Effect of coir geotextile and geocell on ephemeral gully erosion in the Mollisol region of Northeast China

The unique geomorphological features and farming methods in the Mollisol region of Northeast China increase water catchment flow and aggravate the erosion of ephemeral gully(EG).Vegetation suffers from rain erosion and damage during the growth stage,which brings serious problems to the restoration of grass in the early stage.Therefore,effects of coir geotextile and geocell on EG erosion under four confluence intensities were researched in this study.Results of the simulated water discharge erosion test showed that when the confluence strength was less than 30 L/min,geocell and coir geotextile had a good effect on controlling EG erosion,and sediment yield of geocell and coir geotextile was reduced by 25.95%–37.82%and 73.73%–88.96%,respectively.However,when confluence intensity increased to 40 L/min,protective effect of coir geotextile decreased,and sediment yield rate increased sharply by 189.03%.When confluence intensity increased to 50 L/min,the protective effect of coir geotextile was lost.On the other hand,geocell showed that the greater the flow rate,the better the protective effect.In addition,with the increase in confluence intensity,erosion pattern of coir geotextile developed from sheet erosion to intermittent fall and then to completion of main rill,and the protective effect was gradually weakened.In contrast,the protective effect of EG under geocell was gradually enhanced from the continuous rill to the intermittent rill and finally to the intermittent fall.This study shows that coir geotextile and geocell can prevent EG erosion,and the effect of geocell is better than that of coir geotextile on the surface of EG.

Sediment yield and erosion–deposition distribution characteristics in ephemeral gullies in black soil areas under geocell protection

Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies.In this study,an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different confluence flows on the erosion process of ephemeral gullies.Results showed that when the confluence flow was larger,the effect of geocell was more evident,and the protection against ephemeral gully erosion was stronger.When the confluence flow rates were 0.6,1.8,2.4,and 3.0 m^(3)/h,ephemeral gully erosion decreased by 37.84%,26.09%,21.40%,and 35.45%.When the confluence flow rates were 2.4 and 3.0 m^(3)/h,the average sediment yield rate of the ephemeral gully was close to 2.14 kg/(m^(2)•min),and the protective effect of ephemeral gully erosion was enhanced.When the flow rate was higher,the surface fracture of the ephemeral gully was more serious.With an increase in confluence flow rate,the ratio of erosion to deposition increased gradually,the erosion area of ephemeral gullies was expanded,and erosion depth changed minimally.In conclusion,geocell measures changed erosion patterns by altering the rill erosion/deposition ratio,converting erosion from rill erosion to sheet erosion.

Photoprotective Effects of D1 Protein Turnover and the Lutein Cycle on Three Ephemeral Plants under Heat Stress

To clarify the characteristics of photoinhibition and the primary defense mechanisms of ephemeral plant leaves against photodestruction under high temperature stress,inhibitors and the technology to determine chlorophyll fluorescence were used to explore the protective effects of D1 protein turnover and the lutein cycle in the high temperature stress of the leaves of three ephemeral plants.The results showed that the maximum light conversion efficiency(Fv/Fm)of the ephemeral plant leaves decreased,and the initial fluorescence(Fo)increased under 35℃±1℃ heat stress for 1-4 h or on sunny days in the summer.Both Fv/Fm and Fo could be recovered after 8 h of darkness or afternoon weakening of the external temperature.Streptomycin sulfate(SM)or dithiothreitol(DTT)accelerated the decrease of Fv/Fm and the photochemical quenching coefficient(qP)in the leaves of three ephemeral plants at high temperature,and the decrease was greater in the SM than in the DTT treatment.When the high temperature stress was prolonged,the Y(II)values of light energy distribution parameters of PSII decreased,and the Y(NPQ)and Y(NO)values increased gradually in all the treatment groups of the three ephemeral plants.The results showed that the leaves of the three ephemeral plants had their own highly advanced mechanisms to protect against photodamage,which inhibited the turnover of D1 protein and xanthophyll cycle.This can damage the PSII reaction center in the leaves of the three ephemeral plants under high temperature.The protective effect of D1 protein turnover on heat stress in Erodium oxyrrhynchum and Senecio subdentatus was greater than that of the lutein cycle,while the protective effect of lutein cycle was greater than that of D1 protein turnover in Heliotropium acutiflorum subjected to heat damage.

