Spatial patterns of Picea crassifolia driven by environmental heterogeneity and intraspecifi c interactions

Research on the spatial patterns of tree populations is critical for understanding the structure and dynamic processes of forests.However,little is known about how the underlying drivers shape these patterns and species interactions in forest systems.In this study,spatial point pattern analysis investigated the combined eff ects of intraspecifi c interactions and environmental heterogeneity on the spatial structure and internal maintenance mechanisms of Picea crassifolia in the Qilian Mountain National Nature Reserve,China.Data were obtained from a 10.2-ha dynamic monitoring plot(DMP)and sixteen 0.04-ha elevation gradient plots(EGPs).Under complete spatial randomness,both mature trees and saplings in the DMP demonstratedlarge-scale aggregation with negative correlations.In EGPs,saplings were clustered in small mesoscales,mature trees were randomly distributed,and the interactions of saplingstrees at all elevations were not correlated.By eliminating the interference of environmental heterogeneity through the inhomogeneous Poisson process,saplings in the DMP and EGPs were clustered in small scales and trees randomly distributed.Intraspecifi c associations were negatively correlated,in the DMP and at low elevations,and no correlations in high elevations of EGPs.In the vertical scale,saplings showed a small-scale aggregation pattern with increase in elevation,and the aggregation degree fi rst decreased and then increased.The interactions of saplings-trees and saplings–saplings showed inhibitions at small scales,with the degree of inhibition gradually decreasing.Spatial patterns and associations of adults–adults did not change signifi-cantly.The results revealed that intraspecifi c interactions and environmental heterogeneity regulated the spatial patterns of P.crassifolia at small and large scales,respectively.Environmental heterogeneity might be the most decisive factor aff ecting the spatial patterns of saplings,while trees were more aff ected by intraspecifi c interactions.Moreover,competition between trees in this area could be more common than facilitation for the growth and development of individuals.

Environmental heterogeneity and productivity drive the assemblage of benthic diatom:a case study of the Three Gorges Reservoir

Dam construction has a critical effect on river ecosystems in the world,resulting in a rapid decline in biodiversity and ecosystem health.However,the effect of dam construction on the assemblage pattern of benthic diatoms remains unclear.The benthic diatoms assemblages in the tributary backwater area of the Three Gorges Reservoir(TGR)were investigated under low water level(LWL)and high water level(HWL)conditions.Results show that Discostella stelligera,Nitzschia palea,and Craticula subminuscula were dominant species in LWL,while Achnanthidium minutissimum and Nitzschia dissipata were dominant in HWL.Furthermore,environmental variables,productivity parameters,diversity indices,and community similarity were found significantly different between LWL and HWL periods.The Mantel test indicated that both environmental and spatial factors had significant effects on diatom communities in backwater area,while productivity was also a key driving force in LWL.The variation partitioning analysis(VPA)further demonstrated that environment factors could explain the largest variance of diatom assemblages in HWL(9%)and LWL(11%),followed by spatial factors.The relative importance of productivity to diatom community was significantly enhanced in LWL,but only a slight effect was found in HWL.These results indicate that the diatom assemblages were shaped by both environmental filtering and spatial factors.The relative importance of spatial factors depended on the degree of productivity.Therefore,the homogenization of diatom communities due to environmental disturbance,e.g.eutrophication and dam building,is the underlying mechanism in assembling the benthic diatoms.

Spatial distributions of tropical tree species in northern Vietnam under environmentally variable site conditions

Ecological interactions of species and thus their spatial pat- terns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locations of tree individuals from two 1-ha tropicalforest plots in Vietnam. We analyzed the effect of environmental heterogeneity on tree distributions; spatial distribution patterns of dominant species; inter-specific associations; and conspecific associations between life stages. Our analyses showed that： environmental conditions were homo- geneous at plot 1 but heterogeneous at plot 2; in both plots, all six domi- nant species were aggregated at various scales up to 30 m, and tree spe- cies were aggregated at larger scales in the homogeneous site than in the heterogeneous site; attraction between pairs of species was remarkably higher at the homogeneous site while negative associations were more frequent in the heterogeneous site; some species, H. kurzii, T. ilicifolia （homogeneous plot） and D. sylvatica, S. wightianum （heterogeneous plot） showed a lack of early life-stage individuals near conspecific adults. Moreover, additional clustering of young individuals was independent from conspecific adults, except D. sylvatica in both sites. These findings are consistent with the Janzen-ConneU hypothesis. Overall, habitat het- erogeneity influences spatial patterns and inter-specific associations of the tree species and evidences of self-thinning are shown in most species.

