Biomass allocation patterns of alpine grassland species and functional groups along a precipitation gradient on the Northern Tibetan Plateau

Variations in the fractions of biomass allocated to functional components are widely considered as plant responses to resource availability for grassland plants. Observations indicated shoots isometrically relates to roots at the community level but allometrically at the species level in Tibetan alpine grasslands. These differences may result from the specific complementarity of functional groups between functional components, such as leaf, root, stem and reproductive organ. To test the component complementary responses to regional moisture variation, we conducted a multi-site transect survey to measure plant individual size and component biomass fractions of common species belonging to the functional groups： forbs, grasses, legumes and sedges on the Northern Tibetan Plateau in peak growing season in 2010. Along the mean annual precipitation （MAP） gradient, we sampled 7o species, in which 2o are in alpine meadows, 20 in alpine steppes, 15 in alpine desert-steppes and 15 in alpine deserts, respectively. Our results showed that the size of alpine plants is small with individual biomass mostly lower than 1.0 g. Plants keep relative conservative component individual responses moisture functional fractions across alpine grasslands at the level. However, the complementary between functional components to variations specifically differ among groups. These results indicate that functional group diversity may be an effective tool for scaling biomass allocation patterns from individual up to community level. Therefore, it is necessary andvaluable to perform intensive and systematic studies on identification and differentiation the influences of compositional changes in functional groups on ecosystem primary services and processes.     

Vascular plants distribution in relation to topography and environmental variables in alpine zone of Kedarnath Wild Life Sanctuary,West Himalaya

The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient and sampled for detailed vegetation analysis using multi summit approach as per Global observation research initiative in alpine environments(GLORIA). Species richness, diversity, and evenness among four summits as well as the interaction between environmental variables with plant communities were assessed. Monthly mean soil temperature was calculated using data retrieved from geo-precision temperature logger in order to identify the trend of soil temperature among different season and altitudinal gradient and its implications to plant communities. Soil samples were analyzed fromeach summit by collecting randomized composite soil samples. The indirect non-metric multidimensional scaling(NMDS) and direct canonical correspondence analysis(CCA) tools of ordination techniques to determine the linkage between plant species from various sample summits and biotic/abiotic environmental gradients were used in the present study. The results of the study demonstrated increase in species richness as soil temperature increases, the ecotone representing summits were found most warm summits followed by highest species richness. Annual soil temperature increased by 1.43°C at timberline ecotone. Whereas, at upper alpine zone the soil temperature increased by 0.810 C from year 2015 to 2016. S?rensen's similarity index was found to be increased between subalpine and upper alpine zone with increase in the presence of subalpine plant species at upper alpine zone. Both the ordination tools separate the subalpine summit and their respective vegetation from summits representingtimberline ecotone and upper alpine zone. Soil p H, altitude, soil cation exchange capacity were found as the key abiotic drivers for distribution of plant species.     

Degradation induces changes in the soil C:N:P stoichiometry of alpine steppe on the Tibetan Plateau

Due to the Tibetan Plateau's unique high altitude and low temperature climate conditions,the region's alpine steppe ecosystem is highly fragile and is suffering from severe degradation under the stress of increasing population,overgrazing,and climate change.The soil stoichiometry,a crucial part of ecological stoichiometry,provides a fundamental approach for understanding ecosystem processes by examining the relative proportions and balance of the three elements.Understanding the impact of degradation on the soil stoichiometry is vital for conservation and management in the alpine steppe on the Tibetan Plateau.This study aims to examine the response of soil stoichiometry to degradation and explore the underlying biotic and abiotic mechanisms in the alpine steppe.We conducted a field survey in a sequent degraded alpine steppe with seven levels inNorthern Tibet.The plant species,aboveground biomass,and physical and chemical soil properties such as the moisture content,temperature,pH,compactness,total carbon(C),total nitrogen(N),and total phosphorus(P)were measured and recorded.The results showed that the contents of soil C/N,C/P,and N/P consistently decreased along intensifying degradation gradients.Using regression analysis and a structural equation model(SEM),we found that the C/N,C/P,and N/P ratios were positively affected by the soil compactness,soil moisture content and species richness of graminoids but negatively affected by soil pH and the proportion of aboveground biomass of forbs.The soil temperature had a negative effect on the C/N ratio but showed positive effect on the C/P and N/P ratios.The current study shows that degradation-induced changes in abiotic and biotic conditions such as soil warming and drying,which accelerated the soil organic carbon mineralization,as well as the increase in the proportion of forbs,whichwere difficult to decompose and input less organic carbon into soil,resulted in the decreases in soil C/N,C/P,and N/P contents to a great extent.Our results provide a sound basis for sustainable conservation and management of the alpine steppe.     

