[Changes in vegetation and soil characteristics under tourism disturbance in lakeside wetland of northwest Yunnan Plateau, Southwest China].

The characteristics of vegetation and soil were investigated in Bita Lake and Shudu Lake wetlands in northwest Yunnan Plateau under tourism disturbance. The 22 typical plots in the wetlands were classified into 4 types by TWINSPAN, including primary wetland, light degradation, moderate degradation, and severe degradation. Along the degradation gradient, the plant community density, coverage, species number and Shannon diversity index increased and the plant height decreased in Bita Lake and Shudu Lake wetlands, and Whittaker diversity index increased in Bita Lake wetland. Plant species number, soil organic matter, total nitrogen, porosity, available nitrogen, available phosphorus and available potassium contents were higher in Shudu Lake wetland than in Bita Lake wetland, but the plant density, height, soil total potassium and pH were opposite. Canonical correspondence analysis (CCA) by importance values of 42 plants and 11 soil variables showed that soil organic matter, total nitrogen and total potassium were the key factors on plant species distribution in Bita Lake and Shudu Lake wetlands under tourism disturbance. TWINSPAN classification and analysis of vegetation-soil characteristics indicated the effects of tourism disturbance in Bita Lake wetland were larger than in Shudu Lake wetland.

[Evaluation index system of swamp degradation in Zoige Plateau of Sichuan, Southwest China under drainage stress].

The evaluation index system of swamp degradation is one of the key scientific issues in the frontier field of international wetland science research. On the basis of long-term swamp field reconnaissance, and according to the fixed position ecological investigation of plant communities and the analysis of soil samples in 20 swamp plots in three belt transects of swamp degradation research under the stress of drainage in 2009, the swamps in the Zoige Plateau of Sichuan were classified into three groups with seven swamp communities, i. e., undisturbed (A type), disturbed by long-term and weak drainage (B-D type), and disturbed by short-term and strong drainage (E-G type), according to the species importance value and by Two-Way Indicator Species Analysis (TWINSPAN). The degradation degree of the swamps was graded by the method of Principal Components Analysis (PCA), and the swamp vegetation evaluation index (SVEI) and soil evaluation index (SSEI) were developed. Based on the SVEI, the swamps were classified as pristine swamp, lightly degraded swamp, moderately degraded swamp, and severely degraded swamp. Based on the SSEI, the swamps in Hongyuan County were divided into three grades, i. e. pristine swamp, lightly degraded swamp, and severely degraded swamp, while those in Ruoergai County were divided into lightly degraded swamp, moderately degraded swamp, and severely degraded swamp. The similarity of TWINSPAN classification results and SVEI/SSEI evaluation results was above 70%, indicating that both SVEI and SSEI were effective for the swamp degradation grading, and different classification methods should be combined to comprehensively evaluate the swamps in the Plateau.

[Degradation characteristics, patterns, and processes of lakeside wetland in Napahai of northwest Yunnan Plateau, Southwest China].

Two-way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA) were employed to analyze the degradation characteristics, patterns, and processes of lakeside wetland in Napahai of northwest Yunnan Plateau. The plant communities in the lakeside wetland could be classified into four associations, according to the TWINSPAN results. The succession patterns of the plant community were represented by aquatic plant community --> swamp plant community --> swamp meadow plant community --> meadow plant community. During the processes of succession, the plant community coverage, density, Shannon diversity index, species richness, and plant aboveground biomass increased, whereas the community height decreased. The succession of the plant hydro-ecotypes followed the sequence of aquatic --> helophyte --> hygrophyte --> mesophyte. With the succession of the plant community, the wetland water quality indices salinity, alkalinity, and hardness decreased but ammonium nitrogen and total phosphorus concentrations increased, while total nitrogen and nitrate nitrogen concentrations showed no significant changes. Meanwhile, the soil pH and soil organic matter and total nitrogen contents decreased gradually, soil total phosphorous and potassium contents were increasing, whereas soil available phosphorous and potassium contents decreased after an initial increase. The CCA showed that the community species composition and structure were mainly affected by the wetland water gradient. The soil pH and total phosphorus content and the water total nitrogen and ammonium nitrogen concentrations had significant effects on the wetland plant species distribution and plant community succession.