Potential tradeoffs between intraspecific and interspecific trait variations along an environmental gradient in a subtropical forest

There has been growing attention to intraspecific variation in trait-based plant ecology. However, studies on these changes across ontogenetic stages and the potential trade-offs with interspecific traits along environmental gradients are rare. In this study, we measured six wood and bark traits of 1030 trees of six species(Castanopsis nigrescens; C. carlesii; Lithocarpus polystachyus; L. synbalanos; Ormosia glaberrima; O. pachycarpa) from a10-ha plot in a subtropical forest. Mean intraspecific variation in bark thickness and bark percentage to DBH was more than twice that for wood density and bark density.Bark thickness and bark percentage showed a consistent trend with increasing tree size. Small-tree traits were more variable than the same traits in larger trees. Altitude,convexity and soil nutrients explained the majority of the variations in the six traits, while sibling species had similar relationships between traits and environmental variables.Trees with dense wood and thin bark were usually found on steep slopes at lower altitudes. Our findings show intraspecific trait variability has different spatial patterns compared with interspecific variabilities along an environmental gradient.

Heterogeneity-diversity Relationships in Natural Areas of Yunnan,China

Understanding regional environmental heterogeneity(EH)and biodiversity relationships(heterogeneity-diversity relationships:HDRs)is the first step toward coupling environmental variables with biodiversity surrogates into regional systematic conservation planning.However,there is no universal method for determining regional HDRs that considers various environmental variables and biodiversity in different regions.This study selected 32 nature reserves as natural areas in Yunnan,China,to examine regional HDRs in Yunnan.We calculated 17 EH parameters(of soil,topography,and climate)and three(ecosystem,plant,and animal)biodiversity indices in the nature reserves.By examining the explanatory power of each EH parameter and area of the nature reserve,we identified the primary parameters and constructed an optimal model for each biodiversity index.The explanatory powers of these parameters varied for each biodiversity index,and those of climatic parameters were generally higher than soil and topographic heterogeneity ones.Heterogeneity of the temperature annual range,followed by area and heterogeneity of soil type,were important parameters for ecosystem diversity of Yunnan and the optimal model explained 56.9%.Plant diversity was explained 54.5%by its optimal model,consisting of heterogeneity of precipitation of the coldest quarter and annual precipitation.Heterogeneity of temperature annual range was important for animal diversity in Yunnan and explained 29.6%of its optimal model.This study suggests that EH parameters can be an effective surrogate for biodiversity,therefore,we suggested that the significance and role of climatically heterogeneous regions for the conservation of biodiversity in Yunnan should be further studied in the future.

Effects of Soil Nutrient Heterogeneity and Earthworms on Aboveground Biomass of Experimental Plant Communities

Soil nutrients are commonly heterogeneously distributed and earthworms are one of the most common soil organisms.While effects of both soil nutrient heterogeneity and earthworms have been well studied,their interactive effect on plant community productivity has rarely been tested.In a greenhouse experiment,we constructed experimental plant communities by sowing seed mixtures of four grasses,two legumes and two forbs in either a heterogeneous soil consisting of low and high nutrient soil patches or a homogeneous soil where the low and high nutrient soil patches were evenly mixed.The earthworm Eisenia fetida was either added to these soils or not.Aboveground biomass of the whole communities,grasses and legumes did not differ between the homogeneous and heterogeneous soils or between the soils with and without earthworms.However,soil nutrient heterogeneity reduced aboveground biomass of forbs,and such an effect did not interact with earthworms.In response to soil heterogeneity and earthworms,biomass ratio of the three functional groups showed similar patterns as that of their biomass.At the patch level,aboveground biomass of the whole community,grasses and legumes were greater in the high than in the low nutrient soil patches within the heterogeneous soil.A similar pattern was found for the forbs,but this was only true in the absence of earthworms.Our results suggest that soil nutrient heterogeneity and earthworms may not influence aboveground biomass of plant communities,despite the fact that they may modify the growth of certain plant functional groups within the community.

