| 其他摘要 | Karst landform distributes widely in the world and its area is ten percent of the total area of the earth. Total karst area of China accounts for thirteen percent of land area and are mainly distributed in the south.of China. Guizhou karst mountain area locates at center of southwest karst area where karst physiognomy concentrates, distributes widely and developes in diverse type in China even throughout the world. Compared with the non-karst area, karst mountain area has an obviously vulnerable characteristics such as thinner soil layer, uncontinuous soil distribution, higher exposed rock ratio, lower water retaining capacity, less suitable tree species, simpler community structure, slower plant growth rate and weak ecological environment, etc. due to its special physical and chemical charactics of carbonate rocks. The factors mentioned above and unreasonable human activities have led to serious degradation of vegetation in this area. Therefore, the studies of nutrient elements and isotopic compositions of carbon, nitrogen and sulphur of plants in Guizhou karst mountain area is helpful for our understanding of nutrient element status and physiological and ecological characteristics of vegetation and biogeochemical cycling of nutrient elements in this area. Meanwhile, it can provide decision-making references for treatment and recovery of vegetation and forest and protection of ecosystem. In comparison with non-karst area, this study selected a typical area in Guizhou province as study sites. The concentrations of nutrient elements and their inter-relationships in plants and the variations in composition of carbon, nitrogen and sulphur isotopes of plants among different species, habitats and time-space are studied. The main conclusions have been reached as follows:
1. The contents of N, P, K, Ca, Mg and S are greater than 1000 μg•g-1; those of Fe, Mn and Al vary between 100 and 1000 μg•g-1; those of Zn and Sr are within the range of 10～100 μg•g-1; those of Cu and Mo are lower than 10 μg•g-1. The content of Mo is the lowest (only 0.17 μg•g-1). The contents of Ca, P and K are higher than those of the terrestrial plants so far reported. While the content of Mg is lower than that of terrestrial plants and other elements are within the range. The element contents are characterized as being of “Ca>K>Mg” type. Compared with other areas of China, vegetation of karst mountain area has the character of higher Ca content.
2. The elements such as N, P, K and Mg are of normal distribution, while the elements Ca, Al, Fe, Mn, Cu, Zn, Sr and S are of lognormal distribution. The coefficients of variation (C.V.) are >100% for Al, Fe, Mn and Sr; <60% for N, P, K, Ca, Mg, S and Cu; and 11.8% (the lowest value) for Ca, respectively. Correlation analysis indicates that there are very significant correlations between P and K, P and Cu, Al and Fe, Al and Zn, Fe and Zn; while obvious correlations between N and P, P and Mg, K and Al, K and Cu, Ca and Sr, and S and Mo.
3. The contents of nutrient elements of the same plants in different habitats are within twice variations and show great differences. The contents of Mn, Al and Sr are 2.1, 1.5 and 1.4 times, respectively.
4. The values of δ13C, δ15N and δ34S in plants range from -26.98‰ to -29.15‰, -4.08‰ to -0.79‰ and -8.69‰ to -6.04‰, and their average values are -28.14‰, -2.41‰ and -7.53‰, respectively. The mean value of δ13C is lower than that of other areas except for tropical rain area in China, and the change extent is narrower than other areas; the values of δ15N and δ34S vary greatly in different areas.
5. The values of δ13C, δ15N and δ34S vary greatly among different species and the same species grow in different habitats. The value of δ13C tends to decrease from growth initial stages to growth telophase. While, δ15N and δ34S do not show clear trend with seasons and their changes with seasons are different among different species. δ13C and δ34S tends to increase with increasing altitude, while δ15N shows reverse trend. |
修改评论