Spatial pattern of soil organic carbon in desert grasslands of the diluvial-alluvial plains of northern Qilian Mountains

The soil properties in arid ecosystems are important determinants of vegetation distribution patterns. Soil organic carbon （SOC） content, which is closely related to soil types and the holding capacities of soil water and nutrients, exhibits complex variability in arid desert grasslands; thus, it is essentially an impact factor for the distri- bution pattern of desert grasslands. In the present study, an investigation was conducted to estimate the spatial pattern of SOC content in desert grasslands and the association with environmental factors in the diluvial-alluvial plains of northern Qilian Mountains. The results showed that the mean values of SOC ranged from 2.76 to 5.80 g/kg in the soil profiles, and decreased with soil depths. The coefficients of variation （CV） of the SOC were high （ranging from 48.83% to 94.67%）, which indicated a strong spatial variability. SOC in the desert grasslands of the study re- gion presented a regular spatial distribution, which increased gradually from the northwest to the southeast. The SOC distribution had a pattern linked to elevation, which may be related to the gradient of climate conditions. Soil type and plant community significantly affected the SOC. The SOC had a significant positive relationship with soil moisture （P〈0.05）; whereas, it had a more significant negative relationship with the soil bulk density （BD） （P〈0.01）. However, a number of the variations in the SOC could be explained not by the environmental factors involved in this analysis, but rather other factors （such as grazing activity and landscape）. The results provide important references for soil carbon storage estimation in this study region. In addition, the SOC association with environmental variables also provides a basis for a sustainable use of the limited grassland resources in the diluvial-alluvial plains of north- ern Qilian Mountains.

Infl uence of the slope aspect on the ectomycorrhizal fungal community of Quercus variabilis Blume in the middle part of the Taihang Mountains,North China

The slope aspect is one of the most critical topographic factors in mountainous areas.Little is known,however,about the eff ect of the aspect on the ectomycorrhizal(ECM)fungal community.Additionally,we know very little about the composition of ECM fungal communities associated with Quercus variabilis,which is widely distributed in East Asia.In this study,we compared the richness,community composition,and exploration types of ECM fungi associated with Q.variabilis between predominantly south-and north-facing slopes in the Taihang Mountain,North China for the fi rst time.DNA was extracted from the root tips of Q.variabilis,and Illumina MiSeq sequencing was used to identify ECM fungi.In total,168 operational taxonomic units belonging to 28 genera were detected,and the ECM community was found to be dominated by Russula,Inocybe,Tomentella,Scleroderma,and Cortinarius.Compared with the north-facing slopes,the ECM communities on the south-facing slopes had higher diversity.The community composition and exploration types were directly aff ected by the slope aspect.Also,the aspect-induced edaphic variables,such as total phosphorus,total nitrogen,total potassium,pH,and soil water content,were important sources of variation in ECM fungal richness and distributions of exploration types.Diff erent genera tended to be distributed in various slope aspects.Cenococcum,Genea,and Clavulina were signifi cantly enriched in north-facing slopes,while Geopora,Helvelosebacina,Scleroderma,Gyroporus,Astraeus,Boletus,Tricholoma,Hebeloma,Cortinarius and unclassifi ed Thelephoraceae were more abundant in south-facing slopes.Hydrophobic ECM fungi were obviously enriched in the south-facing slope,but there was no statistical diff erence between hydrophilic among the south-and north-facing slopes.Our study deepened our knowledge of the aspect-driven variation in ECM fungal communities associated with Q.variabilis.

