| 1. |
- Ahlström, Anders, et al.
(författare)
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Hydrologic resilience and Amazon productivity
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The Amazon rainforest is disproportionately important for global carbon storage and biodiversity. The system couples the atmosphere and land, with moist forest that depends on convection to sustain gross primary productivity and growth. Earth system models that estimate future climate and vegetation show little agreement in Amazon simulations. Here we show that biases in internally generated climate, primarily precipitation, explain most of the uncertainty in Earth system model results; models, empirical data and theory converge when precipitation biases are accounted for. Gross primary productivity, above-ground biomass and tree cover align on a hydrological relationship with a breakpoint at ~2000 mm annual precipitation, where the system transitions between water and radiation limitation of evapotranspiration. The breakpoint appears to be fairly stable in the future, suggesting resilience of the Amazon to climate change. Changes in precipitation and land use are therefore more likely to govern biomass and vegetation structure in Amazonia.
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| 2. |
- Ahlström, Anders, et al.
(författare)
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Robustness and uncertainty in terrestrial ecosystem carbon response to CMIP5 climate change projections
- 2012
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the spatio-temporal carbon balance patterns resulting from forcing a dynamic global vegetation model with output from 18 climate models of the CMIP5 (Coupled Model Intercomparison Project Phase 5) ensemble. We found robust patterns in terms of an extra-tropical loss of carbon, except for a temperature induced shift in phenology, leading to an increased spring uptake of carbon. There are less robust patterns in the tropics, a result of disagreement in projections of precipitation and temperature. Although the simulations generally agree well in terms of the sign of the carbon balance change in the middle to high latitudes, there are large differences in the magnitude of the loss between simulations. Together with tropical uncertainties these discrepancies accumulate over time, resulting in large differences in total carbon uptake over the coming century (−0.97–2.27 Pg C yr −1 during 2006–2100). The terrestrial biosphere becomes a net source of carbon in ten of the 18 simulations adding to the atmospheric CO 2 concentrations, while the remaining eight simulations indicate an increased sink of carbon.
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| 3. |
- Ahlström, Anders, et al.
(författare)
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The dominant role of semi-arid ecosystems in the trend and variability of the land CO2 sink
- 2015
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 348:6237, s. 895-899
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Tidskriftsartikel (refereegranskat)abstract
- The growth rate of atmospheric carbon dioxide (CO2) concentrations since industrialization is characterized by large interannual variability, mostly resulting from variability in CO2 uptake by terrestrial ecosystems (typically termed carbon sink). However, the contributions of regional ecosystems to that variability are not well known. Using an ensemble of ecosystem and land-surface models and an empirical observation-based product of global gross primary production, we show that the mean sink, trend, and interannual variability in CO2 uptake by terrestrial ecosystems are dominated by distinct biogeographic regions. Whereas the mean sink is dominated by highly productive lands (mainly tropical forests), the trend and interannual variability of the sink are dominated by semi-arid ecosystems whose carbon balance is strongly associated with circulation-driven variations in both precipitation and temperature.
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| 4. |
- Ahlström, Anders, et al.
(författare)
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The large influence of climate model bias on terrestrial carbon cycle simulations
- 2017
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Global vegetation models and terrestrial carbon cycle models are widely used for projecting the carbon balance of terrestrial ecosystems. Ensembles of such models show a large spread in carbon balance predictions, ranging from a large uptake to a release of carbon by the terrestrial biosphere, constituting a large uncertainty in the associated feedback to atmospheric CO 2 concentrations under global climate change. Errors and biases that may contribute to such uncertainty include ecosystem model structure, parameters and forcing by climate output from general circulation models (GCMs) or the atmospheric components of Earth system models (ESMs), e.g. as prepared for use in IPCC climate change assessments. The relative importance of these contributing factors to the overall uncertainty in carbon cycle projections is not well characterised. Here we investigate the role of climate model-derived biases by forcing a single global ecosystem-carbon cycle model, with original climate outputs from 15 ESMs and GCMs from the CMIP5 ensemble. We show that variation among the resulting ensemble of present and future carbon cycle simulations propagates from biases in annual means of temperature, precipitation and incoming shortwave radiation. Future changes in carbon pools, and thus land carbon sink trends, are also affected by climate biases, although to a smaller extent than the absolute size of carbon pools. Our results suggest that climate biases could be responsible for a considerable fraction of the large uncertainties in ESM simulations of land carbon fluxes and pools, amounting to about 40% of the range reported for ESMs. We conclude that climate bias-induced uncertainties must be decreased to make accurate coupled atmosphere-carbon cycle projections.