Habitat associations of saplings and adults in an old-growth temperate forest in the Changbai mountains, northeastern China

Species-habitat association analysis is useful to detect spatial arrangement of individual plants, to discover rules about the distribution of species and to generate hypotheses about the possible underlying process controlling observed structures. Quantifying methods were used to classify habitats in terms of topographical variables in a mixed temperate broad-leaved Korean pine forest of the Changbai mountains in northeastern China. All of the 625 20 m × 20 m quadrats of the plot could be unambiguously assigned to one of three habitat categories （low-plateau, high-plateau and slope）. Torus-translation tests were used to estimate species-habitat associations. Many species are clearly distributed in a biased fashion with respect to habitats. Fifteen （55.6%） out of 27 species showed strong positive or negative association with specific habitats. We compared species-habitat associations at the sapling and adult stages. Adjusted density values indicated few species exhibit extremely strong habitat associations. Only 9 out of 26 species had adjusted densities 〉 3 in the habitat for which they had strong positive affinity. Few species show the same associations at the small tree and large tree stages. Only 3 out of 22 occurring associations with a specific habitat appeared to have a consistent habitat association at the two stages. These results suggest that species-habitat associations exist in the 25-ha plot of the temperate forest of the Chang- bai mountains. Owing to limitations in our statistical methodology, we partly underestimated associations by ignoring rare species. Regeneration niches can contribute to co-existence, but regeneration niches due to habitat associations play a limited role in species co-existence, since most species show a similar trend in habitat associations at the sapling and adult stages. We should pay more attention to shifts in habitat associations, i.e. niche shifts at different stages of existence.

Elevational diversity gradients across seed plant taxonomic levels in the Lancang River Nature Reserve： role of temperature, water and the mid-domain effect

It remains unclear whether the elevational diversity gradients observed in seed plants across different taxonomic levels （family, genus, and species） are driven by the same macro-environmental variables. In this study, seed plant elevational distribution data from the Lancang River Nature Reserve （Yunnan, China） were used to investigate spatial patterns in diversity and their environ- mental correlates, comparing across taxonomic levels. Environmental variables included energy availability, climate seasonality and environmental heterogeneity. All taxonomic levels （family, genus, and species） were found to have strong elevational richness gradients, with the strength of the gradient weakening at higher taxonomic levels. Spatial patterns in richness were explained by a combination of contemporary environmental variables and the mid-domain effect at all taxonomic levels. The independent effects of temperature- and precipitation-related variables were similar in explaining geographical patterns of family, genus and species richness. Energy, seasonality and heterogeneity variables influenced seed plant spatial richness at different taxonomic levels in similar ways.

Scheduling algorithm based on critical tasks in heterogeneous environments

Heterogeneous computing is one effective method of high performance computing with many advantages. Task scheduling is a critical issue in heterogeneous environments as well as in homogeneous environments. A number of task scheduling algorithms for homogeneous environments have been proposed, whereas, a few for heterogeneous environments can be found in the literature. A novel task scheduling algorithm for heterogeneous environments, called the heterogeneous critical task （HCT） scheduling algorithm is presented. By means of the directed acyclic graph and the gantt graph, the HCT algorithm defines the critical task and the idle time slot. After determining the critical tasks of a given task, the HCT algorithm tentatively duplicates the critical tasks onto the processor that has the given task in the idle time slot, to reduce the start time of the given task. To compare the performance of the HCT algorithm with several recently proposed algorithms, a large set of randomly generated applications and the Gaussian elimination application are randomly generated. The experimental result has shown that the HCT algorithm outperforms the other algorithm.

