Aims A plant has a limited amount of resources at any time and it allo-cates them to different structures.in spite of the large number of previous studies on allocation patterns within single species,knowledge of gene...Aims A plant has a limited amount of resources at any time and it allo-cates them to different structures.in spite of the large number of previous studies on allocation patterns within single species,knowledge of general patterns in species allocation is still very limited.This is because each study was done in different condi-tions using different methodology,making generalization dif-ficult.We investigate intraspecific above-versus below-ground biomass allocation among individuals across a spectrum of dry-grassland plant species at two different developmental stages and ask whether allocation is age-and species specific,and whether differences among species can be explained by their life-history traits and phylogeny.Methods We collected data on above-and below-ground biomass of seedlings and adult plants of 20 species from a common garden experiment.We analysed data on shoot-root biomass allocation allometrically and studied the relationship between the allometric exponents(slopes on log-log scale),species life-history traits and phylogenetic distances.Important Findings We found isometric as well as allometric patterns of biomass alloca-tion in the studied species.Seedlings and adult individuals of more than half of the species differed in their above-versus below-ground biomass allometric exponents.Seedlings and adult individuals of the remaining species differed in their allometric coefficients(inter-cepts).Annual species generally allocated proportionally more to above-than below-ground biomass as seedlings than as adults,whereas perennial species showed the opposite pattern.Plant life-history traits,such as plant life span,age of first flowering,month in which the species begin flowering and specific leaf area were much more important in explaining differences in shoot-root allometry among species than were phylogenetic relationships.This suggests that allocation patterns vary greatly among closely related species but can be predicted based on species life-history traits.展开更多
Aims There is much evidence that plant competition below ground is size symmetric,i.e.that competing plants share contested resources in proportion to their sizes.Several researchers have hypothesized that a patchy di...Aims There is much evidence that plant competition below ground is size symmetric,i.e.that competing plants share contested resources in proportion to their sizes.Several researchers have hypothesized that a patchy distribution of soil nutrients could result in size-asymmetric root competition.We tested this hypothesis.Methods In a greenhouse experiment,Triticum aestivum(wheat)individ-uals of different initial sizes were grown alone or with below-ground competition from one neighbour,in 1 m tall,narrow containers in a nitrogen-poor field soil with(i)no added nitro-gen,(ii)nitrogen fertilizer mixed into the upper 50 cm,and(iii)the same amount of fertilizer mixed into a 20-30 cm deep layer.We measured total leaf length throughout the experiment,and above-ground biomass and nitrogen concentration at harvest.We also measured root depth and frequency over time in a subset of containers.Important Findings Competing plants were half the size of non-competing plants,meaning that root competition was very strong.Root competition was size-asym-metric to some degree in all soil treatments.Neighbours larger than the target plant showed a greater per-unit-size effect on target growth than neighbours smaller than the target.Size variation increased over time for competing individuals,but decreased for non-competing pairs.Contrary to expectations,the presence of a high-nutrient patch reduced the strength and size asymmetry of competition temporarily.Size asym-metry in poor,deep soils may result from directionality in resource interception as roots compete for limited nutrients by growing deeper into soil layers that have not yet been exploited.Root competition can be size asymmetric,but not to the same degree as competition for light.展开更多
Aims The community succession theory is much debated in ecology.We studied succession on Zokor rodent mounds on the Tibetan Plateau to address several fundamental questions,among them:(i)During secondary succession,do...Aims The community succession theory is much debated in ecology.We studied succession on Zokor rodent mounds on the Tibetan Plateau to address several fundamental questions,among them:(i)During secondary succession,does the community composition converge towards one community state or multiple states depending on the initial colonization?