Host plant traits play a crucial role in shaping the composition of epiphytic microbiota in the arid desert,Northwest China

Phyllosphere microorganisms are a crucial component of environmental microorganisms,highly influenced by host characteristics,and play a significant role in plant health and productivity.Nonetheless,the impact of host characteristics on shaping phyllosphere microbial communities of plants with different life forms remains ambiguous.Utilizing high-throughput sequencing technology,this study analyzed the diversity and community composition of phyllosphere epiphytic microorganisms(e.g.,bacteria and fungi)of various plant life forms in the hinterland of the Gurbantunggut Desert,Northwest China.Functional annotation of prokaryotic taxa(FAPROTAX)and fungi function guild(FUNGuild)were employed to assess the ecological functions of microorganisms and to investigate the role of stochastic and deterministic processes in shaping phyllosphere microbial communities.Result showed a diverse array of phyllosphere epiphytic microorganisms in the desert plants,with Proteobacteria,Cyanobacteria,and Actinobacteriota dominating bacterial community,while Ascomycota and Basidiomycota were prevalent in fungal community.Comparison across different plant life forms highlighted distinct microbial communities,indicating strong filtering effects by plant characteristics.FAPROTAX prediction identified intracellular parasites(accounting for 27.44%of bacterial community abundance),chemoheterotrophy(10.12%),and phototrophy(17.41%)as the main functions of epiphytic bacteria on leaves of different life form plants.FUNGuild prediction indicated that phyllosphere epiphytic fungi primarily served as Saprotrophs(81.77%),Pathotrophs(17.41%),and Symbiotrophs(0.82%).Co-occurrence network analysis demonstrated a predominance of positive correlations among different microbial taxa.Raup-Crick dissimilarity index analysis revealed that deterministic processes predominantly influenced phyllosphere bacterial and fungal community assembly.Variance partitioning analysis and random forest modeling suggested that plant leaf functional traits significantly impacted both bacterial and fungal community composition,with fungal community composition showing a closer association with leaf nutrients and physiology compared with bacterial community composition.The distinct responses of bacterial and fungal communities to plant traits were attributed to the differing properties of bacteria and fungi,such as bacteria having higher potential dispersal rates and broader ecological niches than fungi.Overall,the results indicate that phyllosphere bacterial and fungal communities undergo similar community assembly processes,with fungi being more influenced by plant characteristics than bacteria.These findings offer novel insights into the ecology of phyllosphere microbial communities of desert plants.

Variations of plant life form diversity along the Northeast China Transect and its direct gradient analysis

Plant life form diversity and its direct gradient analysis on a larger scale climate change gradient were tested, based on the data from Northeast China Transect platform. The results showed that the species numbers, life form richness and life form diversity were relative higher at the eastern forests and the ecotone between typical vegetation, while those on the meadow grasslands and typical steppes were lower. Although plant life forms can reflect the climate variations, life form diversity is not consistent with the major global gradient along the NECT.

Plant communities and reproductive phenology in mountainous regions of northern Libya

Within the semi-desert landscape of northern Libya, two sub-humid escarpments occur: Al-Akhdar in the east and Nafusa (Jabal Al-Gharbi) in the west. This study compares plant communities in the two regions, which are along an elevation gradient, in terms of species composition and diversity, frequency of different Raunkiaer life forms, and reproductive phenology. The two regions differed in species composition and life-form frequency between regions and between elevation zones within each region. Patterns were associated with the lower rainfall and lower moisture-holding capacity of soils at Nafusa, resulting in more xeric conditions. Only 13% of species were shared between the two regional landscapes. Species diversity, life-form frequency, and duration of the flowering-fruiting phenophase were all affected by elevation above sea level. The duration of flowering and fruiting in spring and fall was associated with environmental conditions, although there were different thresholds in the two regions. There was both a spring and fall episode of flowering at Nafusa, but only spring flowering at Al-Akhdar. It is anticipated that there will be a gradual shift of plant communities to higher elevations and loss of certain sensitive species in response to ongoing climate change.

