Anammox bacteria in constructed wetlands(CWs)play pivotal role in sustainable nitrogen transformation,yet existing studies lack comprehensive analysis of environmental gradients and microbial interactions,both key fac...Anammox bacteria in constructed wetlands(CWs)play pivotal role in sustainable nitrogen transformation,yet existing studies lack comprehensive analysis of environmental gradients and microbial interactions,both key factors in anammox bacteria enrichment.This study investigated the mechanisms driving anammox bacteria enrichment in lab-scale simulated CWs treating high-nitrogen wastewater,focusing on bacterial community re-sponses across wetland layers with various strategies,including continuous up-flow influent,nitrogen loading increase,effluent recirculation,intermittent influent,and anammox bacteria inoculation.Results showed that total relative and absolute abundances of anammox bacteria ranged from 0.77%to 12.50%and from 0.13 to 6.46×10^(7) copies/g,respectively.Dissolved oxygen and pH had significant positive correlations with the absolute abundance of anammox bacteria,while organic matter and nitrate negatively impacted their relative abundance.Permutational multivariate analysis of variance indicated that spatial heterogeneity explained more variation in anammox bacteria abundance(43.44%)compared to operational strategies(8.58%).In terms of microbial interactions,60 dominant species exhibited potential correlations with anammox bacteria,comprising 170 interactions(105 positive and 65 negative),which suggested that anammox bacteria generally foster cooperative relationships with dominant bacteria.Notably,significant interspecies interactions were observed between Candidatus Kuenenia(dominant anammox bacteria in CWs)and species within the genera Chitinivibrio-nia and Anaerolineaceae,suggesting that microbial interactions primarily manifest as indirect facilitative effects rather than direct mutualistic relationships.Given that the Normalized Stochasticity Ratio in CWs were<50%,this study inferred that environmental gradients have greater influence on anammox bacteria than microbial interactions.展开更多
Understanding the ecogeographic mechanisms driving morphological variation is pivotal in biogeographic studies. However, patterns and determinants of such variation remain contentious, particularly in amphibians. Alth...Understanding the ecogeographic mechanisms driving morphological variation is pivotal in biogeographic studies. However, patterns and determinants of such variation remain contentious, particularly in amphibians. Although several hypotheses have been formulated and investigated in amphibians, their validity remains disputed with mixed support. Using the Sichuan spiny frog(Nanorana sichuanensis) as an indicator, we investigated the morphological variations across geographic and environmental gradients to explore the underlying ecogeographic mechanisms. We found that both the body size and limb characteristics of N.sichuanensis were not significantly related to latitude or elevation, suggesting that it did not follow Bergmann's or Allen's rules. Eye diameter decreased linearly with increasing elevation and latitude, whereas snout length increased with increasing elevation and latitude. Heat balance, endurance, seasonality, water availability, and primary productivity collectively explain body size variation. Hierarchical partitioning identified primary productivity and thermal excursion as the most influential factors, explaining significant variability in body size and other morphological features. Specifically, primary productivity accounted for 52.40% of the variation in body size, whereas thermal excursion had the greatest impact on eye diameter(36.23%) and snout length(72.17%). Based on body size and dimensionally reduced morphological features, our results identified ecogeographic patterns, assessed the validity of different hypotheses, and examined how environmental factors influence these morphological variations. More generally, our study offers comprehensive insights into the ecogeographic variation observed in mountain amphibians,provides a critical evaluation of existing ecogeographic hypotheses, and infers possible morphological adaptations in response to environmental change.展开更多
Stress in plants refers to adverse changes in their functioning.The occurrence and intensity of a stress can be assessed by alterations in plant traits,termed stress indicators.The ultimate goal of this study was to t...Stress in plants refers to adverse changes in their functioning.The occurrence and intensity of a stress can be assessed by alterations in plant traits,termed stress indicators.The ultimate goal of this study was to test whether six morpho-physiological plant traits,frequently used as stress indicators,respond consistently across species to various environmental stressors,with the aim of detecting universal stress indicators in forest tree species.We examined changes in vertical increment,leaf/needle size,shoot length,needle longevity,photosynthetic efficiency and fluctuating asymmetry in three common European tree species,mountain birch(Betula pubescens var.pumila),Norway spruce(Picea abies)and Scots pine(Pinus sylvestris)along three environmental gradients(elevation,pollution and seashore)from forests to stressful open environments.Data were collected in 2003,2004 and 2005 from 297 trees growing naturally across 36 sites in north-western Russia.Fluctuating asymmetry was the only trait that did not vary among sites with differing levels of environmental stress.Leaf/needle size and shoot length occasionally changed along stress gradients,but the magnitude and direction of these changes differed by gradient type and species,resulting in no significant overall stress effect for either trait.In contrast,photosynthetic efficiency,vertical increment and needle longevity consistently decreased from low-stress to high-stress sites.The overall effect was significant for each of these three traits despite the magnitudes of these decreases differed depending on the gradient type and location,species,study year and individual tree.Replication at spatial,temporal and taxonomic levels ensured the robustness and reliability of our results that photosynthetic efficiency,vertical growth and needle longevity reliably captured a general stress syndrome and may serve as stress indicators in forest species.展开更多
Ecological patterns and processes in dune ecosystems have been a research focus in recent years, however the information on how dune stabilization influences the spatial scale dependence of plant diversity is still la...Ecological patterns and processes in dune ecosystems have been a research focus in recent years, however the information on how dune stabilization influences the spatial scale dependence of plant diversity is still lacking. In this study, we measured the plant species richness, soil properties and altitude across four spatial scales （1, 10, 100 and 1,000 m2） at three different dune stabilization stages （mobile dune, semi-fixed dune and fixed dune） in Horqin Sandy Land, Northern China. We also examined the relationships between plant species richness, community composition and environmental factors along the gradient of dune stabilization. Our results showed that plant species richness increased with the increase of spatial scales in each dune stabilization stage, as well as with the increase of dune stabilization degrees. Canonical correspondence analysis （CCA） showed that plant distribu- tions in the processes of dune stabilization were determined by the combined environmental gradient in relation to soil organic carbon （SOC）, total nitrogen （TN）, carbon/nitrogen （C/N）, pH, electrical conductivity （EC）, soil water content （SWC）, fine sand （FS）, very fine sand （VFS）, silt and clay （SC）, and altitude. Plant species richness was significantly and positively correlated to SOC and TN in mobile dune, and significantly and positively correlated to SOC, TN, C/N, VFS and SC in semi-fixed dune. However, no significant correlation between plant species richness and environmental factors was observed in fixed dune. In addition, plant species richness in different dune stabili- zation stages was also determined by the combined gradient of soil properties and altitude. These results suggest that plant species richness has obvious scale dependence along the gradient of dune stabilization. Soil resources depending on dune habitats and environmental gradients caused by dune stabilization are important factors to de- termine the scale dependence of species diversity in sand dune ecosystems.展开更多
