Species diversity and regeneration of old-growth seasonally dry Shorea robusta forests following gap formation

Diversity and regeneration of woody species were investigated in two ecological niches viz. gap and intact vegetation in old-growth seasonally dry Shorea robusta （Gaertn. f.） forests in Nepal. We also related varieties of diversity measures and regeneration at- tributes to gap characteristics. Stem density of tree and shrub components is higher in the gap than in the intact vegetation. Seedling densities of S. robusta and Terminalia alata （B. Heyne ex Roth.） are higher in the gap than in the intact vegetation, while contrary result is observed for T. bellirica （Gaertn. ex Roxb.） and Syzigium cumini （L. Skeels） in term of seedling density. The complement of Simpson index, Evenness index, and species-individual ratio in the seedling layer are lower in the gap than the intact vegetation. Gap size can explain species richness and species establishment rate. Gaps created by multiple tree falls in different years have higher seedling density of S. robusta than gaps created by single and/or multiple tree falls in the same year. In conclusion, gaps maintain species diversity by increasing seedling density, and favor regeneration of Sal forests. In addition to gap size, other gap attributes also affect species diversity and regeneration.

Effects of land-use types and the exotic species,Hypochaeris radicata,on plant diversity in human-transformed landscapes of the biosphere reserve,Jeju Island,Korea

Land-use and plant invasion influence biodiversity.Understanding the effects of land-use types and invasive plants on the ecosystem is crucial for better management and the development of strategic plans for increasing biodiversity in Jeju Island,Korea,a designated Biosphere Reserve by the United Nations Education,Scientific,and Cultural Organization.The effect of the most dominant invasive exotic species,Hypochaeris radicata,on the four land-use types of Jeju Island was investigated.Plant composition,soil characteristics,and plant diversity among four land-use types(cropland,green space,neglected land,and residential)were compared.Among the land-use types,croplands had the most diverse plant composition and the highest richness in exotic and native plant species.Croplands,such as tangerine orchards,which are widely distributed throughout Jeju Island,showed the highest plant diversity because of medium intensity disturbance caused by weed removal.The relative cover of H.radicata did not differ between land-use types.However,H.radicata invasion was negatively related with plant species richness,making this invasive species a threat to the biodiversity of native herbs present in land-use areas.H.radicata adapts to areas with a broad range of soil properties and a variety of land-use types.Therefore,it is crucial to monitor land-use types and patterns of plant invasion to guide the implementation of consistent management and conservation strategies for maintaining ecosystem integrity of the transformed habitat in Jeju Island.

Bird communities’responses to human-modified landscapes in the southern Anhui Mountainous Area

Conversion of natural environments to human-modified landscapes is continuing at an unprecedented rate,exerting fundamental influences on global biodiversity.Understanding how wildlife communities respond to landscape modifications is critical to improve biodiversity conservation in human-dominated landscapes.In this study,we surveyed bird communities in three common habitats(i.e.,farmland,village,and forest)in the southern Anhui Mountainous Area during summer(August 2019)and winter(December 2020).The diversity metrics and species compositions of the avian communities were compared among the habitats,and the effects of land use composition in these habitats were tested.During the field surveys,we recorded 7599 birds of 120 species along 45 line transects of 1km in length.The land use compositions differed among habitats,and land use diversity was the highest in villages and lowest in forests.The species richness and bird abundance in the two human-dominated habitats(i.e.,farmland and village)were higher than those in forest in both seasons.Bird species composition also differed across habitat types in both seasons.Bird species feeding on vertebrates,fish and carrion,and species feeding on plants and seeds were mainly found in habitats with less construction lands and lower land use diversity,while omnivorous species and species feeding on fruits and nectar or on invertebrates were less affected by these two variables.The indicator species analysis showed that most species associated with forest feed on invertebrates,while species feeding on plants and seeds were more correlated with farmland and village.The results indicated that the conversion of natural habitats to human-dominated landscapes has pronounced impacts on bird communities in the study area.Human-dominated habitats harboured more avian species that deserve conservation attention.Meanwhile,bird conservations should not be relaxed in forests because there were more than 20 species that had a high specificity for forests.

