Correlation of soil properties and fruit size of Callgonum mongolicum and related species

Correlations of soil properties and fruit size of Calligonum mongolicum Turcz. and related species were analyzed. The resullLs showed that the particle size characteristics of soils for growing Calligonum mongolicum and related species were similar, and the soils belonged to sandyones. The organic matter contents of soils were low （averaging 1.772 to 3.054 g/kg）, and the total salt content of soils was low too （averaging 0.471 g/kg）. The pH values indicated that the soils were alkaline, varying from pH 7.65 to 10.25. The results of Principal Component Analysis （PCA） and hierarchical cluster showed that 9 habitats could be divided into 6 types according to salt contents and pH values. Fruit sizes of different populations and the soil properties had significant linear correlations （P〈0.000）. It was concluded that the differences in fruit sizes among the populations of Calligonum mongolicum and related species werre related to soil variability, especially the nutrient contents of soils, and fruit size can not be considered as a taxonomic index of Calligonum mongofcum and related species.

Species Richness, Diversity and Density of Understory Vegetation along Disturbance Gradients in the Himalayan Conifer Forest

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.

Molecular evidence of introgressive hybridization between related species Jankowski's Bunting(Emberiza jankowskii)and Meadow Bunting(Emberiza cioides)(Aves:Passeriformes)

Natural hybridization,which often occurs between closely related species exhibiting sympatric or parapatric distributions,is an important source of genetic variation within populations.The closely related Jankowski’s Bunting(Emberiza jankowskii)and Meadow Bunting(E.cioides)are similar in morphology and genetics,occupy overlapping niches,and are sympatric in eastern Inner Mongolia.Previous studies have reported trans-species polymorphisms of alleles between the two species,as well as an unexpectedly high genetic diversity of the endangered E.jankowskii.We speculate that introgressive hybridization has occurred between the two species and contributed to the additional unexpected variation to E.jankowskii.We used mitochondrial NADH dehydrogenase subunit 2(ND2)gene and 15 nuclear microsatellite markers to compare the genetic diversity of E.jankowskii and E.cioides,and inferred the origin of trans-species polymorphisms between the two species by phylogenetic reconstruction and Bayesian cluster analysis.The two species could be clearly distinguished by population cluster analysis.Despite the large number of mutational differences,we still detected sharing of major haplotypes and the presence of hybrids between the two species.Our study confirmed that weak introgressive hybridization has occurred between sympatric E.jankowskii and E.cioides,which may be mediated by female E.cioides individuals,and that interspecific introgression has contributed to the maintenance of high genetic diversity in E.jankowskii.While being wary of the potential negative effects of introgressive hybridization,we suggest that expanding the habitat of E.jankowskii remains the most effective conservation strategy at present.

Lowland pasture in Himalayan highland: edaphic properties and species composition

This study was carried out to investigate if on-farm cut vs. grazed pastures differed in soil fertility and species density in the temperate Himalayan highlands. Soil fertility and species relative density were measured from 30 cut and 30 grazed dairy pastures. In both types of pasture, soil pH, available phosphorus(P) and exchangeable potassium(K) were negatively correlated with pasture age and slope. In cut pasture, cocksfoot(Dactylis glomerata) and pasture age were positively correlated,whereas in grazed pasture, they were negatively correlated. In grazed pasture, unsown species and pasture age were positively correlated. Soil available P was significantly greater in cut pastures whereas soil exchangeable K was significantly greater in grazed pastures. In terms of species density, cut pasture had greater densities of cocksfoot and Italian ryegrass(Lolium multiflorum), whereas grazed pasture showed greater densities of white clover, sedge and local grass. Our study suggests that, if there are no improvements in the current method of pasture management, the cut pastures in the future are likely to have a simple pasture mixture constituting only cocksfoot and white clover(Trifolium repens).Whereas in grazed pasture, the pasture mixture is likely to be comprised of white clover and unsown species such as sedge, local grass and broadleaf weeds.