The role of graveyards in species conservation and beta diversity:a vegetation appraisal of sacred habitats from Bannu,Pakistan

Graveyards or sacred groves are often places of natural vegetation protected by spiritual believers because of their sacred beliefs and indigenous culture.A study of graveyards was conducted to determine their role in species conservation,community formation,and associated indicators and species composition using multivariate statistical approaches.It was hypothesized that variations in the age of graveyards would give rise to diverse plant communities under the impact of various edaphic and climatic factors.Quantitative ecological techniques were applied to determine various phytosociological attributes.All the data were put in MS Excel for analysis in PCORD and CANOCO softwares for cluster analysis(CA),two-way cluster analysis(TWCA),indicator species analysis and canonical correspondence analysis.CA and TWCA through Sorenson distance measurements identified five major graveyard plant communities:(1)FicusBougainvillea-Chenopodium;(2)Acacia-Datura-Convolvulus;(3)Ziziphus-Vitex-Abutilon;(4)Acacia-Lantana-Salsola;and(5)Melia-Rhazya-Peganum.Species such as Capparis decidua,Herniaria hirsuta,Salvadora oliedes and Populus euphratica were only present inside graveyards rather than outside and advocate the role of graveyards in species conservation.The impact of different environmental and climatic variables plus the age of the graveyards were also assessed for comparison of plant communities and their respective indicator species.The results indicate that higher chlorine concentration,age of graveyards,low soil electrical conductivity,lower anthropogenic activities,higher nitrogen,calcium and magnesium concentrations in the soil,and sandy soils were the strong environmental variables playing a significant role in the formation of graveyard plant communities,their associated indicators and species distribution patterns.These results could further be utilized to evaluate the role of edaphic and climatic factors,indicator species and conservation management practices at a greater scale.

Arbuscular mycorrhizal fungi communities associated with wild plants in a coastal ecosystem

Arbuscular mycorrhizal fungi(AMF)form a near-ubiquitous mutualistic association with roots to help plants withstand harsh environments,and play a key role in the establishment of coastal beach plant communities.Yet little is known about the structure and composition of AMF communities on coastal beaches of eastern China.In this study,we investigated the occurrence,community composition and diversity of AMF associated with common wild plants on a coastal beach of North Jiangsu,China.Almost all of the local wild species were colonized by AMF except for Chenopodium album L.Thirty-seven AMF species were isolated from the rhizosphere belonging to 12 genera in seven families.Glomus was the dominant genus and Funneliformis mosseae the dominant species.The colonization,spore composition and diversity of AMF were strongly related to edaphic factors.Sodium(Na^(+))ions in the soil significantly and negatively affected the colonization rate by AMF and both soil Na^(+)levels and pH had a significant negative effect on AMF spore density and evenness.However,there was a significant positive correlation between species richness and total organic carbon.The results provide insights into soil factors affecting native AMF communities in coastal beach habitats which could benefit vegetation recovery and soil reclamation efforts.

Arbuscular Mycorrhizal Fungal Diversity Associated with Olea europaea L. Growing in Yunnan Province, Southwestern China

Olive(Olea europaea L.)is one of the most important and widely cultivated fruit trees,with high economic,ecological,cultural and scientific value.China began introducing and cultivating olive in the 1960s,and Yunnan Province is one of the main growing areas.Improving the cultivation and productivity of this tree crop species is an important challenge.Olive is a typical mycotrophic species and the potential of arbuscular mycorrhizal fungi(AMF)for this plant is well recognized;nevertheless,studies of olive AMF in China are still very limited.Roots and rhizosphere soils of olive were sampled from five representative growing sites in the Yunnan Province of China to investigate the AMF colonization status in the root systems,the AMF community in the olive orchards and the edaphic factors influencing the arbuscular mycorrhizal(AM)parameters.Root samples of olive trees from different growing sites generally showed AMF colonization,suggesting that autochthonous AMF manifest a high efficiency in colonizing the roots of olive plants.The spore density on the five sites ranged from 81.6 to 350 spores per 20 g soil.Twenty-three AMF species from 9 genera were identified in total,and Glomeraceae was the dominant family.The findings of our study suggested a high AMF diversity harbored by olive growing in different areas of the Yunnan Province,Southwestern China.Furthermore,the hyphal colonization in roots positively correlated with soil pH and EC.The arbuscule colonization in olive roots negatively correlated with soil pH,EC,OM,TN,TP and AN.The spore density positively correlated with OM,TN,AN,AP and sand content.Finally,the Shannon index of AMF in the rhizosphere soil positively correlated with the clay content,but negatively correlated with soil pH,TN and silt content.The high diversity of autochthonous AMF in Yunnan is promising for screening AMF isolates for utilization in the efficient cultivation of this crop.

