As droughts become more frequent and severer,understanding tree resilience and its role in mediating drought legacy effects(LEs)is critical for predicting forest ecosystem responses to future droughts and informing fo...As droughts become more frequent and severer,understanding tree resilience and its role in mediating drought legacy effects(LEs)is critical for predicting forest ecosystem responses to future droughts and informing forest management.Both Pinus tabuliformis and Populus davidiana are widely distributed in the Loess Plateau region of western China and play important roles in provision of ecosystem services.In this study we quantified the LEs and resilience,including resistance(Rt)and recovery(Rc),of radial growth(BAI,basal area increment)and intrinsic water use efficiency(iWUE)of the two species,determined the external and internal factors influencing Rt and Rc,and disentangled the respective contribution of Rt and Rc to LEs in the these two tree species.We found either negative or positive legacy effects in BAI(LEBAI)and iWUE(LEiWUE)in both species,mostly lasting for 1-3 years.Species differences were only detected in LEiWUE during the severer drought event.But species variation in resilience did not differ.P.tabuliformis exhibited lower Rt but higher Rc than P.davidiana.Tree diameter and drought intensity were negatively correlated with Rt and Rc;whereas tree age and growth variability positively influenced both resilience components.In P.tabulaeformis,the influence of Rt was stronger on LE than on Rc during the milder droughts,whereas during the severer droughts LE was affected by Rc.The reversed patterns of the effects were exhibited by P.davidiana.Our findings help advance current understanding on the factors driving resilience and how trees use different resilience strategies under different drought conditions to alleviate negative LEs.展开更多
Extreme climate has increasingly led to negative impacts on forest ecosystems globally,especially in semiarid areas where forest ecosystems are more vulnerable.However,it is poorly understood how tree growth is affect...Extreme climate has increasingly led to negative impacts on forest ecosystems globally,especially in semiarid areas where forest ecosystems are more vulnerable.However,it is poorly understood how tree growth is affected by different drought events.In 2006–2009,the larch plantations in the semiarid areas of Northwest China were negatively affected by four consecutive dry years,which was a very rare phenomenon that may occur frequently under future climate warming.In this study,we analyzed the effect of these consecutive dry years on tree growth based on the data of the tree rings in the dominant layer of the forest canopy on a larch plantation.We found that the tree-ring width index(RWI)in dry years was lower than that in normal years,and it experienced a rapidly decreasing trend from 2006 to 2009(slope=-0.139 year^(-1),r=-0.94)due to water supply deficits in those dry years.Drought induced legacy effects of tree growth reduction,and consecutive dry years corresponded with greater growth reductions and legacy effects.Growth reductions and legacy effects were significantly stronger in the third and fourth consecutive dry years than that of single dry year(p<0.05),which might have been due to the cumulative stress caused by consecutive dry years.Our results showed that larch trees experienced greater tree growth reduction due to consecutive dry years and their legacy effect,and the trees had lower recovery rates after consecutive dry years.Our results highlight that consecutive dry years pose a new threat to plantations under climate warming,and thus,the effect of climate extremes on tree growth should be considered in growth models in semiarid areas.展开更多
The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focus...The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.展开更多
The effect of combined antibiotics exposure on nitrogen removal,microbial community assembly and proliferation of antibiotics resistance genes(ARGs)is a hotspot in activated sludge system.However,it is unclear that ho...The effect of combined antibiotics exposure on nitrogen removal,microbial community assembly and proliferation of antibiotics resistance genes(ARGs)is a hotspot in activated sludge system.However,it is unclear that how the historical antibiotic stress affects the subsequent responses of microbes and ARGs to combined antibiotics.In this study,the effects of combined sulfamethoxazole(SMX)and trimethoprim(TMP)pollution on activated sludge under legacy of SMX or TMP stress with different doses(0.005-30 mg/L)were investigated to clarify antibiotic legacy effects.Nitrification activity was inhibited under higher level of combined exposure but a high total nitrogen removal(∼70%)occurred.Based on the full-scale classification,the legacy effect of past antibiotic stress had a marked effect on community composition of conditionally abundant taxa(CAT)and conditionally rare or abundant taxa(CRAT).Rare taxa(RT)were the keystone taxa in the microbial network,and the responses of hub genera were also affected by the legacy of antibiotic stress.Nitrifying bacteria and genes were inhibited by the antibiotics and aerobic denitrifying bacteria(Pseudomonas,Thaurea and Hydrogenophaga)were enriched under legacy of high dose,as were the key denitrifying genes(napA,nirK and norB).Furthermore,the occurrences and co-selection relationship of 94 ARGs were affected by legacy effect.While,some shared hosts(eg.,Citrobacter)and hub ARGs(eg.,mdtD,mdtE and acrD)were identified.Overall,antibiotic legacy could affect responses of activated sludge to combined antibiotic and the legacy effect was stronger at higher exposure levels.展开更多
