Background: Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diver...Background: Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diversity are expected to accumulate over time. Here, I present findings from a 31-year-old tree diversity experiment(as of2018) in Japan.Results: I find that the net diversity effect on stand biomass increased linearly through time. The species mixture achieved 64% greater biomass than the average monoculture biomass 31 years after planting. The complementarity effect was positive and increased exponentially with time. The selection effect was negative and decreased exponentially with time. In the early stages(≤ 3 years), the positive complementarity effect was explained by enhanced growths of early-and mid-successional species in the mixture. Later on(≥ 15 years), it was explained by their increased survival rates owing to vertical spatial partitioning — i.e. alleviation of self-thinning via canopy stratification. The negative selection effect resulted from suppressed growths of late-successional species in the bottom layer.Conclusions: The experiment provides pioneering evidence that the positive impacts of diversity-driven spatial partitioning on forest biomass can accumulate over multiple decades. The results indicate that forest biomass production and carbon sequestration can be enhanced by multispecies afforestation strategies.展开更多
Background:The importance of biodiversity in maintaining multiple ecosystem functions has been widely accepted.However,the specific mechanisms affecting biodiversity and ecosystem multifunctionality(BEMF)relationships...Background:The importance of biodiversity in maintaining multiple ecosystem functions has been widely accepted.However,the specific mechanisms affecting biodiversity and ecosystem multifunctionality(BEMF)relationships in forests are largely unknown.This is particularly evident for the macroscale of a large forested landscape.Methods:Based on 412 one-tenth hectare field plots distributed over forested areas across northeastern China,we evaluated three alternative hypotheses explaining the relationships between BEMF,namely:niche complementarity,mass ratio,and vegetation quantity effect.We used Rao's quadratic entropy and community weighted mean trait values to quantify forest“biodiversity”.These two variables represent two complementary aspects of functional properties,which are in line with niche complementary and mass ratio effects,respectively.Results:Ecosystem multifunctionality was negatively associated with the community weighted mean values of acquisitive traits(a proxy of mass ratio effect).Rao's quadratic entropy(a proxy of niche complementarity)had no relationship with ecosystem multifunctionality.Higher stand biomass greatly increased ecosystem multifunctionality,which is in line with the vegetation quantity effect.Our results confirm that in the temperate forests of northeastern China,the relationship of BEMF was primarily affected by vegetation quantity,followed by mass ratio effects.Conclusions:The results of this study contribute to a better understanding of the main drivers of ecosystem multifunctionality in forest ecosystems.The results of this study provide additional evidence to support the vegetation quantity and mass ratio hypotheses in forest ecosystems.展开更多
Aims Although the net biodiversity effect(NE)can be statistically partitioned into complementarity and selection effects(CE and SE),there are different underlying mechanisms that can cause a certain partitioning.Our o...Aims Although the net biodiversity effect(NE)can be statistically partitioned into complementarity and selection effects(CE and SE),there are different underlying mechanisms that can cause a certain partitioning.Our objective was to assess the role of resource partitioning and species interactions as two important mechanisms that can bring about CEs by interspecific and intraspecific trait variation.Methods We measured tree height of 2493 living individuals in 57 plots and specific root length(SRL)on first-order roots of 368 of these individuals across different species richness levels(1,2,4,8 species)in a large-scale forest biodiversity and ecosystem functioning experiment in subtropical China(BEF-China)established in 2009.We describe the effects of resource partitioning between species by a fixed component of interspecific functional diversity(RaoQ)and further effects of species interactions by variable components of interspecific and intraspecific functional diversity(community weighted trait similarity and trait dissimilarity,CWS and CWD).Finally,we examined the relationships between biodiversity effects on stand-level tree height and functional diversity(RaoQ,CWS and CWD)in SRL using linear regression and assessed the relative importance of these three components of functional diversity in explaining the diversity effects.Important Findings Our results show that species richness significantly affected SRL in five and tree height in ten out of 16 species.A positive NE was generally brought about by a positive CE on stand-level tree height and related to high values of RaoQ and CWS in SRL.A positive CE was related to high values of all three components of root functional diversity(RaoQ,CWS and CWD).Our study suggests that both resource partitioning and species interactions are the underlying mechanisms of biodiversity effects on stand-level tree growth in subtropical forest.展开更多