Quantifying correlation between the spatial patterns of natural wetland plants and environmental gradient gives better understanding of wetland habitats, which is the fundamental for the strategy making on the protect...Quantifying correlation between the spatial patterns of natural wetland plants and environmental gradient gives better understanding of wetland habitats, which is the fundamental for the strategy making on the protection and restoration of natural wetlands. In this study, the spatial patterns of wetland plants and the environmental gradient of wetland habitats were assessed in the Honghe National Nature Reserve （HNNR） in Northeast China, a wetland of international importance on the Ramsar list. Biophysical parameters’ values of wetland plants were obtained by field sampling methods, and wetland mapping at the community scale was completed using remote sensing techniques. Digital delineation of the surface water system, hydrological zoning and wetness index were produced by spatial analysis methods in Geographic Information System. An ecological ordination method and two clustering methods were used to quantify the relationship between the spatial distribution patterns of wetland plants and the corresponding environmental gradients. Such quantitative analyses also present the specific diversity of different types of wetland plants based on the environmental attributes of their habitats. With the support from modern geo-information techniques, the experimental results indicate how four ecotypes of wetland plants spatially transit from forest swamp, shrub wetland and meadow into marsh wetland with increasing wetness index and water table. And they also show how wetland spatial distribution patterns are controlled by an environmental gradient of wetness. Another key finding of this research work is that our results present the exact fundamental differences between marsh and non-marsh plants of 11 wetland plant communities within the core study area. Hence, this case study gives a good sample for better understanding of the complex correlation between the spatial patterns of wetland plants and their environmental attributes using advanced digital analysis methods. It is also useful to show how to integrate geoinformatic techniques with statistical analysis methods based on the field data base.展开更多
Twenty-three secondary forest communities with different structure were selected in Mao＇er Mountain National Park of Heilongjiang Province, China to study the relationship between diversity of forest plant species an...Twenty-three secondary forest communities with different structure were selected in Mao＇er Mountain National Park of Heilongjiang Province, China to study the relationship between diversity of forest plant species and environmental gradient. The forest plant species diversity was analyzed by the diversity index, and the environmental factors was quantified by the method of Whittaker＇s quantification of environmental gradient. Meanwhile, β-diversity indexes of communities were calculated with similar measurements. The results showed that the Shannon-wiener diversity index of forest plant species increased with the increase of the environmental gradient, and the β-diversity indexes of communities showed a liner increase along with the change of environmental gradient.展开更多
Dry evergreen montane forests in Ethiopia are severely threatened.The status of species composition and structure of forest vegetation are important indicators to understand the trends of threats on local plant commun...Dry evergreen montane forests in Ethiopia are severely threatened.The status of species composition and structure of forest vegetation are important indicators to understand the trends of threats on local plant communities.In the present study,we examined the floristic composition and structure of the Kibate Forest,Wonchi Highland,Ethiopia along environmental gradients.Sixty-six(30 m×30 m)plots were established every 100 m interval along altitudinal gradients(2811‒3073 m a.s.l.)in five transect lines for vegetation and environmental data collection.In total,125 vascular plant species belonging to 104 genera and 52 families were identified.Eighteen species(14%)were endemic to Ethiopia and Eritrea.The two most dominant families,Asteraceae(29 species)and Lamiaceae(eight species)accounted for 30%of the total number of species.The highest number of species(54%)was herbs.Four major community types(viz.,Olinia rochetiana-Myrsine melanophloeos,Ilex mitis-Galiniera saxifraga,Erica arborea-Protea gaguedi,and Hagenia abyssinica-Juniperus procera)were identified.The highest species richness,evenness,diversity,and importance value index were in community types 2 and 4.About 82%of the species and all endemic taxa except five were recorded in these two community types.The most dominant woody species were O.rochetiana,E.arborea,Olea europaea subsp.cuspidata,Myrica salicifolia,I.mitis var.mitis,and H.abyssinica with different patterns of population structure.The results show that there was a weak correlation between species richness and altitude.Our findings confirm that environmental variables both with interactions(such as altitude)and without interactions(such as livestock grazing)significantly(p<0.05)affect species richness.Anthropogenic activities and overgrazing by livestock appear to be the main threat in community types 2 and 3.Urgent management practices and conservation measures such as prohibiting forest clearing and overgrazing and planting indigenous trees through community participation should be considered in community types that are rich in endemic species but are highly threatened.展开更多
Phytoplankton communities can response immediately and directly to environmental changes,and thus have been applied as reliable biotic indicators in aquatic systems.This study provided insights into the relationships ...Phytoplankton communities can response immediately and directly to environmental changes,and thus have been applied as reliable biotic indicators in aquatic systems.This study provided insights into the relationships concerning ecological thresholds of phytoplankton communities and individual taxon in response to environmental changes in coastal waters of northern Zhejiang Province,East China Sea.Results demonstrated that there existed seasonal variations of phytoplankton community ecological thresholds of which spring being higher than those in summer.As for individual species,Prorocentrum donghaiense and Noctiluca scintillans were identified as the most tolerant and sensitive indicator species in spring and summer,respectively.They exhibited strong indications in response to environmental changes.These findings highlighted that phytoplankton community structure in this region was stable when environmental gradients were below the thresholds of sensitive species,whereas potential harmful algal blooms may occur when environmental gradients exceeded the thresholds of tolerant species.展开更多
