Predicting impacts of climate change on the biogeographic patterns of representative species richness in Prydz Bay-Amery Ice Shelf

The research on the biological ecology of the Prydz Bay-Amery Ice Shelf in East Antarctica is inadequate under the increasing threat from climate change,especially for Antarctic fish and krill.The Dynamic Bioclimatic Envelope Model(DBEM)has been widely used in predicting the variation of species distribution and abundance in ocean and land under climate change;it can quantify the spatiotemporal changes of multi population under different climate emission scenarios by identifying the environmental preferences of species.The species richness and geographical pattern of six Antarctic representative species around Prydz Bay-Amery ice shelf were studied under RCP 8.5 and RCP 2.6 emission scenarios from 1970 to 2060 using Geophysical Fluid Dynamics Laboratory(GFDL),Institut Pierre Simon Laplace(IPSL),and Max Planck Institute(MPI)earth system models.The results showed that the species richness decreased as a whole,and the latitude gradient moved to the pole.The reason is that ocean warming,sea ice melting,and human activities accelerate the distribution changes of species biogeographical pattern,and the habitat range of krill,silverfish,and other organisms is gradually limited,which further leads to the change of species composition and the decrease of biomass.It is obvious that priority should be given to Prydz Bay-Amery ice shelf in the planning of Marine Protected Areas(MPAs)in East Antarctica.

Species richness, forest types and regeneration of Schima in the subtropical forest ecosystem of Yunnan, southwestern China

Background: Schima genus of Theaceae is confined to subtropics and tropics of South, East and Southeast Asia.Thirteen species of Schima are distributed in subtropical China. Many of them appear as dominant canopy species in the subtropical forests. To date, Schima species richness distribution patterns of China have remained unknown.Meanwhile, there has been a longtime debate as to whether forests dominated by Schima species are early or late successional forests. We aim to clarify Schima species richness patterns and these species' roles in the forest succession and regeneration dynamics of the subtropical ecosystem in Yunnan Province, China.Method: We mapped Schima species richness distribution patterns in China. Based on 71 vegetation plots, we analyzed forest characteristics, population structure, and regeneration dynamics of Schima species in Yunnan.Results: Yunnan was found to harbor the greatest richness and the highest rarity-weighted richness of Schima species in the subtropical regions of China. We classified five primary and six secondary forest types containing Schima species as one of dominants. Yunnan had the high floristic diversity and varying stand structure of forests containing Schima species. The Schima species studied generally had a sporadic regeneration type and a long lifespan. Four species(Schima argentea, Schima villosa, Schima sinensis, Schima sericans) were shade-intolerant. But three species(Schima noronhae, Schima khasiana and Schima wallichii) were considered as bi-modal type species having shade-intolerant and shade-tolerant traits. Schima noronhae was seen to be a top dominant in late successional forests, while S. wallichii was found as a top-dominant in early or middle or late successional forests. S.khasiana, Schima villosa, Schima sinensis usually appeared as a top dominant in early or middle successional secondary forests, though they also presented as a second dominant in late-successional forests. Schima argentea and Schima sericans dominated only in the early or middle/seral successional forests. Schima species' regeneration establishment depended mainly on forest canopy gap formation through moderate human and natural disturbances.Conclusions: Yunnan has high species richness and rarity-weighted richness of Schima. Both moderate human and natural disturbances have provided regeneration niches for Schima species. Some of the Schima species studied as a second dominant(rare as the top-dominant) present in the late-successional forests. Some of them are more often as the top-dominant in early or middle successional forests, where as time goes by the dominance of Schima species would be replaced by their associated dominant taxa such as Castanopsis species.

Elevational patterns of bird species richness on the eastern slope of Mt.Gongga,Sichuan Province,China

