Island biogeography theory and the habitat heterogeneity jointly explain global patterns of Rhododendron diversity

Mountain biodiversity is of great importance to biogeography and ecology.However,it is unclear what ecological and evolutionary processes best explain the generation and maintenance of its high levels of species diversity.In this study,we determined which of six common hypotheses(e.g.,climate hypotheses,habitat heterogeneity hypothesis and island biogeography theory)best explain global patterns of species diversity in Rhododendron.We found that Rhododendron diversity patterns were most strongly explained by proxies of island biogeography theory(i.e.,mountain area)and habitat heterogeneity(i.e.,elevation range).When we examined other relationships important to island biogeography theory,we found that the planimetric area and the volume of mountains were positively correlated with the Rhododendron diversity,whereas the‘mountains-to-mainland’distance was negatively correlated with Rhododendron diversity and shared species.Our findings demonstrate that Rhododendron diversity can be explained by island biogeography theory and habitat heterogeneity,and mountains can be regarded as islands which supported island biogeography theory.

Logging and topographic effects on tree community structure and habitat associations in a tropical upland evergreen forest,Ghana

We determined the response of tree community structure to logging disturbance and topography,and the patterns of tree-habitat associations in Tano Offin Forest Reserve,Ghana.We sampled trees in 27 20 m× 20 m plots randomly and equally distributed in three topographic habitats(slope,valley,and hilltop) in each of two forests:logged and unlogged.Two topographic features,altitude and degree of slope,were measured and related with species composition.Overall,there were significant effects of logging and topographic habitat and their interaction on species diversity and composition,with the unlogged forest and valley habitat supporting higher diversity.Tree diversity varied among the topographic habitats in the logged but not in the unlogged forest.There were topographic effects on abundance of individual species but not on tree community abundance and basal area.Logging and its interaction with topographic habitat showed significant effects on tree abundance and basal area.Some species were associated with specific topographic habitats or a combination in the logged and unlogged forests.However,the patterns of habitat associations of the species differed between the logged and unlogged forests.

Collaborating with Nature: The Pristine Habitats, in Ugep, Yakurr L.G.A., Nigeria

Pristine habitats serve as ecological resource for educational services and the conservation of biodiversity. The need to maintain a balance between nature and development is very important. When pristine habitats face changes due to anthropogenic activities, species erosion sets in and this will eventually lead to extinction. This subtle move in most cases is unnoticed until the effects are established. The pristine habitats in Ugep are faced with this challenge. The Ugep Urban Landuse Master Plan and Ugep Orthophoto map [1] have been used to identify the pristine habitats and further calculate the total landmass to be approximately 855.38 hectares. Ten (10) pristine habitats were identified within the residential blocks along the drainage corridors of Loblo, Isayi, Mma Oden, Kiwei, Ewiden and Oganghwen. The pristine block at Njelokoko-2 has the highest landmass, 201.01 hectares, representing 23.50 percent while Njelokoko-1 has the least landmass, 18.99 (2.22 percent). The spatial turnover of the species composition shows a trend of direct proportion with the landmass size and anthropogenic activities in the pristine habitats. Tree species such as Albizia zygia and Artocarpus communis rarely occurred together with other tree species. Among the bird species, it was observed that Dendropes goerae, Milvus migrans, Pica pica, and Streptopelia senegalensis roost, breed and feed in pristine habitats with emergent trees while Halocyno leucoephala, Halocyno malimbicus, Frasena clnernscens, Streptopelia semitorguata and Crimifer piscator are restricted to narrow corridors of pristine habitats along stream buffers. The nature that the pristine habitat portends and the species observed in such highly urbanized context as Ugep, are very important in conservation planning and meeting the urban challenges.

THE INFLUENCE OF HETEROGENEOUS HABITATS ON THE GERMINATION OF ACANTHOPANAX SENTICOSUS SEEDS AND THE DYNAMICS OF ITS SEED POOL

Differences in germination of .A. Senticosus, an important shrub under the Korean Pine broad-leavd forest and its secondary forest in heterogeneous habitats and the dynamics of its seed pool have been studied by observations in location. The results showed that transformation rates from seeds to seedlings were in the following order : 16.8% in Larch plantations, 4. 1% in Mongolian oak forests, 2.7% in Birch forests, 1.8% in Korean Pine plantations, and 0.5% in hard wood forests.The life-span of seeds was determined to be four years in the simulating seed pool under Larch plantations. The percentage of the seedling output was, 14.5% in the 2nd year, 10. 1% in the 3rd year, and 1 .8% in the 4th year. Other types of the seed output were those f decayed 33. 1 %, senescent, 22.3%,predated by mice 14. 1%, which was variable due to the variation in the number of mouse, and only 1. 17% were eaten by insects and other soil animals.