The Dance-Ephemeral:With Michel Serres

Short,momentary,temporary,transient,precarious,and labile are adjectives that the current post-pandemic,ecological,climatic,war,political,economic,and social contingencies have accustomed us to employ almost compulsively and indiscriminately by now,and that,beyond everything,are synonyms inter-implicit with and in the ephemerality,which deserves reconsideration in its literalness as epìheméra(for a day),that can take place through a sort of its“double”,not quite mainstream but nonetheless suggestive and perhaps even effective,such as the artistic one of dance.Therefore,it is worth pausing to try and see which streaks/implications of the ephemerality itself the dance-ephemeral conveys and/or produces:the neuralgic concretions that the latter seems to me to involve and permeate,in a perspective of re-cognition/re-discovery/awareness,are time,space and the body,evidently inter-implicated.

Combined effects of snow depth and nitrogen addition on ephemeral growth at the southern edge of the Gurbantunggut Desert,China

Water and nitrogen （N） inputs are considered as the two main limiting factors affecting plant growth.Changes in these inputs are expected to alter the structure and composition of the plant community,thereby influencing biodiversity and ecosystem function.Snowfall is a form of precipitation in winter,and snow melting can recharge soil water and result in a flourish of ephemerals during springtime in the Gurbantunggut Desert,China.A bi-factor experiment was designed and deployed during the snow-covering season from 2009 to 2010.The experiment aimed to explore the effects of different snow-covering depths and N addition levels on ephemerals.Findings indicated that deeper snow cover led to the increases in water content in topsoil as well as density and coverage of ephemeral plants in the same N treatment; by contrast,N addition sharply decreased the density of ephemerals in the same snow treatment.Meanwhile,N addition exhibited a different effect on the growth of ephemeral plants：in the 50％ snow treatment,N addition limited the growth of ephemeral plants,showing that the height and the aboveground biomass of the ephemeral plants were lower than in those without N addition; while with the increases in snow depth （100％ and 150％ snow treatments）,N addition benefited the growth of the dominant individual plants.Species richness was not significantly affected by snow in the same N treatment.However,N addition significantly decreased the species richness in the same snow-covering depth.The primary productivity of ephemerals in the N addition increased with the increase of snow depth.These variations indicated that the effect of N on the growth of ephemerals was restricted by water supply.With plenty of water （100％ and 150％ snow treatments）,N addition contributed to the growth of ephemeral plants; while with less water （50％ snow treatment）,N addition restricted the growth of ephemeral plants.

Distribution of ephemeral plants and their significance in dune stabilization in Gurbantunggut Desert

Based on systematically monitoring plants on dune ridges in the southern part of the Gurbantunggut Desert in 2002, this paper, from the angle of dune stabilization by vegetation, describes the temporal and spatial distribution patterns of ephemeral plants on isolated sand dunes, analyses the natural invasion processes of ephemeral plants on human-disturbed sand surface and expounds the importance of ephemeral plants in stabilizing sand dune surface. A total of 45 plant species were identified in the study area, 29 of which are ephemeral plants. Ephemeral plants sprouted in early April and completed their life-circle within about two months. Just as aeolian sand activities came to the strongest stage from April to June in desert regions of northern Xinjiang, the total coverage of trees, shrubs and herbs of long vegetational period on most dune ridges was less than 10%, while the mean coverage of ephemeral plants reached 13.9% in April, 40.2% in May and 14.1% in June. Therefore ephemeral plants acted as the major contributor to dune surface stabilization in the Gurbantunggut Desert. Investigations of vegetation restoration on engineering-disturbed dune surface show that ephemeral plants first recolonized the disturbed dune surface.

Dynamics of arbuscular mycorrhizal fungi associated with desert ephemeral plants in Gurbantunggut Desert

Previous studies documented that most desert plants can be colonized by arbuscular mycorrhizal （AM） fungi, however, little is known about how the dynamics of AM fungi are related to ephemerals in desert ecosystems. The dynamics of AM fungi with desert ephemerals were examined to determine the effects of host plant life stages on the development of AM fungi. Mean colonization of ephemeral annual plants was 45% lower than that of ephemeral perennial plants. The colonizations were much higher in the early part of the growing season than in later parts, peaking at flowering times. The phenology of AM fungi in root systems varied among different ephem- erals. The density of AM fungal spores increased with the development of ephemeral annual plants, reached its maximum at flowering times, and then plateaued about 20 days after the aboveground senescence. A significant positive correlation was found between AM fungi spore density and biomass of ephemeral annual plants. The life cycles of AM fungi associated with desert ephemerals were very shod, being about 60-70 days. Soil temperature and water content had no direct influence on the development of AM fungal spores. We concluded that the development of AM fungi was in response to desert ephemeral phenology and life history strategy.

