宁夏荒漠草原植物群落特征对不同轮牧开始时间的响应

合理的轮牧开始时间对科学利用荒漠草原具有重要意义。以宁夏荒漠草原为对象,对不同轮牧开始时间下植物群落特征和可食牧草养分含量进行了研究。结果表明,1)经过两年放牧,轮牧开始时间对植物物种组成影响较小;轮牧开始早的草地植物密度高于晚轮牧草地,但盖度和地上生物量相反。2)随轮牧开始时间推后,短花针茅(Stipa breviflora)、牛枝子(Lespedeza potanini)、赖草(Leymus secalinus)、银灰旋花(Conrolulus ammannii)等主要植物的重要值升高,隐子草(Cleistogenes squarrosa)则呈相反趋势,老瓜头(Cynanchum komarovii)变化规律不明显;这几种植物的密度、盖度和地上生物量对轮牧开始时间响应不同。3)轮牧增加了植物物种多样性,晚开始轮牧草地植物物种优势度较早开始草地低,但均匀度和Shannon-Wiener多样性指数增加。4)随轮牧开始时间推后,草地采食率和牧草粗蛋白含量下降。研究认为,固定时间和顺序的轮牧方式会使草地植被异质性增加,应根据植被状况对轮牧时间作适当调整,年度间小区要以不同顺序进行轮牧。

Effect of different rotational grazing start time on plant community characteristics in desert steppe in Ningxia

The reasonable rotational grazing start time had important effects on scientific utilization of desert steppe.In the present paper,plant community characteristics and edible forage nutrients of desert steppe in Ningxia with different rotational grazing start times were studied.The results showed that rotational grazing start time had little influence on species composition of desert steppe after two years of grazing.The plant den-sity in grassland with early rotational grazing was higher than that in grassland with late start rotational graz-ing,however,the coverage and aboveground biomass had opposite performance.With the delay of rotational grazing start time,the important value of Stipa breviflora,Lespedeza potaninii,Leymus secalinus and Con-rolulus ammannii increased,whereas that of Cleistogenes squarrosa decreased,Cynanchum komarovii has no significant difference in different start rotational grazing times.The density,coverage and aboveground biomass of above species had different response to rotational grazing start time.Rotational grazing improved plant spe-cies diversity.The plant species dominance of late rotational grazing region was lower than that of early rota-tional grazing region,however,the uniformity and diversity had opposite performance.With the delay of rota-tional grazing start time,animal feed rate and forage crude protein content gradually decreased and crude fiber content increased.These results suggested that rotational grazing with fixed time and sequence will increase the heterogeneity of grassland vegetation so that the rotational grazing time and sequence should have appropriate adj ustments based on vegetation conditions.