We investigated and monitored a reed community in the fields.Data on the bio-ecological characteristics and β-diversity of reed communities in different environmental gradients(mainly based on water depth)of the Yell...We investigated and monitored a reed community in the fields.Data on the bio-ecological characteristics and β-diversity of reed communities in different environmental gradients(mainly based on water depth)of the Yellow River Delta were collected through multianalysis,extremum analysis and β-diversity index analysis.In accordance with the square sum of deviations(Ward)cluster analysis,10 sampling plots were divided into six types with the dominant plants in different plots varying according to the change in environmental gradients.The dominant plants in these plots varied from aquatic plants to xerophytes and salt tolerant plants as water depth decreased.The average height and diameter of the reeds at breast level were significantly correlated with the average water depth.The fitness curves of average density and coverage with average water depth were nonlinear.When the average water depth was 0.3 m,the average density and coverage of reeds reached the apex value,while the height and diameter of the reeds at breast level increased with the water depth.There were obvious changes to the environmental gradient in the Yellow River Delta.The transitional communities were also found to exist in the Yellow River Delta by β-diversity analysis.Vicarious species appeared with the change in water depth.The occurrence of substitute species is determined by the function of common species between adjacent belts.The different functions of common species led to differences in community structure and function and differences in dominant plants.The result reflects the variations of species present in different habitats and directly reflects environmental heterogeneity.The values of β-diversity indices of adjacent plots were higher than those of nonadjacent plots.There are transition zones between the xerophytes and aquatic plants in the Yellow River Delta.In an aquatic environment,the similarity of reed community is higher than that of xeromorphic plants.The β-diversity index can reflect plant succession trends caused by the change in environmental gradients in the Yellow River Delta.The β-diversity index reveals plant responses to changes in environmental gradient and is helpful in observing changes in patterns of species diversity in relation to environmental gradient change and evolving trends in the future,which in turn plays a prominent role when environmental water requirements of wetland are discussed.展开更多
Human activity and urbanization result in urban-rural environmental gradients. Understanding effect of the gradients on soil properties is necessary for management of the soils around urban areas. In this study, soil ...Human activity and urbanization result in urban-rural environmental gradients. Understanding effect of the gradients on soil properties is necessary for management of the soils around urban areas. In this study, soil quality of some vegetable fields was characterized along an urban-rural gradient in Shaoxing County, Zhejiang Province. Fifteen soil physical and chemical properties were evaluated by using principal component analysis.Results showed that there was a great variation in the soil quality along the gradient. From rural to urban zones, soil organic matter, water-stable aggregates, cation exchangeable capacity (CEC), total N and P, and available K increased, whereas soil pH value decreased. In addition, Pb, Cu, Ni, Co, Zn and Cr in the soils tended to be accumulated toward the urban zone. Sequential chemical extraction showed that mobility of all the heavy metals in the soils tended to increase from the rural to the urban zones. The variation of soil properties accounted for by the first principal component was significantly explained by the difference in application rates of municipal wastes.展开更多
The present study was undertaken in moist temperate forest of Mandal-Chopta area in the Garhwal region of Uttarakhand, India. The aim of the present study was to understand the regeneration dynamics of the dominant tr...The present study was undertaken in moist temperate forest of Mandal-Chopta area in the Garhwal region of Uttarakhand, India. The aim of the present study was to understand the regeneration dynamics of the dominant tree species along an altitudinal gradient in naturally regen- erating, restricted access forest. The overall regeneration status was fairly high in the study area. Most of the native canopy and undercanopy domi- nants had frequent reproduction and expanding populations, which sug- gests the stability of forest structure/composition and further expansion of dominant species. The overall regeneration of trees in the forest had a greater contribution of middle and understurey species. Because of infre- quent rep＇roduction and declining populations of some of the dominant native species viz., Abies pindrow, Alnus nepalensis and Betula alnoides, structural/compositional changes in the future are expected in respective forests dominated by them..4bies pindrow and Taxus baccata need im- mediate attention by forest managers for their survival in the area. Seed- lings were found to be more prone to competition from herb and shrubs than saplings.展开更多
Unraveling the factors that determine variation of diversity in tropical mountain systems is a topic for debate in plant ecology.This is especially true in areas where topography is complex due to volcano elevational ...Unraveling the factors that determine variation of diversity in tropical mountain systems is a topic for debate in plant ecology.This is especially true in areas where topography is complex due to volcano elevational gradients and where forests are vulnerable to human activity.In this study we used a set of climatic(temperature,rainfall,and radiation solar),topographic(elevation,slope aspect,and slope orientation)and human disturbance variables to determine their effect on diversity and composition patterns of a tree community,considering three slope aspects of a tropical volcano in southeastern Mexico.We sampled trees in seventy 0.1-ha plots distributed on three slope aspects of the Tacanávolcano along an elevational gradient of 1500 to 2500 m.We determined diversity patterns(general tree richness,exponential of Shannon index,and pioneer species richness)with linear regression models,and for beta diversity,we used a dissimilarity index(within and between elevational bands 100 m wide).The effect of a set of environmental and human disturbance variables on tree diversity and community composition was analyzed with general linear models and multivariate analyses,respectively.We registered 2,949 individual trees belonging to 176 species and 58families.The average species richness and alpha diversity per plot were 13(standard deviation±6)and 9(±5),respectively.General tree richness and alpha diversity increased in the middle part(unimodal patterns)of the elevational gradient,but pioneer species richness decreased linearly with elevation.The variance explained by general linear models was greater in richness(32%)than in alpha diversity(25.3%).The most important predictor variables were temperature(elevational gradient),which explained the unimodal pattern(richness and alpha diversity increase at intermediate levels of temperature),and slope orientation,which explained the increase in richness and alpha diversity toward the geographic north.Only temperature had a significant effect on pioneer species diversity(22%).For community composition,all the predictor variables evaluated had a significant effect,but the most important were slope aspect and temperature.Assemblages were almost completely different in plots that were farther apart along the elevation gradient and had different slope aspects.Finally,the forests at lower elevations(1500–1900 m)were those that had the most human disturbance.Our study reveals the importance of considering a set of environmental variables related to climate,topography(e.g.,slope aspect),and human disturbance to understand variation in diversity and composition of a tree community on a tropical volcano.With this information,we believe that it is important to implement conservation and restoration measures in the forests of the lower parts of the Tacanávolcano,complemented by studies that contribute to designing better conservation strategies.展开更多