Soil heterogeneity affects ramet placement of Hydrocotyle vulgaris

Aims Soil heterogeneity is common in natural habitats.It may trigger for-aging responses(placing more ramets and/or roots in nutrient-rich patches than in nutrient-poor patches)and further affect the growth of plants.However,the impact of soil heterogeneity on competitive interactions has been little tested.Methods We conducted a greenhouse experiment to investigate the effects of soil heterogeneity on intraspecific competition with a stolonif-erous herb Hydrocotyle vulgaris.We grew one(without com-petition)or nine ramets(with competition)of H.vulgaris under a homogeneous environment and two heterogeneous environ-ments differing in patch size(large or small patches).In the het-erogeneous treatment,the soil consisted of the same number of nutrient-rich and nutrient-poor patches arranged in a chessboard manner,and in the homogeneous treatment,the soil was an even mixture of the same amount of the nutrient-rich and the nutrient-poor soil.Important Findings Irrespective of intraspecific competition,H.vulgaris showed for-aging responses to soil heterogeneity in the large patch treatment,e.g.it produced significantly more biomass,ramets,aboveground mass and root mass in the nutrient-rich patches than in the nutrient-poor patches.In the small patch treatment,foraging responses were observed when intraspecific competition was present,but responses were not observed when there was no competition.However,we find a significant effect of soil heterogeneity on neither overall growth nor competitive intensity of H.vulgaris.Our results suggest that foraging responses to soil heterogeneity may not necessarily be adaptive and intraspecific competition may not be influenced by soil heterogeneity.

Experimental evidence that soil heterogeneity enhances plant diversity during community assembly

Aims Environmental heterogeneity is a primary mechanism explain-ing species coexistence and extant patterns of diversity.Despite strong theoretical support and ample observational evidence,few experimental studies in plant communities have been able to demonstrate a causal link between environmental heterogene-ity and plant diversity.This lack of experimental evidence sug-gests that either fine-scale heterogeneity has weak effects on plant diversity or previous experiments have been unable to effectively manipulate heterogeneity.Here,we utilize a unique soil manipu-lation to test whether fine-scale soil heterogeneity will increase plant richness through species sorting among experimental patch types.Methods This experiment was conducted in the tallgrass prairie region of south-central Kansas,USA.We utilized the inherent variation found in the vertical soil profile,which varied in both biotic and abiotic characteristics,and redistributed these strata into either homoge-neous or heterogeneous spatial arrangements in 2.4×2.4 m plots.After the soil manipulation,34 native prairie species were sown into all plots.We conducted annual censuses at peak biomass to quantify species composition and plant density by species within the experimental communities.Important Findings After 2 years,species richness was significantly higher in heteroge-neous relative to homogeneous plots and this pattern was independ-ent of total plant density.In the heterogeneous plots,13 species had higher establishment in a specific patch type representing one of the three soil strata.Conversely,no species had greater estab-lishment in the mixed stratum,which comprised the homogene-ous plots,relative to the heterogeneous strata.These species sorting patterns suggest that fine-scale heterogeneity creates opportunities for plant establishment due to niche differences,which translates into increased plant diversity at the plot scale.Species richness was more strongly related to plant density among patches comprising homogenous plots-where fine-scale heterogeneity was minimized,but weak in heterogeneous plots.This pattern is consistent with the idea that richness-density relationships dominate when neutral pro-cesses are important but are weak when niche processes operate.Unlike many previous attempts,our results provide clear,experi-mental evidence that fine-scale soil heterogeneity increases species richness through species sorting during community assembly.