Aims Plant nutrient use efficiency,an important factor driving primary production,is sensitive to nitrogen(N)deposition.Because of strengthened regulations of N emissions,atmospheric N deposition is decreasing in many...Aims Plant nutrient use efficiency,an important factor driving primary production,is sensitive to nitrogen(N)deposition.Because of strengthened regulations of N emissions,atmospheric N deposition is decreasing in many countries.It remains unknown whether historical N enrichment would alter plant nutrient use efficiency and whether such impacts would be mitigated by ecosystem management strategy.Methods We assessed the effects of historical N addition and mowing on plant N and phosphorus use efficiency(NUE and PUE)at both functional group and community levels in a temperate steppe after the cessation of 6-year N addition.Important Findings Historical N addition had negative legacy effects on plant NUE but not on PUE at the functional group level.There were negative legacy effects of N addition on community-level NUE and PUE,but only in the unmown plots.Mowing mitigated the negative legacy effects of N enrichment on community-level NUE and PUE by reducing the dominance of tall rhizomatous grass but enhancing that of tall bunchgrass.Our results highlight the importance of community composition variations caused by mowing in driving the legacy effects of N enrichment on community-level nutrient use efficiency.Given the slow recovery of community composition following cessation of N deposition,our findings suggest that the lower nutrient efficiency of plant community would be long-lasting.展开更多
Aims To explore whether grazing-induced legacy effects on plants could benefit plants adaptation to drought.Methods A water-controlled experiment was conducted in the greenhouse,which with Agropyron cristatum and Care...Aims To explore whether grazing-induced legacy effects on plants could benefit plants adaptation to drought.Methods A water-controlled experiment was conducted in the greenhouse,which with Agropyron cristatum and Carex korshinskyi collected from free-grazing and enclosed plots on a typical grassland in Inner Mongolia.Important Findings We found that A.cristatum and C.korshinskyi collected from the free-grazing plot were less affected by drought in terms of ramet biomass,ramet number and total biomass than those collected from the enclosed plot.The enhanced adaptation to drought for plants collected from the free-grazing plot should partly be ascribed to the larger root biomass allocation plasticity under drought treatment.Our findings suggest that grazing management can be used to improve the adaptation of grassland plants to climate change.展开更多
Aims Studying legacy effects(i.e.the indirect effect that persists for a period after casual factors cease)can provide novel insights into the role of ecological drivers.Leaf lifespan is among the key traits with mult...Aims Studying legacy effects(i.e.the indirect effect that persists for a period after casual factors cease)can provide novel insights into the role of ecological drivers.Leaf lifespan is among the key traits with multi-level functions.It is clear about the direct effects of water and nitrogen(N)amendment on leaf lifespan,but it remains unclear about their legacy effects on leaf lifespan and the associated mechanisms.Methods We performed a five-year field experiment with supplemental water and N,and quantified the legacy effects of field water and N addi-tion on the leaf lifespan,length and growth rate of four dominant species,Agropyron cristatum,Cleistogenes squarrosa,Leymus chin-ensis and Stipa grandis in a temperate steppe.Important Findings Across all the species,the legacies of water and N addition increased their leaf length and growth rate directly but decreased their leaf lifespan through direct and indirect pathways.Leaf lifes-pan was positively linked with leaf length but negatively associ-ated to leaf growth rate.the legacy effect of water addition on leaf lifespan was greater than that of N addition.Field N addition induced soil acidification and eutrophication,as well as altered soil microbes,but only eutrophication had negative legacy effects on leaf lifespan.these findings provide substantial evidence that rainfall and N amendment have negative legacy effects on leaf lifespan,and also highlight that multiple mechanisms or pathways determine legacy effects.Additionally,our results suggest that field water and N manipulations may influence the other leaf traits and functions.展开更多
Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil...Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil feedback(PSF),driving community succession remains limited.In this work,we examined the PSF associated with three succession stage species through a 2-year greenhouse experiment.Setaria viridis,Stipa bungeana,and Bothriochloa ischemum were selected to represent dominant and representative early-,mid-,and late-successional stage species,respectively,of semiarid grasslands on the Loess Plateau.In response to the different soil origin,the shoot biomass of early-,mid-,and late-species were all higher when grown in their own soil than in other species’soils,which indicated that the PSF of three species were positive.Over two growth periods,the early-species experienced a negative PSF,but the mid-and late-species experienced negative,neutral and positive PSF in the soil of early-,mid-and late-species,respectively.Our study demonstrates that soil legacy effects and PSF have a significant impact on community succession processes.展开更多
Anthropogenic disturbances are widespread in tropical forests and influence the species composition in the overstory.However,the impacts of historical disturbance on tropical forest overstory recovery are unclear due ...Anthropogenic disturbances are widespread in tropical forests and influence the species composition in the overstory.However,the impacts of historical disturbance on tropical forest overstory recovery are unclear due to a lack of disturbance data,and previous studies have focused on understory species.In this study,the purpose was to deter-mine the influence of historical disturbance on the diver-sity,composition and regeneration of overstory species in present forests.In the 20-ha Xishuangbanna tropical sea-sonal rainforest dynamics plot in southwestern China,the historical disturbance boundaries were delineated based on panchromatic photographs from 1965.Factors that drove species clustering in the overstory layer(DBH≥40 cm)were analyzed and the abundance,richness and composition of these species were compared among different tree groups based on multiple regression tree analysis.The coefficient of variation of the brightness value in historical panchro-matic photographs from 1965 was the primary driver of spe-cies clustering in the overstory layer.The abundance and richness of overstory species throughout the regeneration process were similar,but species composition was always different.Although the proportion of large-seeded and vigorous-sprouting species showed no significant differ-ence between disturbed and undisturbed forests in the tree-let layer(DBH<20 cm),the difference became significant when DBH increased.The findings highlight that historical disturbances have strong legacy effects on functional group composition in the overstory and the recovery of overstory species was multidimensional.Functional group composi-tion can better indicate the dynamics of overstory species replacement during secondary succession.展开更多
