放牧对黑麦草+白三叶混播草地植被构成的作用

Effects of grazing on the vegetation composition of Lolium perenne and Trifolium repens mixed pasture

通过4个放牧强度(轻牧、适牧、重牧和过牧,牧后草层高度分别为7.5、5.5、3.5和<2.0cm)的轮牧试验,对黑麦草(Lolium perenne)、白三叶(Trifolium repens)混播草地土壤化学特性;黑麦草分蘖和白三叶匍匐茎、叶片数及其茎叶构成,牧草高度、生物量与植被构成进行系统研究。结果表明,土壤速效养分含量对放牧强度响应较大,稳定性较弱。随放牧强度的增加,黑麦草分蘖密度和叶片生物量显著增加,黑麦草分蘖质量和白三叶匍匐茎密度及牧草高度和生物量显著下降;黑麦草叶片数,白三叶叶片数、茎叶比和匍匐茎质量在放牧强度间无显著变化。放牧强度在降低黑麦草和白三叶生长特性整齐度的同时,增加其可塑性生长;黑麦草对放牧强度的响应比白三叶敏感,但白三叶的可塑性生长比黑麦草的高。鸭茅(Dactylis glomerata)和非播种植物种的生长特性在放牧强度内变异系数较大。综合分析认为,放牧对草地植被的作用体现于植物个体、种群和群落3个水平,播种的低组分禾草(鸭茅)和非播种禾草是混播草地植被构成变化的关键种。

In order to understand effects of grazing intensities on vegetation composition of Lolium perenne and Trifolium repens mixed pasture, the chemical characteristics of soil, L. perenne tillers, T. repens stolons, the number of leaves, the stem and leaf composition, the height and biomass of herbage under four grazing intensities （light, moderate, heavy and over grazing; with post-grazing height at 7.5 cm, 5.5 cm, 3.5 cm and〈2.0 cm, respectively） were studied at Weining, Guizhou. The results showed that the response of soil available nutrient contents to the grazing intensity was more sensitive, but their stability was lower. Tiller density and leaf biomass of L. perenne increased significantly with increasing grazing intensity, while tiller weight of L. perenne and stolon density of T. repens, height and biomass of herba- ges decreased significantly. Grazing intensities had no effects on the number of leaves of L. perenne and T. repens, the ratio of stem to leaf and stolon weight of T. repens. The homogeneity of growth character- istics of L. perenne and T. repens was reduced and their plasticity was enhanced by the grazing treat- ments. The response of L. perenne to grazing intensity was more sensitive than that did T. repens, whereas the plastieal growth of the former was lower than the latter. Dactylis g lomerata and native spe- cies had higher coefficients of variation under different grazing intensities. Thus, the effect of grazing ani- mals on grassland vegetation could be revealed from three levels： individual plants, populations and corn munities. The low component sown grass （D. glomerata） and native grass species were the key species during the change of vegetation composition of mixed pasture.