Species recognition and the divergences in the chemical and ultrasonic signals between two coexisting Rattus species

The ability to recognize and differentiate between conspecifics and heterospecifics as well as their signals is critical for the coexistence of closely related species.In the genus Rattus,species are morphologically similar and multiple species often coexist.Here,we investigated the interspecific recognition and signal differentiation of two sympatric rat species,the brown rat(Rattus norvegicus,RN)and the Asian house rat(Rattus tanezumi,RT).In a two-way choice test,both RN and RT females showed a preference for conspecific male rats to heterospecific ones.RT females showed a significant preference for accessible urine of males of same species to those of other species,but not for the inaccessi-ble urine.On the other hand,there were significant differences in the structural characteristics of the ultrasonic vocalization emitted by males of these two rat species.Sodium dodecyl sulphate-polyacrylamide gel electrophoresis(SDS-PAGE)and isoelectric focusing electrophoresis unveiled that major urinary proteins(MUPs)in voided urine were more highly expressed in RN males versus RT males.The interspecific dif-ferences of urinary volatile compounds were also discussed.In conclusion,female rats had the ability to distinguish between males of either species.

Response of Polygonum viviparum Species and Community Level to Long-term Livestock Grazing in Alpine Shrub Meadow in Qinghai-Tibet Plateau

Grazing by domestic herbivores is generally recognized as a major ecological factor and an important evolutionary force in grasslands, Grazing has both extensive and profound effects on individual plants and communities, We investigated the response patterns of Polygonum viviparum species and the species diversity of an alpine shrub meadow in response to long-term livestock grazing by a field manipulative experiment controlling livestock numbers on the Qinghai-Tibet Plateau in China, Here, we hypothesize that within a range of grazing pressure, grazing can alter relative allocation to different plant parts without changing total biomass for some plant species if there is life history trade-offs between plant traits, The same type of communities exposed to different grazing pressures may only alter relative species＇ abundances or species composition and not vary species diversity because plant species differ in resistant capability to herbivory, The results show that plant height and biomass of different organs differed among grazing treatments but total biomass remained constant, Biomass allocation and absolute investments to both reproduction and growth decreased and to belowground storage increased with increased grazing pressure, indicating the increasing in storage function was attained at a cost of reducing reproduction of bulbils and represented an optimal allocation and an adaptive response of the species to long- term aboveground damage, Moreover, our results showed multiform response types for either species groups or single species along the gradient of grazing intensity, Heavy grazing caused a 13,2% increase in species richness, There was difference in species composition of about 18%-20% among grazing treatment, Shannon-Wiener （H′） diversity index and species evenness （E） index did not differ among grazing treatments, These results support our hypothesis,

C:N:P stoichiometry of Ericaceae species in shrubland biomes across Southern China:influences of climate,soil and species identity

Aims Carbon(C),nitrogen(N)and phosphorus(P)stoichiometry strongly affect functions and nutrient cycling within ecosystems.However,the related researches in shrubs were very limited.In this study,we aimed to inves-tigate leaf stoichiometry and its driving factors in shrubs,and whether stoichiometry significantly differs among closely related species.Methods We analyzed leaf C,N and P concentrations and their ratios in 32 species of Ericaceae from 161 sites across southern China.We examined the relationships of leaf stoichiometry with environmen-tal variables using linear regressions,and quantified the interactive and independent effects of climate,soil and species on foliar stoi-chiometry using general linear models(GLM).Important Findings The foliar C,N and P contents of Ericaceae were 484.66,14.44 and 1.06 mg g−1,respectively.Leaf C,N and P concentrations and their ratios in Ericaceae were significantly related with latitude and altitude,except the N:P insignificantly correlated with latitude.Climate(mean annual temperature and precipitation)and soil properties(soil C,N and P and bulk density)were significantly influenced element stoichiom-etry.The GLM analysis showed that soil exerted a greater direct effect on leaf stoichiometry than climate did,and climate affected leaf traits mainly via indirect ways.Further,soil properties had stronger influ-ences on leaf P than on leaf C and N.Among all independent factors examined,we found species accounted for the largest proportion of the variation in foliar stoichiometry.These results suggest that species can largely influence foliar stoichiometry,even at a lower taxonomic level.