Background:In biological systems,biological diversity often displays a rapid turn-over across elevations.This defining feature has made mountains classic systems for studying the spatial variation in diversity.Because patterns of elevational diversity can vary among lineages and mountain systems it remains difficult to extrapolate findings from one montane region to another,or among lineages.In this study,we assessed patterns and drivers of avian diversity along an elevational gradient on the eastern slope of Mt.Gongga,the highest peak in the Hengduan Mountain Range in central China,and a mountain where comprehensive studies of avian diversity are still lacking.Methods:We surveyed bird species in eight 400-m elevational bands from 1200 to 4400 m a.s.l.between 2012 and 2017.To test the relationship between bird species richness and environmental factors,we examined the relative importance of seven ecological variables on breeding season distribution patterns:land area(LA),mean daily temperature(MDT),seasonal temperature range(STR),the mid-domain effect(MDE),seasonal precipitation(SP),invertebrate biomass(IB) and enhanced vegetation index(EVI).Climate data were obtained from five local meteorological stations and three temperature/relative humidity smart sensors in 2016.Results:A total of 219 bird species were recorded in the field,of which 204 were recorded during the breeding season(April–August).Species richness curves(calculated separately for total species,large-ranged species,and smallranged species) were all hump-shaped.Large-ranged species contributed more to the total species richness pattern than small-ranged species.EVI and IB were positively correlated with total species richness and small-ranged species richness.LA and MDT were positively correlated with small-ranged species richness,while STR and SP were negatively correlated with small-ranged species richness.MDE was positively correlated with large-ranged species richness.When we considered the combination of candidate factors using multiple regression models and model-averaging,total species richness and large-ranged species richness were correlated with STR(negative) and MDE(positive),while small-ranged species richness was correlated with STR(negative) and IB(positive).Conclusions:Although no single key factor or suite of factors could explain patterns of diversity,we found that MDE,IB and STR play important but varying roles in shaping the elevational richness patterns of different bird species categories.Model-averaging indicates that small-ranged species appear to be mostly influenced by IB,as opposed to large-ranged species,which exhibit patterns more consistent with the MDE model.Our data also indicate that the species richness varied between seasons,offering a promising direction for future work.

Seasonal changes in the relationship between species richness and community biomass in grassland under grazing and exclosure, Horqin Sandy Land, northern China

How species diversityroductivity relationships respond to temporal dynamics and land use is still not clear in semi-arid grassland ecosystems. We analyzed seasonal changes of the relationships between vegetation cover, plant density, species richness, and above- ground biomass in grasslands under grazing and exclosure in the Horqin Sandy Land of northem China. Our results showed that in grazed and fenced grassland, vegetation cover, richness, and biomass were lower in April than in August, whereas plant density showed a reverse trend. Vegetation cover during the growing season and biomass in June and August were higher in fenced grassland than in grazed grassland, whereas plant density in April and June was lower in fenced grassland than in grazed grassland. A negative relationship between species richness and biomass was found in August in fenced grassland, and in grazed grassland the relationship between plant density and biomass changed from positive in April to negative in August. The relationship between the density of the dominant plant species and the total biomass also varied with seasonal changes and land use （grazing and exclosure）. These results suggest that long-term grazing, seasonal changes, and their interaction significantly influence vegetation cover, plant density, and bio- mass in grasslands. Plant species competition in fenced grassland results in seasonal changes of the relationship between species rich- ness and biomass. Long-term grazing also affects seasonal changes of the density and biomass of dominant plant species, which fur- tiler affects the seasonal relationship between plant density and biomass in grasslands. Our study demonstrates the importance of tem- poral dynamics and land use in understanding the relationship between species richness and ecosystem fianction.

Species richness patterns and the determinants of larch forests in China

Larch forests are important for species diversity,as well as soil and water conservation in mountain regions.In this study,we determined large-scale patterns of species richness in larch forests and identified the factors that drive these patterns.We found that larch forest species richness was high in southern China and low in northern China,and that patterns of species richness along an elevational gradient depend on larch forest type.In addition,we found that patterns of species richness in larch forests are best explained by contemporary climatic factors.Specifically,mean annual temperature and annual potential evapotranspiration were the most important factors for species richness of tree and shrub layers,while mean temperature of the coldest quarter and anomaly of annual precipitation from the Last Glacial Maximum to the present were the most important for that of herb layer and the whole community.Community structural factors,especially stand density,are also associated with the species richness of larch forests.Our findings that species richness in China's larch forests is mainly affected by energy availability and cold conditions support the ambient energy hypothesis and the freezing tolerance hypothesis.