Species Composition, Richness and Aboveground Biomass of Natural Grassland in Hilly-Gully Regions of the Loess Plateau, China

In order to study the characteristics of species composition, richness and aboveground biomass of natural grasslands, and then ifnd out the relations between species richness and aboveground productivity of the communities and possible mechanisms to form the relations, four typical grassland communities （Artemisia capillaries （AC）, Thymus quinquecostatus （TQ）, Stipa bungeana （SB） and Stipa grandis （SG）） along with a succession sequence in hilly-gully regions of the Loess Plateau, China, were investigated by ifeld survey and laboratory analysis. The results were summarized as follows：Different succession stages had different species compositions as well as different proportions of plant life forms and photosynthetic types, and Asteraceae, Poaceae and Leguminosae were their dominant species as well as their dominant perennial herb species;and different succession stages had signiifcantly different species richness and aboveground biomasses. There were many relation patterns （linear positive correlation, unrelated relations and unimodal relations） between the species richness and aboveground biomass in different succession stages and a signiifcant unimodal relation between the species richness and aboveground biomass in all the grassland communities and the highest species diversity appeared at a moderate level of productivity. The results suggest the unimodal relations in all the grassland communities are accumulative results of the relations in each succession stage.

A Summary of the Homogeneous 5D Universe Creation Model: Expressed in the Dirac Second-Order Quantization Representation

A summary of the homogeneous 5D universe model is expressed in the Dirac second-order quantized representation for the magnetic monopoles, identified in terms of the Higgs Bosons, and through systematic ordered excitations of the Higgs vacuum obtained the non-homogeneous 4D Lorentz manifolds filled with masses, corresponding to making space dimension reduction projections, and thus realization of Newtonian gravity, followed by the 3D space symmetry breaking into 2D × 1D that produces the Perelmann-entropy and Ricci-Flow mappings, resulting in the realization of Poincare spheres, represented by nucleus such as Carbon 12, all the way to stars, and matter filled discs, such as stars in galaxies and 2D carbon-based molecular structures like nitrogenous bases. Finally, the forming of RNAs and DNAs, then life forms.

Floristics and soil characteristics of Ohud mountain,AlMadinah Al-Munawarah,Western Saudi Arabia

Ohud mountain is one of the main important historic sites in the Arab Peninsula,and it is distinguishable over the rest of the mountains in the region.No extensive floristic survey has been carried out on Ohud mountain because of the rugged topography of this mountain.The current study investigates the floristic diversity and the correspondence of environmental factors of the phytogeographical distribution of plants,based on the floristic analysis of the present region.The research question is about the relationships between the species diversity and the human impacts of populated area at lowlands around Ohud mountain.A total of 59 species belonging to 56 genera and 28 families were recorded.Asteraceae had the highest contribution,about 12%of the total plant species.The analysis of the life forms demonstrated the prevalence of therophytes(68%)followed by chamaephytes(24%),indicating the adaptation of these life forms to hyperarid conditions.The chorological analysis indicated the predominance of the bi-regional taxa over the other phytochoria.Most of the recorded plant species belong to Saharo-Arabian and Sudano-Zambezian(24%)phytochoria.TWINSPAN analysis was performed to detect the indicator species of different vegetation groups and confirmed by detrended correspondence analysis(DCA or DECORANA).It is concluded that species richness and diversity revealed clear variation along the mountain and among the studied sites.Plant species diversity and richness were more pronounced in the intermediate portion of the elevation gradients across the mountain,with a decrease in the high altitudinal belts.The decrease was also recorded at the lower altitudes,where human impacts clearly affected vegetation;leading to a decrease in alpha diversity.In addition,the beta diversity among moderately highlands and lowlands was considerably high indicating the heterogeneous species composition among the studied sites along mountain elevations.The general pattern of vegetation groups distribution is controlled by a number of environmental factors;such as latitude,longitude,elevation,organic matter and some anions and cations.A Canonical Correspondence Analysis(CCA)ordination revealed that the vegetation structure has a strong association with the latitude of the mountain followed by organic matter and Magnesium.It is recommended that the populated area should be subjected to restoration of mountain ecosystem that might be degraded by human activities.