(ii)Do mound communities located in different background communities exhibit different assembly trajectories?Methods In a sub-alpine meadow,we investigated a total of 80 mound com-munities at several successional stages in three different background communities resulting from different management histories and compared their changes in species composition.The distribution of plant communities over time was analyzed with quantitative clas-sification and ordination methods.The co-occurrence patterns of species were evaluated at each successional stage,and the degree of convergence/divergence among communities was obtained by calculating two beta-diversity indices.Important Findings During secondary succession,species richness of mound com-munities changed over time,and this change was dependent on the background community.Five life-form groups exhibited different dynamic patterns in species richness and plant cover.Community composition and the degree of species co-occur-rence between communities increased over time since disturb-ance.There was much variation in species composition at earlier stages of succession,but communities on older mounds became more similar to each other and to their surrounding vegetation over the course of secondary succession.Post-disturbance suc-cession of Zokor mound communities transitioned from‘multiple alternative states’to‘background-based deterministic commu-nity assembly’over time.Tradeoffs between competition and colonization,as well as the characteristics of different life-forms and mass effects within a limited species pool are the mecha-nisms responsible for convergence of mound communities.展开更多
Aims We present an improved model for the growth of individuals in plant populations experiencing competition.Methods Individuals grow sigmoidally according to the Birch model,which is similar to the more commonly use...Aims We present an improved model for the growth of individuals in plant populations experiencing competition.Methods Individuals grow sigmoidally according to the Birch model,which is similar to the more commonly used Richards model,but has the advantage that initial plant growth is always exponential.The individual plant growth models are coupled so that there is a maximum total biomass for the population.The effects of size-asymmetric competition are modeled with a parameter that reflects the size advantage that larger individual have over smaller individuals.We fit the model to data on individual growth in crowded populations of Chenopodium album.Important Findings When individual plant growth curves were not coupled,there was a negative or no correlation between initial growth rate and final size,suggesting that competitive interactions were more important in determining final plant size than were plants’initial growth rates.The coupled growth equations fit the data better than individual,uncoupled growth models,even though the number of estimated parameters in the coupled competitive growth model was far fewer,indicating the importance of modeling competition and the degree of size-asymmetric growth explicitly.A quantitative understanding of stand development in terms of the growth of individuals,as altered by competition,is within reach.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.32101235 (R.C.)Basic Research Program of Shanxi Province under Grant No.20210302124141 (R.C.)+1 种基金Science Foundation of Zhejiang Sci-Tech University under Grant No.22092034-Y (C.T.)Microsoft AI for Earth (C.T.).
基金This study was supported by the Charles University in Prague,project GA UK No.658313.
文摘Aims A plant has a limited amount of resources at any time and it allo-cates them to different structures.in spite of the large number of previous studies on allocation patterns within single species,knowledge of general patterns in species allocation is still very limited.This is because each study was done in different condi-tions using different methodology,making generalization dif-ficult.We investigate intraspecific above-versus below-ground biomass allocation among individuals across a spectrum of dry-grassland plant species at two different developmental stages and ask whether allocation is age-and species specific,and whether differences among species can be explained by their life-history traits and phylogeny.Methods We collected data on above-and below-ground biomass of seedlings and adult plants of 20 species from a common garden experiment.We analysed data on shoot-root biomass allocation allometrically and studied the relationship between the allometric exponents(slopes on log-log scale),species life-history traits and phylogenetic distances.Important Findings We found isometric as well as allometric patterns of biomass alloca-tion in the studied species.Seedlings and adult individuals of more than half of the species differed in their above-versus below-ground biomass allometric exponents.Seedlings and adult individuals of the remaining species differed in their allometric coefficients(inter-cepts).Annual species generally allocated proportionally more to above-than below-ground biomass as seedlings than as adults,whereas perennial species showed the opposite pattern.Plant life-history traits,such as plant life span,age of first flowering,month in which the species begin flowering and specific leaf area were much more important in explaining differences in shoot-root allometry among species than were phylogenetic relationships.This suggests that allocation patterns vary greatly among closely related species but can be predicted based on species life-history traits.