The impact of lag effects produced by disturbances on primary production has been a major concern among ecologists during the last decade.Sudden and extreme climatic events are imposing drastic reductions in radial gr...The impact of lag effects produced by disturbances on primary production has been a major concern among ecologists during the last decade.Sudden and extreme climatic events are imposing drastic reductions in radial growth of trees as evidenced in tree-rings series Dendrochronological samples are obtained at tree level but analyzed at an aggregated scale(i.e.,mean chronologies),although aggregating tree-ring chronology on a regional scale may reduce the possibility of studying the variability of individual tree response to drought,by amplifying the average population response.Here,we conducted experimental research in which 370 trees of 5 species were analyzed to assess the potential statistical and scaling issues that may occur when using regressionbased methods to analyze ecosystem responses to disturbances.Drought legacy effects were quantified using individual and aggregated scales.Then,lag effects were validated using confidence and prediction intervals to identify values falling outside the certainty of the climate-growth model Individual scale legacy effects contrasted with confidence intervals were commonly distributed across species but were scarce when compared with prediction intervals.The analysis of aggregated scale legacies detected significant growth reductions when validated using prediction intervals;however,individual scale legacy lag effects were not detected.This finding directly contrasts the results obtained when using an aggregated scale.Our results provide empirical evidence on how aggregating ecological data to infer processes that emerge from an individual scale can lead to distorted conclusions.We therefore encourage the use of individual based statistical and ecological procedures to analyze tree rings as a means of further understanding the ecosystem responses to disturbances.展开更多
Invasive plant species may alter soil characteristics or interact with the soil microbial community resulting in a competitive advantage.Our objectives were to determine:i)if invasive plant species alter soil properti...Invasive plant species may alter soil characteristics or interact with the soil microbial community resulting in a competitive advantage.Our objectives were to determine:i)if invasive plant species alter soil properties;and ii)the long-term effects of invasive plant species on soil properties and subsequent implications on ecological restoration efforts.We focused on Lespedeza cuneata,a plant that may be allelopathic.Soil samples were collected from four locations in Central Missouri,USA:an old-field with abundant L.cuneata,two reconstructed sites,and a remnant prairie that has never been plowed.Soil health indictors were used to characterize soil properties at these sites.Nearly every soil property differed significantly between the unplowed prairie reference site and the other three sites.The reconstructed sites,however,generally did not differ from the invaded old-field.These results indicate that the reconstructed prairies are not fully recovered.Although above-ground traits,such as the plant community structure,appear similar to the prairie,the soil microbial community structure still resembles that of an invaded old-field site.These results indicate that more time may be needed before soil microbial populations fully recover after invasive plant removal.展开更多
Human activities are strongly modifying the global nitrogen (N) cycle through increasing input, N species diversity, and pool size of industrial reactive N (Nr). However, the fluxes, fates and environmental consequenc...Human activities are strongly modifying the global nitrogen (N) cycle through increasing input, N species diversity, and pool size of industrial reactive N (Nr). However, the fluxes, fates and environmental consequences of industrial Nr (excluding synthesized N fertilizer) remain poorly understood and quantified. We report here that industrial Nr flux has increased 13.4-fold over the past 30 years in China, reaching 3.7Tg N (1 Tg=10 12g) in 2008, accounting for over 50% of China's food Nr flux. Socioeconomic development (per capita GDP, urbanization and household size) significantly drives the growth of industrial Nr fluxes. This leads to "hotspots" of industrial Nr, mainly in relatively developed Eastern China. Industrial Nr loss rate during production is only 5%, much lower than that of cropland (50%) and livestock (80%). However, industrial Nr loss is point source pollution, and Nr release in concentrated doses produces serious risk in small regions. The contribution of structural N to total industrial Nr with a lifespan longer than one year (e.g., synthetic fiber, plastic) increased from 20% in 1980 to 70% in 2008. There was about 2.6 Tg N structural industrial Nr accumulated in human settlements in 2008, which could be one ex- planation of an unknown Nr sink of anthropogenic Nr input (mainly Haber-Bosch N fixation). Legacy effects caused by structural N accumulation have long-term consequences for environmental and human health, although structural N delays Nr release and reduces short-term Nr pollution. Industrial Nr use generates new features of modern global N biogeochemistry, such as increasing Nr species diversity, reducing Nr turnover rate. Future dynamics simulation of the earth system should involve industrial Nr. Explicit consideration and accounting of the fluxes and environmental consequences of industrial Nr would provide decision-makers a novel view of regional sustainable development.展开更多
