Amid global precipitation changes,it remains unclear whether hydrological niche separation(HNS)mechanisms apply to herbaceous plant communities in desert steppes are severely affected by seasonal drought.How these pla...Amid global precipitation changes,it remains unclear whether hydrological niche separation(HNS)mechanisms apply to herbaceous plant communities in desert steppes are severely affected by seasonal drought.How these plants access limited water and tolerate drought to coexist also remains unverified.In this study,we employed stable isotope techniques to examine water acquisition and drought adaptation in coexisting species of the desert steppe in northern China under five precipitation treatments,i.e.,decreased 50%,decreased 30%,ambient,increased 30%,and increased 50%precipitation.The following results showed that:(1)water sources of coexisting species shifted with changes in precipitation amount and timing,i.e.,all coexisting plants exhibited preferential utilization of surface soil moisture.When surface soil moisture was scarce,they shifted to deeper water sources,and when deep water sources remained scarce,they were forced to compete more intensely for surface water sources;(2)community's HNS was affected by precipitation amount but not by timing,i.e.,with adequate soil moisture,plant water source ranges expanded,reducing overlap and enhancing HNS,whereas under extreme drought,the range contracted and increased the overlap,although HNS remained stable;and(3)water acquisition strategies of coexisting species differed along hydrological niche axis defined by water stress adaptability(i.e.,stable carbon isotope composition and proline content).Convolvulus ammannii Desr.had the strongest drought adaptation,although its strategy showed a weak correlation with water uptake.Stipa breviflora Griseb.,with moderate drought resistance,adopted a water-conserving strategy that was suitable for extreme drought.Leymus secalinus(Georgi)Tzvelev,Polygala tenuifolia Willd.,and Larix potaninii Batalin showed resource-dependent and flexible water strategies,thriving in wetter soils but struggling under extreme drought.Our findings indicated that herbaceous species in desert steppes adapted their water uptake and drought tolerance strategies according to changes in precipitation amount and timing.As a core regulatory mechanism,HNS(under increasing precipitation variability due to climate change)not only supports species coexistence by reducing interspecific competition,but also promotes efficient soil moisture use.This mechanism enhances community drought resistance and contributes to ecosystem stability.Overall,this study provides key ecological evidence for understanding plant community adaptation in arid and semi-arid areas facing the influence of global climate change.展开更多
As invasion science accepts that there is no single causal factor for biological invasion, the identification of groups of traits that are often associated, or ＂syndromes＂, is a logical move forward. Invasion syndro...As invasion science accepts that there is no single causal factor for biological invasion, the identification of groups of traits that are often associated, or ＂syndromes＂, is a logical move forward. Invasion syndromes are proposed to identify suites of site conditions （biotic and environmental） that render a site vulnerable to invasion by different types of invaders. This paper proposed four invasion syndromes which relate invader attributes （competitive ability, niche construction, phenotypic plasticity, and phenological niche separation） to the biotic characteristics （biodiversity and enemies） and environmental conditions （resource abundance and fluctuation） of invaded sites. The four invasion syndromes described in this paper are a development of hypotheses of how the many factors that influence species invasion might be associated. Invasion Syndrome 1 proposes that sites with relatively high resource abundance and high diversity should be vulnerable to invasion by species with high competitive ability. Invasion Syndrome 2 hypothesizes that sites with relatively low resource abundance and low diversity should be vulnerable to invasion by species with niche construction ability. Invasion Syndrome 3 postulates that sites with moderate or fluctuating resources and moderate diversity should be vulnerable to invasion by species with high phenotypic plasticity. Invasion Syndrome 4 hypothesizes that species introduced into a site where it has phenological niche separation from natives will not have to contend with interference from the biotic community at a site （diversity or natural enemies） and may invade where ever site environmental conditions suit its life history. Further work is needed to support, contradict, or refine these hypotheses and almost certainly will identify more invasion syndromes.展开更多
Aims Aboveground biomass production commonly increases with species richness in plant biodiversity experiments.Little is known about the direct mechanisms that cause this result.We tested if by occupying different hei...Aims Aboveground biomass production commonly increases with species richness in plant biodiversity experiments.Little is known about the direct mechanisms that cause this result.We tested if by occupying different heights and depths above and below ground,and by optimizing the vertical distribution of leaf nitrogen,species in mixtures can contribute to increased resource uptake and,thus,increased productivity of the community in comparison with monocultures.Methods We grew 24 grassland plant species,grouped into four nonoverlapping species pools,in monoculture and 3-and 6-species mixture in spatially heterogeneous and uniform soil nutrient conditions.Layered harvests of above-and belowground biomass,as well as leaf nitrogen and light measurements,were taken to assess vertical canopy and root space structure.Important Findings The distribution of leaf mass was shifted toward greater heights and light absorption was correspondingly enhanced in mixtures.How ever,only some mixtures had leaf nitrogen concentration profiles predicted to optimize whole-community carbon gain,whereas in other mixtures species seemed to behave more‘selfish’.Nevertheless,even in these communities,biomass production increased with species richness.The distribution of root biomass below ground did not change from monocultures to three-and six-species mixtures and there was also no indication that mixtures were better than monocultures at extracting heterogeneously as compared to homogeneously distributed soil resources.We conclude that positive biodiversity effect on aboveground biomass production cannot easily be explained by a single or few common mechanisms of differential space use.Rather,it seems that mechanisms vary with the particular set of species combined in a community.展开更多
基金funded by the National Natural Science Foundation of China(32160406).