Models and estimators linking individual-based and sample-based rarefaction, extrapolation and comparison of assemblages

Aims In ecology and conservation biology,the number of species counted in a biodiversity study is a key metric but is usually a biased underestimate of total species richness because many rare species are not detected.Moreover,comparing species richness among sites or samples is a statistical challenge because the observed number of species is sensitive to the number of individuals counted or the area sampled.For individual-based data,we treat a single,empirical sample of species abundances from an investigator-defined species assemblage or community as a reference point for two estimation objectives under two sampling models:estimating the expected number of species(and its unconditional variance)in a random sample of(i)a smaller number of individuals(multinomial model)or a smaller area sampled(Poisson model)and(ii)a larger number of individuals or a larger area sampled.For sample-based incidence(presence–absence)data,under a Bernoulli product model,we treat a single set of species incidence frequencies as the reference point to estimate richness for smaller and larger numbers of sampling units.Methods The first objective is a problem in interpolation that we address with classical rarefaction(multinomial model)and Coleman rarefaction(Poisson model)for individual-based data and with sample-based rarefaction(Bernoulli product model)for incidence frequencies.The second is a problem in extrapolation that we address with sampling-theoretic predictors for the number of species in a larger sample(multinomial model),a larger area(Poisson model)or a larger number of sampling units(Bernoulli product model),based on an estimate of asymptotic species richness.Although published methods exist for many of these objectives,we bring them together here with some new estimators under a unified statistical and notational framework.This novel integration of mathematically distinct approaches allowed us to link interpolated(rarefaction)curves and extrapolated curves to plot a unified species accumulation curve for empirical examples.We provide new,unconditional variance estimators for classical,individual-based rarefaction and for Coleman rarefaction,long missing from the toolkit of biodiversity measurement.We illustrate these methods with datasets for tropical beetles,tropical trees and tropical ants.Important Findings Surprisingly,for all datasets we examined,the interpolation(rarefaction)curve and the extrapolation curve meet smoothly at the reference sample,yielding a single curve.Moreover,curves representing 95%confidence intervals for interpolated and extrapolated richness estimates also meet smoothly,allowing rigorous statistical comparison of samples not only for rarefaction but also for extrapolated richness values.The confidence intervals widen as the extrapolation moves further beyond the reference sample,but the method gives reasonable results for extrapolations up to about double or triple the original abundance or area of the reference sample.We found that the multinomial and Poisson models produced indistinguishable results,in units of estimated species,for all estimators and datasets.For sample-based abundance data,which allows the comparison of all three models,the Bernoulli product model generally yields lower richness estimates for rarefied data than either the multinomial or the Poisson models because of the ubiquity of non-random spatial distributions in nature.

The effects of fertilization on the trait-abundance relationships in a Tibetan alpine meadow community

Aims Comparisons of the trait-abundance relationships from various habitat types are critical for community ecology,which can offer us insights about the mechanisms underlying the local community assembly,such as the relative role of neutral vs.niche processes in shaping community structure.Here,we explored the responses of trait-abundance relationships to nitrogen(N),phosphorus(P)and potassium(K)fertilization in an alpine meadow.Methods Five fertilization treatments(an unfertilized control and additions of N,P,K and NPK respectively)were implemented using randomized block design in an alpine Tibetan meadow.Species relative abundance(SRA),plant above-ground biomass and species richness were measured in each plot.For 24 common species,we measured species functional traits:saturated height,specific leaf area(SLA)and leaf dry matter content(LDMC)in each treatment but seed size only in the unfertilized control.Standard major axis(SMA)regression and phylogenetically independent contrasts(PICs)analysis were used to analyse species trait-abundance relationships in response to different fertilization treatments.Important Findings Positive correlations between SRA and saturated height were raised following N,P and NPK fertilizations,which indicated an increase in light competition in these plots.In P fertilized plots,SRA was also positively correlated with LDMC because tall grasses with a nutrients conservation strategy often have a relative competitive advantage in capturing limited light and soil nutrients.In K fertilized plots,neither the trait-abundance relationships nor above-ground biomass or species richness significantly differed from that in the control,which suggests that K was not a limiting resource in our study site.These significant correlations between species traits and relative abundance in fertilized treatment suggest that trait-based selection plays an important role in determining species abundance within local communities in alpine meadows.