Local-scale patterns of genetic variation in coexisting floating-leaved Nymphoides peltata and submerged Myriophyllum spicatum in Donghu Lake

Coexisting floating-leaved and submerged plants experience similar environmental changes but may evolve different patterns of genetic variation.To compare local-scale genetic variation,we collected samples of floating-leaved Nymphoides peltata and submerged Myriophyllum spicatum coexisting in a disturbed urban lake in China.At the subpopulation level,using microsatellites,M.spicatum had higher clonal diversity than N.peltata.M.spicatum had 28.4%multilocus genotypes(MLGs)shared between subpopulations,but N.peltata had only one MLG shared between two adjacent subpopulations.N.peltata displayed more genetic variation between subpopulations than within subpopulations,but the reverse was true for M.spicatum.Principal components and Bayesian cluster analyses showed that individuals from each subpopulation of N.peltata tended to have relatively close genetic relationships.For M.spicatum,individuals from each subpopulation were genetically scattered with those from other subpopulations.Our results imply that in unpredictable adverse environments M.spicatum may be less subjected to local-deme extinction than N.peltata because of genetically diverse clones at the subpopulation level.This characteristic means that following adverse events,M.spicatum may rapidly restore subpopulation distributions via recolonization and intense gene flow among subpopulations.

Environmental heterogeneity regulates species-area relationships through the spatial distribution of species

Species-area relationships(SARs),also known as species-area curves,are fundamental scaling tools for biodiversity research.Sampling design and taxonomic groups affect the widely cited forms of species-area curves.However,the influence of sampling design and related environmental heterogeneity on SAR curves is rarely considered.Here,we investigated the SAR among different plant life forms(herbaceous plants,shrubs,and trees)in a 25.2-ha ForestGEO plot,the Wanglang Plot,in Sichuan,southwestern China,using a non-contiguous quadrat sampling method and power-law model.We compared the estimated parameters(the intercept c and the slope z)of the power-law models among different plant life forms,tested whether the SAR curve forms varied with sampling starting location,and assessed the effect of environmental heterogeneity accumulating with sampling area on curve variation.We found a wider range of variations in the SARs.The estimated c,z-values of power SAR were higher for the herbaceous plants than for the woody plants.A wider variation of SARs for the herbaceous plants than those for the woody plants.The selection of sampling starting location affected the SAR curve forms because of the roles of soil and topographic heterogeneity.We concluded that environmental heterogeneity regulates SAR curves sampled from different starting locations through spatial distribution of plant life forms.Thus,we recommend considering the design of sampling starting location when constructing SAR curves,especially in a heterogeneous habitat with unrandom distribution patterns of species.

Impacts of snow on seed germination are independent of seed traits and plant ecological characteristics in a temperate desert of Central Asia

Seed germination profoundly impacts plant community composition within the plant life cycle.Snow is an important source of water for seed germination in the temperate deserts of Central Asia.Understanding how seed germination responds to variations in snow cover in relation to seed traits and plant ecological characteristics can help predict plant community sustainability and stability in Central Asia under a scenario climate change.This study investigated the seed germination of 35 plant species common to the Gurbantunggut Desert in Central Asia under the three snow treatments:(1)snow addition;(2)ambient snow;and(3)snow removal.Two-way analysis of variance(ANOVA)tests were performed to assess interactions among the impacts of snow treatments,seed traits and plant ecological characteristics on seed germination.Phylogenetic generalized least-squares(PGLS)model was used to test the relationships between seed traits and seed germination.The results demonstrated that snow variations had no significant impacts on seed germination overall.Seed germination under the snow addition treatment was similar with that under the ambient snow treatment,irrespective of seed traits and plant ecological characteristics.Snow removal only had negative impacts on seed germination for certain groups of seed traits and plant ecological characteristics.Seed mass positively affected seed germination,showing a linear increase of arcsin square root-transformed seed germination with log-transformed seed mass.Seed shape also profoundly impacted seed germination,with a higher germination percentage for elongated and flat seeds.Seed germination differed under different plant life forms,with semi-shrub species showing a significantly higher germination percentage.Most importantly,although snow treatments,seed traits and plant ecological characteristics had no interactive effects on seed germination overall,some negative impacts from the snow removal treatment were detected when seeds were categorized on the basis of seed mass and shape.This result suggests that variations of snow cover may change plant community composition in this temperate desert due to their impacts on seed germination.