Aims Diversity-productivity relationships among herbaceous species have mostly been studied in grasslands,while less is known about diversity effects among weedy species with a short life cycle.Methods We studied dive...Aims Diversity-productivity relationships among herbaceous species have mostly been studied in grasslands,while less is known about diversity effects among weedy species with a short life cycle.Methods We studied diversity-productivity relationships,shoot density,size and allometry in experimental communities of different species richness(one,three,six,and nine species),functional group number(one to three functional groups:grasses,small herbs and tall herbs)and functional group evenness(even and uneven number of species per functional group)based on a pool of nine arable weed species with a short life cycle in a 2-year experiment.Important Findings Higher species richness increased above-and belowground biomass production in both years of the experiment.Additive partitioning showed that positive selection effects increased with increasing species richness and functional group number,while positive complementarity effects were greater when tall herbs were present.Relative yield totals were larger than 1 across all species richness levels but did not increase with species richness,which is consistent with constant positive complementarity effects.Community biomass production and diversity effects increased in the second year of the experiment,when communities achieved greater shoot densities and average shoot sizes.At the community level,varying productivity was mainly attributable to variation in mean shoot sizes.Tall herbs reached greater observed/expected relative yields(=overyielding)due to increased shoot sizes,underyielding of small herbs was mainly attributable to decreased shoot sizes,while grasses partly compensated for reduced shoot sizes by increasing densities.Shifts in community-level density-size relationships and changes in shoot allometry in favour of greater height growth indicated that a greater biomass at a given density was due to increased dimensions of occupied canopy space.We conclude that diversity effects are also possible among short-lived arable weed species,but selection effects through sizes differences among species are key for positive species richness-productivity relationships.展开更多
Genotype diversity is an important component of biodiversity,and has potential positive effects on ecological processes,such as primary productivity.Recent studies suggest that crop cultivar mixtures can improve bioma...Genotype diversity is an important component of biodiversity,and has potential positive effects on ecological processes,such as primary productivity.Recent studies suggest that crop cultivar mixtures can improve biomass or yield,however,the generality and size of this effect,as well as the underlying mechanisms are unclear.We selected nine genotypes of spring wheat(Triticum aestivum L.),and tested monocultures(of one genotype)and mixtures(of nine genotypes)to verify whether the positive effect of genotype diversity could be observed.Meanwhile,we arranged two planting environments,real field and artificial pot conditions,to clarify how the effect of genotype diversity depends on environmental conditions.Results showed that the effect of genotype diversity was highly dependent on the planting environment;compared with monocultures,mixtures significantly improved aboveground biomass and grain yield of spring wheat in pots by 14.5%and 8.2%,respectively,while no improvements were observed in the field.In pots,positive complementarity effects dominated the positive net effect by offsetting negative sampling effects,while no significant diversity effects were observed in the field.The greater trait differences in pots were more favorable for resource-use complementarity and reducing intraspecific competition,which might be the main reason for the large positive complementary effect in pots.Our results suggest that increasing the biomass and grain yield of spring wheat by providing genotypic diversity was supported by specific ecological mechanisms and could be achievable.However,environmental conditions in actual production may limit its efficacy,and more extensive field experiments are thus needed to verify the effectiveness of genotype diversity.展开更多
Background:Current theories on biodiversity-carbon sequestration relationship describe biodiversity as an important factor influencing carbon storage,either through complementarity effect or by mass ratio effect.So fa...Background:Current theories on biodiversity-carbon sequestration relationship describe biodiversity as an important factor influencing carbon storage,either through complementarity effect or by mass ratio effect.So far,the expected form of biodiversity-carbon relationships in tropical ecosystems has not been known with certainty.Therefore,we explored the relationship between aboveground carbon stock and different biodiversity measurement indices(i.e.,species richness,species diversity,species evenness,and functional diversity)in different land cover types of Eastern Ethiopia.A total of 48 plots were established using stratified random sampling.Vegetation parameters such as diameter at breast height,diameter at stump height,tree height,and species type were recorded.Results:We found that the average aboveground carbon stock of the study area is 147.6±17.2 t ha^(−1)(mean,SE)across land cover types.Species richness,Shannon index,and functional diversity together explained 73.5%,61.4%,58.9%,and 52.0%of the variation in aboveground carbon storage in woodland,riparian forest,bushland,and farmland,respectively.Functional diversity was a significant predictor explaining the total aboveground carbon stocks(26.7%)across the land cover types.The effects of biodiversity on aboveground carbon storage were mediated by functional diversity and presence and dominance of species.This shows that both the selection effects and the niche complementarity are important for carbon storage.However,the impact of functional diversity effects(niche complementarity)was higher than that of functional dominance effects(selection effects).Conclusions:Implementation of protected area-based ecosystem conservation practices in the country seems feasible to mitigate climate change and Reducing Emissions from Deforestation and Forest Degradation(REDD+)programme should emphasize on biodiversity conservation.展开更多