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| 5. |
- Arneth, Almut, et al.
(författare)
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CO2 inhibition of terrestrial isoprene production stabilises tropospheric oxidation capacity
- 2007
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Ingår i: Geophysical Research Letters. - 1944-8007. ; 34, L18813:18
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Tidskriftsartikel (refereegranskat)abstract
- [1] Isoprene is the dominant volatile organic compound produced by the terrestrial biosphere and fundamental for atmospheric composition and climate. It constrains the concentration of tropospheric oxidants, affecting the lifetime of other reduced species such as methane and contributing to ozone production. Oxidation products of isoprene contribute to aerosol growth. Recent consensus holds that emissions were low during glacial periods ( helping to explain low methane concentrations), while high emissions ( contributing to high ozone concentrations) can be expected in a greenhouse world, due to positive relationships with temperature and terrestrial productivity. However, this response is offset when the recently demonstrated inhibition of leaf isoprene emissions by increasing atmospheric CO2 concentration is accounted for in a process-based model. Thus, isoprene may play a small role in determining pre-industrial tropospheric OH concentration and glacial-interglacial methane trends, while predictions of high future tropospheric O-3 concentrations partly driven by isoprene emissions may need to be revised.
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| 6. |
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| 7. |
- Arneth, Almut, et al.
(författare)
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Global terrestrial isoprene emission models: sensitivity to variability in climate and vegetation
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 11:15, s. 8037-8052
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Tidskriftsartikel (refereegranskat)abstract
- Due to its effects on the atmospheric lifetime of methane, the burdens of tropospheric ozone and growth of secondary organic aerosol, isoprene is central among the biogenic compounds that need to be taken into account for assessment of anthropogenic air pollution-climate change interactions. Lack of process-understanding regarding leaf isoprene production as well as of suitable observations to constrain and evaluate regional or global simulation results add large uncertainties to past, present and future emissions estimates. Focusing on contemporary climate conditions, we compare three global isoprene models that differ in their representation of vegetation and isoprene emission algorithm. We specifically aim to investigate the between-and within model variation that is introduced by varying some of the models' main features, and to determine which spatial and/or temporal features are robust between models and different experimental set-ups. In their individual standard configurations, the models broadly agree with respect to the chief isoprene sources and emission seasonality, with maximum monthly emission rates around 20-25 Tg C, when averaged by 30-degree latitudinal bands. They also indicate relatively small (approximately 5 to 10% around the mean) interannual variability of total global emissions. The models are sensitive to changes in one or more of their main model components and drivers (e. g., underlying vegetation fields, climate input) which can yield increases or decreases in total annual emissions of cumulatively by more than 30 %. Varying drivers also strongly alters the seasonal emission pattern. The variable response needs to be interpreted in view of the vegetation emission capacities, as well as diverging absolute and regional distribution of light, radiation and temperature, but the direction of the simulated emission changes was not as uniform as anticipated. Our results highlight the need for modellers to evaluate their implementations of isoprene emission models carefully when performing simulations that use nonstandard emission model configurations.
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| 8. |
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| 9. |
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| 10. |
- Arneth, Almut, et al.
