放牧强度对羊草草甸草原植物器官及群落氮磷化学计量的影响

目的]以地上植物茎、叶以及群落为研究对象,探究不同放牧强度对植物器官以及群落碳、氮、磷含量及化学计量特征的影响,为深入解析放牧干扰下草地生态系统退化过程,促进草地放牧适应性管理提供科学依据.方法]基于呼伦贝尔羊草草甸草原长期控制放牧试验平台,在6种不同放牧强度(不放牧G0.00、较轻度放牧G0.23、轻度放牧G0....

Effects of Grazing Disturbance on the Stoichiometry of Nitrogen and Phosphorus in Plant Organs of Leymus chinensis Meadow Steppe

【Objective】Taking above-ground communities, stems and leaves as research objects, the effects of different grazing intensities on the contents of carbon (C), nitrogen (N) and phosphorus (P) elements and stoichiometric characteristics of plant components and plant communities were investigated, which provided a scientific basis for in-depth analysis of grassland ecosystem degradation process under grazing disturbance and promotion of adaptive management of grassland grazing. 【Method】Based on the long-term controlled grazing test platform of Leymus chinensis meadow grassland in Hulunbuir, the plant communities and plant samples of different components were collected. The contents of C, N and P were determined by elemental analysis method, and then the changes of C, N and P contents and the measurement ratio under different grazing intensities were analyzed. 【Result】With the increase of grazing intensity, the C content of plant stem, leaf and community showed a significant linear decrease, and the C content of heavy to extremely heavy grazing was significantly lower than that of no grazing (P<0.05). The N and P contents of the community were linearly increased, and the heavy to extremely grazing was significantly higher than that of no grazing (P<0.05). The stem-leaf ratio of C content was the lowest in moderate grazing (G0.46), while the stem-leaf ratio of N content was the highest in heavy grazing (G0.69), and the highest in P content (G0.34). The coefficients of variation of C content and N/P ratio in different plant organs were small, but the coefficients of variation of N and P contents were large. The variation coefficients of C content and N/P ratio of different components ranged from 4.01% to 5.74% and 2.84% to 8.54%, respectively. The variation coefficients of N and P contents of plants ranged from 11.47% to 14.96% and 11.13% to 22.88%, respectively, and the variation coefficients of C/N and C/P ratios ranged from 10.64% to 16.00% and 8.88% to 13.57%, respectively; among them, the coefficient of variation of the N/P ratio of plant leaves is the smallest, and the coefficient of variation of plant stem P content is the largest. The N/P ratio of leaves was between 14 and 16 under light grazing G0.34 and extremely heavy grazing G0.92, which was restricted by both N and P elements; while the other components were all lower than 14 under different grazing intensities, which was restricted by N. There was a significant negative correlation between grazing intensity and C content and C/N ratio of stem, leaf and community, and N/P ratio of stem and community, whilst they were significantly positively related to N content of stem, leaf and community, P content of plant leaf and community, and the N/P ratio of plant stem. The soil moisture was significantly positively correlated with the C content of plant leaves and community, the C/N ratio of stem, leaf and community, and the C/P ratio of stem and community, however, which were significantly negatively correlated the N content of stem, leaf and community and the P content of leaf and community. 【Conclusion】Grazing caused significant changes in plant C, N, P content, ecological stoichiometric ratio, and total community C, N, and P content. Overgrazing not only decreased the C content, C/N ratio and C/P ratio of plant stem, leaf and community, but also reduced the total C, N, and P content of the community, increased the N and P content of plant stem, leaf and community, and N/P ratio of plant stem, leaf and community. Moderate grazing decreased the C/N ratio of stem and leaf, and increased the C/P ratio and N/P ratio of stem and leaf, which was beneficial to promote the sustainable and stable development of grassland ecological functions.