Diversity begets diversity:Low resource heterogeneity reduces the diversity of nut-nesting ants in rubber plantations

One of the most general patterns in ecology is the positive relationship between environmental heterogeneity and local diversity.On the one hand,increased resource heterogeneity provides more resources for diverse consumers in the community.On the other hand,increased structural heterogeneity creates variation in the environment’s physical structure,thus allowing the coexistence of diverse species with different environmental requirements.Here,we examined the relative importance of resource and structural heterogeneity in determining the taxonomic,functional,and phylogenetic diversity of nutnesting ants in natural rainforest and rubber plantation.The species richness of nut-nesting ants was 70%higher in rainforest than in rubber plantation.The clustered functional and phylogenetic structure in rubber plantation suggested a strong effect of environmental filtering in shaping ant functional and phylogenetic structure.Nesting heterogeneity(nut diversity)was the major factor explaining variation in taxonomic,functional,and phylogenetic diversity,suggesting that resource heterogeneity plays a major role in shaping the biodiversity patterns of nut-nesting ants.Overall,these results indicate that decreased resource diversity following the conversion of rainforest to rubber plantation can drive biodiversity loss in nut-nesting ants,through its effect on reducing both ant species,functional,and phylogenetic diversity.The decline in species richness and functional and phylogenetic diversity in the local ant community might have major effects on ecosystem functioning.

Spatial heterogeneity in soil particle size:does it affect the yield of plant communities with different species richness?

Aims Soil heterogeneity is ubiquitous in many ecosystems.We hypothesized that plant communities with higher species richness might be better adapted to soil heterogeneity and produce more biomass than those with lower richness.This is because there is niche differentiation among species and different species can complement each other and occupy a broader range of niches when plant species richness is high.However,no study has tested how soil particle heterogeneity affects the yield of plant communities,and whether such effects depend on the spatial scale of the heterogeneity and the species richness within the communities.Methods In a greenhouse experiment,we sowed seeds of four-species or eight-species mixtures in three heterogeneous treatments consisting of 32,8 or 2 patches of both small(1.5 mm)and large quartz(3.0 mm)particles arranged in a chessboard manner and one homogeneous treatment with an even mixture of small and large quartz particles.Important Findings Biomass production was significantly greater in the communities with high species richness than those with low species richness.However,soil particle heterogeneity or its interactions with patch scale or species richness did not significantly affect biomass production of the experimental communities.This work indicates that plant species richness may have a bigger impact on plant productivity than soil particle heterogeneity.Further studies should consider multiple sets of plant species during longer time periods to unravel the potential mechanisms of soil heterogeneity and its interactions with the impacts of species richness on community yield and species coexistence.

Federatedmutual learning:a collaborative machine learning method for heterogeneous data,models,and objectives

Federated learning(FL)is a novel technique in deep learning that enables clients to collaboratively train a shared model while retaining their decentralized data.However,researchers working on FL face several unique challenges,especially in the context of heterogeneity.Heterogeneity in data distributions,computational capabilities,and scenarios among clients necessitates the development of customized models and objectives in FL.Unfortunately,existing works such as FedAvg may not effectively accommodate the specific needs of each client.To address the challenges arising from heterogeneity in FL,we provide an overview of the heterogeneities in data,model,and objective(DMO).Furthermore,we propose a novel framework called federated mutual learning(FML),which enables each client to train a personalized model that accounts for the data heterogeneity(DH).A“meme model”serves as an intermediary between the personalized and global models to address model heterogeneity(MH).We introduce a knowledge distillation technique called deep mutual learning(DML)to transfer knowledge between these two models on local data.To overcome objective heterogeneity(OH),we design a shared global model that includes only certain parts,and the personalized model is task-specific and enhanced through mutual learning with the meme model.We evaluate the performance of FML in addressing DMO heterogeneities through experiments and compare it with other commonly used FL methods in similar scenarios.The results demonstrate that FML outperforms other methods and effectively addresses the DMO challenges encountered in the FL setting.