Although it has become clear that sexual selection may shape mating systems and drive speciation, the potential constraints of environmental factors on processes and outcomes of sexual selection are largely unexplored...Although it has become clear that sexual selection may shape mating systems and drive speciation, the potential constraints of environmental factors on processes and outcomes of sexual selection are largely unexplored. Here, we investigate the geographic variation of such environmental factors, more precisely the quality and quantity of nest resources （bivalve shells） along a salinity gradient in the Baltic Sea Area （Baltic Sea, Sounds and Belts, and Kattegat）. We further test whether we find any salinity-associated morphological differences in body size between populations of common gobies Pomatoschistus microps, a small marine fish with a resource-based mat- ing system. In a geographically expansive field study, we sampled 5 populations of P. microps occurring along the salinity gradient （decreasing from West to East） in the Baltic Sea Area over 3 consecutive years. Nest resource quantity and quality decreased from West to East, and a correla- tion between mussel size and male body size was detected. Population density, sex ratios, mating- and reproductive success as well as brood characteristics also differed between populations but with a less clear relation to salinity. With this field study we shed light on geographic variation of distinct environmental parameters possibly acting on population differentiation. We provide insights on relevant ecological variation, and draw attention to its importance in the framework of context-dependent plasticity of sexual selection.展开更多
To explore the relationships between community composition and the environment in a reservoir ecosystem, plankton communities from the Three Gorges Reservoir Region were studied by PCR-denaturing gradient gel electrop...To explore the relationships between community composition and the environment in a reservoir ecosystem, plankton communities from the Three Gorges Reservoir Region were studied by PCR-denaturing gradient gel electrophoresis fingerprinting. Bacterial and eukaryotic operational taxonomic units （OTUs）, generated by DGGE analysis of the PCR-amplified 16S and 18S rRNA genes, were used as surrogates for the dominant ＂biodiversity units＂. OTU composition among the sites was heterogeneous; 46.7% of the total bacterial OTUs （45） and 64.1% of the eukaryotic OTUs （39） were identified in less than half of the sampling sites. Unweighted pair group method with arithmetic averages （UPGMA） clustering of the OTUs suggested that the plankton communities in the Xiangxi Rive sites were not always significantly different from those from the Yangtze River sites, despite clear differences in their environmental characterizations. Canonical correspondence analysis （CCA） was applied to further investigate the relationships between OTU composition and the environmental factors. The first two CCA ordination axes suggested that the bacterial community composition was primarily correlated with the variables of NO3^--N, dissolved oxygen （DO）, and SiO3^2--Si, whereas, the eukaryotic community was mainly correlated with the concentrations of DO, PO4^3--P, and SiO3^2--Si.展开更多
Adaptive vegetation management is time-consuming and requires long-term colony monitoring to obtain reliable results. Although vegetation management has been widely adopted, the only method existing at present for eva...Adaptive vegetation management is time-consuming and requires long-term colony monitoring to obtain reliable results. Although vegetation management has been widely adopted, the only method existing at present for evaluating the habitat conditions under management involves observations over a long period of time. The presence of reactive oxygen species （ROS） has long been used as an indicator of environmen- tal stress in plants, and has recently been intensely studied. Among such ROS, hydrogen peroxide （H202） is relatively stable, and can be conveniently and accurately quantified. Thus, the quantification of plant H202 could be applied as a stress indicator for riparian and aquatic vegetation management approaches while evaluating the conditions of a plant species within a habitat. This study presents an approach for elucidating the applicability of H202 as a quantitative indicator of environmental stresses on plants, particularly for vegetation management. Submerged macrophytes and riparian species were studied under laboratory and field conditions （Lake Shinji, Saba River, Eno River, and Hii River in Japan） for H202 formation under various stress conditions. The results suggest that H202 can be conveniently applied as a stress indicator in environmental management.展开更多
Leaf nitrogen(N)and phosphorus(P)levels provide critical strategies for plant adaptions to changing environments.However,it is unclear whether leaf N and P levels of different plant functional groups(e.g.,monocots and...Leaf nitrogen(N)and phosphorus(P)levels provide critical strategies for plant adaptions to changing environments.However,it is unclear whether leaf N and P levels of different plant functional groups(e.g.,monocots and dicots)respond to environmental gradients in a generalizable pattern.Here,we used a global database of leaf N and P to determine whether monocots and dicots might have evolved contrasting strategies to balance N and P in response to changes in climate and soil nutrient availability.Specifically,we characterized global patterns of leaf N,P and N/P ratio in monocots and dicots,and explored the sensitivity of stoichiometry to environment factors in these plants.Our results indicate that leaf N and P levels responded to environmental factors differently in monocots than in dicots.In dicots,variations of leaf N,P and N/P ratio were significantly correlated to temperature and precipitation.In monocots,leaf N/P ratio was not significantly affected by temperature or precipitation.This indicates that leaf N,P and N/P ratio are less sensitive to environmental dynamics in monocots.We also found that in both monocots and dicots N/P ratios are associated with the availability of soil total P rather than soil total N,indicating that P limitation on plant growth is pervasive globally.In addition,there were significant phylogenetic signals for leaf N(λ=0.65),P(λ=0.57)and N/P ratio(λ=0.46)in dicots,however,only significant phylogenetic signals for leaf P in monocots.Taken together,our findings indicate that monocots exhibit a“conservative”strategy(high stoichiometric homeostasis and weak phylogenetic signals in stoichiometry)to maintain their growth in stressful conditions with lower water and soil nutrients.In contrast,dicots exhibit lower stoichiometric homeostasis in changing environments because of their wide climate-soil niches and significant phylogenetic signals in stoichiometry.展开更多
Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradi...Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.展开更多
基金supported by Natural Science Foundation of Xiamen,China(No.3502Z20227232)the STS Project of Fujian-CAS(No.2023T3018)Bureau of International Cooperation,Chinese Academy of Sciences(No.322GJHZ2022035MI).