Harvesting of forest products and implications for Afrotemperate bird communities in a montane forest of the Eastern Cape, South Africa

Background: Harvesting of forest products is a widespread driver of disturbance in developing nations, where policies are increasingly aimed at managing natural forests for sustainable use. There is thus need for research aimed at understanding the impact of resource use on forest habitats and concomitant effects on biodiversity.Afromontane forests in the Eastern Cape, South Africa are harvested informally for poles and medicinal bark and occur along elevational gradients of 800–1600 m above sea level. Patterns of spatial diversity and human disturbance are expected to be affected by elevation. Furthermore, species’ responses to disturbance are expected to vary depending on their level of habitat specialisation. Understanding harvest impacts on forest biodiversity thus requires disentangling the separate effects of elevation and disturbance, and considering forest-specialist and forest-generalist species separately. This study comprises two components. First, harvest activities, resultant harvestmediated habitat heterogeneity, and avifaunal species richness, composition and beta-diversity were compared across two elevational zones in a harvested forest. Second, the role of harvest-mediated habitat heterogeneity in driving patterns of avifaunal diversity were assessed, while controlling for elevation, and considering forest-specialist and forest-generalist species separately.Results: Harvest rates were higher, and activities more varied in the lower elevation zone, with significant impacts of harvesting on habitat features resulting in higher harvest-mediated habitat heterogeneity at lower elevations.Harvest-mediated increases in habitat heterogeneity positively affected forest-generalist species richness, while forest-specialist richness was negatively affected. While species composition of both groups differed across elevational zones, variation in harvest-mediated habitat heterogeneity did not fully account for this, suggesting that factors other than disturbance shape avifaunal communities along the elevation gradient. However, variation in harvest-mediated habitat heterogeneity accounted for the amount of beta-diversity attributed to species turnover in the forest-specialist assemblage, indicating that harvest disturbances affect the mechanisms driving beta-diversity of this group.Conclusion: Spatial patterns of avifaunal diversity are affected by elevation over a 300-m gradient. Harvesting results in increased habitat heterogeneity, which variably affects avifaunal communities at the forest-scale, with positive effects for forest generalists and negative effects for forest-specialists.

Aggregated spatial distributions of species in a subtropical karst forest,southwestern China

Aims spatial distribution patterns of species reflect not only the ecological processes but also the habitat features that are related to species distribution.in karst topography,species distribution patterns provide more specific information about their environments.The objectives of this study are as follows:(i)to analyse and explain the spatial distribution patterns of conspecific trees in an old-growth subtropical karst forest;(ii)to investigate pattern changes at different spatial scales;(iii)to test the spatial pattern similarity(or dissimilarity)between trees at different abundances,diameter at breast height classes,canopy layers and different functional groups(shade tolerance and seed dispersal mode);(iv)to examine whether habitat heterogeneity has an important effect on the species spatial distribution.Methods The spatial distributions of woody species with≥20 individuals in a 1-ha subtropical karst forest plot at maolan in southwestern China were quantified using the relative neighbourhood densityΩbased on the average density of conspecific species in a circular neigh-bourhood around each species.Important Findingsaggregated distribution is the dominant pattern in the karst forest,but the ratio of aggregated species in total species number decreases with an increase in spatial scale.less abundant species are more aggregated than most abundant species.aggregation is weaker in larger diameter classes,which is consistent with the prediction of self-thinning.seed dispersal mode influences spatial patterns,with species dispersed by animals being less aggregated than those dispersed by wind and gravity.other species functional traits(e.g.shade tolerance)also influence the species spatial distributions.moreover,differences among species habitat associations,e.g.with rocky outcrops,play a significant role in species spatial distributions.These results indicate that habitat heterogeneity,seed dispersal limitation and self-thinning primarily contribute to the species spatial distributions in this subtropical karst forest.

The effect of tree size,neighborhood competition and environment on tree growth in an old-growth temperate forest

Aims Understanding the controls influencing tree growth is central to forest ecology.Although many factors such as tree size,neighborhood competition and environmental variables,have been proposed as being important in explaining patterns of tree growth,but their relative contributions are still subject to debate.We aimed to examine the relative importance of tree size,local abiotic conditions and the density and identity of neighbors on tree growth in an old-growth temperate forest in northeast china.Methods We used linear mixed models with data from a 25 ha(500×500 m)broad-leaved Korean pine(Pinus koraiensis)mixed forest perma-nent plot to examine the relative importance of these local drivers on tree growth at three organizational levels(community,guild and species).Subplot was included as a random effect to account for spatial autocorrelation in growth of trees located within the same subplot,and species was included as a random effect to account for variation among species in growth.Important Findings Tree size was typically the most important predictor of growth,followed by neighborhood competition and then soil nutrients.The correlation of tree size to growth varied from strongly positive for large trees and medium trees to slightly positive for small trees.The effect of neighbor-hood competition on growth showed weak negative density dependence as indicated by slightly negative effect of total basal area of neighbors and the proportion of conspecific neighbors.Environmental factors influenced growth of very common species,smaller tree-size classes and shade-tolerant species.We concluded that the relative importance of variables driving patterns of tree growth varied greatly among tree size classes,shade tolerance and abundance classes in this temperate for-est.These results provide critical information for future studies of forest dynamics and offer insight into forest management in this region.

