Community structure and biodiversity in plantations and natural forests of seabuckthorn in southern Ningxia,China

Two types of sampling plots of seabuckthom （Hippophae rhamnoides） communities were investigated in Pengyang County of Ningxia region by a typical sampling method to study the characteristics of community structure and biodiversity. Composition and dominant species of each community were analyzed by the importance value of species as an index. The number of individuals and the importance value, as well as Sorensen＇s similarity coefficient, Shannon-Wiener diversity index, Pielou＇s evenness index and Simpson＇s dominance index, were used as indices to compare characteristics of community structure, similarity and biodiversity between plantations and natural forests of seabuckthom. The results indicate that the importance values of species of natural seabuckthom communities were dispersed and the difference between dominant species was not statistically significant. Diversity indices of natural seabuckthom communities reflected by species richness and evenness were higher than that of plantations. Community structure of natural seabuckthom forests is more complex. We propose that natural forest can be used as sample to guide selection of plant species in silviculture in order to improve biodiversity of plantation.

Succession and biodiversity indices in eutrophication process of static landscaping water body in northern China

Many biodiversity indices were used to indicate the biological contamination degree in studies of lake water or seawater. Some were studied on biodiversity comparison for different areas at the same time, or initial structure succession of some aerial lake water systems. The phytoplankton changed with the development of various dominant species. In this study, the dominant species at these stages were Chlorophyta in the beginning stage, Cyanophyta in the second stage, and Xanthophyta in the last stage. Seven of nine biodiversity indices (Margalef's, IE, Shannon-Wiener, Simpson's, McNaughton's, Species and Odds Measure of Diversity) showed their failure to represent the eutrophication trend, and the other two indices (Menhinick's and Monk) exhibited good efficiency to indicate the eutrophication trend for the static landscaping water body.

Tree structure and diversity shape the biomass of primary temperate mountain forests

Primary forests are spatially diverse terrestrial ecosystems with unique characteristics,being naturally regenerative and heterogeneous,which supports the stability of their carbon storage through the accumulation of live and dead biomass.Yet,little is known about the interactions between biomass stocks,tree genus diversity and structure across a temperate montane primary forest.Here,we investigated the relationship between tree structure(variability in basal area and tree size),genus-level diversity(abundance,tree diversity)and biomass stocks in temperate primary mountain forests across Central and Eastern Europe.We used inventory data from726 permanent sample plots from mixed beech and spruce across the Carpathian Mountains.We used nonlinear regression to analyse the spatial variability in forest biomass,structure,and genus-level diversity and how they interact with plot-level tree age,disturbances,temperature and altitude.We found that the combined effects of genus and structural indices were important for addressing the variability in biomass across different spatial scales.Local processes in disturbance regimes and uneven tree age support forest hete rogeneity and the accumulation of live and dead biomass through the natural regeneration,growth and decay of the forest ecosystem.Structural complexities in basal area index,supporte d by genus-level abundance,positively influence total biomass stocks,which was modulated by tree age and disturbances.Spruce forests showed higher tree density and basal area than mixed beech forests,though mixed beech still contributes significantly to biomass across landscapes.Forest heterogeneity was strongly influenced by complexities in forest composition(tree genus diversity,structure).We addressed the importance of primary forests as stable carbon stores,achieved through structure and diversity.Safeguarding such ecosystems is critical for ensuring the stability of the primary forest,carbon store and biodiversity into the future.

Influence of individual tree characteristics,spatial structure and logging history on tree-related microhabitat occurrence in North American hardwood forests