The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive an...The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive and continuous vegetation greening and no weakened land carbon sink in the maturation phase of the 2015/2016 El Niño event over the NH(mainly in the extra-tropics),based on multiple evidences from remote sensing observations,global ecosystem model simulations and atmospheric CO_(2)inversions.We discovered a significant compensation effect of the enhanced vegetation growth in spring on subsequent summer/autumn vegetation growth that sustained vegetation greening and led to a slight increase in the land carbon sink over the spring and summer of 2015(average increases of 23.34%and 0.63%in net ecosystem exchange from two independent datasets relative to a 5-years average before the El Niño event,respectively)and spring of 2016(6.82%),especially in the extra-tropics of the NH,where the water supply during the pre-growing-season(November of the previous year to March of the current year)had a positive anomaly.This seasonal compensation effect was much stronger than that in 1997 and 1998 and significantly alleviated the adverse impacts of the 2015/2016 El Niño event on vegetation growth during its maturation phase.The legacy effect of water supply during the pre-growing-season on subsequent vegetation growth lasted up to approximately six months.Our findings highlight the role of seasonal compensation effects on mediating the land carbon sink in response to episodic extreme El Niño events.展开更多
Droughts have dramatic direct and indirect impacts on vegetation and terrestrial ecosystem stability, including decreases in growth and subsequent decreases in CO_2 absorption. Although much research has been carried ...Droughts have dramatic direct and indirect impacts on vegetation and terrestrial ecosystem stability, including decreases in growth and subsequent decreases in CO_2 absorption. Although much research has been carried out on the response of vegetation to droughts, it remains unclear whether biomes are becoming more resistant or more vulnerable to drought. In this study, we used the Standardized Precipitation Evapotranspiration Index(SPEI, a multiscalar drought index) and the Normalized Difference Vegetation Index(NDVI, an indicator of vegetation growth) to detect the sensitivity of vegetation growth to droughts across 12–24 month timescales and to detect the change in this sensitivity over recent decades. We found that vegetation growth was most sensitive to 17–18 month droughts in water-limited regions, implying pronounce legacy effects from water conditions in previous years. In addition, we detected reduced coupling between drought and vegetation growth, probably caused by release moisture stress in water limited areas. Meanwhile, we observed a shortening of drought timescale to which vegetation most sensitively responded from an average of 18.1 to 17.2 months, suggesting the weakening of the drought legacy effect on vegetation growth. Results of this study contribute to the overall understanding of the resistance and resilience of ecosystems to drought conditions.展开更多
Increasing intensity and frequency of climate extremes under climate change are expected to affect rainfall-constrained ecosystems,particularly grassland ecosystems in arid and semi-arid zones.However,our understandin...Increasing intensity and frequency of climate extremes under climate change are expected to affect rainfall-constrained ecosystems,particularly grassland ecosystems in arid and semi-arid zones.However,our understanding of the effects of precipitation extremes(extreme drought or wetness)on grassland productivity,especially under naturally occurring conditions,remains limited.Here,we assembled a dataset of aboveground net primary productivity(ANPP)measurements from long-term(26-54 years)observational studies conducted in 13 grasslands worldwide to investigate the direct and legacy responses of grassland ANPP to naturally occurring precipitation extremes.We further examined changes in plant community structure(species richness,life history,growth form and photosynthetic pathway)before,during and after precipitation extremes.We found that extreme drought decreased ANPP by an average of 40%,while extreme wetness had a neutral effect on ANPP.The direct effects of both extreme drought and wetness on ANPP were aridity-dependent,with grassland vulnerability increasing with site aridity.However,we did not detect widespread legacy effects of extreme drought or wetness on ANPP.This is mainly attributable to reorganized plant community structure,which favored rapid recovery of community biomass.The aridity-dependent response of ANPP to precipitation extremes demonstrates the ambient climate-dependent resistance of grasslands to these events.Moreover,the minimal legacy effects of precipitation extremes on ANPP highlight the strong resilience of grasslands.These findings underscore the importance of integrating extreme climate conditions into forecasts of future grassland productivity and stability in a changing climate.展开更多
The pre-phase landslides will have a legacy effect on future landslides,changing the landslide susceptibility.This study attempts to establish a reasonable post-seismic landslide susceptibility model and analyze the s...The pre-phase landslides will have a legacy effect on future landslides,changing the landslide susceptibility.This study attempts to establish a reasonable post-seismic landslide susceptibility model and analyze the spatio-temporal characteristics of landslide susceptibility in the Jiuzhaigou MS7.0 earthquake-struck region.Firstly,an integrated‘spaceground’monitoring technology is used to establish a multi-temporal post-seismic landslide dataset.Then,the buffer analysis method documents the spatio-temporal characteristics of post-seismic landslides.Thirdly,the distance is selected as an indicator to quantify the legacy effect.An improved time-variant model is established to evaluate the post-seismic landslide susceptibility.Finally,the spatiotemporal characteristics of landslide susceptibility are generalized,to sum up the changing law.Our results show that the post-seismic landslides are gradually closer to the pre-phase landslides with time.Distance is a critical factor in measuring the impact of pre-phase landslides on future landslides,which can improve the assessment accuracy of the post-seismic landslide susceptibility model.After a large seismic event,the correlation between landslide susceptibility and earthquakes gradually weakens.Post-seismic landslide prevention should focus on the pre-phase landslide expansion triggered by rainfall.Moreover,it should clean up the landslide deposits in time and reasonably dredge the debris flows to avoid secondary geological disasters.展开更多
基金the National Natural Science Foundation of China(No.41977149).