Identifying ephemeral gullies from high-resolution images and DEMs using flow-directional detection

Ephemeral gullies,which are widely developed worldwide and threaten farmlands,have aroused a growing concern.Identifying and mapping gullies are generally considered prerequisites of gully erosion assessment.However,ephemeral gully mapping remains a challenge.In this study,we proposed a flow-directional detection for identifying ephemeral gullies from high-resolution images and digital elevation models(DEMs).Ephemeral gullies exhibit clear linear features in high-resolution images.An edge detection operator was initially used to identify linear features from high-resolution images.Then,according to gully erosion mechanism,the flow-directional detection was designed.Edge images obtained from edge detection and flow directions obtained from DEMs were used to implement the flow-directional detection that detects ephemeral gullies along the flow direction.Results from ten study areas in the Loess Plateau of China showed that ranges of precision,recall,and Fmeasure are 6 o.66%-90.47%,65.74%-94.98%,and63.10%-91.93%,respectively.The proposed method is flexible and can be used with various images and DEMs.However,analysis of the effect of DEM resolution and accuracy showed that DEM resolution only demonstrates a minor effect on the detection results.Conversely,DEM accuracy influences the detection result and is more important than the DEM resolution.The worse the vertical accuracy of DEM,the lower the performance of the flow-directional detection will be.This work is beneficial to research related to monitoring gully erosion and assessing soil loss.

Is bi-seasonal germination an optimal choice for an ephemeral plant living in a cold desert?

Research on germination strategies has been proposed as a tool for understanding the evolutionary patterns of plant species living in extreme climate conditions. Previous research has concentrated on spring-germinated plants, while there has been little investigation on the ecological significance of ephemeral plants that germinate in both autumn and spring. The biological characteristics and life history strategies of autumn-and spring-germinated plants of Hypecoum erectum L. that belongs to Hypecoum in Papaveraceae family in the southern part of the Gurbantunggut Desert, China, were investigated from 2016 to 2017. Results showed that:(1) the interval from seedling emergence to the end of the life cycle in autumn-germinated plants(202–208 d) was significantly longer than that in spring-germinated plants(53–65 d);(2) the height, crown, principal axis and the number of leaves of autumn-germinated plants were much greater than those of spring-germinated plants;(3) allocation of dry mass to reproduction was 30.24%(±2.41%) and 10.12%(±0.68%) in autumn-and spring-germinated plants, respectively. Autumn-germinated seedlings of H. erectum had an advantage in avoiding the competition between annual and perennial herbs that had longer periods of vegetative growth.Spring-germinated seedlings need to ensure the survival of population when only a fewer autumn-germinated seedlings successfully overwinter. In an unpredictable environment, the germination strategy of bet hedging not only utilizes the resources and reduces the competition intensity in offspring,but also ensures the survival of the plant population.

Arbuscular mycorrhizal fungi improved plant growth and nutrient acquisition of desert ephemeral Plantago minuta under variable soil water conditions

Desert ephemeral plants play an important role in desert ecosystem.Soil water availability is considered as the major restrictive factor limiting the growth of ephemeral plants.Moreover,arbuscular mycorrhizal fungi（AM fungi） are widely reported to improve the growth of desert ephemerals.The present study aimed to test the hypothesis of that AM fungi could alleviate drought stress of desert ephemeral Plantago minuta,and AM fungal functions reduced with the improvement of soil water content.A pot experiment was carried out with three levels of soil water contents（4.5%,9.0%,and 15.8%（w/w））,and three AM inoculation treatments（Glomus mosseae,Glomus etunicatum and non-inoculation）.The results indicate that mycorrhizal colonization rate decreased with the increase of soil water availability.Inoculation improved plant growth and N,P and K acquisition in both shoots and roots regardless water treatments.When comparing the two fungi,plants inoculated with G.mosseae performed better than those inoculated with G.etunicatum in terms of plant growth and nutrient acquisition.These results showed that ameliorative soil water did not suppress arbuscular mycorrhizal fungal functions in improving growth and nutrient acquisition of desert ephemeral Plantago minuta.