(författare)
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Terrestrial biogeochemical feedbacks in the climate system
- 2010
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Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0908 .- 1752-0894. ; 3:8, s. 525-532
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Forskningsöversikt (refereegranskat)abstract
- The terrestrial biosphere is a key regulator of atmospheric chemistry and climate. During past periods of climate change, vegetation cover and interactions between the terrestrial biosphere and atmosphere changed within decades. Modern observations show a similar responsiveness of terrestrial biogeochemistry to anthropogenically forced climate change and air pollution. Although interactions between the carbon cycle and climate have been a central focus, other biogeochemical feedbacks could be as important in modulating future climate change. Total positive radiative forcings resulting from feedbacks between the terrestrial biosphere and the atmosphere are estimated to reach up to 0.9 or 1.5 W m(-2) K-1 towards the end of the twenty-first century, depending on the extent to which interactions with the nitrogen cycle stimulate or limit carbon sequestration. This substantially reduces and potentially even eliminates the cooling effect owing to carbon dioxide fertilization of the terrestrial biota. The overall magnitude of the biogeochemical feedbacks could potentially be similar to that of feedbacks in the physical climate system, but there are large uncertainties in the magnitude of individual estimates and in accounting for synergies between these effects.
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| 11. |
- Arneth, Almut, et al.
(författare)
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Why are estimates of global terrestrial isoprene emissions so similar (and why is this not so for monoterpenes)?
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - 1680-7324. ; 8:16, s. 4605-4620
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Tidskriftsartikel (refereegranskat)abstract
- Emissions of biogenic volatile organic compounds (BVOC) are a chief uncertainty in calculating the burdens of important atmospheric compounds like tropospheric ozone or secondary organic aerosol, reflecting either imperfect chemical oxidation mechanisms or unreliable emission estimates, or both. To provide a starting point for a more systematic discussion we review here global isoprene and monoterpene emission estimates to-date. We note a surprisingly small variation in the predictions of global isoprene emission rate that is in stark contrast with our lack of process understanding and the small number of observations for model parameterisation and evaluation. Most of the models are based on similar emission algorithms, using fixed values for the emission capacity of various plant functional types. In some cases, these values are very similar but differ substantially in other models. The similarities with regard to the global isoprene emission rate would suggest that the dominant parameters driving the ultimate global estimate, and thus the dominant determinant of model sensitivity, are the specific emission algorithm and isoprene emission capacity. But the models also differ broadly with regard to their representation of net primary productivity, method of biome coverage determination and climate data. Contrary to isoprene, monoterpene estimates show significantly larger model-to-model variation although variation in terms of leaf algorithm, emission capacities, the way of model upscaling, vegetation cover or climatology used in terpene models are comparable to those used for isoprene. From our summary of published studies there appears to be no evidence that the terrestrial modelling community has been any more successful in 'resolving unknowns' in the mechanisms that control global isoprene emissions, compared to global monoterpene emissions. Rather, the proliferation of common parameterization schemes within a large variety of model platforms lends the illusion of convergence towards a common estimate of global isoprene emissions. This convergence might be used to provide optimism that the community has reached the 'relief phase', the phase when sufficient process understanding and data for evaluation allows models' projections to converge, when applying a recently proposed concept. We argue that there is no basis for this apparent relief phase. Rather, we urge modellers to be bolder in their analysis, and to draw attention to the fact that terrestrial emissions, particularly in the area of biome-specific emission capacities, are unknown rather than uncertain.
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| 12. |
- Ashworth, Kirsti, et al.
(författare)
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Global modelling of volatile organic compound emissions
- 2013
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Ingår i: Biology, Controls and Models of Tree Volatile Organic Compound Emissions. - Dordrecht : Springer Netherlands. - 1568-2544. - 9789400766051 - 9789400766068 ; 5, s. 451-487
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Bokkapitel (refereegranskat)
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| 13. |
- Chaudhary, Nitin, et al.
