| 1. |
- Akselsson, Cecilia, et al.
(author)
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Carbon sequestration rates in organic layers of boreal and temperate forest soils - Sweden as a case study
- 2005
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In: Global Ecology and Biogeography Letters. - 0960-7447. ; 14:1, s. 77-84
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Journal article (peer-reviewed)abstract
- Aim The aim of this work was to estimate C sequestration rates in the organic matter layer in Swedish forests. Location The region encompassed the forested area (23 x 10(6) ha) of Sweden ranging from about 55degrees N to 69degrees N. Methods We used the concept of limit values to estimate recalcitrant litter remains, and combined it with amount of litter fall. Four groups of tree species were identified (pine, spruce, birch and 'other deciduous species'). Annual actual evapotranspiration (AET) was estimated for 5 x 5 km grids covering Sweden. For each grid, data of forested area and main species composition were available. The annual input of foliar litter into each grid was calculated using empirical relationships between AET and foliar litter fall in the four groups. Litter input was combined with average limit values for decomposition for the four groups of litter, based on empirical data. Finally, C sequestration rate was calculated using a constant factor of the C concentration in the litter decomposed to the limit value, thus forming soil organic matter (SOM). Results We obtained a value of 4.8 x 10(6) metric tons of C annually sequestered in SOM in soils of mature forests in Sweden, with an average of 180 kg ha(-1) and a range from 40 to 410 kg ha(-1). Norway spruce forests accumulated annually an average of 200 kg C ha(-1). The pine and birch groups had an average of 150 kg ha(-1) and for the group of other deciduous trees, which is limited to south Sweden, the C sequestration was around 400 kg ha(-1). Conclusions There is a clear C sequestration gradient over Sweden with the highest C sequestration in the south-west, mainly corresponding to the gradient in litter fall. The limit-value method appears useful for scaling up to a regional level to describe the C sequestration in SOM. A development of the limit value approach in combination with process-orientated dynamic models may have a predictive value.
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| 2. |
- Akselsson, Cecilia, et al.
(author)
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Regionalized nitrogen budgets in forest soils for different deposition and forestry scenarios in Sweden
- 2005
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In: Global Ecology and Biogeography Letters. - 0960-7447. ; 14:1, s. 85-95
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Journal article (peer-reviewed)abstract
- Aim The aim of this work was to estimate on a regional scale the effects of nitrogen (N) deposition and harvest intensity on N-budgets in forest soils as a basis for strategies of emission reduction and sustainable forest management methods. Location The calculations were applied to Sweden, a country with a managed forest area of 23 x 10(6) ha. Methods Mass balance calculations, including N-deposition, N-fixation, N-loss through harvest, and N-leaching, were performed on a GIS platform using 5 x 5 km grids. Modelled deposition data together with spatial data obtained from the National Forest Inventory served as the basis for the calculations. Four different scenarios were run: a 'base scenario' involving present deposition and conventional forestry (stem harvest only); a 'whole-tree harvesting scenario' with present deposition and the harvesting of stems, branches and needles; a 'decreased deposition scenario'; and a 'whole-tree harvesting and decreased deposition scenario'. Results There was a sharp N-accumulation gradient with an increase in accumulation in the direction of the south-western part of Sweden. In the 'base scenario', N-accumulation appeared in the country as a whole, apart from certain small areas in the northern part. Whole-tree harvesting led to net losses in extensive areas located mainly in northern and central Sweden. In most parts of the country, whole-tree harvesting combined with decreased deposition was found to result in net losses. Main conclusions The intensity of the forestry has a strong impact on the N-budget. Conventional forestry in combination with the present deposition level results in a high net accumulation of N in the south-western parts of Sweden and accordingly, in a risk of unwanted environmental effects such as increased N-leaching. With whole-tree harvesting, the N-balance is negative in parts of Sweden, mainly in the northern and central parts. N-fertilization may become necessary there if the present level of forest production is to be maintained.
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| 3. |
- Bennett, KD, et al.
(author)
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Effect of global atmospheric carbon dioxide on glacial-interglacial vegetation change
- 2000
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In: GLOBAL ECOLOGY AND BIOGEOGRAPHY. - : BLACKWELL SCIENCE LTD. - 0960-7447. ; 9:5, s. 355-361
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Journal article (peer-reviewed)abstract
- Global vegetation changes at the time-scale of the Earth's orbital variations (10(4)-10(5) years) have been interpreted as a direct effect of consequential climatic changes, especially temperature. At mid- and high latitudes, the evidence from fossil data
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| 4. |
- Fosaa, Anna Maria, et al.
