Functional diversity of Cercidiphyllum japonicum, communities in the Shennongjia Reserve, central China

Functional diversity is significant to ecological processes of plant communities. We analyzed the variation of functional diversity of endangered species, Cercidiphyllum japonicum, communities along an elevational gradient in the Shennongjia Reserve, central China. Sixty plots of 10 9 20 m from 1,350 to 2,050 m were set up and species composition, traits and environmental variables were measured and recorded. These data were analyzed using five functional diversity indices, functional attribute diversity, modified functional attribute diversity, plot based functional diversity, community based functional diversity and Rao＇s functional diversity indices（Rao＇s index）,Functional diversities of C. japonicum communities were rich and varied greatly. Functional diversity declined nonlinearly with increasing elevation. Functional diversity was significantly correlated with species richness and heterogeneity. Elevation was a key environmental variable influencing functional diversity and species diversity. The five functional diversity indices were all effective for measuring functional diversity of communities. Functional diversity can be used as an indicator of conservation efficiency of endangered species such as C. japonicum.

Effects of Topography and Land use on Woody Plant Species Composition and Beta Diversity in an Arid Trans-Himalayan Landscape, Nepal

Distribution patterns of plant species are believed to be impacted by small-scale habitat heterogeneity. However, there have been few comparative studies examining how woody vegetation composition and diversity varies with aspects of different orientations in the Trans-Himalayan region at a local scale. Here, we examined the effects of incoming solar radiation on variation in woody species composition and compared the diversity between the northeast- and southwest-facing slopes in a Trans-Himalayan valley of Nepal. We also examined the implicit interactions between slope orientation and land use in determining the compositional variations between the slopes. We selected two pairs of northeast- and southwest-facing slopes where the first pair has a similar land use and differs in exposure only(Pisang site) while the other pair has clear differences in land use in addition to slope exposure(Braka site). In each site, we sampled 72 plots(36 on each slope) in which the presence and absence of woody species, environmental variables, and disturbance were recorded. Correspondence Analysis(CA) results suggested that the woody species composition significantly varied between northeast- and southwest-facing slopes at both sites, and was significantly correlated with measured environmental variables such as radiation index, altitude, and canopy openness. In the Braka site,mean alpha diversity was significantly higher on southwest-facing slopes. In contrast, beta diversity and gamma diversity were greater on northeast-facing slopes at both sites. Our results suggest that topographic variables(e.g., radiation index) affect species composition between the slopes, likely due to their influence on small scale abiotic environmental variables. However, the effects of land use, such as livestock browsing/grazing may interact with the effects of slope exposure, effectively reducing differences in species composition within slopes but enhancing the differences in beta diversity between contrasting slopes in the Braka. We conclude that slope orientation and land use are important factors in structuring the woody species composition and diversity in the arid Trans-Himalayan region. We suggest that both environmental and land use variables should be taken into consideration in future studies on plant community structure along the cultural landscapes.

Problems Related to Divers Health and Comfort in Hyperbaric He-O_2 Environment

The Diver Gas Recovery System(DGRS)is an important accessory equipment of the 300m Saturation Dive System. The system facilitates the recycling of the breathing gases for divers,therefore,it has great economic benefits. In April 1995, a 300 m unmanned test and a 100 m manned test on the HY2031 DGRSwere carried out successively.Ten months later,another manned test on the HY2032 DGRS