文摘As droughts become more frequent and severer,understanding tree resilience and its role in mediating drought legacy effects(LEs)is critical for predicting forest ecosystem responses to future droughts and informing forest management.Both Pinus tabuliformis and Populus davidiana are widely distributed in the Loess Plateau region of western China and play important roles in provision of ecosystem services.In this study we quantified the LEs and resilience,including resistance(Rt)and recovery(Rc),of radial growth(BAI,basal area increment)and intrinsic water use efficiency(iWUE)of the two species,determined the external and internal factors influencing Rt and Rc,and disentangled the respective contribution of Rt and Rc to LEs in the these two tree species.We found either negative or positive legacy effects in BAI(LEBAI)and iWUE(LEiWUE)in both species,mostly lasting for 1-3 years.Species differences were only detected in LEiWUE during the severer drought event.But species variation in resilience did not differ.P.tabuliformis exhibited lower Rt but higher Rc than P.davidiana.Tree diameter and drought intensity were negatively correlated with Rt and Rc;whereas tree age and growth variability positively influenced both resilience components.In P.tabulaeformis,the influence of Rt was stronger on LE than on Rc during the milder droughts,whereas during the severer droughts LE was affected by Rc.The reversed patterns of the effects were exhibited by P.davidiana.Our findings help advance current understanding on the factors driving resilience and how trees use different resilience strategies under different drought conditions to alleviate negative LEs.
基金the National Natural Science Foundation of China(Nos.42161144008U21A2005+3 种基金U20A2085)the National Key Research and Development Program of China(2022YFF08018042022YFF08018032022YFF1300404)。
文摘Extreme climate has increasingly led to negative impacts on forest ecosystems globally,especially in semiarid areas where forest ecosystems are more vulnerable.However,it is poorly understood how tree growth is affected by different drought events.In 2006–2009,the larch plantations in the semiarid areas of Northwest China were negatively affected by four consecutive dry years,which was a very rare phenomenon that may occur frequently under future climate warming.In this study,we analyzed the effect of these consecutive dry years on tree growth based on the data of the tree rings in the dominant layer of the forest canopy on a larch plantation.We found that the tree-ring width index(RWI)in dry years was lower than that in normal years,and it experienced a rapidly decreasing trend from 2006 to 2009(slope=-0.139 year^(-1),r=-0.94)due to water supply deficits in those dry years.Drought induced legacy effects of tree growth reduction,and consecutive dry years corresponded with greater growth reductions and legacy effects.Growth reductions and legacy effects were significantly stronger in the third and fourth consecutive dry years than that of single dry year(p<0.05),which might have been due to the cumulative stress caused by consecutive dry years.Our results showed that larch trees experienced greater tree growth reduction due to consecutive dry years and their legacy effect,and the trees had lower recovery rates after consecutive dry years.Our results highlight that consecutive dry years pose a new threat to plantations under climate warming,and thus,the effect of climate extremes on tree growth should be considered in growth models in semiarid areas.
基金financially supported by the Key Research Program of Frontier Sciences,the Chinese Academy of Sciences (No.QYZDY-SSW-SMC014)the National Natural Science Foundation of China (No.32171576)。
文摘The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.
基金supported by the National Natural Science Foundation of China(No.51808013)Connotation Development Quota Project of High-top Talent of BJUT(No.YS20-1006757-056).
文摘The effect of combined antibiotics exposure on nitrogen removal,microbial community assembly and proliferation of antibiotics resistance genes(ARGs)is a hotspot in activated sludge system.However,it is unclear that how the historical antibiotic stress affects the subsequent responses of microbes and ARGs to combined antibiotics.In this study,the effects of combined sulfamethoxazole(SMX)and trimethoprim(TMP)pollution on activated sludge under legacy of SMX or TMP stress with different doses(0.005-30 mg/L)were investigated to clarify antibiotic legacy effects.Nitrification activity was inhibited under higher level of combined exposure but a high total nitrogen removal(∼70%)occurred.Based on the full-scale classification,the legacy effect of past antibiotic stress had a marked effect on community composition of conditionally abundant taxa(CAT)and conditionally rare or abundant taxa(CRAT).Rare taxa(RT)were the keystone taxa in the microbial network,and the responses of hub genera were also affected by the legacy of antibiotic stress.Nitrifying bacteria and genes were inhibited by the antibiotics and aerobic denitrifying bacteria(Pseudomonas,Thaurea and Hydrogenophaga)were enriched under legacy of high dose,as were the key denitrifying genes(napA,nirK and norB).Furthermore,the occurrences and co-selection relationship of 94 ARGs were affected by legacy effect.While,some shared hosts(eg.,Citrobacter)and hub ARGs(eg.,mdtD,mdtE and acrD)were identified.Overall,antibiotic legacy could affect responses of activated sludge to combined antibiotic and the legacy effect was stronger at higher exposure levels.
基金This work was supported by National NaturalScience Foundation of China(31770503and31822006)Liaoning Revitalizing Talents Program(XLYC1807061)+1 种基金K.C.Wong Education Foundation(GJTD-2019-10)Youth Innovation PromotionAssociation CAS(2018032).