Soil microbial community composition and its driving factors in alpine grasslands along a mountain elevational gradient

Understanding the vertical distribution patterns of soil microbial community and its driving factors in alpine grasslands in the humid regions of the Tibet Plateau might be of great significance for predicting the soil microbial community of this type of vegetation in response to environmental change.Using phospholipid fatty acids(PLFA),we investigated soil microbial community composition along an elevational gradient(3094~4131 m above sea level) on Mount Yajiageng,and we explored the impact of plant functional groups and soil chemistry on the soil microbial community.Except for Arbuscular Mycorrhizal fungi(AM fungi) biomarker18:2ω6,9 increasing significantly,other biomarkers did not show a consistent trend with the elevational gradient.Microbial biomass quantified by total PLFAs did not show the elevational trend and had mean values ranging from 1.64 to 4.09 μmol per g organic carbon(OC),which had the maximum value at the highest site.Bacterial PLFAs exhibited a similar trend with total PLFAs,and its mean values ranged from0.82 to 1.81 μmol(g OC)~(-1).The bacterial to fungal biomass ratios had the minimum value at the highest site,which might be related to temperature and soil total nitrogen(TN).The ratios of Gram-negative to Gram-positive bacteria had a significantly negative correlation with soil TN and had the maximum value at the highest site.Leguminous plant coverage and soil TN explained 58% of the total variation in the soil microbial community and could achieve the same interpretation as the whole model.Other factors may influence the soil microbial community through interaction with leguminous plant coverage and soil TN.Soil chemistry and plant functional group composition in substantial amounts explained different parts of the variation within the soil microbial community,and the interaction between them had no impact on the soil microbial community maybe because long-term grazing greatly reduces litter.In sum,although there were obvious differences in soil microbial communities along the elevation gradient,there were no clear elevational trends found in general.Plant functional groups and soil chemistry respectively affect the different aspects of soil microbial community.Leguminous plant coverage and soil TN had important effects in shaping soil microbial community.     

Phenotypic plasticity of floral traits and pollination adaption in an alpine plant Pedicularis siphonantha D. Don when transplanted from higher to lower elevation in Eastern Himalaya

Phenotypic plasticity and/or pollinatormediated selection may be responsible for the changes in floral traits of plants when they are forced to live in new conditions. Although the two events could be independent, we hypothesized that phenotypic plasticity in floral traits might help to coordinate plant-pollinator interactions and enhance plant reproductive success in changing habitats. To test this hypothesis, we investigated floral traits and pollination on three natural populations of a lousewort(Pedicularis siphonantha) ranging at different elevations, as well as two downward transplanted populations in Shangeri-La County and Deqin County, northwest Yunnan, China. The results indicated that floral traits, i.e. phenology, longevity,display size, corolla tube length and pollen production differed significantly among populations. Moreover,or the two transplanted populations, floral traits diverged from their original populations, but converged to their host populations. Although the phenotypic plasticity in floral traits might be a rapid response to abiotic factor such as warmer environment, the changes in floral traits were found to be well adapted to pollination environment of the host population. Compared with plants of their original habitats in higher elevation, the transplanted individuals advanced flowering time, shortened flower longevity, reduced floral display size and pollen production, received higher visiting frequency and yielded more seeds. These findings suggested that phenotypic plasticity of floral traits might help plants adjust their resource allocation strategy between preand post-pollination stages in response to harsh or temperate conditions, which might correspondingly meet a pollinator-poor or hyphen rich environment.This would be beneficial for the widely-distributed species to adapt to various environmental changes.     