Similar mycorrhizal fungal communities associated with epiphytic and lithophytic orchids of Coelogyne corymbosa

Mycorrhizal fungi are essential for the growth and development of both epiphytic(growing on trees)and lithophytic(growing on rocks)orchids.Previous studies indicate that in lowland tropical areas,orchid mycorrhizal fungal compositions are correlated with the life form(i.e.,epiphytic,lithophytic,or terrestrial)of their host plants.We therefore tested if a similar correlation exists in an orchid distributed at higher elevations.Coelogyne corymbosa is an endangered ornamental orchid species that can be found as a lithophyte and epiphyte in subtropical to subalpine areas.Based on high-throughput sequencing of the fungal internal transcribed spacer 2(ITS2)-rDNA region of mycorrhizae of C.corymbosa,we detected 73 putative mycorrhizal fungal Operational Taxonomic Units(OTUs).The OTUs of two dominant lineages(Cantharellales and Sebacinales)detected from C.corymbosa are phylogenetically different from those of other species within the genus Coelogyne,indicating that different orchid species prefer specific mycorrhizal fungi.We also found that the Non-metric multidimensional scaling(NMDS)plots of orchid mycorrhizal fungi were not clustered with life form,the variations among orchid mycorrhizal fungal communities of different life forms were not significant,and most of the OTUs detected from epiphytic individuals were shared by the lithophytic plants,suggesting that orchid mycorrhizal associations of C.corymbosa were not affected by life form.These findings provide novel insights into mycorrhizal associations with endangered ornamental orchids.

Floristic analysis and dominance pattern of sal(Shorea robusta)forests in Ranchi,Jharkhand,eastern India

The present study describes the floristic composition and dominance pattern of sal forests in Ranchi,Jharkhand,eastern India.Vegetation was studied in 47 belt transects(509100 m)that had 137 plant species(110 identified and 27 unidentified)belonging to 51 families.The family Fabaceae with 17 species(8 spp.belonging to subfamily Faboideae,6 spp.to Caesalpinioideae and 3 spp.to Mimosoidieae)contributed the most to diversity,followed by Rubiaceae(8 spp.)and Euphorbiaceae(6 spp.).Tree density in sal was inversely related to species richness.Total tree density(C 10 cm GBH)in the studied forests was 397 individuals ha-1,with a basal cover of 262.50 m2 ha-1.Important plants of conservation concern are Pterocarpus marsupium Roxb,Andrographis paniculata(Burm.f.)Wall,Sterculiaurens Roxb.,Tinospora cordifolia(Willd.)Miers,and Asparagus densiflorus(Kunth)Jessop.Phanerophytes had the highest percentage(71%,with percentage deviation from normal life form of?25)followed by therophyte(15%,with percentage deviation?2).Observed percentage deviation from normal life form was much lower(with?2 percentage deviation)in both chamaephytes(8%)and therophytes(15%),suggesting that the studied sal forests are favorable for supporting various plants species.The forest management strategies should focus on the increasing demands for different timber and non-timber forest products to conserve the plant diversity of these natural forests.

Ecophysiological aspects and photosynthetic pathways in 105 plants species in saline and arid environments of Tunisia

In Tunisian arid regions, plant life forms, ecotypes, physiological types and photosynthetic pathways （03, 04 or CAM） remain unclear. Understanding the characters of these plant species could be important for land restoration. A literature survey was conducted for 105 plants species in arid regions of Tunisia. These plant species belong to several ecotypes： halophytes, xerophytes, gypsophytes, psamophytes, xero-halophytes, gypso-halophytes, psamo-halophytes, psamo-xerophytes, xero-gypsophytes and hygro-halophytes. The variation of photosynthetic pathway types in the 105 studied species shows that 56.2% were C3, 41.0% were C4, 1.9% were CAM and 1.0% were C3-CAM. The C3 pathway was more abundant in the halophytes, whereas the C4 one was more common in the xerophytes, gypsophytes, gyp- so-halophytes and psamo-halophytes. The ratio of C3 to C4 species （C3/C4 ratio） was 0.2 in the psamo-halophytes, 0.8 in the gypso-halophytes, 1.1 in the xerophytes, 1.6 in the xero-halophytes, 1.8 in the hygrohalophytes, 2.0 in the psamo- phytes and 3.8 in the halophytes. The annuals were mainly C3 plants whereas most of perennials were C4 ones. The C3/C4 ratio was 1.3 in succulent species and 1.4 in non-succulent species. Thus, succulence seems not to affect the distribution of C3 and C4 pathways within the studied plants. This investigation shows high percentages of C4 plants occurred in Tuni- sian arid regions. However, there were significant differences in their abundance among ecotypes. Basing on C3/C4 ratio, we can find that the abundance of the C4 pathway was in the following order： psamo-halophytes, gypso-halophytes, xe- rophytes, xero-halophytes, hygro-halophytes, psamophytes and halophytes. In Tunisian arid regions, C4 species were most abundant in xerophytes and less abundant in halophytes. In the Chenopodiaceae the number of C3 plants was 13 and the number of C4 species was 20 and in the Poaceae the number of C3 was 23 and the number of C4 was 19 species. Thus, the most C4 proportion was in the Chenopodiaceae and Poaceae species. This confirms the fact that the Cheno- podiaceae and the Poaceae were the leading families that tolerate salinity and aridity.