(författare)
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Modelling past and future peatland carbon dynamics across the pan-Arctic
- 2020
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26:7, s. 4119-4133
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Tidskriftsartikel (refereegranskat)abstract
- The majority of northern peatlands were initiated during the Holocene. Owing to their mass imbalance, they have sequestered huge amounts of carbon in terrestrial ecosystems. Although recent syntheses have filled some knowledge gaps, the extent and remoteness of many peatlands pose challenges to developing reliable regional carbon accumulation estimates from observations. In this work, we employed an individual- and patch-based dynamic global vegetation model (LPJ-GUESS) with peatland and permafrost functionality to quantify long-term carbon accumulation rates in northern peatlands and to assess the effects of historical and projected future climate change on peatland carbon balance. We combined published datasets of peat basal age to form an up-to-date peat inception surface for the pan-Arctic region which we then used to constrain the model. We divided our analysis into two parts, with a focus both on the carbon accumulation changes detected within the observed peatland boundary and at pan-Arctic scale under two contrasting warming scenarios (representative concentration pathway-RCP8.5 and RCP2.6). We found that peatlands continue to act as carbon sinks under both warming scenarios, but their sink capacity will be substantially reduced under the high-warming (RCP8.5) scenario after 2050. Areas where peat production was initially hampered by permafrost and low productivity were found to accumulate more carbon because of the initial warming and moisture-rich environment due to permafrost thaw, higher precipitation and elevated CO2 levels. On the other hand, we project that areas which will experience reduced precipitation rates and those without permafrost will lose more carbon in the near future, particularly peatlands located in the European region and between 45 and 55 degrees N latitude. Overall, we found that rapid global warming could reduce the carbon sink capacity of the northern peatlands in the coming decades.
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| 14. |
- Guan, Qi, et al.
(författare)
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Eutrophication changes in fifty large lakes on the Yangtze Plain of China derived from MERIS and OLCI observations
- 2020
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Ingår i: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257. ; 246
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Tidskriftsartikel (refereegranskat)abstract
- The eutrophication problems in lakes on the Yangtze Plain of China have attracted global concern. However, a comprehensive assessment of the eutrophication status and its evolution is still lacking for these regional lakes, mostly because of technical difficulties and/or insufficient data to cover the large region. Our study attempts to fill this knowledge gap by using the entire archive of remote sensing images from two satellite ocean color missions (MEdium Resolution Imaging Spectrometer, or MERIS (2003−2011), and Ocean and Land Color Instrument, or OLCI (2017–2018)), together with in situ data on remote sensing reflectance and chlorophyll-a (Chla) concentrations across various lakes on the Yangtze Plain. A machine learning-based piecewise Chla algorithm was developed in this study, with special considerations to improve algorithm performance under lower Chla conditions. Remotely sensed Chla and algal bloom areas were then used to classify the eutrophication status of 50 large lakes on the Yangtze Plain, and the frequent satellite observations enabled us to estimate the probability of eutrophication occurrence (PEO) for each examined lake. The long-term mean Chla ranged from 17.58 mg m−3 to 43.86 mg m−3 on the Yangtze Plain, and severe floating algal blooms were found in 7 lakes. All 50 lakes had high climatological PEO values (50%) during the study period, indicating a generally high probability of eutrophication in lakes on the Yangtze Plain. However, 21 out of 51 lakes exhibited statistically significant (p < .05) decreasing trends in PEO during the observation period, suggesting an overall improvement in the water quality of lakes on the Yangtze Plain in recent years. The methods developed here are expected to contribute to real-time monitoring of drinking water safety for local regions, and the long-term results provide valuable baseline information for future lake conservation and restoration efforts.
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| 15. |
- Guan, Qi, et al.
