放牧对峰丛洼地植物-土壤C、N、P化学计量特征的影响

以西南典型岩溶峰丛洼地平果石漠化区为研究区，选取受放牧干扰和未受放牧干扰植被样地，开展放牧干扰对植物-土壤C、N、P元素生态化学计量学特征影响的研究。结果显示，（1）6种受放牧干扰样地土壤（0～20 cm）的C、N、P含量均值分别为6.27 %、0.57 %、0.088 %；植物根、茎、叶和凋落物C、N、P含量均值分别为442.15 g·kg-1、8.33 g·kg-1、0.73 g·kg-1。放牧干扰下，植物和土壤C、N、P含量减少，变异系数增大，容易导致石漠化发生和恶化；（2）6种典型样地土壤C∶N、C∶P、N∶P均值分别为10.76、73.94、6.76；植物根、茎、叶和凋落物C∶N、C∶P、N∶P分别为53.62、669.50、12.53。与无放牧干扰样地相比较，受放牧干扰的样地植物和土壤C∶N、C∶P、N∶P化学计量比呈下降趋势，放牧干扰在一定范围内能提高土壤P的有效性，但当N∶P比值减少到一定程度时，植物的生长受N限制。（3）恢复样地的土壤-植被C、N、P及其比值都优于干扰样地，放牧干扰能在短时间内造成环境迅速退化和石漠化的发生和加剧。禁牧后土壤和植物养分能在短时间内得到修复和改善，尤其是草本饲料类植物经短时间自然恢复后得以恢复正常生长发育。（4）在岩溶峰丛洼地石漠化区，土壤和植物的C、N、P、C∶N、C∶P、N∶P关系密切，相互之间具有促进或抑制的作用，共同影响植物的生长发育和石漠化演变方向。 

Influence of grazing on characteristics of chemical metrology for C, N and P in plants and soil of peak-cluster depressions

The study area of this work is the Pinguo rock desertification region is a typical karst peak-cluster depression of southwestern China. Choosing vegetation sites with and without grazing, we examine the influence of grazing on the features of metrology of ecological chemistry for elements C, N, and P in plants and soil. Results show that (1) in six sites with grazing, average contents of C, N and P in the soil (0~20 cm) are 6.27%, 0.57%, and 0.088%, respectively; those in roots, stem, leaf and fallen materials are 442.15 g·kg-1, 8.33 g·kg-1and 0.73 g·kg-1, respectively. It means that due to grazing, contents of C, N and P in plants and soil decrease and variation coefficients become larger, leading to occurrence or deterioration of desertification. (2) The average values of C∶N, C∶P and N∶P at the six sites are 10.76, 73.94 and 6.76, respectively; those in roots, stem, leaf and fallen materials are 53.62, 669.50, and 12.53, respectively. Compared with the sites without grazing, these ratios of chemical metrology at grazed sites tend to decline. To some extent, grazing can enhance effectiveness of P in soil, but the growth of plants will be limited by N when N∶P reduces to a threshold. (3) C, N and P and their ratios in soil and plants at sites without grazing are all better than those at sites with grazing. It implies that in a short time grazing can cause rapid degeneration of the environment and occurrence or acceleration of rock desertification. After grazing is stopped, nutrient in soil and plants can recover in a short time, especially the plants of herbaceous feed can grow normally again. (4) In karst desertification regions of karst peak-cluster depressions, C, N, P, C∶N, C∶P and N∶P are closely related in samples of soil and plants. These variables can promote or suppress between each other, jointly affecting growth and development of plants and evolution trend of desertification in the study area.