Nitrogen deposition alters soil chemical properties and bacterial communities in the Inner Mongolia grassland

Nitrogen deposition has dramatically altered biodiversity and ecosystem functioning on the earth; however, its effects on soil bacterial community and the underlying mechanisms of these effects have not been thoroughly examined. Changes in ecosystems caused by nitrogen deposition have traditionally been attributed to increased nitrogen content. In fact, nitrogen deposition not only leads to increased soil total N content, but also changes in the NIL^-N content, NO3--N content and pH, as well as changes in the heterogeneity of the four indexes. The soil indexes for these four factors, their heterogeneity and even the plant community might be routes through which nitrogen deposition alters the bacterial community. Here, we describe a 6-year nitrogen addition experiment conducted in a typical steppe ecosystem to investigate the ecological mechanism by which nitrogen deposition alters bacterial abundance, diversity and composition. We found that various characteristics of the bacterial community were explained by different environmental factors. Nitrogen deposition decreased bacterial abundance that is positively related to soil pH value. In addition, nitrogen addition decreased bacterial diversity, which is negatively related to soil total N content and positively related to soil NOa--N heterogeneity. Finally, nitrogen.addition altered bacterial composition that is significantly related to soil NH4＋-N content. Although nitrogen deposition significantly altered plant biomass, diversity and composition, these characteristics of plant community did not have a significant impact on processes of nitrogen deposition that led to alterations in bacterial abundance, diversity and composition. Therefore, more sensitive molecular technologies should be adopted to detect the subtle shifts of microbial community structure induced by the changes of plant community upon nitrogen deposition.

Topographic species-habitat associations of tree species in a heterogeneous tropical karst seasonal rain forest, China

Aims Tropical and subtropical karst forests of south China are under increas-ing pressure from over-exploitation causing widespread habitat degra-dation and biodiversity loss.Previous research has demonstrated that topography,as a proxy for resource availability,plays an important role in shaping tree species distributions in tropical forests.However,the association between growth stages and habitats types has not been considered in this analysis.Our aim was to examine the differences among different habitat types to determine whether tree species show similar species-habitat associations at young and mature life stages.Methods We used multivariate regression tree analysis to examined species-habitat associations among eight topographically defined habitats.The results were tested with a torus-translation test and canonical correspondence analysis(CCA)for 74 species in a 15 ha karst tropi-cal seasonal rain forest at the Nonggang National Natural Reserve in south China.We considered two life stages(young and mature)of trees species that showed a positive association with topography.Important Findings We found marked differences in community characteristics and number of associations among the eight habitats.Of the 74 species subjected to torus-translation test,63 had significant positive and 70 had significant negative associations with one or more of the eight habitats.Positive associations were more frequent in higher elevation habitats and negative associations were more frequent in lower eleva-tion habitats.This suggests that edaphic and hydrological variation related to topography play important roles in habitat partitioning in heterogeneous karst forests.For the 63 tree species with significant positive associations to at least one habitat,40 of them had the same positive association at young and mature life stages.The CCA revealed that the six topographic variables considered had consistent relation-ships with species distribution among all individuals and their two life stages.This indicates that most of the karst forest tree species show consistent associations with a single habitat throughout their life.We conclude that niche differentiation plays an important role in main-taining the diversity of this heterogeneous species-rich karst forest.

Commensal microbiota and host metabolic divergence are associated with the adaptation of Diploderma vela to spatially heterogeneous environments

Heterogeneous environment adaptation is critical to understand the species evolution and response to climate change.However,how narrow-range species adapt to micro-geographic heterogeneity has been overlooked,and there is a lack of insights from metabolism and commensal microbiota.Here,we studied the environmental adaptation for 3 geographic populations(>40 km apart)of Diploderma vela,a lizard endemic to dry-hot valleys of the Hengduan Mountain Region.The climatic boundary caused a cooler,droughtier,and barren environment for northernmost population(RM)than the middle(QZK)and southernmost populations(FS).Correspondingly,significant divergences in liver and muscle metabolism and commensal microbiota were detected between RM and QZK or FS individuals,but not between QZK and FS individuals.Phospholipid composition,coenzyme level(i.e.pyridoxal and NAD^(+)),and cholesterol metabolism(e.g.androgen and estriol synthesis)constituted the major metabolic difference between RM and QZK/FS groups.FS and QZK individuals kept abundant Proteobacteria and antifungal strains,while RM individuals maintained more Firmicutes and Bacteroidota.Strong associations existed between varied host metabolite and gut microbes.How were these interpopulation variations associated to the environment adaptation were discussed.These results provided some novel insights into the environmental adaptation and implicated the consequence of climate change on narrow-range species.