(författare)
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Long-term changes of nitrogen leaching and the contributions of terrestrial nutrient sources to lake eutrophication dynamics on the Yangtze Plain of China
- 2023
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Ingår i: Biogeosciences. - 1726-4170. ; 20:8, s. 1635-1648
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Tidskriftsartikel (refereegranskat)abstract
- Over the past half-century, drastically increased chemical fertilizers have entered agricultural ecosystems to promote crop production on the Yangtze Plain, potentially enhancing agricultural nutrient sources for eutrophication in freshwater ecosystems. However, long-term trends of nitrogen dynamics in terrestrial ecosystems and their impacts on eutrophication changes in this region remain poorly studied. Using a process-based ecosystem model, we investigated the temporal and spatial patterns of nitrogen use efficiency (NUE) and nitrogen leaching on the Yangtze Plain from 1979-2018. The agricultural NUE for the Yangtze Plain significantly decreased from 50g€¯% in 1979 to 25g€¯% in 2018, with the largest decline of NUE in soybean, rice, and rapeseed. Simultaneously, the leached nitrogen from cropland and natural land increased, with annual rates of 4.5 and 0.22g€¯kgg€¯Ng€¯ha-1g€¯yr-2, respectively, leading to an overall increase of nitrogen inputs to the 50 large lakes. We further examined the correlations between terrestrial nutrient sources (i.e., the leached nitrogen, total phosphorus sources, and industrial wastewater discharge) and the satellite-observed probability of eutrophication occurrence (PEO) at an annual scale and showed that PEO was positively correlated with the changes in terrestrial nutrient sources for most lakes. Agricultural nitrogen and phosphorus sources were found to explain the PEO trends in lakes in the western and central part of the Yangtze Plain, and industrial wastewater discharge was associated with the PEO trends in eastern lakes. Our results revealed the importance of terrestrial nutrient sources for long-term changes in eutrophic status over the 50 lakes of the Yangtze Plain. This calls for region-specific sustainable nutrient management (i.e., nitrogen and phosphorus applications in agriculture and industry) to improve the water quality of lake ecosystems.
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| 16. |
- Hantson, Stijn, et al.
(författare)
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Global isoprene and monoterpene emissions under changing climate, vegetation, CO2 and land use
- 2017
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 155, s. 35-45
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Tidskriftsartikel (refereegranskat)abstract
- Plants emit large quantities of isoprene and monoterpenes, the main components of global biogenic volatile organic compound (BVOC) emissions. BVOCs have an important impact on the atmospheric composition of methane, and of short-lived radiative forcing agents (e.g. ozone, aerosols etc.). It is therefore necessary to know how isoprene and monoterpene emissions have changed over the past and how future changes in climate, land-use and other factors will impact them. Here we present emission estimates of isoprene and monoterpenes over the period 1901–2 100 based on the dynamic global vegetation model LPJ-GUESS, including the effects of all known important drivers. We find that both isoprene and monoterpene emissions at the beginning of the 20th century were higher than at present. While anthropogenic land-use change largely drives the global decreasing trend for isoprene over the 20th century, changes in natural vegetation composition caused a decreasing trend for monoterpene emissions. Future global isoprene and monoterpene emissions depend strongly on the climate and land-use scenarios considered. Over the 21st century, global isoprene emissions are simulated to either remain stable (RCP 4.5), or decrease further (RCP 8.5), with important differences depending on the underlying land-use scenario. Future monoterpene emissions are expected to continue their present decreasing trend for all scenarios, possibly stabilizing from 2050 onwards (RCP 4.5). These results demonstrate the importance to take both natural vegetation dynamics and anthropogenic changes in land-use into account when estimating past and future BVOC emissions. They also indicate that a future global increase in BVOC emissions is improbable.
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| 17. |
- Hari, Pertti, et al.
(författare)
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Prediction of photosynthesis in Scots pine ecosystems across Europe by a needle-level theory
- 2018
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:18, s. 13321-13328
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthesis provides carbon for the synthesis of macromolecules to construct cells during growth. This is the basis for the key role of photosynthesis in the carbon dynamics of ecosystems and in the biogenic CO2 assimilation. The development of eddy-covariance (EC) measurements for ecosystem CO2 fluxes started a new era in the field studies of photosynthesis. However, the interpretation of the very variable CO2 fluxes in evergreen forests has been problematic especially in transition times such as the spring and autumn. We apply two theoretical needle-level equations that connect the variation in the light intensity, stomatal action and the annual metabolic cycle of photosynthesis. We then use these equations to predict the photosynthetic CO2 flux in five Scots pine stands located from the northern timberline to Central Europe. Our result has strong implications for our conceptual understanding of the effects of the global change on the processes in boreal forests, especially of the changes in the metabolic annual cycle of photosynthesis.
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| 18. |
- Jönsson, Anna Maria, et al.
(författare)
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Enhanced science-stakeholder communication to improve ecosystem model performances for climate change impact assessments.