Aims Biodiversity-ecosystem function experiments can test for causal relationships between planting diversity and community productivity.Planting diversity is routinely introduced as a design element in created wetlan...Aims Biodiversity-ecosystem function experiments can test for causal relationships between planting diversity and community productivity.Planting diversity is routinely introduced as a design element in created wetlands,yet substantive support for the finding that early diversity positively affects ecosystem functioning is lacking for wetlands.We conducted a 2-year diversity-productivity experiment using freshwater wetland mesocosms to investigate community biomass production as affected by planted macrophyte functional richness.Methods A richness gradient of macrophytes in four emergent wetland plant functional groups was established in freshwater mesocosms for two consecutive years.Species-specific aboveground morphological traits of plant size were measured at peak growth in both years;rooting depth was measured for each species in the second year.Aboveground biomass(AGB)and belowground biomass(BGB)were harvested after peak growth in the second year;first year AGB was estimated from morphological traits in constructed regression equations.Net richness effects(i.e.both complementarity effects and selection effects)were calculated using an additive partitioning method.Important Findings Species richness had a positive effect on community AGB relative to monocultures in the first year.In the second year,mean AGB was significantly reduced by competition in the most species-rich mixtures and all mixtures underyielded relative to the average monoculture.Competition for soil resources was weaker belowground,whereby root distribution at depths>20cm was reduced at the highest richness levels but overall BGB production was not affected.Changes in species biomass were strongly reflected by variation in species morphological traits,and species above and belowground performances were highly correlated.The obligate annual(Eleocharis obtusa),a dominant competitor,significantly contributed to the depression of perennial species’growth in the second growing season.To foster primary productivity with macrophyte richness in early successional communities of created wetlands where ruderal strategies are favored and competition may be stronger than species complementarity,unsystematic planting designs such as clustering the same or similar species could provide protection for some individuals.Additionally,engineering design elements fostering spatial or temporal environmental variability(e.g.microtopography)in newly created wetlands helps diversify the responses of wetland macrophyte species to their environment and could allow for greater complementarity in biomass production.展开更多
基金a Grant-in-Aid for Young Scientists B (No. 16 K18715)a JSPS Overseas Research Fellowship (No. 201860500) from the Japan Society for the Promotion of Science。
文摘Background: Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diversity are expected to accumulate over time. Here, I present findings from a 31-year-old tree diversity experiment(as of2018) in Japan.Results: I find that the net diversity effect on stand biomass increased linearly through time. The species mixture achieved 64% greater biomass than the average monoculture biomass 31 years after planting. The complementarity effect was positive and increased exponentially with time. The selection effect was negative and decreased exponentially with time. In the early stages(≤ 3 years), the positive complementarity effect was explained by enhanced growths of early-and mid-successional species in the mixture. Later on(≥ 15 years), it was explained by their increased survival rates owing to vertical spatial partitioning — i.e. alleviation of self-thinning via canopy stratification. The negative selection effect resulted from suppressed growths of late-successional species in the bottom layer.Conclusions: The experiment provides pioneering evidence that the positive impacts of diversity-driven spatial partitioning on forest biomass can accumulate over multiple decades. The results indicate that forest biomass production and carbon sequestration can be enhanced by multispecies afforestation strategies.
基金supported by the Program of National Natural Science Foundation of China(No.31971650)the Key Project of National Key Research and Development Plan(No.2017YFC0504005)the National Natural Science Foundation of China(No.31800362).
文摘Background:The importance of biodiversity in maintaining multiple ecosystem functions has been widely accepted.However,the specific mechanisms affecting biodiversity and ecosystem multifunctionality(BEMF)relationships in forests are largely unknown.This is particularly evident for the macroscale of a large forested landscape.Methods:Based on 412 one-tenth hectare field plots distributed over forested areas across northeastern China,we evaluated three alternative hypotheses explaining the relationships between BEMF,namely:niche complementarity,mass ratio,and vegetation quantity effect.We used Rao's quadratic entropy and community weighted mean trait values to quantify forest“biodiversity”.These two variables represent two complementary aspects of functional properties,which are in line with niche complementary and mass ratio effects,respectively.Results:Ecosystem multifunctionality was negatively associated with the community weighted mean values of acquisitive traits(a proxy of mass ratio effect).Rao's quadratic entropy(a proxy of niche complementarity)had no relationship with ecosystem multifunctionality.Higher stand biomass greatly increased ecosystem multifunctionality,which is in line with the vegetation quantity effect.Our results confirm that in the temperate forests of northeastern China,the relationship of BEMF was primarily affected by vegetation quantity,followed by mass ratio effects.Conclusions:The results of this study contribute to a better understanding of the main drivers of ecosystem multifunctionality in forest ecosystems.The results of this study provide additional evidence to support the vegetation quantity and mass ratio hypotheses in forest ecosystems.