Sexual and Breeding Systems in a Xerophytic Shrubland

Reproductive systems are fundamental attributes for understanding life cycle and regeneration processes and provide information about seed production and genetic diversity. Analyses of reproductive strategies within communities and their associations with functional groups can indicate how physical and biological characteristics may influence the reproductive ecology of such communities. The main goal was to determine if the reproductive systems and their associated functional groups have particular characteristics related to extreme conditions and disturbance within xerophytic shrubland. Floral morphology analysis and four experimental tests were conducted to determine the reproductive systems of species and their associations with the life form, succulence, carbon metabolism, dispersal syndrome, pollination, and disturbance. Of the 144 plant species studied, 72.9% were hermaphrodite, 22.9% were monoecious, and 4.2% were dioecious. Dioecy was associated with woodiness, frugivory and undisturbed areas, while monoecy was more common in herbs. Adichogamy, protandry and herkogamy were more frequent than dichogamy, protogyny and no herkogamy, respectively. Xenogamous species tend to be woody and grow in undisturbed areas, while partially xenogamous species were mainly herbs occurring in disturbed areas. The majority of species were partially self-incompatible. High levels of outbreeding strategies tended to occur mainly in woody K-strategy species from undisturbed areas, mixed breeding strategies occurred in disturbed areas and overall community, and inbreeding strategies were associated with mostly herbaceous r-strategy primarily in disturbed areas.

Latitudinal pattern and the driving factors of leaf functional traits in 185 shrub species across eastern China

Aims To explore the pattern of the leaf functional traits of shrub species along a latitudinal gradient in eastern China and determine the driv-ing factors of leaf trait variation at a large scale.Methods We investigated the leaf thickness(LT),leaf area(LA),specific leaf area(SLA)and leaf dry mass content(LDMC)of 185 shrub species from 13 sites across eastern China.The trends of these four-leaf traits were ana-lyzed with respect to latitude,and the differences between different life forms(e.g.,evergreen and deciduous)and habitats(e.g.,understory and typical)were compared.We quantified the effects of the plant life forms and environmental factors on the leaf traits via mixed-model analyses.Important Findings The LT and LA decreased,whilst and the LDMC increased,as the latitude increased,and significant differences in these traits were observed between the different plant life forms.The LT and LA were smaller,whereas the SLA and LDMC were larger in decidu-ous shrubs than in evergreen shrubs.Among the different habitats,the LA and SLA were larger,while the LDMC was smaller in under-story shrubs than in typical shrub species.These results indicate that typical shrub species are better adapted to drier environments,as indicated by a reduced LT and increased LDMC.Furthermore,general linear models showed that variations in the four-leaf traits with respect to latitude were mainly caused by a shift in plant life forms.

The relationship between relative growth rate and whole-plant C:N:P stoichiometry in plant seedlings grown under nutrient-enriched conditions

Aims Recent theories indicate that N is more in demand for plant growth than P;therefore,N concentration and N:C and N:P ratios are predicted to be positively correlated with relative growth rate(RGR)in plants under nutrient-enriched conditions.This prediction was tested in this study.Methods We examined the whole-plant concentrations of C,N and P and RGR,as well as the relationship between RGR and the concentrations and the ratios of N:C,P:C and N:P,for different harvest stages(the days after seed germination)of the seedlings of seven shrub species and four herbaceous species grown in N and P non-limiting conditions.The relationships among plant size,nutrient concentrations and ratios were subsequently determined.Important Findings RGR was positively correlated with N concentration and the ratios of N:PandN:C when the data were pooled for all species and for each shrub species,but not for individual herbaceous species.However,the relationship between RGR and P concentration and P:C was not significantly correlated for either shrubs or herbs.The variation of N among harvest stages and species was much greater than that of P,and the variation in N:P ratio was determined primarily by changes in N concentration.The shrub species differed from the herbaceous species in their N and P concentrations,nutrient ratios and in intraspecific relationships between RGR and nutrient ratios.These differences possibly reflect differences in the capacity for P storage and biomass allocation patterns.In general,our data support recent theoretical predictions regarding the relationship between RGR and C:N:P stoichiometry,but they also show that species with different life forms differ in the relationships among RGR and C:N:P stoichimetries.