文摘Aims Plant nutrient use efficiency,an important factor driving primary production,is sensitive to nitrogen(N)deposition.Because of strengthened regulations of N emissions,atmospheric N deposition is decreasing in many countries.It remains unknown whether historical N enrichment would alter plant nutrient use efficiency and whether such impacts would be mitigated by ecosystem management strategy.Methods We assessed the effects of historical N addition and mowing on plant N and phosphorus use efficiency(NUE and PUE)at both functional group and community levels in a temperate steppe after the cessation of 6-year N addition.Important Findings Historical N addition had negative legacy effects on plant NUE but not on PUE at the functional group level.There were negative legacy effects of N addition on community-level NUE and PUE,but only in the unmown plots.Mowing mitigated the negative legacy effects of N enrichment on community-level NUE and PUE by reducing the dominance of tall rhizomatous grass but enhancing that of tall bunchgrass.Our results highlight the importance of community composition variations caused by mowing in driving the legacy effects of N enrichment on community-level nutrient use efficiency.Given the slow recovery of community composition following cessation of N deposition,our findings suggest that the lower nutrient efficiency of plant community would be long-lasting.
基金This research was supported by the Inner Mongolia Science and Technology project(201802081)the National Natural Science Foundation of China(32071882)the Inner Mongolia Natural Science Foundation(2020MS03070).
文摘Aims To explore whether grazing-induced legacy effects on plants could benefit plants adaptation to drought.Methods A water-controlled experiment was conducted in the greenhouse,which with Agropyron cristatum and Carex korshinskyi collected from free-grazing and enclosed plots on a typical grassland in Inner Mongolia.Important Findings We found that A.cristatum and C.korshinskyi collected from the free-grazing plot were less affected by drought in terms of ramet biomass,ramet number and total biomass than those collected from the enclosed plot.The enhanced adaptation to drought for plants collected from the free-grazing plot should partly be ascribed to the larger root biomass allocation plasticity under drought treatment.Our findings suggest that grazing management can be used to improve the adaptation of grassland plants to climate change.
基金This work was funded by the Ministry of Science and Technology of China(2015BAC02B05)National Natural Science Foundation of China(31570538).
文摘Aims Studying legacy effects(i.e.the indirect effect that persists for a period after casual factors cease)can provide novel insights into the role of ecological drivers.Leaf lifespan is among the key traits with multi-level functions.It is clear about the direct effects of water and nitrogen(N)amendment on leaf lifespan,but it remains unclear about their legacy effects on leaf lifespan and the associated mechanisms.Methods We performed a five-year field experiment with supplemental water and N,and quantified the legacy effects of field water and N addi-tion on the leaf lifespan,length and growth rate of four dominant species,Agropyron cristatum,Cleistogenes squarrosa,Leymus chin-ensis and Stipa grandis in a temperate steppe.Important Findings Across all the species,the legacies of water and N addition increased their leaf length and growth rate directly but decreased their leaf lifespan through direct and indirect pathways.Leaf lifes-pan was positively linked with leaf length but negatively associ-ated to leaf growth rate.the legacy effect of water addition on leaf lifespan was greater than that of N addition.Field N addition induced soil acidification and eutrophication,as well as altered soil microbes,but only eutrophication had negative legacy effects on leaf lifespan.these findings provide substantial evidence that rainfall and N amendment have negative legacy effects on leaf lifespan,and also highlight that multiple mechanisms or pathways determine legacy effects.Additionally,our results suggest that field water and N manipulations may influence the other leaf traits and functions.
基金funded by the National Natural Science Foundation of China(42130717)the Shaanxi Science Fund for Distinguished Young Scholars(2021JC-50)。
文摘Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil feedback(PSF),driving community succession remains limited.In this work,we examined the PSF associated with three succession stage species through a 2-year greenhouse experiment.Setaria viridis,Stipa bungeana,and Bothriochloa ischemum were selected to represent dominant and representative early-,mid-,and late-successional stage species,respectively,of semiarid grasslands on the Loess Plateau.In response to the different soil origin,the shoot biomass of early-,mid-,and late-species were all higher when grown in their own soil than in other species’soils,which indicated that the PSF of three species were positive.Over two growth periods,the early-species experienced a negative PSF,but the mid-and late-species experienced negative,neutral and positive PSF in the soil of early-,mid-and late-species,respectively.Our study demonstrates that soil legacy effects and PSF have a significant impact on community succession processes.
基金supported by the Natural Science Foundation of Yunnan Province(Grant No:202301AT070356)the Open Fund of the Key Laboratory of Tropical Forest Ecology,Chinese Academy of Sciences,National Science Foundation of China(Grant No.32061123003)+1 种基金the Joint Fund of the National Natural Science Foundation of China-Yunnan Province(Grant No.U1902203)the Field Station Foundation of the Chinese Academy of Sciences.
文摘Anthropogenic disturbances are widespread in tropical forests and influence the species composition in the overstory.However,the impacts of historical disturbance on tropical forest overstory recovery are unclear due to a lack of disturbance data,and previous studies have focused on understory species.In this study,the purpose was to deter-mine the influence of historical disturbance on the diver-sity,composition and regeneration of overstory species in present forests.In the 20-ha Xishuangbanna tropical sea-sonal rainforest dynamics plot in southwestern China,the historical disturbance boundaries were delineated based on panchromatic photographs from 1965.Factors that drove species clustering in the overstory layer(DBH≥40 cm)were analyzed and the abundance,richness and composition of these species were compared among different tree groups based on multiple regression tree analysis.The coefficient of variation of the brightness value in historical panchro-matic photographs from 1965 was the primary driver of spe-cies clustering in the overstory layer.The abundance and richness of overstory species throughout the regeneration process were similar,but species composition was always different.Although the proportion of large-seeded and vigorous-sprouting species showed no significant differ-ence between disturbed and undisturbed forests in the tree-let layer(DBH<20 cm),the difference became significant when DBH increased.The findings highlight that historical disturbances have strong legacy effects on functional group composition in the overstory and the recovery of overstory species was multidimensional.Functional group composi-tion can better indicate the dynamics of overstory species replacement during secondary succession.