(author)
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Potential effects of climate change on plant species in the Faroe Islands
- 2004
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In: Global Ecology and Biogeography Letters. - 0960-7447. ; 13:5, s. 427-437
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Journal article (peer-reviewed)abstract
- Aim To identify the effect of climate change on selected plant species representative of the main vegetation types in the Faroe Islands. Due to a possible weakening of the North Atlantic Current, it is difficult to predict whether the climate in the Faroe Islands will be warmer or colder as a result of global warming. Therefore, two scenarios are proposed. The first scenario assumes an increase in summer and winter temperature of 2 degreesC, and the second a decrease in summer and winter temperature of 2 degreesC. Location Temperate, low alpine and alpine areas in the northern and central part of the Faroe Islands. Methods The responses of 12 different plant species in the Faroe Islands were tested against measured soil temperature, expressed as T-min, T-max, snow cover and growing degree days (GDD), using generalised linear modelling (GLM). Results The tolerance to changes in winter soil temperature (0.3-0.8 degreesC) was found to be lower than the tolerance to changing summer soil temperature (0.7-1.0 degreesC), and in both cases lower than the predicted climate changes. Conclusions The species most affected by a warming scenario are those that are found with a limited distribution restricted to the uppermost parts of the mountains, especially Salix herbacea, Racomitrium fasciculare, and Bistorta vivipara. For other species, the effect will mainly be a general upward migration. The most vulnerable species are those with a low tolerance, especially Calluna vulgaris, and also Empetrum nigrum, and Nardus stricta. If the climate in the Faroe Islands should become colder, the most vulnerable species are those at low altitudes. A significantly lower temperature would be expected to produce a serious reduction in the extent of Vaccinium myrtillus and Galium saxatilis. Species like Empetrum nigrum, Nardus stricta, and Calluna vulgaris may also be vulnerable. In any case, these species can be expected to migrate downwards.
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| 5. |
- Gachet, S, et al.
(author)
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A probabilistic approach to the use of pollen indicators for plant attributes and biomes: an application to European vegetation at 0 and 6 ka
- 2003
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In: Global Ecology and Biogeography Letters. - 0960-7447. ; 12:2, s. 103-118
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Journal article (peer-reviewed)abstract
- Aim This paper presents a probabilistic method for the characterization of pollen taxa using attributes, and for the reconstitution of past biomes. The probabilities are calculated on the basis of European floristic and pollen databases sufficiently large and exhaustive to provide robust estimates. Location The analysis is based on data from approximately 1000 sites throughout Europe. Method We use all the pollen data from the European Pollen Database (EPD), which contains about 50 000 pollen assemblages distributed across Europe and covering the period from the Last Glacial Maximum to the present. Using existing floras, each pollen taxon has been characterized by allocating one or more modes of several attributes, chosen according to the biogeography and phenology of the taxon. With this information, conditional probabilities are defined, representing the chance of a given attribute mode occurring in a given pollen spectrum, when the taxa assemblage is known. The concept of co-occurrence is used to provide a greater amount of information to compensate for difficulties in the identification of pollen grains, allowing a better interpretation when there is little diversity in the pollen assemblage. Results The method has been validated using a dataset of modern samples against existing methods of biome classification and remote sensing data. An application is proposed in which the new method is used to produce biomes for pollen data 6000 years ago. This confirms previous results showing an extension of the deciduous forest to the north, east and south, explained by milder winters in western and northern Europe, and cooler and wetter climate in the Mediterranean region. Conclusion The results show the new method to be efficient, reliable and flexible and to be an improvement over the previous method of biomization. They will be used to test simulations of earth system models running on periods with climate significantly different from the present day, enabling a robust test of the validity of applying these models to the future.
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| 6. |
- Gritti, Emmanuel, et al.
(author)
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An extended probabilistic approach of plant vital attributes: an application to European pollen records at 0 and 6 ka
- 2004
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In: Global Ecology and Biogeography Letters. - 0960-7447. ; 13:6, s. 519-533
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Journal article (peer-reviewed)abstract
- Aim This paper presents a probabilistic method of pollen spectra analysis. The method relies on a pollen taxon characterization using biotic and abiotic plant attribute modes, and their occurrence in a given pollen spectrum at a specific site. This type of analysis can provide an interpretation, which can lead to the reconstruction of the biome and, to an extent, of the abiotic conditions at the site. Methods The analysis has been carried out at the European scale using data provided by the European Pollen Database for about 1000 sites. This dataset contains about 50,000 pollen spectra from the last 21 ka. In these spectra, each pollen taxon has been characterized by a set of 10 chosen attributes. These have been selected with regard to their relevance in biome reconstruction, but also on the basis of available literature. By using the probability of occurrence of each taxon in a given pollen spectrum, it is possible to calculate an affinity index for the spectrum to the attribute considered. To overcome difficulties caused by pollen identification in low diversified pollen spectra, a co-occurrence concept has been used to give more information. Results The method has been validated on a set of 1327 modern surface samples by comparing the results to the major climatic and environmental variables that control the distribution of the vegetation. A reconstruction exercise on various characteristics of the plants was then carried out on a 6-ka dataset. This confirmed previous studies by showing a strong dominance of deciduous forest over most of Europe, related to a milder climate than at present in the north and a wetter and colder climate than at present in the south. By analysing the change in pollen/seed dispersion strategies and the light requirement, we show that the history of vegetation dynamics in relation to human influences can be assessed using this method. Main conclusions Our results show that the probabilistic method is an objective tool for pollen assemblage analysis. It allows reconstruction of various characteristics of the vegetation at the continental and global scale for periods and sites with significantly different climate conditions. This method can also be used to compare maps of vegetation attributes for the validation of the new generalized dynamic ecosystems models.