Aboveground Biomass and Water Storage Allocation in Alpine Willow Shrubs in the Qilian Mountains in China

The aboveground biomass allocation and water relations in alpine shrubs can provide useful information on analyzing their ecological and hydrological functions in alpine regions. The objectives of this study were to compare the aboveground biomass allocation, water storage ratio and distribution between foliage/woody components,and to investigate factors affecting aboveground biomass allocation and water storage ratio in alpine willow shrubs in the Qilian Mountains, China. Three experimental sites were selected along distance gradients from the riverside in the Hulu watershed in the Qilian Mountains. The foliage, woody component biomass, and water allocation of Salix cupularis Rehd.and Salix oritrepha Schneid. shrubs were measured using the selective destructive method. The results indicated that the foliage component had higher relative water and biomass storage than the woody component in the upper part of the crown in individual shrubs. However, the woody component was the major biomass and water storage component in the whole shrub level for S. cupularis and S.oritrepha. Moreover, the foliage/woody component biomass ratio decreased from the top to the basal level of shrubs. The relative water storage allocation was significantly affected by species types, but was not affected by sites and interaction between species and sites. Meanwhile, relative water storage was affectedby sites as well as by interaction between sites and species type.     

Phenotypic plasticity of floral traits and pollination adaption in an alpine plant <Emphasis Type="Italic">Pedicularis siphonantha</Emphasis> D. Don when transplanted from higher to lower elevation in Eastern Himalaya

Phenotypic plasticity and/or pollinator-mediated selection may be responsible for the changes in floral traits of plants when they are forced to live in new conditions. Although the two events could be independent, we hypothesized that phenotypic plasticity in floral traits might help to coordinate plant-pollinator interactions and enhance plant reproductive success in changing habitats. To test this hypothesis, we investigated floral traits and pollination on three natural populations of a lousewort (Pedicularis siphonantha) ranging at different elevations, as well as two downward transplanted populations in Shangeri-La County and Deqin County, northwest Yunnan, China. The results indicated that floral traits, i.e. phenology, longevity, display size, corolla tube length and pollen production differed significantly among populations. Moreover, or the two transplanted populations, floral traits diverged from their original populations, but converged to their host populations. Although the phenotypic plasticity in floral traits might be a rapid response to abiotic factor such as warmer environment, the changes in floral traits were found to be well adapted to pollination environment of the host population. Compared with plants of their original habitats in higher elevation, the transplanted individuals advanced flowering time, shortened flower longevity, reduced floral display size and pollen production, received higher visiting frequency and yielded more seeds. These findings suggested that phenotypic plasticity of floral traits might help plants adjust their resource allocation strategy between preand post-pollination stages in response to harsh or temperate conditions, which might correspondingly meet a pollinator-poor or hyphen rich environment. This would be beneficial for the widely-distributed species to adapt to various environmental changes.     

Vertical patterns in plant diversity and their relations with environmental factors on the southern slope of the Tianshan Mountains (middle section) in Xinjiang (China)

The investigation of distribution patterns of species diversity is significant for successful biodiversity conservation. The spatial patterns of vegetation and different life-forms species diversity along an elevation gradient in the middle section of the southern slope of the Tianshan Mountains in Xinjiang, China were explored, using the detrended canonical correspondence analysis(DCCA) and the generalized additive model(GAM) methods based on a field survey of 53 sampling plots. In this work 158 species of seed plants were recorded, including 141 herbaceous, 14 shrub, and 2 tree species, in which the woody plants are very limited. 53 sampling plots were classified into 9 major plant communities. The results indicate that the herb communities were the most sensitive to changes in elevation gradient. The diversity indices of the community as a whole presented bimodal patterns. The peak values for the species diversities were found in the transition region between mountain steppe desert and mountain desert steppe(2,200–2,300m), and in the alpine grassland region(2,900–3,100m), while maximum species diversities were in the areas of intermediate environmental gradient. The main environmental factors on the distribution patterns in plant diversity were the elevation, soil water, total nitrogen, available nitrogen, organic matter, and total salt. The response tendency of the four diversity indices for the whole community to the soil environment was the same as that of the herb layers.     