Neighborhood diversity structure and neighborhood species richness effects differ across life stages in a subtropical natural secondary forest

Natural secondary forest has a strong capacity to regrow naturally and recover biodiversity rapidly on abandoned lands.However,at the neighborhood scale,which can truly reflect the facilitative or competitive interactions among individual plants,the local diversity spatial structure in secondary forest and the feedback effects of neighborhood diversity on natural regeneration remain unclear,and this may be the key to properly understand the mechanisms of natural secondary forest species diversity recovery.To this end,this study established a dynamic plot in a rehabilitated secondary forest after disturbance and conducted a comprehensive survey of 68,336 individual plants with repeated measurements at 5-year interval to assess the characteristics of neighborhood diversity structure across life history stages and link the neighborhood species richness(NSR)effect translated by species interactions at species diversity structure with individual trees recruitment/mortality in secondary forest regeneration.The results showed that,compared with tropical and temperate natural forests,a higher proportion of diversity accumulators and a lower proportion of repellers in subtropical secondary forests resulted in neighborhood diversity structures characterized by heterospecific or high-diversity patches,which are beneficial to the maintenance or restoration of biodiversity.As an important supplement to the research on the relationship between diversity and productivity,our findings show a positive diversity-survival relationship in subtropical secondary forests.Importantly,we observed that the neighborhood diversity structure exhibited a trend of accumulator-dominated to neutral-dominant changes with life stage from sapling to adult,which,in turn,determined the direction and strength of NSR effects on recruitment/mortality.Specifically,diverse local neighborhoods at a later successional stage characterized with‘neutral’species-species interactions can act as a‘welfare net’by offering favorable microhabitats for the most vulnerable recruitments or saplings,i.e.,the NSR effects that promoted individual recruitment/survival in our study.These results not only enrich our understanding of the biodiversity-productivity-survival relationship but also highlight the importance of retaining latesuccessional species of native trees in intensive forest production or in situ conservation policies.

Relationship between species richness and biomass on environmental gradient in natural forest communities on Mt.Xiaolongshan,northwest China

We analyzed the relationship between species richness and biomass in natural forest communities at two similar sites on Mt. Xiaolongshan, northwest China. At both sites, a wide range of tree layer biomass levels was available by local biomass estimation models. In order to identify underlying mechanism of the species richness-biomass relationship, we included different water resource levels and number of individuals in each plot in our analysis. We sampled 15 and 20 plots （20 m ×20 m）, respectively, at both two sites. These plots were sampled equally on the sunny slope and the shady slope. Species richness, number of individuals of each species and diameter at breast height （DBH） as a substitute of biomass of tree layer were recorded in each sample. At one site, the relationship between species richness and biomass was significant on the sunny slope, and this relationship disappeared on the shady slope due to more environmental factors. The relations between species richness and number of individuals and between number of individuals and biomass paralleled the species richness-biomass relation on both slopes. The difference in number of individuals-biomass relationships on the sunny slope and the shady slope revealed ＂interspecific competitive exclusion＂ even though the species richness-biomass relationships were not hump-shaped. At the other site, species richness was not related to biomass or to number of individuals. Our study demonstrated the importance of environmental stress and succession of community in the understanding of species diversity-productivity patterns.

Area, isolation, disturbance and age effects on species richness of summer waterbirds in post-mining subsidence lakes,Anhui, China

Background: The species–area relationship is one of the best documented patterns in community ecology.Factors influencing species–area relationship are still not well understood.Since the proposal of the equilibrium theory of island biogeography, many studies have tested the effects of area and isolation, estimating effects of disturbance and patch age were scarce and should also be important bearing.Methods: We investigated summer waterbird species richness in 38 post?mining subsidence lakes in Huainan and Fuyang, Anhui, China, May 25–June 12, 2016.We examined the effects of lake area, isolation(distance to natural water bodies), aquaculture disturbance, lake age and lake state(still sinking or not sinking) on summer waterbird species richness with multivariable linear regression method and model selection method.Results: Our results from multivariable linear regression and model selection were consistent, which showed that species richness was positively related with lake area and negatively related with isolation.Aquaculture disturbance negatively influenced species richness.Highest species richness were found in lakes under intermediate intensity of aquaculture activities with area less than 100 ha and lakes under low intensity of aquaculture activities with area greater than 100 ha.Lake age and lake state had no significant effects on species richness.Conclusions: Species richness was most related with lake area, aquaculture disturbance, and isolation, with lake area had a positive effect, while aquaculture activities and isolation had a negative effect.What's more, aquaculture activi?ties significantly changed the slope of species–area relationship and might impede us finding a relationship between species richness and lake age.

