Background： Tropical forests play an important role in the global carbon（C） cycle.However, tropical montane forests have been studied less than tropical lowland forests, and their role in carbon storage is not well...Background： Tropical forests play an important role in the global carbon（C） cycle.However, tropical montane forests have been studied less than tropical lowland forests, and their role in carbon storage is not well understood.Montane forests are highly endangered due to logging, land-use and climate change.Our objective was to analyse how the carbon balance changes during forest succession.Methods： In this study, we used a method to estimate local carbon balances that combined forest inventory data with process-based forest models.We utilised such a forest model to study the carbon balance of a tropical montane forest in South Ecuador, comparing two topographical slope positions（ravines and lower slopes vs upper slopes and ridges）.Results： The simulation results showed that the forest acts as a carbon sink with a maximum net ecosystem exchange（NEE） of 9.3 Mg C？（ha？yr）-1during its early successional stage（0–100 years）.In the late successional stage, the simulated NEE fluctuated around zero and had a variation of 0.77 Mg C？（ha？yr）–1.The simulated variability of the NEE was within the range of the field data.We discovered several forest attributes（e.g., basal area or the relative amount of pioneer trees） that can serve as predictors for NEE for young forest stands（0–100 years） but not for those in the late successional stage（500–1,000 years）.In case of young forest stands these correlations are high, especially between stand basal area and NEE.Conclusion： In this study, we used an Ecuadorian study site as an example of how to successfully link a forest model with forest inventory data, for estimating stem-diameter distributions, biomass and aboveground net primary productivity.To conclude, this study shows that process-based forest models can be used to investigate the carbon balance of tropical montane forests.With this model it is possible to find hidden relationships between forest attributes and forest carbon fluxes.These relationships promote a better understanding of the role of tropical montane forests in the context of global carbon cycle, which in future will become more relevant to a society under global change.展开更多
Ecological interactions of species and thus their spatial pat- terns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locat...Ecological interactions of species and thus their spatial pat- terns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locations of tree individuals from two 1-ha tropicalforest plots in Vietnam. We analyzed the effect of environmental heterogeneity on tree distributions; spatial distribution patterns of dominant species; inter-specific associations; and conspecific associations between life stages. Our analyses showed that： environmental conditions were homo- geneous at plot 1 but heterogeneous at plot 2; in both plots, all six domi- nant species were aggregated at various scales up to 30 m, and tree spe- cies were aggregated at larger scales in the homogeneous site than in the heterogeneous site; attraction between pairs of species was remarkably higher at the homogeneous site while negative associations were more frequent in the heterogeneous site; some species, H. kurzii, T. ilicifolia （homogeneous plot） and D. sylvatica, S. wightianum （heterogeneous plot） showed a lack of early life-stage individuals near conspecific adults. Moreover, additional clustering of young individuals was independent from conspecific adults, except D. sylvatica in both sites. These findings are consistent with the Janzen-ConneU hypothesis. Overall, habitat het- erogeneity influences spatial patterns and inter-specific associations of the tree species and evidences of self-thinning are shown in most species.展开更多
Background Krill(Euphausia superba)and salps(Salpa thompsoni)are key macrozooplankton grazers in the Southern Ocean ecosystem.However,due to differing habitat requirements,both species previously exhibited little spat...Background Krill(Euphausia superba)and salps(Salpa thompsoni)are key macrozooplankton grazers in the Southern Ocean ecosystem.However,due to differing habitat requirements,both species previously exhibited little spatial overlap.With ongoing climate change-induced seawater temperature increase and regional sea ice loss,salps can now extend their spatial distribution into historically krill-dominated areas and increase rapidly due to asexual reproduction when environmental conditions are favorable.Understanding the potential effects on krill is crucial,since krill is a species of exceptional trophic significance in the Southern Ocean food web.Negative impacts on krill could trigger cascading effects on its predators and prey.To address this question,we combined two individual-based models on salps and krill,which describe the whole life cycle of salp individuals and the dynamic energy budget of individual krill.The resulting new model PEKRIS(PErformance of KRIll vs.Salps)simulates a krill population for 100 years under varying chlorophyll-a concentrations in the presence or absence of salps.Results All of the investigated krill population properties(abundance,mean length,and yearly egg production)were significantly impacted by the presence of salps.On the other hand,salp density was not impacted if krill were present.The medians of krill population properties deviated during variable maximum chlorophyll-a density per year when salps were introduced by−99.9%(−234 individuals per 1000 m3)for krill density,−100%(−22,062 eggs per 1000 m3)for krill eggs and−0.9%(−0.3 mm)for mean length of krill.Conclusions If both species compete for the same food resource in a closed space,salps seem to inhibit krill populations.Further simulation studies should investigate whether this effect prevails if different phytoplankton sizes and consumption preferences of krill are implemented.Furthermore,direct predation of the two species or consumption of krill fecal pellets by salps could change the impact size of the food competition.展开更多