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| 7. |
- Ni, J, et al.
(author)
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Modelling the vegetation of China using the process-based equilibrium terrestrial biosphere model BIOME3
- 2000
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In: Global Ecology and Biogeography Letters. - : Wiley. - 0960-7447 .- 1466-822X. ; 9:6, s. 463-480
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Journal article (peer-reviewed)abstract
- 1 We model the potential vegetation and annual net primary production (NPP) of China on a 10' grid under the present climate using the processed-based equilibrium terrestrial biosphere model BIOME3. The simulated distribution of the vegetation was in general in good agreement with the potential natural vegetation based on a numerical comparison between the two maps using the DeltaV statistic (DeltaV = 0.23). Predicted and measured NPP were also similar, especially in terms of biome-averages. 2 A coupled ocean-atmosphere general circulation model including sulphate aerosols was used to drive a double greenhouse gas scenario for 2070-2099. Simulated vegetation maps from two different CO2 scenarios (340 and 500 p.p.m.v.) were compared to the baseline biome map using DeltaV. Climate change alone produced a large reduction in desert, alpine tundra and ice/polar desert, and a general pole-ward shift of the boreal, temperate deciduous, warm-temperate evergreen and tropical forest belts, a decline in boreal deciduous forest and the appearance of tropical deciduous forest. The inclusion of CO2 physiological effects led to a marked decrease in moist savannas and desert, a general decrease for grasslands and steppe, and disappearance of xeric woodland/scrub. Temperate deciduous broadleaved forest, however, shifted north to occupy nearly half the area of previously temperate mixed forest. 3 The impact of climate change and increasing CO2 is not only on biogeography, but also on potential NPP. The NPP values for most of the biomes in the scenarios with CO2 set at 340 p.p.m.v. and 500 p.p.m.v. are greater than those under the current climate, except for the temperate deciduous forest, temperate evergreen broadleaved forest, tropical rain forest, tropical seasonal forest, and xeric woodland/scrub biomes. Total vegetation and total carbon is simulated to increase significantly in the future climate scenario, both with and without the CO2 direct physiological effect. 4 Our results show that the global process-based equilibrium terrestrial biosphere model BIOME3 can be used successfully at a regional scale.
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| 8. |
- Xu, Chi, et al.
(author)
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Macroecological factors explain large-scale spatial population patterns of ancient agriculturalists
- 2015
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In: Global Ecology and Biogeography. - : Wiley. - 0960-7447 .- 1466-822X. ; 24:9, s. 1030-1039
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Journal article (peer-reviewed)abstract
- Aim: It has been well demonstrated that the large-scale distribution patterns of numerous species are driven by similar macroecological factors. However, understanding of this topic remains limited when applied to our own species. Here we take a large-scale look at ancient agriculturalist populations over the past two millennia. The main aim of this study was to test the hypothesis that the patterns of agriculturalist populations were shaped by relevant macroecological factors.Location: China.Methods: Using detailed historical census data, we reconstructed spatial patterns of human population density over 13 imperial dynasties in ancient China, which was dominated by agrarian societies. We used simultaneous autoregressive models to examine the population densities of agriculturalists in relation to climatic, topographic, edaphic and hydrological variables, together with the spatial structure of a concentration of population toward national capitals. The pure and shared effects of these variables and the population-concentration structure were decomposed using a variation partitioning procedure.Results: Spatial population patterns of ancient agriculturalists can be well modelled by climate, topography, soil properties and local hydrological systems. A plausible explanation is that by influencing crop yield these environmental factors essentially drive the distribution of agriculturalists. The population-concentration structure can also explain agriculturalist patterns to a considerable extent. This structure and those environmental factors have largely shared effects in simultaneously shaping these agriculturalist patterns.Main conclusions: While humans can effectively temper environmental constraints at small spatial scales, our results demonstrate that macroecological factors underpin the spatial patterns of humans at large scales. Macroecological constraints and their relative importance are found to be similar for humans and other species, suggesting that similar mechanisms are likely to underlie these macroecological patterns. Our findings have potential implications for the assessment of future responses of humans to global environmental changes.
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