Influence of experimental soil disturbances on the diversity of plants in agricultural grasslands

Aims and Methods Disturbance is supposed to play an important role for biodiversity and ecosystem stability as described by the intermediate disturbance hypoth-esis(IDH),which predicts highest species richness at intermediate levels of disturbances.In this study,we tested the effects of artificial soil distur-bances on diversity of annual and perennial vascular plants and bryo-phytes in a field experiment in 86 agricultural grasslands differing in land use in two regions of Germany.On each grassland,we implemented four treatments:three treatments differing in application time of soil dis-turbances and one control.One year after experimental disturbance,we recorded vegetation and measured biomass productivity and bare ground.We analysed the disturbance response taking effects of region and land-use-accompanied disturbance regimes into account.Important Findings Region and land-use type strongly determined plant species rich-ness.Experimental disturbances had small positive effects on the species richness of annuals,but none on perennials or bryophytes.Bare ground was positively related to species richness of bryophytes.However,exceeding the creation of 12%bare ground further distur-bance had a detrimental effect on bryophyte species richness,which corresponds to the IDH.As biomass productivity was unaffected by disturbance our results indicate that the disturbance effect on spe-cies richness of annuals was not due to decreased overall produc-tivity,but rather due to short-term lowered inter-and intraspecific competition at the newly created microsites.Generally,our results highlight the importance of soil disturbances for species richness of annual plants and bryophytes in agricultural grasslands.However,most grasslands were disturbed naturally or by land-use practices and our additional experimental soil dis-turbances only had a small short-term effect.Overall,total plant diversity in grasslands seemed to be more limited by the availabil-ity of propagules rather than by suitable microsites for germination.Thus,nature conservation efforts to increase grassland diversity should focus on overcoming propagule limitation,for instance by additional sowing of seeds,while the creation of additional open patches by disturbance might only be appropriate where natural disturbances are scarce.

Genotypic diversity of a dominant C_(4) grass across a long-term fire frequency gradient

Aims and Methods Diversity-disturbance research has focused on community diversity,but disturbance frequency could impact diversity within species as well,with important consequences for community diversity and ecosystem function.We examined patterns of genetic diversity of a dominant grass species,Andropogon gerardii,in native North American tallgrass prairie sites located in eastern Kansas that have been subjected to a gradient of fire frequency treatments(burned every 1,2,4 or 20 years)since the 1970s.In addition,we were able to assess the relationships between genetic diversity of A.gerardii,species diversity and productivity across this range of fire frequencies.Important Findings We found no significant relationships between genetic diversity of A.gerardii at the local scale(1 m^(2) plot level)and disturbance frequency(burned 2 to 32 times over a 38-year period).However,at the site level(i.e.across all plots sampled within a site,~100 m^(2))there were differences in genotype richness and composition,as well as genomic dissimilarity among individuals of A.gerardii.Genotype richness was greatest for the site burned at an intermediate(4-year)frequency and lowest for the infrequently(20-year)burned site.In addition,genotypes found in the frequently burned sites were more similar from each other than expected by random chance than those found in the infrequently burned sites.Genotype composition of A.gerardii was not significantly different between the frequently burned sites(annual vs.2 year)but did differ between frequently burned and infrequently burned sites(1 and 2 year vs.4 and 20 year,etc.).Together,these results suggest site-level ecological sorting of genotypes in intact prairie across a broad gradient of disturbance frequencies,likely driven by alterations in environmental conditions.Frequent fire promotes the abundance of dominant grass species,reduces plant community diversity and impacts ecosystem processes such as productivity.Our study suggests that genetic diversity within dominant grass species also may be affected by disturbance frequency,which could have important implications for how species are able to respond to disturbance.