文摘Anammox bacteria in constructed wetlands(CWs)play pivotal role in sustainable nitrogen transformation,yet existing studies lack comprehensive analysis of environmental gradients and microbial interactions,both key factors in anammox bacteria enrichment.This study investigated the mechanisms driving anammox bacteria enrichment in lab-scale simulated CWs treating high-nitrogen wastewater,focusing on bacterial community re-sponses across wetland layers with various strategies,including continuous up-flow influent,nitrogen loading increase,effluent recirculation,intermittent influent,and anammox bacteria inoculation.Results showed that total relative and absolute abundances of anammox bacteria ranged from 0.77%to 12.50%and from 0.13 to 6.46×10^(7) copies/g,respectively.Dissolved oxygen and pH had significant positive correlations with the absolute abundance of anammox bacteria,while organic matter and nitrate negatively impacted their relative abundance.Permutational multivariate analysis of variance indicated that spatial heterogeneity explained more variation in anammox bacteria abundance(43.44%)compared to operational strategies(8.58%).In terms of microbial interactions,60 dominant species exhibited potential correlations with anammox bacteria,comprising 170 interactions(105 positive and 65 negative),which suggested that anammox bacteria generally foster cooperative relationships with dominant bacteria.Notably,significant interspecies interactions were observed between Candidatus Kuenenia(dominant anammox bacteria in CWs)and species within the genera Chitinivibrio-nia and Anaerolineaceae,suggesting that microbial interactions primarily manifest as indirect facilitative effects rather than direct mutualistic relationships.Given that the Normalized Stochasticity Ratio in CWs were<50%,this study inferred that environmental gradients have greater influence on anammox bacteria than microbial interactions.
基金supported by the National Natural Science Foundation of China (32071544, 32271737)the Interdisciplinary Innovation Team of the Chinese Academy of Sciences (CAS) “Light of West China” Program (xbzg-zdsys-202207)。
文摘Understanding the ecogeographic mechanisms driving morphological variation is pivotal in biogeographic studies. However, patterns and determinants of such variation remain contentious, particularly in amphibians. Although several hypotheses have been formulated and investigated in amphibians, their validity remains disputed with mixed support. Using the Sichuan spiny frog(Nanorana sichuanensis) as an indicator, we investigated the morphological variations across geographic and environmental gradients to explore the underlying ecogeographic mechanisms. We found that both the body size and limb characteristics of N.sichuanensis were not significantly related to latitude or elevation, suggesting that it did not follow Bergmann's or Allen's rules. Eye diameter decreased linearly with increasing elevation and latitude, whereas snout length increased with increasing elevation and latitude. Heat balance, endurance, seasonality, water availability, and primary productivity collectively explain body size variation. Hierarchical partitioning identified primary productivity and thermal excursion as the most influential factors, explaining significant variability in body size and other morphological features. Specifically, primary productivity accounted for 52.40% of the variation in body size, whereas thermal excursion had the greatest impact on eye diameter(36.23%) and snout length(72.17%). Based on body size and dimensionally reduced morphological features, our results identified ecogeographic patterns, assessed the validity of different hypotheses, and examined how environmental factors influence these morphological variations. More generally, our study offers comprehensive insights into the ecogeographic variation observed in mountain amphibians,provides a critical evaluation of existing ecogeographic hypotheses, and infers possible morphological adaptations in response to environmental change.
基金supported by the Research Council(formerly Academy)of Finland(projects 122133,214824,362731,and researcher posts of M.V.Kozlov)EC through the BALANCE project carried out under contract EVK2-2002-00169,and the University of Turku。
文摘Stress in plants refers to adverse changes in their functioning.The occurrence and intensity of a stress can be assessed by alterations in plant traits,termed stress indicators.The ultimate goal of this study was to test whether six morpho-physiological plant traits,frequently used as stress indicators,respond consistently across species to various environmental stressors,with the aim of detecting universal stress indicators in forest tree species.We examined changes in vertical increment,leaf/needle size,shoot length,needle longevity,photosynthetic efficiency and fluctuating asymmetry in three common European tree species,mountain birch(Betula pubescens var.pumila),Norway spruce(Picea abies)and Scots pine(Pinus sylvestris)along three environmental gradients(elevation,pollution and seashore)from forests to stressful open environments.Data were collected in 2003,2004 and 2005 from 297 trees growing naturally across 36 sites in north-western Russia.Fluctuating asymmetry was the only trait that did not vary among sites with differing levels of environmental stress.Leaf/needle size and shoot length occasionally changed along stress gradients,but the magnitude and direction of these changes differed by gradient type and species,resulting in no significant overall stress effect for either trait.In contrast,photosynthetic efficiency,vertical increment and needle longevity consistently decreased from low-stress to high-stress sites.The overall effect was significant for each of these three traits despite the magnitudes of these decreases differed depending on the gradient type and location,species,study year and individual tree.Replication at spatial,temporal and taxonomic levels ensured the robustness and reliability of our results that photosynthetic efficiency,vertical growth and needle longevity reliably captured a general stress syndrome and may serve as stress indicators in forest species.