[Degradation characteristics of swamps in Zoige Plateau induced by drainage based on quantitative classification of vegetation].

Based on the field survey of swamp ecological characteristics and environmental quality and the ecological investigation of drained swamp transects in Zoige Plateau of Tibet in 2009, twenty typical swamp plots in the Plateau were classified into three types by TWINSPAN, i. e., primary swamp, long-term drained degraded swamp, and short-term drained degraded swamp, and each type of the degraded swamps was divided into three degradation grades, i. e., light degradation, moderate degradation, and severe degradation, with the degradation characteristics of vegetation and soil along the swamp degraded gradient studied. The swamp degradation in the Plateau was mainly driven by drainage pattern, drainage intensity, and soil moisture gradient, and the vegetation degradation was more obvious than the soil degradation. In the vegetation degradation, the structural change of hydro-type functional assemblage was most obvious, e. g., the importance value of helophytes under the stress of long-term drainage and short-term drainage decreased from 0.920 to 0.183 and 0.053, while that of mesophytes increased from 0.029 to 0.613 and 0.686, respectively. The soil response to the swamp degradation was in hysteresis, i. e., the soil physical and chemical properties presented definite variations but the differences were not significant among the swamps with different grades of degradation. The results of CCA indicated that soil moisture and nitrogen and potassium contents were the most important factors affecting the plant species distribution in drained degraded swamps in Zoige Plateau.

[Spatial patterns of plant species diversity in a degraded successional series of fragmented Leymus chinensis meadow in Songnen Plain of Northeast China].

Species diversity pattern is a hot topic in the forward field of international biodiversity research. Taking a degraded successional series (six communities distributed in 144 isolated patches) of fragmented Leymus chinensis meadow in Songnen Plain as test objects, this paper studied the spatial patterns of alpha, beta, and gamma diversities and related mechanisms. Eighty seven plant species were recorded, but none of them were distributed across all patches. L. chinensis + Kalimeris integrifolia community or L. chinensis community had higher alpha, beta, and gamma diversities, with more rare species and endemic species, while Kochia sieversiana community had lower alpha, beta, and gamma diversities, with few rare species and no endemic species. The gamma diversity showed significant positive correlation with a diversity, but no correlation with beta diversity. There was a significant power function correlation between the a diversity and the area of single patch of the six communities, but no correlation between the beta diversity (Bray-Curtis similarity index, Sjk ) and the area of single patch of the communities except for L. chinensis + K. integrifolia. Both the alpha angamma diversity showed significant correlations with the mean patch area and total patch area, but the p3beta diversity did not. The higher the species richness in the communities, the more the rare species and endemic species, the larger the possibility of species depopulation in local patches was. The importance of beta diversity for shaping species diversity pattern was related to the degree of habitat fragmentation.

[The P and K concentration characteristics and their effect factors in the meadow albic bleached soil in the Sanjiang Plain].

During the growth season of wetland plant in the Sanjiang Plain, the representative meadow albic bleached soil developed in the Deyeuxia angustifolia wetland was chosen as the study objects, soil was sampled by soil layer monthly, their P and K concentration and correlative environmental factors were measured synchronously. Based on these data, with SPSS software and grey relating analyse means, this paper discussed the P and K concentration characteristics and their effect degree in the meadow albic bleached soil. The results were as following: The P and K concentration has obvious layered phenomenon in the soil profile, the correlations between P and K concentration and soil layer are remarkable, all their correlation coefficients are above 0.94. The P and K concentrations of every soil layer have an obvious seasonal dynamics in plant growth season. Their one-factor non-linear regression simulation models are suitable. The same environmental factor's affection degrees on the total P, total K, rapidly available P and rapidly available K of same layer or different layer are not same. Different environmental factor's affection degrees on same object are different also. Rainfall has the biggest affection degree in all environmental factors. The surface soil layer is more sensitive than bottom soil layer in the affection degree of environmental factors.