Study on the rainfall and aftershock threshold for debris flow of post-earthquake

Due to the special condition of provenance and disaster environment after "5·12" Earthquake, the probability and conditions of the occurrence of gully debris flow change greatly after the event, which make it difficult to prevent disaster effectively. In this study the hydrological model of ground water table in loose sediment is established. According to infinite slope theory, the safety factor of deposits is defined as the ratio of resistance force to driving force. The starting condition of post-earthquake gully debris flow is clearly studied by analyzing the effects of rainfall intensity, seismic strength, slope gradient and mechanical properties on the balance of accumulation body. Then the formulas of rainfall and aftershock threshold for starting of gully debris flow are proposed, and an example is given to illustrate the effect of rainfall, aftershocks and their coupling action on a debris flow. The result shows the critical rainfall intensity decreases as the lateral seismic acceleration and channel gradient increases, while the critical intensity linearly increases as the friction angle increases.     

Unusual hydrocarbon waxes detected in Salix oritrepha leaf from Nianbaoyeze Mountains,eastern Qinghai-Tibetan Plateau

Plant biomarkers, such as hydrocarbon waxes, are frequently found in various sediments and could be adopted as paleovegetation and paleoclimate indicators. Nevertheless, scarce researches have focused on leaf waxes in higher plants of alpine region.Herein, hydrocarbon leaf wax components of Salix oritrepha, which flourish in Nianbaoyeze Mountains in eastern Tibetan Plateau were fully discussed. The n-alkane distribution in leaves ranges from n-C_(21) to nC_(29) with maxima at n-C_(25), which were entirely different with Salix taxa displayed in previous surveys in non-alpine regions. The unusual even carbon nalkenes from n-C_(22:1) to n-C_(30:1), which were thought to appear only in aquatic organisms, were firstly reported in an alpine plant. Additionally, iso-(2-methyl) alkanes, ranging from i-C_(23) to i-C_(29) with maxima at i-C_(25), which have been commonly reported in microorganisms, were also identified in an alpine plant for the first time. Unusual hydrocarbon distribution detected in Salix oritrepha leaf from Nianbaoyeze Mountains is most likely due to the extreme environment in such alpine region.     

Plant species diversity along an altitudinal gradient of Bhabha Valley in western Himalaya

The present study highlights the rich species diversity of higher plants in the Bhabha Valley of western Himalaya in India. The analysis of species diversity revealed that a total of 313 species of higher plants inhabit the valley with a characteristic of moist alpine shrub vegetation. The herbaceous life forms dominate and increase with increasing altitude. The major representations are from the families Asteraceae, Rosaceae, Lamiaceae and Poaceae, suggesting thereby the alpine meadow nature of the study area. The effect of altitude on species diversity displays a hump-shaped curve which may be attributed to increase in habitat diversity at the median ranges and relatively less habitat diversity at higher altitudes. The anthropogenic pressure at lower altitudes results in low plant diversity towards the bottom of the valley with most of the species being exotic in nature. Though the plant diversity is less at higher altitudinal ranges, the uniqueness is relatively high with high species replacement rates. More than 90 % of variability in the species diversity could be explained using appropriate quantitative and statistical analysis along the altitudinal gradient. The valley harbours 18 threatened and 41 endemic species, most of which occur at higher altitudinal gradients due to habitat specificity.     