基金financially supported by the National Natural Science Foundation of China (41171414)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-EW-QN313)+1 种基金the Chinese Academy of Sciences Visiting Professorships for Senior International Scientists (2011T2Z36)the Key Project of Scientific and Technical Supporting Programs (2011BAC07B02-09), and the National Basic Research Program of China (2009CB421303)
文摘Ecological patterns and processes in dune ecosystems have been a research focus in recent years, however the information on how dune stabilization influences the spatial scale dependence of plant diversity is still lacking. In this study, we measured the plant species richness, soil properties and altitude across four spatial scales （1, 10, 100 and 1,000 m2） at three different dune stabilization stages （mobile dune, semi-fixed dune and fixed dune） in Horqin Sandy Land, Northern China. We also examined the relationships between plant species richness, community composition and environmental factors along the gradient of dune stabilization. Our results showed that plant species richness increased with the increase of spatial scales in each dune stabilization stage, as well as with the increase of dune stabilization degrees. Canonical correspondence analysis （CCA） showed that plant distribu- tions in the processes of dune stabilization were determined by the combined environmental gradient in relation to soil organic carbon （SOC）, total nitrogen （TN）, carbon/nitrogen （C/N）, pH, electrical conductivity （EC）, soil water content （SWC）, fine sand （FS）, very fine sand （VFS）, silt and clay （SC）, and altitude. Plant species richness was significantly and positively correlated to SOC and TN in mobile dune, and significantly and positively correlated to SOC, TN, C/N, VFS and SC in semi-fixed dune. However, no significant correlation between plant species richness and environmental factors was observed in fixed dune. In addition, plant species richness in different dune stabili- zation stages was also determined by the combined gradient of soil properties and altitude. These results suggest that plant species richness has obvious scale dependence along the gradient of dune stabilization. Soil resources depending on dune habitats and environmental gradients caused by dune stabilization are important factors to de- termine the scale dependence of species diversity in sand dune ecosystems.
基金Knowledge Innovation Program of the Chinese Academy of Sciences,No.KZCX2-YW-Q06-03 National Natural Science Foundation of China,No.40871241
文摘Quantifying correlation between the spatial patterns of natural wetland plants and environmental gradient gives better understanding of wetland habitats, which is the fundamental for the strategy making on the protection and restoration of natural wetlands. In this study, the spatial patterns of wetland plants and the environmental gradient of wetland habitats were assessed in the Honghe National Nature Reserve （HNNR） in Northeast China, a wetland of international importance on the Ramsar list. Biophysical parameters’ values of wetland plants were obtained by field sampling methods, and wetland mapping at the community scale was completed using remote sensing techniques. Digital delineation of the surface water system, hydrological zoning and wetness index were produced by spatial analysis methods in Geographic Information System. An ecological ordination method and two clustering methods were used to quantify the relationship between the spatial distribution patterns of wetland plants and the corresponding environmental gradients. Such quantitative analyses also present the specific diversity of different types of wetland plants based on the environmental attributes of their habitats. With the support from modern geo-information techniques, the experimental results indicate how four ecotypes of wetland plants spatially transit from forest swamp, shrub wetland and meadow into marsh wetland with increasing wetness index and water table. And they also show how wetland spatial distribution patterns are controlled by an environmental gradient of wetness. Another key finding of this research work is that our results present the exact fundamental differences between marsh and non-marsh plants of 11 wetland plant communities within the core study area. Hence, this case study gives a good sample for better understanding of the complex correlation between the spatial patterns of wetland plants and their environmental attributes using advanced digital analysis methods. It is also useful to show how to integrate geoinformatic techniques with statistical analysis methods based on the field data base.
基金Foundation project： The paper was supported by National Natural Science Foundation of China （39899370）.
文摘Twenty-three secondary forest communities with different structure were selected in Mao＇er Mountain National Park of Heilongjiang Province, China to study the relationship between diversity of forest plant species and environmental gradient. The forest plant species diversity was analyzed by the diversity index, and the environmental factors was quantified by the method of Whittaker＇s quantification of environmental gradient. Meanwhile, β-diversity indexes of communities were calculated with similar measurements. The results showed that the Shannon-wiener diversity index of forest plant species increased with the increase of the environmental gradient, and the β-diversity indexes of communities showed a liner increase along with the change of environmental gradient.
基金The work was supported by the Regional Capacity Building for Sustainable Natural Resource Management and Agricultural Improvement under Climate Change(CAPSNAC)Project of the Norwegian Program for Capacity Building in Higher Education and Research for Development(NORHED).
文摘Dry evergreen montane forests in Ethiopia are severely threatened.The status of species composition and structure of forest vegetation are important indicators to understand the trends of threats on local plant communities.In the present study,we examined the floristic composition and structure of the Kibate Forest,Wonchi Highland,Ethiopia along environmental gradients.Sixty-six(30 m×30 m)plots were established every 100 m interval along altitudinal gradients(2811‒3073 m a.s.l.)in five transect lines for vegetation and environmental data collection.In total,125 vascular plant species belonging to 104 genera and 52 families were identified.Eighteen species(14%)were endemic to Ethiopia and Eritrea.The two most dominant families,Asteraceae(29 species)and Lamiaceae(eight species)accounted for 30%of the total number of species.The highest number of species(54%)was herbs.Four major community types(viz.,Olinia rochetiana-Myrsine melanophloeos,Ilex mitis-Galiniera saxifraga,Erica arborea-Protea gaguedi,and Hagenia abyssinica-Juniperus procera)were identified.The highest species richness,evenness,diversity,and importance value index were in community types 2 and 4.About 82%of the species and all endemic taxa except five were recorded in these two community types.The most dominant woody species were O.rochetiana,E.arborea,Olea europaea subsp.cuspidata,Myrica salicifolia,I.mitis var.mitis,and H.abyssinica with different patterns of population structure.The results show that there was a weak correlation between species richness and altitude.Our findings confirm that environmental variables both with interactions(such as altitude)and without interactions(such as livestock grazing)significantly(p<0.05)affect species richness.Anthropogenic activities and overgrazing by livestock appear to be the main threat in community types 2 and 3.Urgent management practices and conservation measures such as prohibiting forest clearing and overgrazing and planting indigenous trees through community participation should be considered in community types that are rich in endemic species but are highly threatened.
基金The Quantitative Analysis of Distribution Pattern of Water Quality and Design of Monitoring Networks in Xiangshan Bay and its Adjacent Waters,Northern Coastal Zhejiang under contract No.15130401。
文摘Phytoplankton communities can response immediately and directly to environmental changes,and thus have been applied as reliable biotic indicators in aquatic systems.This study provided insights into the relationships concerning ecological thresholds of phytoplankton communities and individual taxon in response to environmental changes in coastal waters of northern Zhejiang Province,East China Sea.Results demonstrated that there existed seasonal variations of phytoplankton community ecological thresholds of which spring being higher than those in summer.As for individual species,Prorocentrum donghaiense and Noctiluca scintillans were identified as the most tolerant and sensitive indicator species in spring and summer,respectively.They exhibited strong indications in response to environmental changes.These findings highlighted that phytoplankton community structure in this region was stable when environmental gradients were below the thresholds of sensitive species,whereas potential harmful algal blooms may occur when environmental gradients exceeded the thresholds of tolerant species.