- 2015
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Ingår i: Ambio: a Journal of Human Environment. - : Springer Science and Business Media LLC. - 0044-7447. ; 44:3, s. 249-255
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, climate impact assessments of relevance to the agricultural and forestry sectors have received considerable attention. Current ecosystem models commonly capture the effect of a warmer climate on biomass production, but they rarely sufficiently capture potential losses caused by pests, pathogens and extreme weather events. In addition, alternative management regimes may not be integrated in the models. A way to improve the quality of climate impact assessments is to increase the science-stakeholder collaboration, and in a two-way dialog link empirical experience and impact modelling with policy and strategies for sustainable management. In this paper we give a brief overview of different ecosystem modelling methods, discuss how to include ecological and management aspects, and highlight the importance of science-stakeholder communication. By this, we hope to stimulate a discussion among the science-stakeholder communities on how to quantify the potential for climate change adaptation by improving the realism in the models.
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| 19. |
- Jönsson, Anna Maria, et al.
(författare)
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Modellering av klimatets påverkan på produktion och risk för skadegörare inom jordbruket.
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I den här kunskapssammanställningen tar vi upp frågor som rör hur ett förändrat klimat kan komma att påverka tillväxt och skörd av olika jordbruksgrödor, samt hur klimatet kan påverka risken för angrepp av nya och redan etablerade skadegörare och växtsjukdomar i Sverige. Ökad temperatur leder till förlängning av växtsäsongen och utrymme för produktionsökning. I takt med att klimatet blir varmare kan nya grödor odlas. Men ett ändrat klimat kommer också att medföra en ändrad risk för skador, och ökande kostnader för skadebekämpning kan påverka ekonomin inom jordbruket negativt. Modellering är ett verktyg för att uttrycka kunskap kring komplexa processer och skeenden. Empiriska (statistiska) modeller kan användas för att kvantifiera samvariation, och processbaserade effektmodeller för att göra framtidssimuleringar. Utifrån den till synes enkla frågan om hur en temperaturökning kan komma att påverka en gröda kan man ta flera processbaserade modelleringssteg, från en fenologisk beskrivning av grödan, via en ekosystemmodelleringsansats där man inkluderar effekter av viktiga skadegörare, till frågor som rör anpassning av brukningsmetod, ekonomi och hantering av klimatrelaterade osäkerheter. För hantering av skadegörare kan det sista steget vara väl så viktigt som de två tidigare, då beslutsfattare är i behov av information för att kunna vidta lämpliga åtgärder i relation till begränsade resurser. Vid varje modelleringsansats behöver man fundera igenom hur resultaten ska användas. Givet studiens avgränsning, vilka ekosysteminteraktioner behöver studeras för att ge en rimligt bra bild av utfallet? Hur pass detaljerad behöver modellens tidsmässiga och rumsliga upplösning vara för att kunna ge ett bra beslutsstöd? Genom en litteraturstudie av internationella vetenskapliga publikationer drar vi slutsatserna att: - det finns både empiriska och processbaserade modeller för flertalet grödor och de ekonomiskt viktigaste skadegörarna - för skadegörare är modellering av klimatrelaterad fenologi och utbredning vanligare än modellering av populationsdynamik och skaderisk - endast ett fåtal modelleringsstudier belyser interaktionen mellan gröda och skadegörare, och det saknas ofta information om hur skaderisken påverkas av anpassning till lokala förhållanden, väderleksextremer, predatorer och parasiter - endast ett fåtal studier analyserar beslutssituationer, och hitintills har ingen studie använt den kunskap kring sannolikhet och osäkerhet i utfallet som följer med klimatprojektionerna - samlad och likvärdig information för potentiellt viktiga grödor och skadegörare i Sverige behövs för att kommunicera kunskap kring klimatförändringseffekter och för att få en helhetsbild av anpassningsutrymmet - modellutveckling bör bedrivas i dialog mellan forskare och olika aktörer inom jordbrukssektorn för att öka användbarheten av den information som tas fram.
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| 20. |
- Kuemmerle, Tobias, et al.