A method for simulating sediment incipient motion varying with time and space in an ocean model(FVCOM):development and validation

We modified the sediment incipient motion in a numerical model and evaluated the impact of this modification using a study case of the coastal area around Weihai, China. The modified and unmodified versions of the model were validated by comparing simulated and observed data of currents, waves, and suspended sediment concentrations(SSC) measured from July 25~(th) to July 26~(th), 2006. A fitted Shields diagram was introduced into the sediment model so that the critical erosional shear stress could vary with time. Thus, the simulated SSC patterns were improved to more closely reflect the observed values, so that the relative error of the variation range decreased by up to 34.5% and the relative error of simulated temporally averaged SSC decreased by up to 36%. In the modified model, the critical shear stress values of the simulated silt with a diameter of 0.035 mm and mud with a diameter of 0.004 mm varied from 0.05 to 0.13 N/m~2, and from 0.05 to 0.14 N/m~2, respectively, instead of remaining constant in the unmodified model. Besides, a method of applying spatially varying fractions of the mixed grain size sediment improved the simulated SSC distribution to fit better to the remote sensing map and reproduced the zonal area with high SSC between Heini Bay and the erosion groove in the modified model. The Relative Mean Absolute Error was reduced by between 6% and 79%, depending on the regional attributes when we used the modified method to simulate incipient sediment motion. But the modification achieved the higher accuracy in this study at a cost of computation speed decreasing by 1.52%.     

Variation in carbon,nitrogen and phosphorus partitioning between above- and belowground biomass along a precipitation gradient at Tibetan Plateau

Precipitation is a potential factor that significantly affects plant nutrient pools by influencing biomass sizes and nutrient concentrations. However, few studies have explicitly dissected carbon(C), nitrogen(N) and phosphorus(P) pools between above- and belowground biomass at the community level along a precipitation gradient. We conducted a transect(approx. 1300 km long) study of Stipa purpurea community in alpine steppe on the Tibet Plateau of China to test the variation of N pool of aboveground biomass/N pool of belowground biomass(AB/BB N) and P pool of aboveground biomass/P pool of belowground biomass(AB/BB P) along a precipitation gradient. The proportion of aboveground biomass decreased significantly from mesic to drier sites. Along the belt transect, the plant N concentration was relatively stable; thus, AB/BB N increased with moisture due to the major influences by above- and belowground biomass allocation. However, P concentration of aboveground biomass decreased significantly with increasing precipitation and AB/BB P did not vary with aridity because of the offset effect of the P concentration and biomass allocation. Precipitation gradients do decouple the N and P pool of a S. purpurea community along a precipitation gradient in alpine steppe. The decreasing of N:P in aboveground biomass in drier regions may indicate much stronger N limitation in more arid area.     

Variations in leaf functional traits and physiological characteristics of Abies georgei var. smithii along the altitude gradient in the Southeastern Tibetan Plateau?

Variations in leaf functional traits of Abies georgei var. smithii at 3700, 3900, 4100, 4300, and 4390 m altitude were investigated in 15 typical plots in the Southeastern Tibetan Plateau. In each plot, three seedlings were selected, of which functional leaves in current-year sunny branches were chosen for the measurement of morphological, photosynthetic, and physiological and biochemical characteristics, and their variations were analyzed. Results showed that significant variations existed among the leaf functional traits of A. georgei var. smithii along the altitudinal gradient, as well as their physiological adaption indicators. Leaf area decreased, while the mass per area and thickness of leaf increased at an altitude above 4,100 m. The maxima of pigment, total nitrogen concentration, net photosynthesis rate during light-saturated, and when water use efficiency appeared at 4100 m altitude. In addition, A. georgei var. smithii seedlings regulated the activities of superoxide dismutase and ascorbate peroxidase to resist abiotic stress under 4100 m altitude. Meanwhile, malondialdehyde concentration and the dark respiration rate rapidly increased, which indicates that A. georgei var. smithii seedlingssuffered from heavy abiotic stress from 4100 m to 4390 m altitude. Basing on variations in leaf functional traits along the altitude gradient, we inferred that 4100 m altitude was the suitable region for A. georgei var. smithii growth in the Sygera Mountain. Moreover, the harsh environment was the main limiting factor for A. georgei var. smithii population expansion to high altitude.     