Background:Tree-related microhabitats(hereafter,"TreMs")are key components of forest biodiversity but they are still poorly known in North American hardwood forests.The spatial patterns of living trees bearing TreMs(hereafter,"TreM-trees")also remain to be determined.As logging practices can lead to a loss of TreM-trees and of their associated biodiversity,it is essential to identify the factors explaining TreM occurrence to better integrate them into forest management.We therefore inventoried TreMs in 40.5-ha survey strips in northern hardwood forests in Quebec,Canada,while recording the spatial location of each tree.Two strips were located in unmanaged oldgrowth forests,and 2 were in forests managed under selection cutting.All 4 stands were dominated by sugar maple(Acer saccharum Marsh.)and American beech(Fagus grandifolia Ehrn.).Beech bark disease,an exotic pathology,was observed in all the strips.Results:Large diameter at breast height and low tree vigor were the main characteristics explaining the presence of TreMs at the tree scale.TreM-trees presented slight spatial aggregation patterns.These aggregates,however,were not well-defined and were generally constituted by a large number of trees bearing few different types of TreMs.Two TreM classes(broken branch or top and woodpecker lodge)also presented a spatial aggregation.Logging practices had no significant effect on TreM occurrence.Beech bark disease increased the frequency of senescent beeches.The impact of this pathology on TreMs was however mitigated by the small size of infected trees and probably by the short time elapsed since its appearance.Conclusion:The factors explaining the presence and abundance of TreMs on trees has so far been little studied in North American hardwood forests.Our results highlight that TreM-tree characteristics in the surveyed forests are consistent with those of previous studies conducted in other forest types and regions(e.g.,Europe or Northwestern America).To our knowledge,this study is also the first to identify a spatial aggregation of TreM-trees and of specific TreM classes.It will be nevertheless necessary to determine whether the small impact of logging activities we observed results from current or past management practices.

Effects of grassland management on the community structure, aboveground biomass and stability of a temperate steppe in Inner Mongolia, China

Plant community structure responds strongly to anthropogenic disturbances, which greatly influence community stability. The changes in community structure, aboveground biomass（AGB）, biodiversity and community stability associated with different management practices were studied with a three-year field investigation in a temperate steppe of Inner Mongolia, China. The species richness, Shannon-Wiener index, evenness, plant functional type abundance, AGB, temporal community stability, summed covariance, scaling coefficient and dominant species stability were compared among areas subjected to long-term reservation（R）, long-term grazing（G）, mowing since enclosure in 2008（M） and grazing enclosure since 2008（E）. Site R had higher perennial grass abundance and lower species richness than sites G, M and E, although the AGB was not significantly different among the four sites. The species structure varied from a single dominant species at site R to multiple dominant species at sites G, M and E. The long-term reservation grassland had lower biodiversity but higher stability, whereas the enclosed grassland with/without mowing had higher biodiversity but lower stability. Different stability mechanisms, such as the compensatory dynamics, mean-variance scaling and dominant species stability were examined. Results showed that community stability was most closely related to the relative stability of the dominant species, which supports the biomass ratio hypothesis proposed by Grime.

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

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

Ecotourist trail-use affects the taxonomic, functional and phylogenetic diversity of mammals in a protected area: lessons for conservation management

Ecotourism,by definition,aims to engage peoples’interest in wildlife and the environment.The use of tourist roads and trails to access sites within protected areas(PAs)can detrimentally affect the behavior and distribution of species.The way mammals respond to anthropogenic pressures may differ across taxonomic,functional,and phy-logenetic groups;nevertheless,how ecotourist trail-use affects these different diversity remains under-investigated.Here,we assessed 6 metrics of taxonomic,phylogenetic,and functional diversity for a mammal community in a PA in central China,recording how Trail use(using Trail type as a proxy)and habitat variables affected sightings and signs of mammals across 60 replicate 0.5 km transects.We then examined how Trail use affected the taxonomic,functional,and phylogenetic diversity indices of species(>1 kg).Using generalized liner mixed modeling,we identified that more used trail types had a greater adverse effect on all diversity richness indices than did less used trail types.Consequently,tourist pressure was associated with a general tendency to homogenize the site’s mammal community.In contrast,the effects of Trail Types on all diversity evenness indices were non-significant.Further-more,more developed and more heavily used trail types had a greater,significant negative effect on taxonomic,functional,and phylogenetic richness,whereas these richness indices were unaffected by minor trail types,used less intensively.As a general principle,lower biodiversity indices reduce ecosystem resilience,and so it is vital to better understand these responses to balance public access against biodiversity management in PAs.