(författare)
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Reconstructing range dynamics and range fragmentation of European bison for the last 8000 years
- 2012
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Ingår i: Diversity and Distributions. - : Wiley. - 1366-9516. ; 18:1, s. 47-59
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Tidskriftsartikel (refereegranskat)abstract
- Aim Understanding what constituted species ranges prior to large-scale human influence, and how past climate and land use change have affected range dynamics, provides conservation planners with important insights into how species may respond to future environmental change. Our aim here was to reconstruct the Holocene range of European bison (Bison bonasus) by combining a time-calibrated species distribution models (SDM) with a dynamic vegetation model. Location Europe. Method We used European bison occurrences from the Holocene in a maximum entropy model to assess bison range dynamics during the last 8000 years. As predictors, we used bioclimatic variables and vegetation reconstructions from the generalized dynamic vegetation model LPJ-GUESS. We compared our range maps with maps of farmland and human population expansion to identify the main species range constraints. Results The Holocene distribution of European bison was mainly determined by vegetation patterns, with bison thriving in both broadleaved and coniferous forests, as well as by mean winter temperature. The heartland of European bison was in Central and Eastern Europe, whereas suitable habitat in Western Europe was scarce. While environmentally suitable regions were overall stable, the expansion of settlements and farming severely diminished available habitat. Main conclusions European bison habitat preferences may be wider than previously assumed, and our results suggest that the species had a more eastern and northern distribution than previously reported. Vegetation and climate transformation during the Holocene did not affect the bison's range substantially. Conversely, human population growth and the spread of farming resulted in drastic bison habitat loss and fragmentation, likely reaching a tipping point during the last 1000 years. Combining SDM and dynamic vegetation models can improve range reconstructions and projections, and thus help to identify resilient conservation strategies for endangered species.
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| 21. |
- Kuemmerle, Tobias, et al.
(författare)
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Refugee species: which historic baseline should inform conservation planning?
- 2012
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Ingår i: Diversity and Distributions. - : Wiley. - 1366-9516. ; 18:12, s. 1258-1261
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Tidskriftsartikel (refereegranskat)abstract
- Understanding species’ historical ranges can provide important information for conservation planning in the face of environmental change. Cromsigt et al. (this issue) comment on our recent European bison (Bison bonasus) range reconstruction, suggesting that bison were already 8000 years ago a refugee species (i.e. restricted to marginal habitat due to past human pressure) and that species distribution models (SDM) are generally of limited use for refugee species conservation. While we welcome this discussion, we find no evidence for the claim that human pressure prior to 8000 BP determined where bison occurred. More importantly, as human pressure is generally high and increasing, attempts to restore species across their former range may fail where the factors that relegated species into refugee status are still at play or where their optimal habitat has vanished. Identifying areas where human pressure is low and where refugee species have persisted over the last millennia is crucial, and SDM based on historical data are important for doing so. Refugee species suffer from the shifting baseline syndrome, but careful reality checks are needed and all available data should be considered before determining the baseline that should inform conservation planning.
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| 22. |
- Lehsten, Dörte, et al.
(författare)
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Modelling the Holocene migrational dynamics of Fagus sylvatica L. and Picea abies (L.) H. Karst
- 2014
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-8238 .- 1466-822X. ; 23:6, s. 658-668
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Tidskriftsartikel (refereegranskat)abstract
- Aim Vegetation dynamics and the competitive interactions involved are assumed to restrict the ability of species to migrate. But in most migration modelling approaches disturbance-driven succession and competition processes are reduced to simple assumptions or are even missing. The aim of this study was to test a combination of a migration model and a dynamic vegetation model to estimate the migration of tree species controlled by climate, environment and local species dynamics such as succession and competition. Location Europe. Methods To estimate the effect of vegetation dynamics on the migration of European beech and Norway spruce, we developed a post-process migration tool (LPJ-CATS). This tool integrates outputs of the migration model CATS and the dynamic vegetation model LPJ-GUESS. The model LPJ-CATS relies on a linear dependency between the dispersal kernel and migration rate and is based on the assumption that competition reduces fecundity. Results Simulating potential migration rates with the CATS model, which does not account for competition and disturbance, resulted in mean Holocene migration rates of 435 +/- 55 and 330 +/- 95 m year(-1) for the two species Picea abies and Fagus sylvatica, respectively. With LPJ-CATS, these mean migration rates were reduced to 250 +/- 75 and 170 +/- 60 m year(-1) for spruce and beech, respectively. Moreover, LPJ-CATS simulated migration pathways of these two species that generally comply well with those documented in the palaeo-records. Main conclusions Our 'hybrid' modelling approach allowed for the simulation of generally realistic Holocene migration rates and pathways of the two study species on a continental scale. It suggests that competition can considerably modify spread rates, but also the magnitude of its effect depends on how close climate conditions are to the niche requirements of a particular species.