Expression,purification, and subcellular localization of phospholipase C in Dunaliella salina

Plants possess effective mechanisms to respond quickly to the external environment.Rapid activation of phosphatidylinositol-specific phospholipase C(PLC)enzymes occurs after a stimulus.The PLC in Dunaliella salina play s important roles in growth and stress responses.However,the molecular basis of PLC action in D.salina remains little understood.To gain insight into the potential biological functions of this enzyme,we cloned a phospholipase C gene from D.salina in a previous study,named DsPLC(GenBank No.KF573428).Here,we present the prokaryotic expression,purification,and characterization of the DsPLC gene.The entire coding region of DsPLC was inserted into an expression vector pET32 a,and the DsPLC gene was successfully expressed in Escherichia coli.The DsPLC protein was purified and identified using a polyclonal antibody and western blotting.Expressing DsPLC fused with a green fluorescent protein(GFP)in onion showed that DsPLC-GFP was localized to the intracellular membrane.Quantitative real-time PCR analysis revealed that the relative expression of the DsPLC gene was induced significantly by 3.0-mol/L NaCl at 4 h.Our results support the importance of PLC enzymes in plant defense signaling.This study provides a basis for further functional studies of the DsPLC gene and for additional analysis of the potential roles of PLC enzymes in response to abiotic stress.     

Trait complementarity between fine roots of Stipa purpurea and their associated arbuscular mycorrhizal fungi along a precipitation gradient in Tibetan alpine steppe

Development of fine roots and formation of symbiosis with arbuscular mycorrhizal(AM) fungi represent two strategies for plants to acquire nutrient and water from soil. Here, we elucidated how fine root development and symbolized mycorrhizal fungi with Stipa purpurea responded to the precipitation change in Tibetan alpine steppe ecosystem across a precipitation gradient from 50 mm to 400 mm. As precipitation increased, the proportion of thinner fine roots(diameter 0.4 mm) in total roots increased significantly; while the mycorrhizal colonization percentage, either associated with thinner or thicker roots, decreased. This phenomenon indicated that fine root development and symbolized mycorrhizal fungi are likely alternative, and plant preferred to develop fine root rather than build a symbiotic relationship with mycorrhizal fungi in more benign niches with higher precipitation. Also, root diameter was negatively correlated with specific root length(SRL), but positively correlated with AM fungal colonization percentage, indicating thicker-root species rely more on mycorrhizal fungi in alpine steppe. The complementarity between fine root and mycorrhizal fungi of S. purpurea is mediated by precipitation in Tibetan alpine steppe.     

Implications of tree species–environment relationships for the responsiveness of Himalayan krummholz treelines to climate change

Climate warming is expected to advance treelines to higher elevations. However, empirical studies in diverse mountain ranges give evidence of both advancing alpine treelines as well as rather insignificant responses. In this context, we aim at investigating the sensitivity and responsiveness of the near-natural treeline ecotone in Rolwaling Himal, Nepal, to climate warming. We analysed population densities of tree species along the treeline ecotone from closed forest stands via the krummholz belt to alpine dwarf shrub heaths (3700-4200 m) at 50 plots in 2013 and 2014. We quantified species - environment relationships, i.e. the change of environmental conditions (e.g., nutrient and thermal deficits, plant interactions) across the ecotone by means of redundancy analyses, variation partitioning and distance-based Moran's eigenvector maps. In particular, we focus on explaining the high competitiveness of Rhododendron campanulatum forming a dense krummholz belt and on the implications for the responsiveness of Himalayan krummholz treelines to climate change. Results indicate that treeline trees in the ecotone show species-specific responses to the influence of environmental parameters, and that juvenile and adult tree responses are modulated by environmental constraints in differing intensity. Moreover, the species - environment relationships suggest that the investigated krummholz belt will largely prevent the upward migration of other tree species and thus constrain the future response of Himalayan krummholz treelines to climate warming.     