Aims Topography has long been recognized as an important factor in shaping species distributions.Many studies revealed that species may show species-habitat associations.However,few studies inves-tigate how species as...Aims Topography has long been recognized as an important factor in shaping species distributions.Many studies revealed that species may show species-habitat associations.However,few studies inves-tigate how species assemblages are associated with local habitats,and it still remains unclear how the community-habitat associa-tions vary with species abundance class and life stage.In this study,we analyzed the community-habitat associations in a subtropical montane forest.Methods The fully mapped 25-ha(500×500 m)forest plot is located in Badagongshan Nature Reserve in Hunan Province,Central China.It was divided into 625(20×20 m)quadrats.Habitat types were classified by multivariate regression tree analyses that cluster areas with similar species composition according to the topographic characteristics.Indicator species analysis was used to identify the most important species for structuring species assemblages.We also compared the community-habitat associations for two levels of species abundances(i.e.abundant and rare)and three different life stages(i.e.saplings,juveniles and adults),while accounting for sample size effects.Important Findings The Badagongshan plot was divided into five distinct habitat types,which explained 34.7%of the variance in tree species composi-tion.Even with sample size taken into account,community-habi-tat associations for rare species were much weaker than those for abundant species.Also when accounting for sample size,very small differences were found in the variance explained by topography for the three life stages.Indicator species of habitat types were mainly abundant species,and nearly all adult stage indicator species were also indicators in juvenile and sapling stages.Our study manifested that topographical habitat filtering was important in shaping over-all local species compositions.However,habitat filtering was not important in shaping rare species’distributions in this forest.The community-habitat association patterns in this forest were mainly shaped by abundant species.In addition,during the transitions from saplings to juveniles,and from juveniles to adults,the relative importance of habitat filtering was very weak.展开更多
Aims Phenotypic optimality models neglect genetics.However,especially when heterozygous genotypes are fittest,evolving allele,genotype and phenotype frequencies may not correspond to predicted optima.This was not prev...Aims Phenotypic optimality models neglect genetics.However,especially when heterozygous genotypes are fittest,evolving allele,genotype and phenotype frequencies may not correspond to predicted optima.This was not previously addressed for organisms with complex life histories.Methods Therefore,we modelled the evolution of a fitness-relevant trait of clonal plants,stolon internode length.We explored the likely case of an asymmetric unimodal fitness profile with three model types.In constant selection models(CSMs),which are gametic,but not spatially explicit,evolving allele frequencies in the one-locus and fiveloci cases did not correspond to optimum stolon internode length predicted by the spatially explicit,but not gametic,phenotypic model.This deviation was due to the asymmetry of the fitness profile.Gametic,spatially explicit individual-based(SEIB)modeling allowed us relaxing the CSM assumptions of constant selection with exclusively sexual reproduction.Important findings For entirely vegetative or sexual reproduction,predictions of the gametic SEIB model were close to the ones of spatially explicit nongametic phenotypic models,but for mixed modes of reproduction they approximated those of gametic,not spatially explicit CSMs.Thus,in contrast to gametic SEIB models,phenotypic models and,especially for few loci,also CSMs can be very misleading.We conclude that the evolution of traits governed by few quantitative trait loci appears hardly predictable by simple models,that genetic algorithms aiming at technical optimization may actually miss the optimum and that selection may lead to loci with smaller effects in derived compared with ancestral lines.展开更多
Global,fast and accessible monitoring of biodiversity is one of the main pillars of the efforts undertaken in order to revert it loss.The Group on Earth Observations Biodiversity Observation Network(GEO-BON)provided a...Global,fast and accessible monitoring of biodiversity is one of the main pillars of the efforts undertaken in order to revert it loss.The Group on Earth Observations Biodiversity Observation Network(GEO-BON)provided an expert-based definition of the biological properties that should be monitored,the Essential Biodiversity Variables(EBVs).Initiatives to provide indicators for EBVs rely on global,freely available remote sensing(RS)products in combination with empirical models and field data,and are invaluable for decision making.In this study,we provide alternatives for the expansion and improvement of the EBV indicators,by suggesting current and future data from the European Space Agencýs COPERNICUS and explore the potential of RS-integrated Dynamic Global Vegetation Models(DGVMs)for the estimation of EBVs.Our review found that mainly due to the inclusion of the Sentinel constellation,Copernicus products have similar or superior potential for EBV indicator estimation in relation to their NASA counterparts.DGVMs simulate the ecosystem level EBVs(ecosystem function and structure),and when integrated with remote sensing data have great potential to not only offer improved estimation of current states but to provide projection of ecosystem impacts.We suggest that focus on producing EBV relevant outputs should be a priority within the research community,to support biodiversity preservation efforts.展开更多
