| 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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