Modelling the upwelling offthe east Hainan Island coast in summer 2010

A synoptic-scale upwelling event that developed off the east coast of the Hainan Island(EHIU) in the summer of 2010 is defi ned well via processing the Moderate Resolution Imaging Spectroradiometer(MODIS) sea surface temperature(SST) data. The Regional Ocean Modeling System(ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo fl oat profi les and MODIS SST, it is confi rmed that the ROMS reproduces the EHIU well. The cooler-water core(CWC) distinguished by waters(27) 27.5°C in the EHIU, which occurred in the east Qiongzhou Strait mouth area and was bounded by a high temperature gradient, was the focus of this paper. Vertical structure of the CWC suggests that interaction between the westward fl ow and the bathymetry slope played a signifi cant role in the formation of CWC. Numerical experiments indicated that the westward fl ow in the Qiongzhou Strait was the result of tidal rectifi cation over variable topography(Shi et al., 2002), thus tides played a critical role on the development of the CWC. The negative wind stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2–0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefi t the development of the CWC.     

Evaluating the effect of input variables on quantifying the spatial distribution of croaker Johnius belangerii in Haizhou Bay,China

A habitat model has been widely used to manage marine species and analyze relationship between species distribution and environmental factors.The predictive skill in habitat model depends on whether the models include appropriate explanatory variables.Due to limited habitat range,low density,and low detection rate,the number of zero catches could be very large even in favorable habitats.Excessive zeroes will increase the bias and uncertainty in estimation of habitat.Therefore,appropriate explanatory variables need to be chosen first to prevent underestimate or overestimate species abundance in habitat models.In addition,biotic variables such as prey data and spatial autocovariate(SAC) of target species are often ignored in species distribution models.Therefore,we evaluated the effects of input variables on the performance of generalized additive models(GAMs) under excessive zero catch(70%).Five types of input variables were selected,i.e.,(1) abiotic variables,(2) abiotic and biotic variables,(3) abiotic variables and SAC,(4) abiotic,biotic variables and SAC,and(5) principal component analysis(PCA) based abiotic and biotic variables and SAC.Belanger 's croaker Johnius belangerii is one of the dominant demersal fish in Haizhou Bay,with a large number of zero catches,thus was used for the case study.Results show that the PCA-based GAM incorporated with abiotic and biotic variables and SAC was the most appropriate model to quantify the spatial distribution of the croaker.Biotic variables and SAC were important and should be incorporated as one of the drivers to predict species distribution.Our study suggests that the process of input variables is critical to habitat modelling,which could improve the performance of habitat models and enhance our understanding of the habitat suitability of target species.     

Assessing adaptability and response of vegetation to glacier recession in the afro-alpine moorland terrestrial ecosystem of Rwenzori Mountains

The objective of this study was to explore vegetation adaptability in a changing afro-alpine moorland terrestrial ecosystem on Mt. Rwenzori and to determine whether there were any links with response of vegetation to glacier recession. We analyzed the composition and distribution of plant species in relation to soils, geomorphic processes, and landscape positions in the Alpine zone. To accomplish this objective, archival data sources and published reports for this ecosystem were reviewed. A field trip was conducted in 2010 to study in detail seven vegetation sampling plots that were systematically selected using GIS maps and a nested-quadrat sampling design framework along an altitudinal gradient in the lower and upper alpine zones. Using these sampling plots, 105 vegetation and 13 soil samples were assessed in the alpine zone. Soil samples were taken for laboratory testing and analysis. The results show statistically significant differences in p H, OM, N, P, Ca, Mg, and K pools between soils samples drawn from the lower and upper alpine sites(p 0.0033). Furthermore, we observed a significant vegetation formation with numerous structural forms, but there was a limited diversity of species. The mostsignificant forms included Alchemilla carpets, Bogs, Dendrosenecio woodland, and Scree slopes. The lower alpine area(3500–3900 masl) had a more diverse plant species than other areas, especially Alchemilla argyrophylla and Dendrosenecio adnivalis species that were evident due to well-drained deeper soils. The Alchemilla subnivalis were evident at a higher altitude of above 4000 masl. Shifts in the Astareceae(e.g. Senecio species) were particularly prominent even on recently deglaciated areas. The spatial variations of species distribution, structure, and composition suggest there are serious implications in terms of ecosystem adaptability, resilience, and stability that require further evaluation.