The compromising foraging of a clonal submerged plant in variable environments of substrate type and light condition: a simulation study

Aims Foraging behavior was concerned less in plants especially for clonal aquatic species.The goal of this study was to test the foraging behav-ior and the function of phenotypic plasticity of a clonal submerged plant,Potamogeton maackianus A.Benn in variable manipulative environments.Methods To explore the foraging behavior of a clonal submerged plant,clones of P.maackianus were cultivated in variable environments of different substrate types and light conditions.We measured bio-mass,specific root area(SRA),specific root length(SRL),branch-ing angle of the ramet,chlorophyll content of apical leaves(CCAL),Fv/Fm(chlorophyll fluorescence parameter that indicates maximal photosystem II(PS II)efficiency)and biomass distribution in soil and light contrast treatments after harvest.Important Findings We found that the atypical non-clonal-like foraging behavior homogenized the performance of the stoloniferous clonal spe-cies,P.maackianus,in the measurement of biomass in our study.Substrate type had significant effects on most traits of P.maackianus,except on total biomass,shoot biomass distribution and CCAL.Patchy substrate mediated more root distribution into sand patch rather than into clay patch.Increase of SRA,SRL and Fv/Fm might be adaptive to substrate heterogeneity.Moreover,substrate hetero-geneity induced‘sidewalk’stolon lineage on the edge of sand patch along the patch border.Light condition only had significant effects on branching angle,shoot biomass distribution and Fv/Fm.Shade led to more shoot assignment in light-rich zone than in light-poor zone.Potamogeton maackianus adjusted the branching angle of ramet rather than clonal exploitation in heterogeneous substrates with patchy shade.Moreover,shade led to higher Fv/Fm.A com-promising foraging strategy promoted P.maackianus to escape unfa-vorable environments.Phenotypic plasticity,which maximized the performance of P.maackianus in the measurement of biomass in variable environments,may explain its domination in some shallow lakes of the middle and lower reaches of Yangtze River.

Unified Enclave Abstraction and Secure Enclave Migration on Heterogeneous Security Architectures

Nowadays,application migration becomes more and more attractive.For example,it can make computation closer to data sources or make service closer to end-users,which may significantly decrease latency in edge computing.Yet,migrating applications among servers that are controlled by different platform owners raises security issues.We leverage hardware-secured trusted execution environment(TEE,aka.,enclave)technologies,such as Intel SGX,AMD SEV,and ARM TrustZone,for protecting critical computations on untrusted servers.However,these hardware TEEs propose non-uniform programming abstractions and are based on heterogeneous architectures,which not only forces programmers to develop secure applications targeting some specific abstraction but also hinders the migration of protected applications.Therefore,we propose UniTEE which gives a unified enclave programming abstraction across the above three hardware TEEs by using a microkernel-based design and enables the secure enclave migration by integrating heterogeneous migration techniques.We have implemented the prototype on real machines.The evaluation results show the migration support incurs nearly-zero runtime overhead and the migration procedure is also efficient.

The diffusive model for West Nile virus with advection and expanding fronts in a heterogeneous environment

In this paper,we investigate a reaction-diffusion-advection model with expanding fronts,which models the spatial transmission of West Nile virus(WNv)in a heterogeneous environment.A free boundary problem is formulated and the global existence and uniqueness of the solution is presented.In addition to a classical basic reproduction number,the spatial-temporal basic reproduction number for the model with null Dirichlet boundary condition is introduced and the risk index associated with the virus in spatial setting is defined,and their properties are discussed.Sufficient conditions for the WNv to vanish or spread are given,and the asymptotic behavior of the solution to the free boundary problem when the spreading occurs is established.Our results show that the initial number of infected populations and the expanding capability of the expanding fronts exhibit important impacts on the extinction or persistence of the virus.