文摘The impact of lag effects produced by disturbances on primary production has been a major concern among ecologists during the last decade.Sudden and extreme climatic events are imposing drastic reductions in radial growth of trees as evidenced in tree-rings series Dendrochronological samples are obtained at tree level but analyzed at an aggregated scale(i.e.,mean chronologies),although aggregating tree-ring chronology on a regional scale may reduce the possibility of studying the variability of individual tree response to drought,by amplifying the average population response.Here,we conducted experimental research in which 370 trees of 5 species were analyzed to assess the potential statistical and scaling issues that may occur when using regressionbased methods to analyze ecosystem responses to disturbances.Drought legacy effects were quantified using individual and aggregated scales.Then,lag effects were validated using confidence and prediction intervals to identify values falling outside the certainty of the climate-growth model Individual scale legacy effects contrasted with confidence intervals were commonly distributed across species but were scarce when compared with prediction intervals.The analysis of aggregated scale legacies detected significant growth reductions when validated using prediction intervals;however,individual scale legacy lag effects were not detected.This finding directly contrasts the results obtained when using an aggregated scale.Our results provide empirical evidence on how aggregating ecological data to infer processes that emerge from an individual scale can lead to distorted conclusions.We therefore encourage the use of individual based statistical and ecological procedures to analyze tree rings as a means of further understanding the ecosystem responses to disturbances.
文摘Invasive plant species may alter soil characteristics or interact with the soil microbial community resulting in a competitive advantage.Our objectives were to determine:i)if invasive plant species alter soil properties;and ii)the long-term effects of invasive plant species on soil properties and subsequent implications on ecological restoration efforts.We focused on Lespedeza cuneata,a plant that may be allelopathic.Soil samples were collected from four locations in Central Missouri,USA:an old-field with abundant L.cuneata,two reconstructed sites,and a remnant prairie that has never been plowed.Soil health indictors were used to characterize soil properties at these sites.Nearly every soil property differed significantly between the unplowed prairie reference site and the other three sites.The reconstructed sites,however,generally did not differ from the invaded old-field.These results indicate that the reconstructed prairies are not fully recovered.Although above-ground traits,such as the plant community structure,appear similar to the prairie,the soil microbial community structure still resembles that of an invaded old-field site.These results indicate that more time may be needed before soil microbial populations fully recover after invasive plant removal.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41201502 and 31170305)China Postdoctoral Science Special Foundation (Grant No. 2012T50508)China Postdoctoral Science Foundation (Grant No. 2011M501010)
文摘Human activities are strongly modifying the global nitrogen (N) cycle through increasing input, N species diversity, and pool size of industrial reactive N (Nr). However, the fluxes, fates and environmental consequences of industrial Nr (excluding synthesized N fertilizer) remain poorly understood and quantified. We report here that industrial Nr flux has increased 13.4-fold over the past 30 years in China, reaching 3.7Tg N (1 Tg=10 12g) in 2008, accounting for over 50% of China's food Nr flux. Socioeconomic development (per capita GDP, urbanization and household size) significantly drives the growth of industrial Nr fluxes. This leads to "hotspots" of industrial Nr, mainly in relatively developed Eastern China. Industrial Nr loss rate during production is only 5%, much lower than that of cropland (50%) and livestock (80%). However, industrial Nr loss is point source pollution, and Nr release in concentrated doses produces serious risk in small regions. The contribution of structural N to total industrial Nr with a lifespan longer than one year (e.g., synthetic fiber, plastic) increased from 20% in 1980 to 70% in 2008. There was about 2.6 Tg N structural industrial Nr accumulated in human settlements in 2008, which could be one ex- planation of an unknown Nr sink of anthropogenic Nr input (mainly Haber-Bosch N fixation). Legacy effects caused by structural N accumulation have long-term consequences for environmental and human health, although structural N delays Nr release and reduces short-term Nr pollution. Industrial Nr use generates new features of modern global N biogeochemistry, such as increasing Nr species diversity, reducing Nr turnover rate. Future dynamics simulation of the earth system should involve industrial Nr. Explicit consideration and accounting of the fluxes and environmental consequences of industrial Nr would provide decision-makers a novel view of regional sustainable development.
基金This study was financially supported by the National Key Research and Development Program of China(Grant No.2022YFF0801802)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0306)+2 种基金the National Natural Science Foundation of China(Grant No.42171050)the China Postdoctoral Science Foundation(Grant No.2023M730281)the State Key Laboratory of Earth Surface Processes and Resource Ecology of Beijing Normal University(Grant No.2023-KF-07).