文摘Aims There is much evidence that plant competition below ground is size symmetric,i.e.that competing plants share contested resources in proportion to their sizes.Several researchers have hypothesized that a patchy distribution of soil nutrients could result in size-asymmetric root competition.We tested this hypothesis.Methods In a greenhouse experiment,Triticum aestivum(wheat)individ-uals of different initial sizes were grown alone or with below-ground competition from one neighbour,in 1 m tall,narrow containers in a nitrogen-poor field soil with(i)no added nitro-gen,(ii)nitrogen fertilizer mixed into the upper 50 cm,and(iii)the same amount of fertilizer mixed into a 20-30 cm deep layer.We measured total leaf length throughout the experiment,and above-ground biomass and nitrogen concentration at harvest.We also measured root depth and frequency over time in a subset of containers.Important Findings Competing plants were half the size of non-competing plants,meaning that root competition was very strong.Root competition was size-asym-metric to some degree in all soil treatments.Neighbours larger than the target plant showed a greater per-unit-size effect on target growth than neighbours smaller than the target.Size variation increased over time for competing individuals,but decreased for non-competing pairs.Contrary to expectations,the presence of a high-nutrient patch reduced the strength and size asymmetry of competition temporarily.Size asym-metry in poor,deep soils may result from directionality in resource interception as roots compete for limited nutrients by growing deeper into soil layers that have not yet been exploited.Root competition can be size asymmetric,but not to the same degree as competition for light.
基金Fund for Zokor Experiment:National Natural Science Foundation of China(No.31601984,41101524)Fundamental Research Funds for the Central Universities(lzujbky-2012-108,lzujbky-2015-191)the Special Fund for Agro-scientific Research in the Public Interest(No.201203006).
文摘Aims The community succession theory is much debated in ecology.We studied succession on Zokor rodent mounds on the Tibetan Plateau to address several fundamental questions,among them:(i)During secondary succession,does the community composition converge towards one community state or multiple states depending on the initial colonization?(ii)Do mound communities located in different background communities exhibit different assembly trajectories?Methods In a sub-alpine meadow,we investigated a total of 80 mound com-munities at several successional stages in three different background communities resulting from different management histories and compared their changes in species composition.The distribution of plant communities over time was analyzed with quantitative clas-sification and ordination methods.The co-occurrence patterns of species were evaluated at each successional stage,and the degree of convergence/divergence among communities was obtained by calculating two beta-diversity indices.Important Findings During secondary succession,species richness of mound com-munities changed over time,and this change was dependent on the background community.Five life-form groups exhibited different dynamic patterns in species richness and plant cover.Community composition and the degree of species co-occur-rence between communities increased over time since disturb-ance.There was much variation in species composition at earlier stages of succession,but communities on older mounds became more similar to each other and to their surrounding vegetation over the course of secondary succession.Post-disturbance suc-cession of Zokor mound communities transitioned from‘multiple alternative states’to‘background-based deterministic commu-nity assembly’over time.Tradeoffs between competition and colonization,as well as the characteristics of different life-forms and mass effects within a limited species pool are the mecha-nisms responsible for convergence of mound communities.
基金supported,in part,by a Sabbatical Fellowship to J.W.from the National Center for Ecological Analysis and Synthesis,a Center funded by NSF(Grant#DEB-0553768)the University of California,Santa Barbara,and the State of California.
文摘Aims We present an improved model for the growth of individuals in plant populations experiencing competition.Methods Individuals grow sigmoidally according to the Birch model,which is similar to the more commonly used Richards model,but has the advantage that initial plant growth is always exponential.The individual plant growth models are coupled so that there is a maximum total biomass for the population.The effects of size-asymmetric competition are modeled with a parameter that reflects the size advantage that larger individual have over smaller individuals.We fit the model to data on individual growth in crowded populations of Chenopodium album.Important Findings When individual plant growth curves were not coupled,there was a negative or no correlation between initial growth rate and final size,suggesting that competitive interactions were more important in determining final plant size than were plants’initial growth rates.The coupled growth equations fit the data better than individual,uncoupled growth models,even though the number of estimated parameters in the coupled competitive growth model was far fewer,indicating the importance of modeling competition and the degree of size-asymmetric growth explicitly.A quantitative understanding of stand development in terms of the growth of individuals,as altered by competition,is within reach.