基金financial support of the German Research Foundation(DFG,Research Unit 816)for initializing the forest plots and the plot census as well as a first model parameterisationthe Helmholtz Alliance:Remote Sensing and Earth System Dynamics for financing the work on the further parameterisation of the model and analysis of the data
文摘Background： Tropical forests play an important role in the global carbon（C） cycle.However, tropical montane forests have been studied less than tropical lowland forests, and their role in carbon storage is not well understood.Montane forests are highly endangered due to logging, land-use and climate change.Our objective was to analyse how the carbon balance changes during forest succession.Methods： In this study, we used a method to estimate local carbon balances that combined forest inventory data with process-based forest models.We utilised such a forest model to study the carbon balance of a tropical montane forest in South Ecuador, comparing two topographical slope positions（ravines and lower slopes vs upper slopes and ridges）.Results： The simulation results showed that the forest acts as a carbon sink with a maximum net ecosystem exchange（NEE） of 9.3 Mg C？（ha？yr）-1during its early successional stage（0–100 years）.In the late successional stage, the simulated NEE fluctuated around zero and had a variation of 0.77 Mg C？（ha？yr）–1.The simulated variability of the NEE was within the range of the field data.We discovered several forest attributes（e.g., basal area or the relative amount of pioneer trees） that can serve as predictors for NEE for young forest stands（0–100 years） but not for those in the late successional stage（500–1,000 years）.In case of young forest stands these correlations are high, especially between stand basal area and NEE.Conclusion： In this study, we used an Ecuadorian study site as an example of how to successfully link a forest model with forest inventory data, for estimating stem-diameter distributions, biomass and aboveground net primary productivity.To conclude, this study shows that process-based forest models can be used to investigate the carbon balance of tropical montane forests.With this model it is possible to find hidden relationships between forest attributes and forest carbon fluxes.These relationships promote a better understanding of the role of tropical montane forests in the context of global carbon cycle, which in future will become more relevant to a society under global change.
基金supported with funds from the Ministry of Education and Training of Vietnam
文摘Ecological interactions of species and thus their spatial pat- terns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locations of tree individuals from two 1-ha tropicalforest plots in Vietnam. We analyzed the effect of environmental heterogeneity on tree distributions; spatial distribution patterns of dominant species; inter-specific associations; and conspecific associations between life stages. Our analyses showed that： environmental conditions were homo- geneous at plot 1 but heterogeneous at plot 2; in both plots, all six domi- nant species were aggregated at various scales up to 30 m, and tree spe- cies were aggregated at larger scales in the homogeneous site than in the heterogeneous site; attraction between pairs of species was remarkably higher at the homogeneous site while negative associations were more frequent in the heterogeneous site; some species, H. kurzii, T. ilicifolia （homogeneous plot） and D. sylvatica, S. wightianum （heterogeneous plot） showed a lack of early life-stage individuals near conspecific adults. Moreover, additional clustering of young individuals was independent from conspecific adults, except D. sylvatica in both sites. These findings are consistent with the Janzen-ConneU hypothesis. Overall, habitat het- erogeneity influences spatial patterns and inter-specific associations of the tree species and evidences of self-thinning are shown in most species.
基金Open Access funding enabled and organized by Projekt DEALThis work was supported by the Federal Ministry of Education and Research of Germany(BMBF,Grant number 03F0828B).
文摘Background Krill(Euphausia superba)and salps(Salpa thompsoni)are key macrozooplankton grazers in the Southern Ocean ecosystem.However,due to differing habitat requirements,both species previously exhibited little spatial overlap.With ongoing climate change-induced seawater temperature increase and regional sea ice loss,salps can now extend their spatial distribution into historically krill-dominated areas and increase rapidly due to asexual reproduction when environmental conditions are favorable.Understanding the potential effects on krill is crucial,since krill is a species of exceptional trophic significance in the Southern Ocean food web.Negative impacts on krill could trigger cascading effects on its predators and prey.To address this question,we combined two individual-based models on salps and krill,which describe the whole life cycle of salp individuals and the dynamic energy budget of individual krill.The resulting new model PEKRIS(PErformance of KRIll vs.Salps)simulates a krill population for 100 years under varying chlorophyll-a concentrations in the presence or absence of salps.Results All of the investigated krill population properties(abundance,mean length,and yearly egg production)were significantly impacted by the presence of salps.On the other hand,salp density was not impacted if krill were present.The medians of krill population properties deviated during variable maximum chlorophyll-a density per year when salps were introduced by−99.9%(−234 individuals per 1000 m3)for krill density,−100%(−22,062 eggs per 1000 m3)for krill eggs and−0.9%(−0.3 mm)for mean length of krill.Conclusions If both species compete for the same food resource in a closed space,salps seem to inhibit krill populations.Further simulation studies should investigate whether this effect prevails if different phytoplankton sizes and consumption preferences of krill are implemented.Furthermore,direct predation of the two species or consumption of krill fecal pellets by salps could change the impact size of the food competition.