文摘The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive and continuous vegetation greening and no weakened land carbon sink in the maturation phase of the 2015/2016 El Niño event over the NH(mainly in the extra-tropics),based on multiple evidences from remote sensing observations,global ecosystem model simulations and atmospheric CO_(2)inversions.We discovered a significant compensation effect of the enhanced vegetation growth in spring on subsequent summer/autumn vegetation growth that sustained vegetation greening and led to a slight increase in the land carbon sink over the spring and summer of 2015(average increases of 23.34%and 0.63%in net ecosystem exchange from two independent datasets relative to a 5-years average before the El Niño event,respectively)and spring of 2016(6.82%),especially in the extra-tropics of the NH,where the water supply during the pre-growing-season(November of the previous year to March of the current year)had a positive anomaly.This seasonal compensation effect was much stronger than that in 1997 and 1998 and significantly alleviated the adverse impacts of the 2015/2016 El Niño event on vegetation growth during its maturation phase.The legacy effect of water supply during the pre-growing-season on subsequent vegetation growth lasted up to approximately six months.Our findings highlight the role of seasonal compensation effects on mediating the land carbon sink in response to episodic extreme El Niño events.
基金supported by the National Natural Science Foundation of China (Grant No. 41671083)the National Key R&D Program of China (Grant Nos. 2017YFA0603601 & 2015CB953600)the Fundamental Research Funds for the Central Universities (Grant No. 312231103)
文摘Droughts have dramatic direct and indirect impacts on vegetation and terrestrial ecosystem stability, including decreases in growth and subsequent decreases in CO_2 absorption. Although much research has been carried out on the response of vegetation to droughts, it remains unclear whether biomes are becoming more resistant or more vulnerable to drought. In this study, we used the Standardized Precipitation Evapotranspiration Index(SPEI, a multiscalar drought index) and the Normalized Difference Vegetation Index(NDVI, an indicator of vegetation growth) to detect the sensitivity of vegetation growth to droughts across 12–24 month timescales and to detect the change in this sensitivity over recent decades. We found that vegetation growth was most sensitive to 17–18 month droughts in water-limited regions, implying pronounce legacy effects from water conditions in previous years. In addition, we detected reduced coupling between drought and vegetation growth, probably caused by release moisture stress in water limited areas. Meanwhile, we observed a shortening of drought timescale to which vegetation most sensitively responded from an average of 18.1 to 17.2 months, suggesting the weakening of the drought legacy effect on vegetation growth. Results of this study contribute to the overall understanding of the resistance and resilience of ecosystems to drought conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.32130065 and 32192461).
文摘Increasing intensity and frequency of climate extremes under climate change are expected to affect rainfall-constrained ecosystems,particularly grassland ecosystems in arid and semi-arid zones.However,our understanding of the effects of precipitation extremes(extreme drought or wetness)on grassland productivity,especially under naturally occurring conditions,remains limited.Here,we assembled a dataset of aboveground net primary productivity(ANPP)measurements from long-term(26-54 years)observational studies conducted in 13 grasslands worldwide to investigate the direct and legacy responses of grassland ANPP to naturally occurring precipitation extremes.We further examined changes in plant community structure(species richness,life history,growth form and photosynthetic pathway)before,during and after precipitation extremes.We found that extreme drought decreased ANPP by an average of 40%,while extreme wetness had a neutral effect on ANPP.The direct effects of both extreme drought and wetness on ANPP were aridity-dependent,with grassland vulnerability increasing with site aridity.However,we did not detect widespread legacy effects of extreme drought or wetness on ANPP.This is mainly attributable to reorganized plant community structure,which favored rapid recovery of community biomass.The aridity-dependent response of ANPP to precipitation extremes demonstrates the ambient climate-dependent resistance of grasslands to these events.Moreover,the minimal legacy effects of precipitation extremes on ANPP highlight the strong resilience of grasslands.These findings underscore the importance of integrating extreme climate conditions into forecasts of future grassland productivity and stability in a changing climate.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program[grant number STEP 2019QZKK0901]Integrated‘Space-Ground’of Jiuzhai Valley World Natural Heritage Site[grant number E0H20501].
文摘The pre-phase landslides will have a legacy effect on future landslides,changing the landslide susceptibility.This study attempts to establish a reasonable post-seismic landslide susceptibility model and analyze the spatio-temporal characteristics of landslide susceptibility in the Jiuzhaigou MS7.0 earthquake-struck region.Firstly,an integrated‘spaceground’monitoring technology is used to establish a multi-temporal post-seismic landslide dataset.Then,the buffer analysis method documents the spatio-temporal characteristics of post-seismic landslides.Thirdly,the distance is selected as an indicator to quantify the legacy effect.An improved time-variant model is established to evaluate the post-seismic landslide susceptibility.Finally,the spatiotemporal characteristics of landslide susceptibility are generalized,to sum up the changing law.Our results show that the post-seismic landslides are gradually closer to the pre-phase landslides with time.Distance is a critical factor in measuring the impact of pre-phase landslides on future landslides,which can improve the assessment accuracy of the post-seismic landslide susceptibility model.After a large seismic event,the correlation between landslide susceptibility and earthquakes gradually weakens.Post-seismic landslide prevention should focus on the pre-phase landslide expansion triggered by rainfall.Moreover,it should clean up the landslide deposits in time and reasonably dredge the debris flows to avoid secondary geological disasters.