基金supported by the Major State Basic Research Development Program of China (No.2006CB403303)National Natural Science Foundation of China (Grant No.40571149)the Program for New Century Excellent Talents in University (NCET).
文摘We investigated and monitored a reed community in the fields.Data on the bio-ecological characteristics and β-diversity of reed communities in different environmental gradients(mainly based on water depth)of the Yellow River Delta were collected through multianalysis,extremum analysis and β-diversity index analysis.In accordance with the square sum of deviations(Ward)cluster analysis,10 sampling plots were divided into six types with the dominant plants in different plots varying according to the change in environmental gradients.The dominant plants in these plots varied from aquatic plants to xerophytes and salt tolerant plants as water depth decreased.The average height and diameter of the reeds at breast level were significantly correlated with the average water depth.The fitness curves of average density and coverage with average water depth were nonlinear.When the average water depth was 0.3 m,the average density and coverage of reeds reached the apex value,while the height and diameter of the reeds at breast level increased with the water depth.There were obvious changes to the environmental gradient in the Yellow River Delta.The transitional communities were also found to exist in the Yellow River Delta by β-diversity analysis.Vicarious species appeared with the change in water depth.The occurrence of substitute species is determined by the function of common species between adjacent belts.The different functions of common species led to differences in community structure and function and differences in dominant plants.The result reflects the variations of species present in different habitats and directly reflects environmental heterogeneity.The values of β-diversity indices of adjacent plots were higher than those of nonadjacent plots.There are transition zones between the xerophytes and aquatic plants in the Yellow River Delta.In an aquatic environment,the similarity of reed community is higher than that of xeromorphic plants.The β-diversity index can reflect plant succession trends caused by the change in environmental gradients in the Yellow River Delta.The β-diversity index reveals plant responses to changes in environmental gradient and is helpful in observing changes in patterns of species diversity in relation to environmental gradient change and evolving trends in the future,which in turn plays a prominent role when environmental water requirements of wetland are discussed.
基金Project supported by the National Key Basic Research Support Foundation (NKBRSF) of China (No. 1999011809).
文摘Human activity and urbanization result in urban-rural environmental gradients. Understanding effect of the gradients on soil properties is necessary for management of the soils around urban areas. In this study, soil quality of some vegetable fields was characterized along an urban-rural gradient in Shaoxing County, Zhejiang Province. Fifteen soil physical and chemical properties were evaluated by using principal component analysis.Results showed that there was a great variation in the soil quality along the gradient. From rural to urban zones, soil organic matter, water-stable aggregates, cation exchangeable capacity (CEC), total N and P, and available K increased, whereas soil pH value decreased. In addition, Pb, Cu, Ni, Co, Zn and Cr in the soils tended to be accumulated toward the urban zone. Sequential chemical extraction showed that mobility of all the heavy metals in the soils tended to increase from the rural to the urban zones. The variation of soil properties accounted for by the first principal component was significantly explained by the difference in application rates of municipal wastes.
基金supported by the Department of Science and Technology, Government of India, New Delhi, vide its Project No. SP/SO/PS-52/2004
文摘The present study was undertaken in moist temperate forest of Mandal-Chopta area in the Garhwal region of Uttarakhand, India. The aim of the present study was to understand the regeneration dynamics of the dominant tree species along an altitudinal gradient in naturally regen- erating, restricted access forest. The overall regeneration status was fairly high in the study area. Most of the native canopy and undercanopy domi- nants had frequent reproduction and expanding populations, which sug- gests the stability of forest structure/composition and further expansion of dominant species. The overall regeneration of trees in the forest had a greater contribution of middle and understurey species. Because of infre- quent rep＇roduction and declining populations of some of the dominant native species viz., Abies pindrow, Alnus nepalensis and Betula alnoides, structural/compositional changes in the future are expected in respective forests dominated by them..4bies pindrow and Taxus baccata need im- mediate attention by forest managers for their survival in the area. Seed- lings were found to be more prone to competition from herb and shrubs than saplings.
基金funded by the Comisión Nacional deáreas Naturales Protegidas(CONANP)-Reserva de la Biosfera Volcán Tacaná(CONANP/PROCODES/6799/2017)through a grant to Manuel Martínez Meléndez。
文摘Unraveling the factors that determine variation of diversity in tropical mountain systems is a topic for debate in plant ecology.This is especially true in areas where topography is complex due to volcano elevational gradients and where forests are vulnerable to human activity.In this study we used a set of climatic(temperature,rainfall,and radiation solar),topographic(elevation,slope aspect,and slope orientation)and human disturbance variables to determine their effect on diversity and composition patterns of a tree community,considering three slope aspects of a tropical volcano in southeastern Mexico.We sampled trees in seventy 0.1-ha plots distributed on three slope aspects of the Tacanávolcano along an elevational gradient of 1500 to 2500 m.We determined diversity patterns(general tree richness,exponential of Shannon index,and pioneer species richness)with linear regression models,and for beta diversity,we used a dissimilarity index(within and between elevational bands 100 m wide).The effect of a set of environmental and human disturbance variables on tree diversity and community composition was analyzed with general linear models and multivariate analyses,respectively.We registered 2,949 individual trees belonging to 176 species and 58families.The average species richness and alpha diversity per plot were 13(standard deviation±6)and 9(±5),respectively.General tree richness and alpha diversity increased in the middle part(unimodal patterns)of the elevational gradient,but pioneer species richness decreased linearly with elevation.The variance explained by general linear models was greater in richness(32%)than in alpha diversity(25.3%).The most important predictor variables were temperature(elevational gradient),which explained the unimodal pattern(richness and alpha diversity increase at intermediate levels of temperature),and slope orientation,which explained the increase in richness and alpha diversity toward the geographic north.Only temperature had a significant effect on pioneer species diversity(22%).For community composition,all the predictor variables evaluated had a significant effect,but the most important were slope aspect and temperature.Assemblages were almost completely different in plots that were farther apart along the elevation gradient and had different slope aspects.Finally,the forests at lower elevations(1500–1900 m)were those that had the most human disturbance.Our study reveals the importance of considering a set of environmental variables related to climate,topography(e.g.,slope aspect),and human disturbance to understand variation in diversity and composition of a tree community on a tropical volcano.With this information,we believe that it is important to implement conservation and restoration measures in the forests of the lower parts of the Tacanávolcano,complemented by studies that contribute to designing better conservation strategies.