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| 23. |
- Martín Belda, David, et al.
(författare)
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LPJ-GUESS/LSMv1.0 : A next-generation land surface model with high ecological realism
- 2022
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 15:17, s. 6709-6745
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Tidskriftsartikel (refereegranskat)abstract
- Land biosphere processes are of central importance to the climate system. Specifically, ecosystems interact with the atmosphere through a variety of feedback loops that modulate energy, water, and CO2 fluxes between the land surface and the atmosphere across a wide range of temporal and spatial scales. Human land use and land cover modification add a further level of complexity to land-atmosphere interactions. Dynamic global vegetation models (DGVMs) attempt to capture land ecosystem processes and are increasingly incorporated into Earth system models (ESMs), which makes it possible to study the coupled dynamics of the land biosphere and the climate. In this work we describe a number of modifications to the LPJ-GUESS DGVM, aimed at enabling direct integration into an ESM. These include energy balance closure, the introduction of a sub-daily time step, a new radiative transfer scheme, and improved soil physics. The implemented modifications allow the model (LPJ-GUESS/LSM) to simulate the diurnal exchange of energy, water, and CO2 between the land ecosystem and the atmosphere and thus provide surface boundary conditions to an atmospheric model over land. A site-based evaluation against FLUXNET2015 data shows reasonable agreement between observed and modelled sensible and latent heat fluxes. Differences in predicted ecosystem function between standard LPJ-GUESS and LPJ-GUESS/LSM vary across land cover types. We find that the emerging ecosystem composition and carbon fluxes are sensitive to both the choice of stomatal conductance model and the response of plant water uptake to soil moisture. The new implementation described in this work lays the foundation for using the well-established LPJ-GUESS DGVM as an alternative land surface model (LSM) in coupled land-biosphere-climate studies, where an accurate representation of ecosystem processes is essential.
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| 24. |
- Olin, Stefan, et al.
(författare)
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Modelling the response of yields and tissue C:N to changes in atmospheric CO2 and N management in the main wheat regions of western Europe
- 2015
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 12, s. 2489-2515
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) is a key element in terrestrial ecosystems as it influences both plant growth and plant interactions with the atmosphere. Accounting for carbon–nitrogen interactions has been found to alter future projections of the terrestrial carbon (C) cycle substantially. Dynamic vegetation models (DVMs) aim to accurately represent both natural vegetation and managed land, not only from a carbon cycle perspective but increasingly so also for a wider range of processes including crop yields. We present here the extended version of the DVM LPJ-GUESS that accounts for N limitation in crops to account for the effects of N fertilisation on yields and biogeochemical cycling. The performance of this new implementation is evaluated against observations from N fertiliser trials and CO2 enrichment experiments. LPJ-GUESS captures the observed response to both N and CO2 fertilisation on wheat biomass production, tissue C to N ratios (C : N) and phenology. To test the model's applicability for larger regions, simulations are subsequently performed that cover the wheat-dominated regions of western Europe. When compared to regional yield statistics, the inclusion of C–N dynamics in the model substantially increase the model performance compared to an earlier version of the model that does not account for these interactions. For these simulations, we also demonstrate an implementation of N fertilisation timing for areas where this information is not available. This feature is crucial when accounting for processes in managed ecosystems in large-scale models. Our results highlight the importance of accounting for C–N interactions when modelling agricultural ecosystems, and it is an important step towards accounting for the combined impacts of changes in climate, [CO2] and land use on terrestrial biogeochemical cycles.
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| 25. |
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