Traditional grazing management creates heterogeneous swards and fosters grasshopper densities

Common pastures were once the dominant type of land use in many Euro-pean regions.However,during the past 150 years,they have declined dramatically.Recent studies have shown that they are hotspots for rare plant,butterfly,and bird species in the study area,the Bavarian pre-Alps(southern Germany).However,studies on the value of these pastures for Orthoptera(hereinafter termed"grasshoppers")have been scarce.Here,we studied the effects of traditional summer grazing in common pastures on grasshopper assemblages.Our study revealed that grasshopper species richness did not differ between common pastures(n=57)and controls(n=57).By contrast,density of all and of threat-ened species varied between common pastures and controls in all plots and within the two vegetation types with the highest grasshopper abundance,grasslands on mineral soil and fens.Two threatened species,Pseudochorthippus montanus and Stethophyma grossum,were identified as indicators for common pastures;controls had no indicative species.Traditional low-intensity grazing in common pastures has resulted in open and heteroge-neous swards with some bare ground,a low cover of litter and an intermediate vegetation height favouring high densities of grasshopper species in general and threatened species in particular.This is especially true for the two most productive vegetation types,grasslands on mineral soil and fens.To promote biodiversity in general and grasshopper densities in particular,we recommend maintaining traditional cattle grazing(stocking capacities:0.5-2.0 livestock units/ha)in common pastures.Where possible,this grazing regime should also be introduced in the surrounding landscape.

Exogenous and endogenous determinants of spatial aggregation patterns in tibetan Plateau meadow vegetation

Aims We aim to quantify the relative importance of various endogenous and exogenous processes influencing the spatial distribution of the individuals of plant species at different temporal and spatial scales in a species-rich and high-cover meadow in the eastern tibetan Plateau.Methods We calculated green’s index of dispersion to infer the spatial dis-tribution patterns of 73 herbaceous species at two scales(0.25 and 1.0 m2).We constructed a series of generalized linear models to test the hypotheses that different species traits such as mean plant stem density,per capita dry biomass,maximum plant height and mean seed mass contribute to their spatial distribution.We used the first principal component of soil C,N and P to explain abundance vari-ation across quadrats and sub-plots.Important Findingsthe individuals of the species studied were highly spatially aggregated.at both spatial scales,biomass and stem density explained the most variation in aggregation,but there was no evidence for an effect of mean seed mass on aggregation intensity.the effects of soil carbon,nitrogen and phosphorus at different depths affected plant abundance mostly at the broader spatial scale.our results demonstrate that self-thinning and habitat heterogeneity all contribute to determine the spatial aggregation patterns of plant individuals in alpine meadow vegetation in the eastern tibetan Plateau.

Ecological niche modelling of a critically endangered species Commiphora wightii (Arn.) Bhandari using bioclimatic and non-bioclimatic variables

Background The aim of this study is to examine the effects of four different bioclimatic predictors(current,2050,2070,and 2090 under Shared Socioeconomic Pathways SSP2-4.5)and non-bioclimatic variables(soil,habitat heterogeneity index,land use,slope,and aspect)on the habitat suitability and niche dimensions of the critically endangered plant species Commiphora wightii in India.We also evaluate how niche modelling affects its extent of occurrence(EOO)and area of occupancy(AOO).Results The area under the receiver operating curve(AUC)values produced by the maximum entropy(Maxent)under various bioclimatic time frames were more than 0.94,indicating excellent model accuracy.Non-bioclimatic characteristics,with the exception of terrain slope and aspect,decreased the accuracy of our model.Additionally,Maxent accuracy was the lowest across all combinations of bioclimatic and non-bioclimatic variables(AUC=0.75 to 0.78).With current,2050,and 2070 bioclimatic projections,our modelling revealed the significance of water availability parameters(BC-12 to BC-19,i.e.annual and seasonal precipitation as well as precipitation of wettest,driest,and coldest months and quarters)on habitat suitability for this species.However,with 2090 projection,energy variables such as mean temperature of wettest quarter(BC-8)and isothermality(BC-3)were identified as governing factors.Excessive salt,rooting conditions,land use type(grassland),characteristics of the plant community,and slope were also noticed to have an impact on this species.Through distribution modelling of this species in both its native(west-ern India)and exotic(North-east,Central Part of India,as well as northern and eastern Ghat)habitats,we were also able to simulate both its fundamental niche and its realized niche.Our EOO and AOO analysis reflects the possibility of many new areas in India where this species can be planted and grown.Conclusion According to the calculated area under the various suitability classes,we can conclude that C.wight-ii’s potentially suitable bioclimatic distribution under the optimum and moderate classes would increase under all future bioclimatic scenarios(2090>2050≈current),with the exception of 2070,demonstrating that there are more suitable habitats available for C.wightii artificial cultivation and will be available for future bioclimatic projections of 2050 and 2090.Predictive sites indicated that this species also favours various types of landforms outside rocky environments,such as sand dunes,sandy plains,young alluvial plains,saline areas,and so on.Our research also revealed crucial information regarding the community dispersion variable,notably the coefficient of variation that,when bioclimatic non-bioclimatic variables were coupled,disguised the effects of bioclimatic factors across all time frames.