-89
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Tidskriftsartikel (refereegranskat)abstract
- We tested the sensitivity of a dynamic ecosystem model (LPJ-GUESS) to the representation of soil moisture and soil temperature and to uncertainties in the prediction of precipitation and air temperature. We linked the ecosystem model with an advanced hydrological model (JULES) and used its soil moisture and soil temperature as input into the ecosystem model. We analysed these sensitivities along a latitudinal gradient in northern Russia. Differences in soil temperature and soil moisture had only little influence on the vegetation carbon fluxes, whereas the soil carbon fluxes were very sensitive to the JULES soil estimations. The sensitivity changed with latitude, showing stronger influence in the more northern grid cell. The sensitivity of modelled responses of both soil carbon fluxes and vegetation carbon fluxes to uncertainties in soil temperature were high, as both soil and vegetation carbon fluxes were strongly impacted. In contrast, uncertainties in the estimation of the amount of precipitation had little influence on the soil or vegetation carbon fluxes. The high sensitivity of soil respiration to soil temperature and moisture suggests that we should strive for a better understanding and representation of soil processes in ecosystem models to improve the reliability of predictions of future ecosystem changes.
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| 30. |
- Wolf, Annett, et al.
(författare)
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Storm damage and long-term mortality in a semi-natural, temperate deciduous forest
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 188:1-3, s. 197-210
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Tidskriftsartikel (refereegranskat)abstract
- 1.Wind-damaged trees, following the severe storm of 1999, are compared with data from a 50-year monitoring of Draved Forest, Denmark, to assess differing causes of mortality through time in an unmanaged semi-natural forest. Species-specific mortality characteristics and the changing effects of tree size and growth rate (diameter increment) on mortality through time are also investigated.2.Storm was found to be the major mortality factor affecting large trees in this forest. For smaller trees, competition was an important cause of death, as trees that were found standing dead had a slower growth rate (diameter increment) than survivors.3.Individual species showed different mortality patterns. Betula died more often and Fagus less often than expected from their abundance. Betula, Fagus and Tilia were mainly wind-thrown, whereas for Alnus and Fraxinus, 50% of the mortality was observed as standing dead trees.4.Both wind and competition are important mortality factors in Draved Forest.
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| 31. |
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| 32. |
- Wolf, Annett, et al.
(författare)
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The relative importance of land use and climatic change in Alpine catchments
- 2012
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Ingår i: Climatic Change. - : Springer Science and Business Media LLC. - 0165-0009 .- 1573-1480. ; 111:2, s. 279-300
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Tidskriftsartikel (refereegranskat)abstract
- Carbon storage and catchment hydrology are influenced both by land use changes and climatic changes, but there are few studies addressing both responses under both driving forces. We investigated the relative importance of climate change vs. land use change for four Alpine catchments using the LPJ-GUESS model. Two scenarios of grassland management were calibrated based on the more detailed model PROGRASS. The simulations until 2100 show that only reforestation could lead to an increase of carbon storage under climatic change, whereby a cessation of carbon accumulation occurred in all catchments after 2050. The initial increase in carbon storage was attributable mainly to forest re-growth on abandoned land, whereas the stagnation and decline in the second half of the century was mainly driven by climate change. If land was used more intensively, i.e. as grassland, litter input to the soil decreased due to harvesting, resulting in a decline of soil carbon storage (1.2−2.9 kg C m–2) that was larger than the climate-induced change (0.8–1.4 kg C m−2). Land use change influenced transpiration both directly and in interaction with climate change. The response of forested catchments diverged with climatic change (11–40 mm increase in AET), reflecting the differences in forest age, topography and water holding capacity within and between catchments. For grass-dominated catchments, however, transpiration responded in a similar manner to climate change (light management: 23–32 mm AET decrease, heavy management: 29–44 mm AET decrease), likely because grassroots are concentrated in the uppermost soil layers. Both the water and the carbon cycle were more strongly influenced by land use compared to climatic changes, as land use had not only a direct effect on carbon storage and transpiration, but also an indirect effect by modifying the climate change response of transpiration and carbon flux in the catchments. For the carbon cycle, climate change led to a cessation of the catchment response (sink/source strength is limited), whereas for the water cycle, the effect of land use change remains evident throughout the simulation period (changes in evapotranspiration do not attenuate). Thus we conclude that management will have a large potential to influence the carbon and water cycle, which needs to be considered in management planning as well as in climate and hydrological modelling.
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| 33. |
- Yurova, Alla, et al.
(författare)
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Variations in net ecosystem exchange of carbon dioxide in a boreal mire: Modeling mechanisms linked to water table position
- 2007
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Ingår i: Journal of Geophysical Research. - : John Wiley & Sons. - 2156-2202 .- 0148-0227. ; 112:G2
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Tidskriftsartikel (refereegranskat)abstract
- [1] In mires, which occupy large areas of the boreal region, net ecosystem CO2 exchange ( NEE) rates vary significantly over various timescales. In order to examine the effect of one of the most influencing variables, the water table depth, on NEE the general ecosystem model GUESS-ROMUL was modified to predict mire daily CO2 exchange rates. A simulation was conducted for a lawn, the most common microtopographical feature of boreal oligotrophic minerotrophic mires. The results were validated against eddy covariance CO2 flux measurements from Degero Stormyr, northern Sweden, obtained during the period 2001 - 2003. Both measurements and model simulations revealed that CO2 uptake was clearly controlled by interactions between water table depth and temperature. Maximum uptake occurred when the water table level was between 10 and 20 cm and the air temperature was above 15 degrees C. When the water table was higher, the CO2 uptake rate was lower, owing to reduced rates of photosynthetic carbon fixation. When the water table was lower, NEE decreased owing to the increased rate of decomposition of organic matter. When the water table level was between 10 and 20 cm, the NEE was quite stable and relatively insensitive to both changes within this range and any air temperature changes above + 15 degrees C. The optimal water table level range for NEE corresponds to that characteristic of mire lawn plant communities, indicating that the annual NEE will not change dramatically if climatic conditions remain within the optimal range for the current plant community.
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| 34. |
- Zöckler, Christoph, et al.
(författare)
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Potential impact of climate change and reindeer density on tundra indicator species in the Barents Sea region
- 2008
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Ingår i: Climatic Change. - : Springer. - 0165-0009 .- 1573-1480. ; 87:1-2, s. 119-130
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to alter the distribution of habitats and thus the distribution of species connected with these habitats in the terrestrial Barents Sea region. It was hypothesised that wild species connected with the tundra and open-land biome may be particularly at risk as forest area expands. Fourteen species of birds were identified as useful indicators for the biodiversity dependent upon this biome. By bringing together species distribution information with the LPJ-GUESS vegetation model, and with estimates of future wild and domestic reindeer density, potential impacts on these species between the present time and 2080 were assessed. Over this period there was a net loss of open land within the current breeding range of most bird species. Grazing reindeer were modelled as increasing the amount of open land retained for nine of the tundra bird species.
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| 35. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 36. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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