Vegetation dynamics of ephemeral and perennial streams in mountainous headwater catchments

Ephemeral and perennial streams of mountainous catchments in Sabaragamuwa Province of Sri Lanka and Hong Kong of China were studied for two years on vegetation dynamics.Each year,sampling was conducted during a period when ephemeral streams had low surface flows.Sampling was realized contiguously using belt transects.The standing crop biomass(hereafter biomass)of herbaceous vegetation in ephemeral channels was comparatively lower than perennials and so was the herb diversity.Herb diversity showed a peak from 1.5 to 4.5 m from the centerline/thalweg of ephemeral and perennial streams.Out of 24 herbs,only three were common for both.A peak herb biomass zone was observed in perennials in the same region where diversity peaked.In ephemerals,herb biomass increased laterally up to^1.5 m,and was constant thereafter.Seedling experiment results tallied with the field diversity observations of both stream types,and suggested that seed dispersion was the main reason for herb colonization.Furthermore,it showed sapling emergence to be significantly higher in perennials than ephemerals.Return period of annual maximum monthly rainfall was a strong indicator of age of trees in ephemeral streams,and elucidated the possibility of hindcasting past flow episodes.Electrical conductivity was significantly high in ephemeral streams among all the water quality parameters.The contents of the water nutrients were approximately the same in both stream types.While recommending further studies on eco-hydrology of ephemerals,we recognize ephemeral streams to be valuable references in climate change studies due to their responsiveness and representativeness in long term hydrological changes.

Ecological distribution and population structure of Litsea glaucescens(Lauraceae)in the ravines of Sierra Fría and Sierra Laurel,Central Mexico

Litsea glaucescens Kunth(Mexican bay leaf,laurel)has a wide distribution in Mexico,growing at both riparian and rupicolous environments in the mountainous region of the Central Highlands of the country.Sierra Fría-Sierra Laurel is a protected natural area covered by a dry forest.The Mexican bay leaf is associated with the oak forest,especially on ravines.The species has been considered at risk in recent years.This research is focused on analyzing the elements of the environment of the ravines,which are influencing the distribution and establishment of laurel populations in the region.Two mountainous regions of Aguascalientes were selected,Sierra Fría and Sierra Laurel.Three ravines of the basin were selected to obtain environmental data.Variables registered were topographic,edaphic,and biotic.Principal component analysis was used to identify ecological factors associated with the presence of L.glaucescens.Mexican bay leaf populations were registered in 10 ravines.At the structural level in the community,29 woody species were registered,Mexican bay leaf had an Importance Value Index of 15.8,ranking 10th among all species.Individuals of laurel were classified by size classes(S,individuals with heights ranging from 0 to 20 cm;S,heights ranging from 0.2 to 1.0 m;S,heights between 1 and 2 m with light trace of flowering;S,heights greater than 2 m with flowering greater than 30% of the canopy;and S,individuals with heights greater than 5 m,curved trunk and basal regrowth)to obtain the population structure.The importance index value for all the species in the riparian community was calculated to the community level.Edaphic factors that characterized the presence of Mexican bay leaf were a high percentage of rock coverage(90%),less mulch depth,and sandy loam shallow soils.Sites that showed higher cation exchange capacity had a higher presence of individuals of the S,S,and Ssize classes.Class Sindividuals were found in shady places with 97% of intercepted light.Individuals of classes Sand Sendure less shady places(75%–85% of intercepted light),and individuals class Sand Sare more frequent in open canopies and crag conditions.Regarding the ecological site factors,such as riverside stream,and rocks on mountain slopes,L.glaucescens life form is riparian and rupicolous.Cation exchange capacity,sodium and calcium levels play an important role in the presence of Mexican bay leaf.Distribution on the ravine and recruitment of the Mexican bay leaf populations are associated with shaded sites,mainly for individuals of size classes Sand S,versus sunny places for individuals of size classes Sand S.The overall population structure had a positive kurtosis with all plant size categories well represented;statistically,the population structure of L.glaucescens is very close to the normal distribution.The information obtained allows us to affirm that the laurel populations in the mountainous areas of Sierra Fría and Sierra Laurel from central Mexico are in good demographic condition.