Noisy environments:untangling the role of anthropogenic noise on bird species richness in a Neotropical city

Background:Among urban stimuli,anthropogenic noise has been identified to be one of the behavioral drivers of species that rely on acoustic signals for communication.Studies have shown both species‑specific and assemblage responses to urban noise,ranging from the modulation of their acoustic frequencies and spatiotemporal adjustments to declines in species richness.In this study,we assessed the citywide relationship between two anthropogenic noise variables(noise levels recorded during bird surveys and daily average noise levels)and vegetation cover with bird species richness.Methods:This study was conducted in the city of Xalapa(Mexico)through a 114 citywide point‑count survey.We recorded bird communities at each sampling site.We measured noise levels using a sound level meter while performing point‑counts.Then,we generated a map of average daily noise of the city using an array of 61 autonomous recording units distributed across the city of Xalapa and calculated daily noise levels for the 114 points.We ran a linear model(LM)to assess potential relationships between both point‑count and daily(24 h)noise values and vegetation cover with bird richness.Results:Results from the LM show:(1)a negative relationship between maximum point‑count noise and avian species richness,(2)no relationship between 24 h noise and bird species richness,and(3)a positive relationship between vegetation cover and bird species richness.Conclusions:Results provide evidence that decreases in urban bird species richness do not necessarily imply the permanent absence of species,suggesting that birds can temporarily fly away from or avoid sites when noisy,become cryptic while noisy events are occurring,or be undetected due to our inability to record them in the field during noisy events.

Polyplacophora species richness,composition and distribution of its community associated with the intertidal rocky substrate in the marine priority region No.32 in Guerrero,Mexico

The coast of Acapulco is located within the Marine Priority Region No. 32 (MPR No. 32) at the State of Guerrero, Mexico. The National Commission for the Knowledge and Use of Biodiversity has stated the lack of information on marine species that live there, among which are the Class Polyplacophora. This study aimed to: 1) determine species richness, 2) the community structure based on the representative families, 3) estimate the density, 4) locate species distribution, 5) determine their degree of occurrence (hierarchical position) within the community, 6) analyze the structure of length and width across the populations and 7) estimate the diversity index. The intertidal rocky substrate at seven beaches was sampled from 2009 to 2012. The sampling unit 1 m2, while the area sampled was 10 m2. It was analyzed 2.548 specimens of Polyplacophora, with 20 species identified. Tonicellidae and Ischnochitonidae were the Families better represented inspecies richness and Chitonidae in abundance. Lepidochitona flectens is a new record for the Mexican Tropical Pacific and Stenoplax mariposa for MPR. No. 32. The density was 25.48 specimens/m2. Eight dominant species were determined. Chiton albolineatus had the highest density. Ischnochiton muscarius, Chaetopleura unilineata, Chiton albolineatus and Chiton articulatus presented wide distribution. Chiton articulatus showed the largest size in length and width. H’ = 2.01 bits/ individual. Numerous dominant species were present with broad and regular distribution, probably due to Polyplacophora body design, which allows for better adaptation to the rigorous environmental conditions of the rocky intertidal.

Ecological constraints on elevational gradients of bird species richness in Tajikistan

The avifauna in Tajikistan has been widely studied for the last century,but specific work on species richness pattern along elevation gradients in Tajikistan is rarely investigated.Here,we reported the first study of bird species richness(BSR)in the high-altitude mountain systems(Tien Shan and Pamir-Alay)of Tajikistan which are very sensitive to the recent climate changes.We aim to explore the relationship of BSR pattern with elevation gradient and to determine the potential drivers underlying the patterns.We collected occurrence data from field surveys,published articles,and open access websites to compile a list of bird species along elevational gradients across the whole country.The BSR was counted by 100 m elevational bands ranging from 294 m to 5146 m.The patterns of BSR were calculated separately for five groups:all breeding birds,Passeriformes,Non-Passeriformes,large elevational range species,and small elevational range species.We calculated ecological and climatic factors of planimetric area,mid-domain effect(MDE),habitat heterogeneity(HH),mean annual temperature(MAT),temperature annual range(TAR),annual precipitation(AP),normalized difference vegetation index(NDVI),human influence index(HII),and human disturbance(HD)in each elevational band.A combination of polynomial regression,Pearson’s correlation,and general least squares model analyses were used to test the effects of these factors on the BSR.A unimodal distribution pattern with a peak at 750-1950 m was observed for all breeding birds.The similar pattern was explored for Passeriformes and Non-Passeriformes,while species with different elevational range sizes had different shapes and peak elevations.For all the breeding birds and Passeriformes,BSR was significantly related to spatial,climate and human influence factors,while BSR of Non-Passeriformes positively correlated with all the given factors.First,second and fourth range classes of birds were significantly correlated with human influence factors.Moreover,large-ranged species had positive correlations with the middomain effect and weakly with habitat heterogeneity.We found that area,MAT and AP were the main factors to explain the richness pattern of birds,and the species richness increases with these three factors increasing.Multiple factors such as area and climate explain 84%of the variation in richness.Bivariate and multiple regression analyses revealed a consistent influence of spatial and climate factors in shaping the richness pattern for nearly all bird groups.