文摘Amid global precipitation changes,it remains unclear whether hydrological niche separation(HNS)mechanisms apply to herbaceous plant communities in desert steppes are severely affected by seasonal drought.How these plants access limited water and tolerate drought to coexist also remains unverified.In this study,we employed stable isotope techniques to examine water acquisition and drought adaptation in coexisting species of the desert steppe in northern China under five precipitation treatments,i.e.,decreased 50%,decreased 30%,ambient,increased 30%,and increased 50%precipitation.The following results showed that:(1)water sources of coexisting species shifted with changes in precipitation amount and timing,i.e.,all coexisting plants exhibited preferential utilization of surface soil moisture.When surface soil moisture was scarce,they shifted to deeper water sources,and when deep water sources remained scarce,they were forced to compete more intensely for surface water sources;(2)community's HNS was affected by precipitation amount but not by timing,i.e.,with adequate soil moisture,plant water source ranges expanded,reducing overlap and enhancing HNS,whereas under extreme drought,the range contracted and increased the overlap,although HNS remained stable;and(3)water acquisition strategies of coexisting species differed along hydrological niche axis defined by water stress adaptability(i.e.,stable carbon isotope composition and proline content).Convolvulus ammannii Desr.had the strongest drought adaptation,although its strategy showed a weak correlation with water uptake.Stipa breviflora Griseb.,with moderate drought resistance,adopted a water-conserving strategy that was suitable for extreme drought.Leymus secalinus(Georgi)Tzvelev,Polygala tenuifolia Willd.,and Larix potaninii Batalin showed resource-dependent and flexible water strategies,thriving in wetter soils but struggling under extreme drought.Our findings indicated that herbaceous species in desert steppes adapted their water uptake and drought tolerance strategies according to changes in precipitation amount and timing.As a core regulatory mechanism,HNS(under increasing precipitation variability due to climate change)not only supports species coexistence by reducing interspecific competition,but also promotes efficient soil moisture use.This mechanism enhances community drought resistance and contributes to ecosystem stability.Overall,this study provides key ecological evidence for understanding plant community adaptation in arid and semi-arid areas facing the influence of global climate change.
基金supported by the US National Science Foundation (1047575)
文摘As invasion science accepts that there is no single causal factor for biological invasion, the identification of groups of traits that are often associated, or ＂syndromes＂, is a logical move forward. Invasion syndromes are proposed to identify suites of site conditions （biotic and environmental） that render a site vulnerable to invasion by different types of invaders. This paper proposed four invasion syndromes which relate invader attributes （competitive ability, niche construction, phenotypic plasticity, and phenological niche separation） to the biotic characteristics （biodiversity and enemies） and environmental conditions （resource abundance and fluctuation） of invaded sites. The four invasion syndromes described in this paper are a development of hypotheses of how the many factors that influence species invasion might be associated. Invasion Syndrome 1 proposes that sites with relatively high resource abundance and high diversity should be vulnerable to invasion by species with high competitive ability. Invasion Syndrome 2 hypothesizes that sites with relatively low resource abundance and low diversity should be vulnerable to invasion by species with niche construction ability. Invasion Syndrome 3 postulates that sites with moderate or fluctuating resources and moderate diversity should be vulnerable to invasion by species with high phenotypic plasticity. Invasion Syndrome 4 hypothesizes that species introduced into a site where it has phenological niche separation from natives will not have to contend with interference from the biotic community at a site （diversity or natural enemies） and may invade where ever site environmental conditions suit its life history. Further work is needed to support, contradict, or refine these hypotheses and almost certainly will identify more invasion syndromes.
基金Swiss National Science Foundation(31-65224-01 to B.S.).
文摘Aims Aboveground biomass production commonly increases with species richness in plant biodiversity experiments.Little is known about the direct mechanisms that cause this result.We tested if by occupying different heights and depths above and below ground,and by optimizing the vertical distribution of leaf nitrogen,species in mixtures can contribute to increased resource uptake and,thus,increased productivity of the community in comparison with monocultures.Methods We grew 24 grassland plant species,grouped into four nonoverlapping species pools,in monoculture and 3-and 6-species mixture in spatially heterogeneous and uniform soil nutrient conditions.Layered harvests of above-and belowground biomass,as well as leaf nitrogen and light measurements,were taken to assess vertical canopy and root space structure.Important Findings The distribution of leaf mass was shifted toward greater heights and light absorption was correspondingly enhanced in mixtures.How ever,only some mixtures had leaf nitrogen concentration profiles predicted to optimize whole-community carbon gain,whereas in other mixtures species seemed to behave more‘selfish’.Nevertheless,even in these communities,biomass production increased with species richness.The distribution of root biomass below ground did not change from monocultures to three-and six-species mixtures and there was also no indication that mixtures were better than monocultures at extracting heterogeneously as compared to homogeneously distributed soil resources.We conclude that positive biodiversity effect on aboveground biomass production cannot easily be explained by a single or few common mechanisms of differential space use.Rather,it seems that mechanisms vary with the particular set of species combined in a community.