Distinct edaphic habitats are occupied by discrete legume assemblages with unique indicator species in the Cape Peninsula of South Africa

Aims the Cape Peninsula is a small area(471 km2)situated on the south-westernmost tip of the Core Cape Subregion(CCR)of South Africa.Within the Cape Peninsula,Fabaceae are the third most species-rich plant family(162 species)and they have the second highest number of endemic species after the Ericaceae.However,legumes are not the dominant taxa in the vegetation.they tend to show patchy distributions within the landscape and different species assemblages usually occupy particular niches at any given locality.the present study undertook to establish if edaphic factors influence legume species distribution in the Cape Peninsula and to determine the key indicator species for the different assemblages.Methods Soils from 27 legume sites,spanning all major geological substrates of the Cape Peninsula,were analysed for 31 chemical and physi-cal properties.Legume species present at each site were recorded and a presence/absence matrix was generated.Cluster analysis and discriminant function analysis(DFA)were run to group the sites based on overall similarity in edaphic characteristics and to identify the soil parameters contributing towards discriminating the groups.Canonical correspondence analysis(CCA)was used to test for a cor-relation between legume species compositions and edaphic factors.the strength of the association between legume species and site groupings based on edaphic properties was assessed using indicator species analysis.Important findings Based on similarity in overall soil characteristics,the sites formed three clusters:one comprising sites of sandstone geology,one with dune sand sites and the third cluster comprising sites of both shale and granite geologies(hereafter referred to as soil types).the DFA confirmed the distinctness of these clusters and the CCA showed a significant correlation between legume species composition and edaphic factors.the key edaphic parameters were clay content,iron(Fe),potassium(K),sulphur(S)and zinc(Zn).these findings reveal that the Cape Peninsula is edaphically heterogeneous and edaphically distinct habitats contain discrete legume species assemblages that can be distinguished by unique indicator species.Furthermore,multiple soil parameters,rather than a single parameter,are involved.therefore,edaphic factors play a significant role in driving the distribution of legume species in the Cape Peninsula and discrete legume species assemblages occupy distinct habitats.

Biochar increases soil microbial biomass with changes in extra-and intracellular enzyme activities:a global meta-analysis

Biochar application to soil has been proposed as a potential management strategy to enhance soil carbon(C)sequestration,reduce greenhouse gas emission,improve soil quality,and increase crop productivity.The effects of biochar on soil microbial and enzyme activities are integrally linked to the potential of biochar in achieving these benefits.We conducted a global meta-analysis to assess the effects of biochar on soil microbial biomass C and nitrogen(N)and the activities of 12 enzymes,and identify key factors affecting those soil microbial properties using 964 data points from 72 papers.We found that biochar effects on enzyme activities vary widely with soil type,biochar property and the type of enzyme studied.Biochar significantly increased microbial biomass C(MBC)and urease,alkaline phosphatase and dehydrogenase activities by 21.7%,23.1%,25.4%and 19.8%,respectively,with no significant negative effects on any of the enzymes analyzed in this study.Biochar application was more effective in increasing MBC and enzyme activities in soils with low pH(<6.5),TC(<20 g kg^(−1)),TN(<2 g kg^(−1)),and a fine texture(including clay,clay loam and silt clay).Biochars produced at pyrolysis temperature of 350-550℃ with a high pH(>10)and low C/N ratio(<50)increased MBC and urease and dehydrogenase activities.Biochar increased MBC and N-acquisition enzyme activities in the field but not in lab incubation experiments.Urease was increased in short-term studies(within 100 days of biochar application)while alkaline phosphatase was increased in long-term studies that span more than 1 year.The increase in MBC and activities of some soil enzymes in response to biochar application with no negative effects on any hydrolytic and oxidative enzymes illustrate its potential to enhance soil quality particularly in the degraded soils with low nutrient availability and fertility due to limited soil microbial and enzymatic activities.This study also shows that biochars can be designed to achieve specific properties for enhancing microbial and enzymatic activities for specific soils.