基金funded by the National Natural Science Foundation of China(No.31300353)China Postdoctoral Science Foundation(No.2014M561089)+4 种基金Science and Technology Planning Project of Jiangxi Provincial Education Department(No.GJJ150384)the entire BEF-China research group for their supportfunded by the German Research Foundation(DFG FOR891)National Natural Science Foundation of China(NSFC)the Swiss National Science Foundation(SNSF).
文摘Aims Although the net biodiversity effect(NE)can be statistically partitioned into complementarity and selection effects(CE and SE),there are different underlying mechanisms that can cause a certain partitioning.Our objective was to assess the role of resource partitioning and species interactions as two important mechanisms that can bring about CEs by interspecific and intraspecific trait variation.Methods We measured tree height of 2493 living individuals in 57 plots and specific root length(SRL)on first-order roots of 368 of these individuals across different species richness levels(1,2,4,8 species)in a large-scale forest biodiversity and ecosystem functioning experiment in subtropical China(BEF-China)established in 2009.We describe the effects of resource partitioning between species by a fixed component of interspecific functional diversity(RaoQ)and further effects of species interactions by variable components of interspecific and intraspecific functional diversity(community weighted trait similarity and trait dissimilarity,CWS and CWD).Finally,we examined the relationships between biodiversity effects on stand-level tree height and functional diversity(RaoQ,CWS and CWD)in SRL using linear regression and assessed the relative importance of these three components of functional diversity in explaining the diversity effects.Important Findings Our results show that species richness significantly affected SRL in five and tree height in ten out of 16 species.A positive NE was generally brought about by a positive CE on stand-level tree height and related to high values of RaoQ and CWS in SRL.A positive CE was related to high values of all three components of root functional diversity(RaoQ,CWS and CWD).Our study suggests that both resource partitioning and species interactions are the underlying mechanisms of biodiversity effects on stand-level tree growth in subtropical forest.
文摘Aims Diversity-productivity relationships among herbaceous species have mostly been studied in grasslands,while less is known about diversity effects among weedy species with a short life cycle.Methods We studied diversity-productivity relationships,shoot density,size and allometry in experimental communities of different species richness(one,three,six,and nine species),functional group number(one to three functional groups:grasses,small herbs and tall herbs)and functional group evenness(even and uneven number of species per functional group)based on a pool of nine arable weed species with a short life cycle in a 2-year experiment.Important Findings Higher species richness increased above-and belowground biomass production in both years of the experiment.Additive partitioning showed that positive selection effects increased with increasing species richness and functional group number,while positive complementarity effects were greater when tall herbs were present.Relative yield totals were larger than 1 across all species richness levels but did not increase with species richness,which is consistent with constant positive complementarity effects.Community biomass production and diversity effects increased in the second year of the experiment,when communities achieved greater shoot densities and average shoot sizes.At the community level,varying productivity was mainly attributable to variation in mean shoot sizes.Tall herbs reached greater observed/expected relative yields(=overyielding)due to increased shoot sizes,underyielding of small herbs was mainly attributable to decreased shoot sizes,while grasses partly compensated for reduced shoot sizes by increasing densities.Shifts in community-level density-size relationships and changes in shoot allometry in favour of greater height growth indicated that a greater biomass at a given density was due to increased dimensions of occupied canopy space.We conclude that diversity effects are also possible among short-lived arable weed species,but selection effects through sizes differences among species are key for positive species richness-productivity relationships.
基金supported by the Gansu Provincial Fund for Distinguished Young Scholars(21JR7RA530)the National Natural Science Foundation of China(31670401)+1 种基金the‘111’Project(BP0719040)the Fundamental Research Funds for the Central Universities(lzujbky-2021-sp42).
