【作者】 侯扶江；

【导师】 任继周； 胡自治；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2000， 博士

【摘要】 在系统调查肃南鹿场土壤、草地和马鹿状况的基础上，重点探讨冬季牧场和春秋季牧场不同放牧压力下的土壤和植被动态，对于认识甘肃马鹿放牧系统的草地结构特征和马鹿在系统中的地位和功能、土-草-畜之间的关系，以及保护、恢复与重建放牧草地退化生态系统具有一定现实意义。 1 马鹿放牧对土壤的影响 冬季牧场和春秋季牧场土壤水分、土壤全氮和速效氮、有效磷含量、有机质、土壤总盐含量和0-20cm土层平均C/N比值随牧压下降而逐渐上升，土壤容重降低。马鹿冬季放牧在草地上践踏出的路径密度、深度和宽度以及在单位草地面积上的排粪数量、重量、每个类颗粒重量与牧压正相关，路径上残存的植物数量与牧压负相关；建立综合指数表征马鹿放牧对土壤的践踏强度，放牧较重的土壤对践踏作用的响应较不敏感。冬季牧场土壤日平均呼吸强度和土壤调温能力随放牧增强而减弱；春秋季牧场清晨土壤呼吸强度随牧压下降而降低，与群落盖度的关系较为密切。放牧较重导致根系与土壤要素的空间配置失调，与毒杂草的生长关系密切，有利于退化群落的发展。表层土壤的理化性质对放牧响应敏感，有效磷含量对放牧的敏感性高于其它要素。两个季节牧场的土壤各单项质量指数和综合指数以及土壤资源适宜度随放牧减弱呈上升趋势，速效磷和有机质的单质量指数较小；土壤资源适宜度结合草地植被分析，肃南鹿场马鹿放牧草地健康的土壤适宜度、牧草现存量和可食牧草比例分别为0.59、190.58g/m~2和99.03％。土壤聚类分析能够较好地揭示土壤放牧演替阶段。 放牧较重减少土壤水分和矿质营养，对上层土壤的作用较为显著，致使土壤要素与根系的垂直分布格局失调，可能是植被因重牧而退化的主要原因。 2 马鹿放牧对植被的影响 随牧压下降，短花针茅和赖草叶片的光合速率减小，醉马草则相反；这三种植物叶片的量子效率、叶片和生殖枝温度、暗呼吸以及短花针茅和赖草叶片的蒸腾作用减少，叶片的Chla/b比值和类胡萝卜素含量、水分利用效率、短花针茅和赖草叶片与生殖校调节温度的能力上升；醉马草营养和生殖器官的非可溶性碳水化合物和总碳水化合物含量、短花针茅和醉马草地上部分含氮量（单位重量干物质）和C/N比值、群落地上部分氮含量（单位干物质）增加，醉马草营养器官中的可溶性碳水化合物减少。 冬季牧场种群平均株高及一些植物种群的高度随放牧减弱而增加。可食牧草短花针茅和冷蒿种群分盖度与放牧强度负相关，不食草醉马草和银灰旋花的种群分盖度则正相关。可食禾草种群的个体体积随牧压下降呈上升趋势，醉马草则相反。放牧较重促进短花针茅和醉马草在水平方向的生长，反之则有利于垂直方向的生长，两种植物在垂直方向的物质分配对干物质积累响应敏感，短花针茅比醉马草敏感。禾草种群的分桑数目与牧压正相关，短花针茅和醉马草单株分蔡重负相关。短花针茅种群占据空间的能力随放牧减弱而增强，个体分布不均匀性随尺度的变幅增大。 冬季放牧较重延迟牧草返青和群落密度到达峰值的时间，增加双于叶类植物密度。两个牧场的群落密度在牧压梯度上的分布格局相反，春秋季牧场更新较好，冬季牧场小个体物种居多。放牧较轻有利于草地凋落物和立枯物的积累，群落分层明显。春秋季牧场根系干鲜重随放牧减弱而增加。放牧增强引起发发草群落边界复杂化，降低持久性。刘割干扰对冬季放牧较重的群落影响较小。三个牧场群落口多样性基本随放牧减弱呈增加趋势，放牧较重促进群落之间物种更替，群落功能和组成多样性与草地状况关系密切。更多还原

【Abstract】 Gansu Wapiti (Cervus ealphus kansuenswas) plays an important role in the alpine grassland ecosystem in Qilianshan Mountain. On the base of comprehensively studying the soil, vegetation and wapiti of the Sunan Deer Farm, the dynamics of soil and vegetation with the different grazing pressure in the overgrazed winter pasture (WP) and the relatively light-grazed spring- autumn pasture (SAP) of Gansu wapiti was paid more attention. It could be useful to find out the structural characteristics of grassland, the role of wapiti in the grazing system, the relationship between soil-vegetation-animal and to restore and reconstruct the degenerated grassland ecosystem. 1 Effects of Wapiti Grazing on Soil The increased grazing pressure reduced the content of water, total N, available N, available P, organic matter, total salt and mean ratio of C/N in soil of both WP and SAP, but increased the soil bulk density. There were a positive relationship between the density, depth, width of the trampled path, the number, dry weight of the feces and the grazing intensity and a negative relationship between the number of the left plant in path and the grazing intensity in WP. The soil with the relatively heavy grazing was less susceptive to trampling than that with relatively light one in terms of the relationship between the comprehensive index of trampling and the distance of site from the door of WP. The daily mean respiration and the capacity of regulating temperature of soil reduced while the grazing intensity rose in WP, but soil respiration in early morning increased in SAP which closely related to the coverage of community. The heavy grazing resulted in the discordance of spatial pattern between soil characters and root which was advantageous to the growth of the poisonous plants such as horse-drunken grass (Achnatherum inebrians) and the development of the degenerated community with horse-drunken grass as the dominant species. The topsoil and available P was more susceptive to grazing than subsoil and the other characteristics of soil respectively. iii The quality indices of both single factor and comprehensive factors rose as well as the suitability of soil resources (SSR) while the grazing intensity reduced. Basing on relationship between SSR and vegetation, the reasonable SSR, standing crop of herbage and ratio of palatable herbage were suggested to be 0.59, 190.58g/m2 and 99.03% respectively, in order to keep a healthful grazing ecosystem in Sunan Deer Farm. The clustering analysis could well showed the succession stages of soil in the wapiti grazing grassland. The reduced content of water and mineral elements, especially in topsoil, and the discordance of vertical distribution between the soil characteristics and root could play an important role in the degeneration of grassland as a result of overgrazing. 2 Effects of Wapiti Grazing on Vegetation Due to the decrease of grazing intensity of Gansu wapiti in winter, the photosynthetic active radiation, air temperature and vapor pressure difference in canopy of community declined, but the relative humidity in the middle and top of canopy rose; net photosynthetic rate (Pn) became low in shortflower needlegrass (Stipa brevalora) and common aneurolepidium (Leymus secalinus), but high in horse-drunken grass; the apparent quanta efficiency, the temperature of leaf and reproductive branch and更多还原