Changes in the relationship between species richness and belowground biomass among grassland types and along environmental gradients in Xinjiang, Northwest China

The association between biodiversity and belowground biomass(BGB) remains a central debate in ecology.In this study, we compared the variations in species richness(SR) and BGB as well as their interaction in the top(0–20 cm), middle(20–50 cm) and deep(50–100 cm) soil depths among 8 grassland types(lowland meadow, temperate desert, temperate desert steppe, temperate steppe desert, temperate steppe, temperate meadow steppe, mountain meadow and alpine steppe) and along environmental gradients(elevation, energy condition(annual mean temperature(AMT) and potential evapotranspiration(PET)), and mean annual precipitation(MAP)) based on a 2011–2013 survey of 379 sites in Xinjiang, Northwest China.The SR and BGB varied among the grassland types.The alpine steppe had a medium level of SR but the highest BGB in the top soil depth, whereas the lowland meadow had the lowest SR but the highest BGB in the middle and deep soil depths.The SR and BGB in the different soil depths were tightly associated with elevation, MAP and energy condition;however, the particular forms of trends in SR and BGB depended on environmental factors and soil depths.The relationship between SR and BGB was unimodal in the top soil depth, but SR was positively related with BGB in the middle soil depth.Although elevation, MAP, energy condition and SR had significant effects on BGB, the variations in BGB in the top soil depth were mostly determined by elevation, and those in the middle and deep soil depths were mainly affected by energy condition.These findings highlight the importance of environmental factors in the regulations of SR and BGB as well as their interaction in the grasslands in Xinjiang.

Spatial variation of plant species richness in a sand dune field of northeastern Inner Mongolia, China

Species richness is an important indicator of species diversity. Different sampling intensities will very likely produce different species richness values. Substantial efforts have already been made to explicitly quantify the spatial variability of soil properties in different ecosystems. However, concerns still remain on how to characterize the effect of different sampling intensities on plant species richness within a given region. This study characterized the spatial variability of plant species richness and the species distribution pattern in a 25-hm2 sand dune plot in northeastern Inner Mongolia, China by using an intense sampling method（n=10,000）. We also evaluated the overall effect of information loss associated with the spatial variability and distribution patterns of species richness under various scenarios of sampling intensities（n=10,000 to 289）. Our results showed that semi-variograms of species richness were best described by the spherical and exponential models. As indicated by the nugget/sill ratio, species richness was different in terms of the strength of the spatial relationship. The different spatial metrics of species richness with increasing sampling intensities can represent different responses of the spatial patterns when compared with the reference set（n=10,000）. This study indicated that an appropriate sampling intensity should be taken into account in field samplings for evaluating species biodiversity properly. A sampling intensity of n＆gt;2,500 for species richness yielded satisfactory results to resemble the spatial pattern of the above-quantified reference set（n=10,000） in this sand dune region of China.

Effects of fertilizer and weed species richness on soil nematode community in a microcosm field experiment

Both fertilizer and plant species richness may affect the soil nematode community.However,the influence of fertilizer and weed species richness interaction is unclear.Nematode abundance and biodiversity in wheat and weed plots soil treated with nitrogen,phosphate and potassium fertilizer addition and weed species richness(0,1,2 and 4 weed levels)were investigated in a long-term microcosm experiment established in 2010 at Kaifeng,China.The results demonstrated that fertilizer treatment increased the abundance of total nematode,bacterivores,and plant parasites whereas it decreased the total genera number,the Shannon-Wiener diversity index(H'),Margalef richness index(SR),the total maturity index(∑MI),and structure index(SI),and degraded the structure of the nematode community.In contrast,weed species richness increased these ecological indices and enhanced the structure of the nematode community.Principal component analysis(PCA)indicated that the fertilizer's effect was more significant than weed species richness.Redundancy analysis(RDA)demonstrated that fertilizer affected soil nematode mainly through increasing soil available phosphorus by 4.71 times and ammonium nitrogen content by 74.03%;weed species richness increased the diversity indices of soil nematode mainly through enhancing soil moisture by 2.07%.Our results suggest weed species richness may relieve the negative effect of fertilizer on the diversity of soil nematode community.