Vegetation composition of old extensive green roofs(from 1980s Germany)

Introduction:Since their development in the late 1970s in Germany,extensive green roofs(EGR)have become increasingly popular as mitigation tools for urban environmental issues around the world.EGRs are planted with select species,which ensure consistent cover and performance over time.This research presented herein is part of a systematic re-evaluation of EGR technology since the German industry began.Methods:Given the opportunity to access a small sample of old EGRs installed over 20 years ago in south-west Germany,this research surveyed the vegetation and substrate with an interest in describing these parameters with time-through-space substitution.Results:Similar to previous studies,this preliminary work found correlations between roof age with vegetation(cover abundance and species diversity)and substrate properties(e.g.,depth,organic content,pH,and nutrients).Roof age had positive relationship with soil organic content(Corg),and negative relationships with substrate depth and soil pH.These soil variables are inter-related,as shallow acidic substrates create unfavourable conditions for decomposition and thereby the accumulation of duff.Substrate variables correlated with EGR vegetation,suggesting a trend of simplified species composition over time.Indeed,Corg had a negative relationship with cover and species diversity of most life forms;only Sedum species had positive associations with Corg.Conclusions:Considering the dynamics associated with shallow mineral substrates,and the greater floristic diversity of younger roofs,simple Sedum-based vegetation may represent a steady state for conventional EGRs.

Transition along gradient from warm to mesic temperate forests evaluated by GAMM

Aims The aim of the study was to discover what set of variables best explains the transition from warm to mesic forest vegetation.Based on various variables grouped into sets(geomorphological,ecological,structural,soil characteristics and chorological),six models were built and tested by generalized additive mixed models(GAMMs).We assumed that each set of variables has different explanatory power.Our aim was to compare the six different models(sets of variables),to test which model best explains the species turnover in forest communities along the transition between warm and mesic temperate forests and to try to find reasons for the different explanatory power of the models.Methods The research took place in the southern part of the Balkan Peninsula.Field sampling was done according to standard methods.The gradient from warm to mesic forests was defined as the turnover of species and evaluated by projection of samples on the first unconstrained DCA axis.Geomorphological,ecological,structural and soil characteristics,together with chorological sets of variables,were regressed on the turnover of species composition.Based on the five sets of variables,six models were constructed and tested by generalized additive mixed models.Important Findings Ecological conditions best explain the change of forest communities along the gradient;evolution and the development of vegetation reflected in chorotypes are also of high importance;geomorphology and structure seem not to change so dramatically and soil shows the least significant differences of all.Ecological variables are the most important set of variables in the transition between warm and mesic temperate forests but eco-evolutionary dynamics after the Pleistocene should also be taken into consideration.

Effects of environmental conditions and space on species turnover for three plant functional groups in Brazilian savannas

Aims Different plant functional groups display diverging responses to the same environmental gradients.Here,we assess the effects of environmental and spatial predictors on species turnover of three functional groups of Brazilian savannas(Cerrado)plants—trees,palms and lianas—across the transition zone between the Cerrado and Amazon biomes in central Brazil.Methods We used edaphic,climatic and plant composition data from nine one-hectare plots to assess the effects of the environment and space on species turnover using a Redundancy Analysis and Generalized Dissimilarity Modeling(GDM),associated with variance partitioning.Important Findings We recorded 167 tree species,5 palms and 4 liana species.Environmental variation was most important in explaining species turnover,relative to geographic distance,but the best predictors differed between functional groups:geographic distance and silt for lianas;silt for palms;geographic distance,temperature and elevation for trees.Geographic distances alone exerted little influence over species turnover for the three functional groups.The pure environmental variation explained most of the liana and palm turnover,while tree turnover was largely explained by the shared spatial and environmental contribution.The effects of geographic distance upon species turnover leveled off at about 300 km for trees,and 200 km for lianas,whereas they were unimportant for palm species turnover.Our results indicate that environmental factors that determine floristic composition and species turnover differ substantially between plant functional groups in savannas.Therefore,we recommend that studies that aim to investigate the role of environmental conditions in determining plant species turnover should examine plant functional groups separately.

