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2 Polish Journal of Ecology

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Effects of environmental variation and spatial distance on the beta diversity of woody plant functional groups in a tropical forest

Zhang Z., Zang R., Wang L., Wang G., Zhang J.

Polish Journal of Ecology

2012

Vol. 60, nr 3

525-533

Tropical forests are among the most complex ecosystems on Earth. The high alpha-diversity of tropical forests has been amply documented, however, beta diversity, equally important for us to understand the mechanism of biodiversity maintenance, has seldom been studied. The main current hypotheses about the origin of beta diversity are as follows: (1) species composition is uniform over large areas; (2) species composition fluctuates in a random, auto-correlated way emphasizing spatially limited dispersal; (3) species composition is related to environmental conditions. Testing these hypotheses is important to understand ecosystem function and to manage ecosystems effectively. In this study, we quantified the relative influence of environmental variation and spatial distance on the beta diversity of woody plant functional groups in a tropical forest of Hainan Island, China. Floristic and environmental data were collected from 135 grid-sample plots. We classified woody plant functional groups based on frequency, growth forms and successional status, respectively. To see whether environmental variation and spatial distance influence beta diversity, the simple and partial Mantel tests, in conjunction with linear and spline regression models were performed. The results showed that environmental heterogeneity and spatial distance were the primary determinants of pair-wise species composition differences between plots in the study area. Common, tree and climax species were more sensitive than the others to changes in environmental heterogeneity and spatial distance. Except for rare, pioneer and shrub species, the others had apparently negative relationship between spatial distance and similarity. The distance decay of similarity was determined by joint influences of spatial distance and spatially-structured environmental variables. Spatial distance had the clearest effect on beta diversity at distances <15 km and with the increase in spatial distance, beta diversity was gradually controlled by environmental heterogeneity. This study provides further support for neutral theory and environmental control hypothesis as opposed to uniformly distributed hypothesis.

Intra-versus inter-population variation of cone and seed morphological traits of Pinus tabulaeformis Carr. in northern China : impact of climate-related conditions

Ji M., Zhang Q., Deng J., Zhang X., Wang Z.

Polish Journal of Ecology

2011

Vol. 59, nr 4

717-727

Morphological traits of conifer species are known to vary adaptively with the geographic and climatic variables, but little is known about intra- and inter-population variation and impact of associated climate factors on the morphological variation. Chinese hard pine (Pinus tabulaeformis Carr) is a major and widespread component of coniferous forests in the temperate and semi-humid zone in northern China. Here we investigated 12 life history traits involving cone length (CL), width (CW) and dry weight (CDW), cone length to width ratio (CLW), seed length (SL), width (CW) and total weight (STW), seed length to width ratio (SLW), seed wing length (SWL), width (SWW) and total weight (SWTW), seed wing length to width ration (SWLW) at 12 sites between longitudes (102[degrees]E to 122[degrees]E) and latitudes (32[degrees]N to 43[degrees]N) covering an altitude range of 125.2581 m. Our results showed that each morphological character presented a large variation both within and among populations. Moreover, we found that proportion of phenotypic variation (i.e. V[st], %) of the all cone traits except for the cone width was over 50% among populations, indicating that the variation of these traits was mainly controlled by the environmental variables. Although the mean proportion of phenotypic variation of all measured traits was only about 28% among populations of this species, it was much higher than those of other conifers, which further suggested that this species held the higher adaptive phenotypic variation or stress-tolerance ability under varying environmental conditions. Furthermore, the phenotypic variation presented a general pattern that almost all measured traits were negatively correlated with the potential evapotranspiration which reflected the synthetic effects of multiple factors such as the temperature and rainfall, rather than a single environmental or climatic factor. In conclusion, according to the relationship between phenotypic variation and climate factors, it will undoubtedly provide important information for the reforestation and genetic conservation for this species in the changing climate.