Assessing Forest Cover Distribution, Species Diversity, and Richness of the Buffer Zone for Strategic Forest Management Planning for Nimule National Park, South Sudan

Natural forest ecosystems play an essential role in the conservation of biodiversity of many plants and animals by providing them with habitat and suitable environments. Studies have shown that biodiversity-protected areas reduce the loss and degradation of natural habitats to various wild species of plants. This study examined the forest resources in five subzones by conducting tree/shrub species inventory to be able to develop an effective forest management plan for the Buffer Zone Forest Reserve for the sustainable conservation of flora and fauna of Nimule National Park. This is with the view to identify the main tree and shrub species;assess the composition, distribution, and abundance of various tree/shrub species;to determine the species diversity as well as the richness of these areas in terms of growth and performance where DBH and heights of trees/shrubs in the circular sample plots were measured. The results revealed the overall mean DBH and H of 13.83 cm and 6.61 m respectively. The highest number of trees was obtained in subzone B followed by D, while the least were found in subzone A. The overall mean tree/shrub density was 0.83 tons/ha. The mean total basal area and volume per hectare were 3252.74 m2/ha and 46,540.82 m3/ha respectively. The overall species abundance and distribution indicate Combretum spp, Cedrella spp., Grewia mollis, Acacia Sieberiana, Ziziphus abysinica, and Acacia seyal were the most dominant species, with over 12 species richness at the deposition side of the River Nile, 13 species at the western side of the Nile, the Administration site shows only 7 species, the lowland of Mt. Gordon show over 14 different species, whereas over 10 species were found on the top of Mt. Gordon. The overall mean diversity indices and evenness of H’, D, and E depicted 2.507, 0.871, and 0.840 respectively. These results yielded are relatively moderate. Therefore, conservation efforts are very necessary to improve and maintain the quality of vegetation cover.

Seedling potential of trees species along the elevational gradient in temperate hill forest of central Nepal

Regeneration status of tree species along elevation gradient in temperate hill forest was not understood greatly.Present research examined the tree diversity and its regeneration patterns along an elevation gradient in temperate hill forest,central Nepal.Data were collected from 300 sample plots within vertical elevation bands of 10,ranging from 1365 to 2450 m asl.A random sampling method was used for data collection in three seasons,winter,pre-monsoon and post monsoon seasons.Diameter at breast height(DBH)was used to broadly categorize the plant individual into trees,saplings and seedlings.The tree species richness ranged from 12 to 25 with density of 350 to 1200 individuals per hectare.Species richness of tree and sapling showed statistically significant unimodal pattern,which peaked at mid-elevation.Elevation showed a strong and positive linear correlation with the seedling density(Deviance=0.99,p<0.001)and a significant hump-shaped relationship with sapling density(Deviance=0.95,p<0.001).Similarly,elevations showed a statistically significant negative hump-shaped relationship with all trees,saplings and seedling stages(Deviances=0.89,0.87 and 0.57).The highest values of the Shannon-Wiener index and the lowest value of the Simpson index were found at mid-elevation for all growth forms.Nearly 92%of tree species were found at regenerating stage;49%in a good renewal regeneration status,32%in fair renewal regeneration,and 11%at a poor regenerating condition.Nevertheless,4%of tree species were reported as non-regenerating stages and 4%were newly introduced species.Hence,the regeneration status of the study area was considered fairly well since sapling(78.5%)>seedling(10.6%)≤mature(10.9%).Among tested environmental variables,elevation and annual mean rainfall were the most influential factors in the regeneration of tree species.