Structural Features of the Leaf of Ephemeral Species of Representatives of the Brassicaceae Burnett Family in Southwestern Kyzylkum (Uzbekistan)

The results of a study conducted by light microscopy of the anatomical structure of the leaf in ephemeral species from the family Brassicaceae growing under the conditions of Kyzylkum (Uzbekistan) are presented. The following diagnostic, structural adaptive features were revealed: a leaf lamellar, dentate (Diptychocarpus strictus), in Leptaleum filifolium—valky. It is pubescent with various types of trichomes: stellate, dendroid (Meniocus linifolius), equilateral (Streptoloma desertorum) and unequal (Strigosella, Leptaleum filifolium species), unicellular hooked (Leptaleum filifolium). Epidermal cells flattened with wavy or winding walls. The stomata are numerous, not submerged, anomocytic, hemiparacytic, anisocytic types are noted. In all species, the isolate-palisade type of leaf mesophyll predominates. Vascular bundles of all species are sclerified. The main protective features of the leaf of species of the family Brassicaceae are pubescence and sclerification of vascular bundles. We consider the mesomorphic and xeromorphic lines of development ancient and independent. Identified and described signs that can be used in taxonomy and ecology.

Effect of Terrestrial LiDAR Point Sampling Density in Ephemeral Gully Characterization

Gully erosion can account for significant volumes of sediment exiting agricultural landscapes, but is difficult to monitor and quantify its evolution with traditional surveying technology. Scientific investigations of gullies depend on accurate and detailed topographic information to understand and evaluate the complex interactions between field topography and gully evolution. Detailed terrain representations can be produced by new technologies such as terrestrial LiDAR systems. These systems are capable of collecting information with a wide range of ground point sampling densities as a result of operator controlled factors. Increasing point density results in richer datasets at a cost of increased time needed to complete field surveys. In large research watersheds, with hundreds of sites being monitored, data collection can become costly and time consuming. In this study, the effect of point sampling density on the capability to collect topographic information was investigated at individual gully scale. This was performed through the utilization of semi-variograms to produce overall guiding principles for multi-temporal gully surveys based on various levels of laser sampling points and relief variation (low, moderate, and high). Results indicated the existence of a point sampling density threshold that produces little or no additional topographic information when exceeded. A reduced dataset was created using the density thresholds and compared to the original dataset with no major discrepancy. Although variations in relief and soil roughness can lead to different point sampling density requirements, the outcome of this study serves as practical guidance for future field surveys of gully evolution and erosion.

Influence of Temperature, Moisture, and Light Conditions on the Germination of Seeds of <i>Erythronium japonicum</i>Decne

Erythronium japonicum is a representative species of spring ephemeral, forest floor plants in substitution forests in Japan. Seed germination tests were conducted to observe the effects of temperature, light, and moisture content on the germination of E. japonicum. E. japonicum seeds did not germinate at constant temperatures of 5&#176C, 10&#176C, 15&#176C, 20&#176C, or 25&#176C. Seeds germinated at 5&#176C and 10&#176C after storage at 20&#176C for 1 or 2 months. Seed germinability was affected by desiccation to only 40% moisture content. Seeds germinated well in both light and dark conditions. Conditions under the leaf litter layer showed unique characteristics of temperature, light, and moisture content. The temperature was around 20&#176C under the leaf litter layer, even though it was 30&#176C above. The moisture content under the leaf litter layer was higher than that above. The leaf litter blocked out the sunlight. The temperature of 20&#176C necessary for E. japonicum germination occurred below, but not above, the leaf litter layer. The avoidance of decreasing in germinability from reduced seed moisture content in a short time is consistent with the high moisture conditions under the leaf litter layer. The leaf litter layer plays an important role in providing optimal conditions of temperature, light, and moisture content for the germination of E. japonicum seeds.

Public Key Infrastructure: A Survey

As security is essential in communications through electronic networks, development of structures providing high levels of security is needed. Public Key Infrastructure (PKI) is a way of providing security measures by implementing the means of key pairs among users. In this paper, an overview of the public key infrastructure is discussed that includes various components and operation, some well known PKIs and their comparisons. Also we discuss current implementations, risk and challenges of PKIs.