基金National Natural Science Foundation of China(31270562,30900178,31200329 and 31500337)Key Laboratory of Aquatic Botany and Watershed Ecology,CAS(Y455432J02)the Chinese Forest Biodiversity Monitoring Network(29200931131101919).
文摘Aims Topography has long been recognized as an important factor in shaping species distributions.Many studies revealed that species may show species-habitat associations.However,few studies inves-tigate how species assemblages are associated with local habitats,and it still remains unclear how the community-habitat associa-tions vary with species abundance class and life stage.In this study,we analyzed the community-habitat associations in a subtropical montane forest.Methods The fully mapped 25-ha(500×500 m)forest plot is located in Badagongshan Nature Reserve in Hunan Province,Central China.It was divided into 625(20×20 m)quadrats.Habitat types were classified by multivariate regression tree analyses that cluster areas with similar species composition according to the topographic characteristics.Indicator species analysis was used to identify the most important species for structuring species assemblages.We also compared the community-habitat associations for two levels of species abundances(i.e.abundant and rare)and three different life stages(i.e.saplings,juveniles and adults),while accounting for sample size effects.Important Findings The Badagongshan plot was divided into five distinct habitat types,which explained 34.7%of the variance in tree species composi-tion.Even with sample size taken into account,community-habi-tat associations for rare species were much weaker than those for abundant species.Also when accounting for sample size,very small differences were found in the variance explained by topography for the three life stages.Indicator species of habitat types were mainly abundant species,and nearly all adult stage indicator species were also indicators in juvenile and sapling stages.Our study manifested that topographical habitat filtering was important in shaping over-all local species compositions.However,habitat filtering was not important in shaping rare species’distributions in this forest.The community-habitat association patterns in this forest were mainly shaped by abundant species.In addition,during the transitions from saplings to juveniles,and from juveniles to adults,the relative importance of habitat filtering was very weak.
文摘Aims Phenotypic optimality models neglect genetics.However,especially when heterozygous genotypes are fittest,evolving allele,genotype and phenotype frequencies may not correspond to predicted optima.This was not previously addressed for organisms with complex life histories.Methods Therefore,we modelled the evolution of a fitness-relevant trait of clonal plants,stolon internode length.We explored the likely case of an asymmetric unimodal fitness profile with three model types.In constant selection models(CSMs),which are gametic,but not spatially explicit,evolving allele frequencies in the one-locus and fiveloci cases did not correspond to optimum stolon internode length predicted by the spatially explicit,but not gametic,phenotypic model.This deviation was due to the asymmetry of the fitness profile.Gametic,spatially explicit individual-based(SEIB)modeling allowed us relaxing the CSM assumptions of constant selection with exclusively sexual reproduction.Important findings For entirely vegetative or sexual reproduction,predictions of the gametic SEIB model were close to the ones of spatially explicit nongametic phenotypic models,but for mixed modes of reproduction they approximated those of gametic,not spatially explicit CSMs.Thus,in contrast to gametic SEIB models,phenotypic models and,especially for few loci,also CSMs can be very misleading.We conclude that the evolution of traits governed by few quantitative trait loci appears hardly predictable by simple models,that genetic algorithms aiming at technical optimization may actually miss the optimum and that selection may lead to loci with smaller effects in derived compared with ancestral lines.
基金The authors would like to acknowledge the European Commission‘Horizon 2020 Program’that funded ERA-PLANET/GEOEssential(Grant Agreement no.689443)project.H2020 Societal Challenges.
文摘Global,fast and accessible monitoring of biodiversity is one of the main pillars of the efforts undertaken in order to revert it loss.The Group on Earth Observations Biodiversity Observation Network(GEO-BON)provided an expert-based definition of the biological properties that should be monitored,the Essential Biodiversity Variables(EBVs).Initiatives to provide indicators for EBVs rely on global,freely available remote sensing(RS)products in combination with empirical models and field data,and are invaluable for decision making.In this study,we provide alternatives for the expansion and improvement of the EBV indicators,by suggesting current and future data from the European Space Agencýs COPERNICUS and explore the potential of RS-integrated Dynamic Global Vegetation Models(DGVMs)for the estimation of EBVs.Our review found that mainly due to the inclusion of the Sentinel constellation,Copernicus products have similar or superior potential for EBV indicator estimation in relation to their NASA counterparts.DGVMs simulate the ecosystem level EBVs(ecosystem function and structure),and when integrated with remote sensing data have great potential to not only offer improved estimation of current states but to provide projection of ecosystem impacts.We suggest that focus on producing EBV relevant outputs should be a priority within the research community,to support biodiversity preservation efforts.