Effects of resource additions on species richness and ANPP in an alpine meadow community

Aims Theories based on resource additions indicate that plant species richness is mainly determined by the number of limiting resources.However,the individual effects of various limiting resources on species richness and aboveground net primary productivity(ANPP)are less well understood.Here,we analyzed potential linkages between additions of limiting resources,species loss and ANPP increase and further explored the underlying mechanisms.Methods Resources(N,P,K and water)were added in a completely randomized block design to alpine meadow plots in the Qinghai-Tibetan Plateau.Plant aboveground biomass,species composition,mean plant height and light availability were measured in each plot.Regression and analysis of variance were used to analyze the responses of these measures to the different resource-addition treatments.Important Findings Species richness decreased with increasing number of added limiting resources,suggesting that plant diversity was apparently determined by the number of limiting resources.Nitrogen was the most important limiting resource affecting species richness,whereas Pand K alone had negligible effects.The largest reduction in species richness occurred when all three elements were added in combination.Water played a different role compared with the other limiting resources.Species richness increased when water was added to the treatments with N and P or with N,P and K.The decreases in species richness after resource additions were paralleled by increases in ANPP and decreases in light penetration into the plant canopy,suggesting that increased light competitionwas responsible for the negative effects of resource additions on plant species richness.

Species richness loss after nutrient addition as affected by N:C ratios and phytohormone GA_(3)contents in an alpine meadow community

Aims From the light-competition hypothesis,competition for light is asymmetric and the observed increases in plant-size variability with increasingly denser canopies are primarily due to competition for light.Greater plant height provides pre-emptive access to light and produces increased height differences among species.The question is what produces these differences in plant height or height growth response among species in response to fertilization.Methods In 2009,a field experiment of N,P and N+P enrichments at three levels each was initiated in an alpine meadow on the northeast Qinghai-Tibet Plateau.Effects of fertilization on species richness,aboveground net primary production(ANPP),relative light intensity and plant height of different plant functional groups were determined.Festuca ovina(grass),Kobresia humilis(sedge),Oxytropis ochrocephala(legume),Taraxacum lugubre(rosette forb)and Geranium pylzowianum(upright forb)were selected as exemplars of each of the indicated functional groups.The N:C ratios in aboveground biomass,gibberellic acid(GA_(3))concentrations in leaves,plant heights and height relative growth rate(RGR)of these exemplar species were analyzed in detail.Important Findings Species richness of grasses significantly increased with increasing N+P levels.Species richness of legumes and upright forbs decreased after N and N+P additions.P addition had no significant effect on species richness.The effects of N+P addition on species richness and ANPP were consistently stronger than those of the single N or P fertilization.Reductions in species richness caused by nutrient addition paralleled the increases in ANPP and decreases in light intensity under the canopies,indicating indirect effect of nutrient addition on species richness via ANPP-induced light competition.The exemplar species that responded most positively to fertilization in height and RGR also displayed stronger increases in their GA_(3) content and N:C ratios.GA_(3) concentrations and N:C ratios were positively correlated with height RGR when the data were pooled for all species.The tallest and the fastest-growing grass,F.ovina,had the largest increase in N:C ratios and the highest leaf GA_(3) concentrations after nutrient addition.These results indicated that differential responses of GA_(3) concentrations and N:C ratios to fertilization were related to the inequality in plant heights among species.

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.

Species richness estimations of the megadiverse scuttle fly genus Megaselia （Diptera： Phoridae） in a wildfire-affected hemiboreal forest

The species richness of the scuttle fly （Diptera： Phoridae） genus Megaselia was estimated by various non-parametric estimators from EstimateS, Species Prediction And Diversity Estimation （SPADE） and Ws2m, based on material from a Swedish hemiboreal forest area recently affected by major wildfires, Yyresta National Park and Nature Reserve （TNPNR）, south of Stockholm. A total of 21 249 individuals were collected in Malaise traps, of which males constituted 16 976 and females 4 273. The analysed dataset represents 37 samples containing 18 549 specimens sorted into 330 species （184 described, 146 are either undescribed or of unsettled taxonomic status）. It was not possible to estimate the total species richness using all samples due to heterogeneity caused by inclusion of different communities and temporal incoherencies between samples within and between years. Even with material obtained from a sampling program that was not designed for species richness estimates, it was possible to obtain reliable results when sample heterogeneity was minimized. By dividing the data into community-specific datasets - for bog, forest and wildfire - it was possible to obtain asymptotic curves for the smaller of the two wildfire datasets. A total estimate of 357~439 （95% CI） was attained by using the smaller wildfire dataset and adding the 85 unique species from the samples not included in the estimation analysis. TNPNR has one of the richest known scuttle fly communities in Europe, consisting of almost 50% of the currently named Megaselia species; 48 of these species are reported as new records for Sweden in this study.