Experiment meets biogeography:plants of river corridor distribution are not more stress tolerant but benefit less from more benign conditions elsewhere

Aims Factors limiting distributions of species are fundamental to ecology and evolution but have rarely been addressed experimentally for multiple species.The conspicuous linear distribution patterns of plant species confined to river corridors in the Central European lowlands constitute an especially long-standing distribution puzzle.We experimentally tested our novel hypothesis that the tolerance of species to river corridor conditions is independent of the degree of confinement to river corridor habitats,but that species not confined to river corridors are better able to take advantage of the more benign non-river corridor conditions.Methods We grew 42 herbaceous species differing in their confinement to river corridors in a common garden experiment on loamy soil typical for river corridor areas and sandy soil typical for non-river corridor areas,and with and without a flooding period.For a subset of species,we grew plants of both river corridor and non-river corridor origin to test for adaptation to river corridor conditions.Important findings Species more confined to river corridor areas benefited less from the more benign non-flooded and non-river corridor soil conditions than species of wider distributional range did.For subsets of 7 and 12 widespread species,the response to flooding and soil origin,respectively,did not differ between plants from river corridor sites and plants from other sites,suggesting that the habitat tolerance of widespread species is due to phenotypic plasticity rather than to local adaptation.Overall,we found clear support for our novel hypothesis that species not confined to river corridors are more able to take advantage of the more benign non-river corridor conditions.Our study provides a general hypothesis on differences between species confined to stressful habitats and widespread species out for test in further multispecies comparative experiments.

Pattern and drivers of species- genetic diversity correlation in natural forest tree communities across a biodiversity hotspot

Aims Exploring species-genetic diversity correlation(SGDC)is essential for understanding spatial patterns of diversity and the underlying mechanisms.Until now,latitudinal patterns of species diversity(SD)and genetic diversity(GD)were rarely studied simultaneously.As the freezing-tolerance hypothesis predicts a decrease of SD from low to high latitudes and the central-marginal hypothesis predicts a unimodal pattern of GD along latitude,we hypothesized that SD and GD are uncorrelated.We also tested how climatic and edaphic factors affect the correlation between the two levels of biodiversity.Methods We measured(i)SD(species richness and Simpson’s diversity index)and community dissimilarity of woody plants(63 plots),(ii)GD(al-lelic richness and expected heterozygosity)and genetic differen-tiation of a dominant tree species(Euptelea pleiospermum;678 individuals from 21 populations)using nuclear microsatellite data,and(iii)climatic(annual mean precipitation,annual mean tempera-ture,minimum temperature,maximum temperature,annual rela-tive moisture,solar radiation,photosynthetically active radiation)and edaphic(total C,total N,total P,available P,K,Ca,Mg,Al,Fe,Mn,Ni,Zn,B,Mo,Cu,pH)variables of 21 sites.We conducted both linear and quadratic regression analyses of diversity param-eters against latitude.Relationships between SD and GD were tested using Pearson’s correlation.Pearson’s and Spearman’sρcor-relation coefficients were calculated between diversity parameters and environmental variables.We used stepwise multiple regression analysis to identify the significant environmental predictors of SD and GD.Important Findings We observed no significant correlation between measures of SD and GD.SD decreases with increasing latitude,which can be partly explained by the freezing-tolerance hypothesis,whereas GD pre-sents a unimodal pattern along the latitudinal gradient,which is consistent with the prediction of the central-marginal hypothesis.The contrasting latitudinal patterns of SD and GD indicate that the two levels of biodiversity do not co-vary in space.Based on both correlation analysis and stepwise multiple regression analysis,SD is only related to climatic variables,whereas GD is mainly related to edaphic variables.Our results show that different geographical and environmental factors affect SD and GD,driving the non-significant correlation between the two fundamental levels of biodiversity.Furthermore,a significantly positive correlation was observed be-tween genetic distance and community dissimilarity,both of which were significantly correlated with geographical distance.