The Influence of a Retail Store’s Atmosphere on Consumer’s Reactions: The Case of Ephemeral Stores

Pop-up stores present many advantages to brands and customers.They take advantage of seasonality and events and manifest themselves in a relevant way in front of the targeted customer.Following a mixed-method approach,semi-structured interview outcomes were used to enrich the proposed research model,which was then tested by a questionnaire.Our research’s results highlighted interesting components respective to the Lebanese market’s pop-up stores;test and experimentation,collection presentation,communication and buzz creation.Test results showed that Lebanese pop-up store atmospheres are characterized by their social dimension;customers are less affected by the aesthetics and more affected by the crowd who frequents the pop-up.Results showed that customers feel happier and are more likely to stay and to spend time in the store than to make purchases.

Morphologic Response of a River Channel to Sand Mining in River Tyaa,Kitui County,Kenya

Over 40 billion tons of sand is mined worldwide every year which isestimated to be higher than the natural replacement rates. In Kenya, therate of sand mining is raising concerns over its environmental effects sinceit is not regulated. This paper presents findings on the geomorphic effectsof sand mining in the ephemeral River Tyaa channel in Kitui County. Thestudy adopts the concept of feedback response mechanism of a naturalgeomorphic system. Through purposive sampling River Tyaa was selectedfor the study, where rampant sand mining was reportedly taking place.Random sampling on the five sand mining sites identified came up with arepresentative site namely Kanginga on which systematic sampling wasapplied while collecting data at both the active and control sites. Dataon channel width, depth and slope angles was obtained through physicalmeasurements while data on quantity of sand mined was obtained fromMwingi Sand Mining Cooperative. Multiple logistic regression analysiswas used to analyse data whereby the model compared active and controlsites. Test results indicated that sand mining had significantly increasedriver channel’s width (O.R. =1.531), depth (O.R. =1.527) and slope angles(O.R. =1.634) at active mining sites compared to control sites as deducedfrom the respective Odds Ratios. It concluded that sand mining had alteredchannel’s morphology resulting to adverse environmental effects such asloss of riparian vegetation and channel incision. It recommended curbingof illegal sand mining through licencing operators and reducing quantity ofsand mined by closing some mines. Furthers, it recommended monitoringthrough regular Environmental Impact Assessment (E.I.A) and Audit (E.A)to inform protection of the river system from degrading.

USDA-ARS National Sedimentation Laboratory:A Historic Perspective

Most authorities concede sediment from soil erosion to be the largest single stream pollutant. Physical damage from sediment includes reservoir storage loss, navigation channel filling, stream channel morphology alterations, ecological impacts, and clogging of drainage pathways. Ultimately, soil erosion is a very expensive problem. In the United States, accelerated soil erosion has been an ongoing issue since the establishment of the colonies. Through the initiative of great minds and the labor of countless individuals, the USDA was established and continues to fight for the people, providing assistance, guidance, and research. In this manuscript, the historical groundwork is laid for the establishment of the USDA-ARS National Sedimentation Laboratory (NSL) and a synopsis of NSL research is provided. This brief perspective of soil erosion research conducted on behalf of the people is but a small portion of the illustrious history of the USDA.

spatial and environmental determinants of plant species diversity in a temperate desert

Aims Deserts are one of the ecosystems most sensitive to global climate change.However,there are few studies examining how changing abiotic and biotic factors under climate change will affect plant species diversity in the temperate deserts of Asia.This study aimed to:(i)characterize species distributions and diversity patterns in an Asian temperate desert;and(ii)to quantify the effects of spatial and environment variables on plant species diversity.Methods We surveyed 61 sites to examine the relationship between plant species diversity and several spatial/environmental variables in the Gurbantunggut Desert.Spatial and environmental variables were used to predict plant species diversity in separate multiple regression and ordination models.Variation in species responses to spatial and environmental conditions was partitioned by combining these variables in a redundancy analysis(RDA)and by creating multivariate regression trees(MRT).Important Findings We found 92 plant species across the 61 sites.Elevation and geographic location were the dominant environmental factors underlying variation in site species richness.A RDA indicated that 93%of the variance in the species–environment relationships was explained by altitude,latitude,longitude,precipitation and slope position.Precipitation and topographic heterogeneity,through their effects on water availability,were more important than soil chemistry in determining the distribution of species.MRT analyses categorized communities into four groups based on latitude,soil pH and elevation,explaining 42.3%of the standardized species variance.Soil pH strongly influenced community composition within homogeneous geographic areas.Our findings suggest that precipitation and topographic heterogeneity,rather than edaphic heterogeneity,are more closely correlated to the number of species and their distributions in the temperate desert.