文摘Although it has become clear that sexual selection may shape mating systems and drive speciation, the potential constraints of environmental factors on processes and outcomes of sexual selection are largely unexplored. Here, we investigate the geographic variation of such environmental factors, more precisely the quality and quantity of nest resources （bivalve shells） along a salinity gradient in the Baltic Sea Area （Baltic Sea, Sounds and Belts, and Kattegat）. We further test whether we find any salinity-associated morphological differences in body size between populations of common gobies Pomatoschistus microps, a small marine fish with a resource-based mat- ing system. In a geographically expansive field study, we sampled 5 populations of P. microps occurring along the salinity gradient （decreasing from West to East） in the Baltic Sea Area over 3 consecutive years. Nest resource quantity and quality decreased from West to East, and a correla- tion between mussel size and male body size was detected. Population density, sex ratios, mating- and reproductive success as well as brood characteristics also differed between populations but with a less clear relation to salinity. With this field study we shed light on geographic variation of distinct environmental parameters possibly acting on population differentiation. We provide insights on relevant ecological variation, and draw attention to its importance in the framework of context-dependent plasticity of sexual selection.
基金This work was supported by the National Natural Science Foundation of China(No.30490232,30570240)the Major State Basic Research Development Program of China(No.2002CB412308).
文摘To explore the relationships between community composition and the environment in a reservoir ecosystem, plankton communities from the Three Gorges Reservoir Region were studied by PCR-denaturing gradient gel electrophoresis fingerprinting. Bacterial and eukaryotic operational taxonomic units （OTUs）, generated by DGGE analysis of the PCR-amplified 16S and 18S rRNA genes, were used as surrogates for the dominant ＂biodiversity units＂. OTU composition among the sites was heterogeneous; 46.7% of the total bacterial OTUs （45） and 64.1% of the eukaryotic OTUs （39） were identified in less than half of the sampling sites. Unweighted pair group method with arithmetic averages （UPGMA） clustering of the OTUs suggested that the plankton communities in the Xiangxi Rive sites were not always significantly different from those from the Yangtze River sites, despite clear differences in their environmental characterizations. Canonical correspondence analysis （CCA） was applied to further investigate the relationships between OTU composition and the environmental factors. The first two CCA ordination axes suggested that the bacterial community composition was primarily correlated with the variables of NO3^--N, dissolved oxygen （DO）, and SiO3^2--Si, whereas, the eukaryotic community was mainly correlated with the concentrations of DO, PO4^3--P, and SiO3^2--Si.
基金financially supported by grant-in-aid from the Japan Society for the Promotion of Science Scientific Research (15H04045)+5 种基金Development Grant for River Management Technology from the Ministry of Land Infrastructure Transportation and Tourism JapanRiver Fund from the River Foundation of Japan and Watershed Ecology Research Group of WEC
文摘Adaptive vegetation management is time-consuming and requires long-term colony monitoring to obtain reliable results. Although vegetation management has been widely adopted, the only method existing at present for evaluating the habitat conditions under management involves observations over a long period of time. The presence of reactive oxygen species （ROS） has long been used as an indicator of environmen- tal stress in plants, and has recently been intensely studied. Among such ROS, hydrogen peroxide （H202） is relatively stable, and can be conveniently and accurately quantified. Thus, the quantification of plant H202 could be applied as a stress indicator for riparian and aquatic vegetation management approaches while evaluating the conditions of a plant species within a habitat. This study presents an approach for elucidating the applicability of H202 as a quantitative indicator of environmental stresses on plants, particularly for vegetation management. Submerged macrophytes and riparian species were studied under laboratory and field conditions （Lake Shinji, Saba River, Eno River, and Hii River in Japan） for H202 formation under various stress conditions. The results suggest that H202 can be conveniently applied as a stress indicator in environmental management.
基金supported by the National Science Foundation of China(Grant No.32271774,42301071)the China Postdoctoral Science Foundation(Grant No.2023M743633).
文摘Leaf nitrogen(N)and phosphorus(P)levels provide critical strategies for plant adaptions to changing environments.However,it is unclear whether leaf N and P levels of different plant functional groups(e.g.,monocots and dicots)respond to environmental gradients in a generalizable pattern.Here,we used a global database of leaf N and P to determine whether monocots and dicots might have evolved contrasting strategies to balance N and P in response to changes in climate and soil nutrient availability.Specifically,we characterized global patterns of leaf N,P and N/P ratio in monocots and dicots,and explored the sensitivity of stoichiometry to environment factors in these plants.Our results indicate that leaf N and P levels responded to environmental factors differently in monocots than in dicots.In dicots,variations of leaf N,P and N/P ratio were significantly correlated to temperature and precipitation.In monocots,leaf N/P ratio was not significantly affected by temperature or precipitation.This indicates that leaf N,P and N/P ratio are less sensitive to environmental dynamics in monocots.We also found that in both monocots and dicots N/P ratios are associated with the availability of soil total P rather than soil total N,indicating that P limitation on plant growth is pervasive globally.In addition,there were significant phylogenetic signals for leaf N(λ=0.65),P(λ=0.57)and N/P ratio(λ=0.46)in dicots,however,only significant phylogenetic signals for leaf P in monocots.Taken together,our findings indicate that monocots exhibit a“conservative”strategy(high stoichiometric homeostasis and weak phylogenetic signals in stoichiometry)to maintain their growth in stressful conditions with lower water and soil nutrients.In contrast,dicots exhibit lower stoichiometric homeostasis in changing environments because of their wide climate-soil niches and significant phylogenetic signals in stoichiometry.
基金based upon work while an author served at the National Science Foundation(USA)
文摘Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.
