Spatial patterns and associations between species belonging to four genera of the Lauraceae family.

Spatial distribution pattern of biological related species present unique opportunities and challenges to explain species coexistence. In this study, we explored the spatial distributions and associations among congeneric species at both the species and genus levels to explain their coexistence through examining the similarities and differences at these two levels. We first used DNA and cluster analysis to confirmed the relative relationship of eight species within a 20 ha subtropical forest in southern China. We compared Diameter at breast height (DBH) classes, aggregation intensities and spatial patterns, associations, and distributions of four closely related species pairs to reveal similarities and differences at the species and genus levels. These comparisons provided insight into the mechanisms of coexistence of these congeners. O-ring statistics were used to measure spatial patterns of species. Ω0-10, the mean conspecific density within 10 m of a tree, was used as a measure of the intensity of aggregation of a species, and g-function was used to analyze spatial associations. Our results suggested that spatial aggregations were common, but the differences between spatial patterns were reduced at the genus level. Aggregation intensity clearly reduced at the genus level. Negative association frequencies decreased at the genus level, such that independent association was commonplace among all four genera. Relationships between more closely related species appeared to be more competitive at both the species and genus levels. The importance of competition on interactions is most likely influenced by similarity in lifestyle, and the habitat diversity within the species' distribution areas. Relatives with different lifestyles likely produce different distribution patterns through different interaction process. In order to fully understand the mechanisms generating spatial distributions of coexisting siblings, further research is required to determine the spatial patterns and associations at other classification levels.

Which models are appropriate for six subtropical forests: species-area and species-abundance models.

The species-area relationship is one of the most important topic in the study of species diversity, conservation biology and landscape ecology. The species-area relationship curves describe the increase of species number with increasing area, and have been modeled by various equations. In this paper, we used detailed data from six 1-ha subtropical forest communities to fit three species-area relationship models. The coefficient of determination and F ratio of ANOVA showed all the three models fitted well to the species-area relationship data in the subtropical communities, with the logarithm model performing better than the other two models. We also used the three species-abundance distributions, namely the lognormal, logcauchy and logseries model, to fit them to the species-abundance data of six communities. In this case, the logcauchy model had the better fit based on the coefficient of determination. Our research reveals that the rare species always exist in the six communities, corroborating the neutral theory of Hubbell. Furthermore, we explained why all species-abundance figures appeared to be left-side truncated. This was due to subtropical forests have high diversity, and their large species number includes many rare species.

Spatial patterns and interspecific associations of three canopy species at different life stages in a subtropical forest, China.

Spatial patterns of species at different life stages are an important aspect for understanding causal mechanisms that facilitate species co-existence. Using Ripley's univariate L(t) and bivariate L(12)(t) functions, we analyzed the spatial patterns and interspecific associations of three canopy species at different life history stages in a 20-ha subtropical forest plot in Dinghushan Nature Reserve. Based on diameter at breast height (DBH), four life stages were distinguished. Castanopsis chinensis and Schima superba showed a unimodal DBH distribution. Engelhardtia roxburghiana showed a bimodal curve. L(t) function analysis showed significantly aggregated distributions of all three species at later life stages and random distribution at early life stages at some scales. From the analysis of L(12)(t) function, the results showed the positive association was a dominant pattern for most species pairs at most scales but the intensity of association decreases with the increase of life stages. Juveniles of the three species had no negative intra- and interspecific associations with the older life stages. Only premature trees were suppressed by overmature trees at some scales. Considering these results, we found three canopy-dominant species that lacked regeneration. There was no direct competition occurring between understorey individuals. Young trees can grow well under conspecific species with two other species. Longevity and lack of regeneration led to a large number of trees stored in mature and overmature stages, therefore, intra- and inter-competition can be strong at later life stages.

[Soil organic carbon and nitrogen mineralization along a forest successional gradient in Southern China].

With incubation test, this paper studied the characteristics of organic C and N mineralization in 0-10 cm soil layer under three forest types, i. e., pine (Pinus massoniana) forest (PMF), pine and broad-leaved mixed forest (PBMF) and monsoon evergreen broad-leaved forest (MEBF), which were in a successional series in Dinghushan Mountain of Southern China. The results showed that after incubation for 52 weeks, the cumulative emission of CO2-C from PMF, PBMF and MEBF soil was 30.66 +/- 3.36, 58.17 +/- 7.25 and 59.31 +/- 13.58 mg x kg(-1), respectively, and 64.12%, 64.41% and 65.12% of which were released in the first 9 weeks. The cumulative emission of CO2-C was always significantly smaller from PMF soil than from PBMF and MEBF soils, and its change pattern over time fitted well with a two-pool kinetic model. The parameters based on the model implicated that the mineralization rates of soil labile and recalcitrant organic carbon tended to decrease with the forest type changing from PMF to PBMF and MEBF. The cumulative amount of CH4 after 52 weeks incubation and the net production of available N and nitrate after 20 weeks incubation were significantly higher in MEBF soil than in PBMF soil, and also, in PBMF soil than in PMF soil. NO3(-) -N was the dominant form in net available N production. The change in soil organic carbon mineralization rate caused by forest type change was an inherent way to affect soil organic carbon content.

[Clinical effect of treatment with lipo-prostaglandin E1 on the patients with chronic glomerulonephritis].

OBJECTIVE: To investigate potential mechanism underlying lipo-prostaglandin E1 (PGE1) in treatment of patients with chronic glomerulonephritis. METHODS: The recommended dose of 20 microg lipo-PGE1 for treatment of chronic glomerulonephritis was as a daily dose by continuous intravenous infusion or intravenous injection for 4 weeks. The levels of interleukin-1 (IL- 1), tumor necrosis factor-alpha (TNF-alpha), blood urea nitrogen (BUN), serum creatinine (SCr) and clearance of creatinine (CCr) were measured before and after treatment. RESULTS: After treatment with lipo-PGE1, levels of IL-1, TNF-alpha, BUN and SCr were lower than those before treatment (all P<0.01), but CCr values were higher than those before treatment (P<0.05). CONCLUSION: Lipo-PGE1 can reduce the renal inflammatory response and improve the renal function in the patients with chronic glomerulonephritis.