文摘Genotype diversity is an important component of biodiversity,and has potential positive effects on ecological processes,such as primary productivity.Recent studies suggest that crop cultivar mixtures can improve biomass or yield,however,the generality and size of this effect,as well as the underlying mechanisms are unclear.We selected nine genotypes of spring wheat(Triticum aestivum L.),and tested monocultures(of one genotype)and mixtures(of nine genotypes)to verify whether the positive effect of genotype diversity could be observed.Meanwhile,we arranged two planting environments,real field and artificial pot conditions,to clarify how the effect of genotype diversity depends on environmental conditions.Results showed that the effect of genotype diversity was highly dependent on the planting environment;compared with monocultures,mixtures significantly improved aboveground biomass and grain yield of spring wheat in pots by 14.5%and 8.2%,respectively,while no improvements were observed in the field.In pots,positive complementarity effects dominated the positive net effect by offsetting negative sampling effects,while no significant diversity effects were observed in the field.The greater trait differences in pots were more favorable for resource-use complementarity and reducing intraspecific competition,which might be the main reason for the large positive complementary effect in pots.Our results suggest that increasing the biomass and grain yield of spring wheat by providing genotypic diversity was supported by specific ecological mechanisms and could be achievable.However,environmental conditions in actual production may limit its efficacy,and more extensive field experiments are thus needed to verify the effectiveness of genotype diversity.
文摘Background:Current theories on biodiversity-carbon sequestration relationship describe biodiversity as an important factor influencing carbon storage,either through complementarity effect or by mass ratio effect.So far,the expected form of biodiversity-carbon relationships in tropical ecosystems has not been known with certainty.Therefore,we explored the relationship between aboveground carbon stock and different biodiversity measurement indices(i.e.,species richness,species diversity,species evenness,and functional diversity)in different land cover types of Eastern Ethiopia.A total of 48 plots were established using stratified random sampling.Vegetation parameters such as diameter at breast height,diameter at stump height,tree height,and species type were recorded.Results:We found that the average aboveground carbon stock of the study area is 147.6±17.2 t ha^(−1)(mean,SE)across land cover types.Species richness,Shannon index,and functional diversity together explained 73.5%,61.4%,58.9%,and 52.0%of the variation in aboveground carbon storage in woodland,riparian forest,bushland,and farmland,respectively.Functional diversity was a significant predictor explaining the total aboveground carbon stocks(26.7%)across the land cover types.The effects of biodiversity on aboveground carbon storage were mediated by functional diversity and presence and dominance of species.This shows that both the selection effects and the niche complementarity are important for carbon storage.However,the impact of functional diversity effects(niche complementarity)was higher than that of functional dominance effects(selection effects).Conclusions:Implementation of protected area-based ecosystem conservation practices in the country seems feasible to mitigate climate change and Reducing Emissions from Deforestation and Forest Degradation(REDD+)programme should emphasize on biodiversity conservation.
基金Thomas F.and Kate Miller Jeffress Memorial Trust Fund(222101)Virginia Academy of Sciences small project research grantthe George Mason University Patriot Green Fund.
文摘Aims Biodiversity-ecosystem function experiments can test for causal relationships between planting diversity and community productivity.Planting diversity is routinely introduced as a design element in created wetlands,yet substantive support for the finding that early diversity positively affects ecosystem functioning is lacking for wetlands.We conducted a 2-year diversity-productivity experiment using freshwater wetland mesocosms to investigate community biomass production as affected by planted macrophyte functional richness.Methods A richness gradient of macrophytes in four emergent wetland plant functional groups was established in freshwater mesocosms for two consecutive years.Species-specific aboveground morphological traits of plant size were measured at peak growth in both years;rooting depth was measured for each species in the second year.Aboveground biomass(AGB)and belowground biomass(BGB)were harvested after peak growth in the second year;first year AGB was estimated from morphological traits in constructed regression equations.Net richness effects(i.e.both complementarity effects and selection effects)were calculated using an additive partitioning method.Important Findings Species richness had a positive effect on community AGB relative to monocultures in the first year.In the second year,mean AGB was significantly reduced by competition in the most species-rich mixtures and all mixtures underyielded relative to the average monoculture.Competition for soil resources was weaker belowground,whereby root distribution at depths>20cm was reduced at the highest richness levels but overall BGB production was not affected.Changes in species biomass were strongly reflected by variation in species morphological traits,and species above and belowground performances were highly correlated.The obligate annual(Eleocharis obtusa),a dominant competitor,significantly contributed to the depression of perennial species’growth in the second growing season.To foster primary productivity with macrophyte richness in early successional communities of created wetlands where ruderal strategies are favored and competition may be stronger than species complementarity,unsystematic planting designs such as clustering the same or similar species could provide protection for some individuals.Additionally,engineering design elements fostering spatial or temporal environmental variability(e.g.microtopography)in newly created wetlands helps diversify the responses of wetland macrophyte species to their environment and could allow for greater complementarity in biomass production.