Diversity patterns, environmental drivers and changes in vegetation composition in dry inter-Andean valleys

Aims We studied diversity,patterns of endemism and turnover of veg-etation composition in dry inter-Andean valleys(DIAVs)where lit-tle is known about the influence of the abiotic drivers controlling plant species composition and occurrences,and the life forms that contribute most toα-andβ-diversity,respectively.This study was focused on DIAVs located in the highlands(800-2800 m)around the Equator(1°N-5°S).The following questions were addressed:(i)what differences exist between endemic and non-endemic species in terms of species number,frequency and abundance?(ii)are pat-terns ofα-andβ-diversity correlated with latitude?(iii)what are the major environmental drivers controlling spatial patterns in species composition and occurrence?Methods We established 63 transects of 5×100 m in areas with DIAV vegetation,impacted as little as possible by human activities.In each transect,all mature trees and shrubs were identified and counted to determine their density.The coverage of terrestrial herbs was estimated.Generalized additive models were used to quantify the relationship betweenα-andβ-diversity with latitude.To recordα-diversity,we used the exponential Shannon index.The Sørensen index was used to measureβ-diversity or species turnover.We used canonical correspondence analysis to deter-mine species composition and generalized linear mixed models to quantify simultaneously the determinants of species occur-rence across species and sites.The models were evaluated using the Akaike information criterion.All analyses were run separately for trees,herbs and shrubs.Important Findings Overall,we found that shrubs was the most diverse life form,constituting 43%(12%endemic)of the 313 species,followed by herbs(36%;11.5%endemic)and trees(20%;5%endemic).Trees comprise mostly species with low abundance(e.g.<3 individuals ha^(−1)),which was also true for herbs,whereas shrubs showed a larger number of abundant species(>30 individuals ha^(−1)),includ-ing four endemic species.Most of the endemic species were locally rare,and most of them were restricted to southern valleys,suggesting low migration rates due to local barriers.We identified seven species distribution patterns that gave rise to high β-diversity in the dry inter-Andean valleys.Theβ-diversity of trees was the lowest.Herbs had the highestβ-diversity,which increased steadily with geographic distance.Our results further highlight the influ-ence of disturbance,water availability and low temperature on plant species composition and occurrence.We also found signifi-cant,contrasting patterns in responses to environmental drivers,when analyzing our data separately by life form.Our results show that analyzing diversity patterns separately by life form can shed new light on the mechanisms that have generated present-day pat-terns of plant diversity in DIAVs.

Distribution of Vascular Plant Species Richness Along an Elevational Gradient in the Dongling Mountains, Beijing, China

Quantifying spatial patterns of species richness and determining the processes that give rise to these patterns are core problems In blodlverslty theory. The aim of the present paper was to more accurately detect patterns of vascular species richness at different scales along altitudinal gradients In order to further our understanding of blodlverslty patterns and to facilitate studies on relationships between blodlverslty and environmental factors. Species richness patterns of total vascular plants species, Including trees, shrubs, and herbs, were measured along an altitudinal gradient on one transect on a shady slope In the Dongllng Mountains, near Beljlng, China. Direct gradient analysis, regression analysis, and geostatlstlcs were applied to describe the spatial patterns of species richness. We found that total vascular species richness did not exhibit a linear pattern of change with altitude, although species groups with different ecological features showed strong elevatlonal patterns different from total species richness. In addition to total vascular plants, analysis of trees, shrubs, and herbs demonstrated remarkable hierarchical structures of species richness with altitude （I.e. patchy structures at small scales and gradients at large scales）. Species richness for trees and shrubs had similar spatial character-Istics at different scales, but differed from herbs. These results Indicated that species groups with similar ecological features exhibit similar blodlverslty patterns with altitude, and studies of blodlverslty based on species groups with similar ecological properties or life forms would advance our understanding of variations In species diversity. Furthermore, the gradients or trends appeared to be due mainly to local variations In species richness means with altitude. We also found that the range of spatial scale dependencies of species rlchnese for total vascular plants, trees, shrubs, and herbs was relatively large. Thus, to detect the relationships between species richness with environmental factors along altitudinal gradients, It was necessary to quantify the scale dependencies of environmental factors In the sampling design or when establishing non-linear models.