不同放牧强度下绵羊采食方式的变化特征

本研究将绵羊对禾本科植物的采食方式主要分为摘叶、拔芯和去顶3种类型.研究发现采食方式受植物种类、季节和放牧压的影响.对羊草(Leymus chinensis)的采食方式以去顶和摘叶为主, 对芦苇(Phragmites communis)的采食方式以去顶和拔芯为主.具体表现为,羊草的去顶率,8月以前随放牧强度减小、季节推移而降低,8月后则相反;摘叶率随放牧压增加和时间推移大致是先增加后减少;拔芯率随放牧压的增加而增大,6月最高,9月最低;总体上,未被采食的羊草比例随放牧压降低而增大,在生长季后期相应增加.芦苇去顶率随时间推移先降低后增加;拔芯率在6月随放牧压减小而降低,其它月份里主要随放牧压减小而升高,从整个生长季看,芦苇拔芯率在6月初最大;芦苇摘叶率的变化受前2种采食方式制约;未被采食的芦苇比例随放牧压降低而增加,但在7月后中牧要比轻牧和重牧低,在放牧干扰下,生长季里未被采食的芦苇比例在8月达最大.

Ingestion behaviour changes of sheep under different grazing intensities

Ingestion behaviour of sheep grazing Leymus chinensis and Phragmites communis under different (grazing) intensities was the focus of this study. Ingestion behavior was divided into three types,namely top-(removal),stem-pulling,and defoliation. The experimental results indicated that ingestion behaviour was (influenced) by grass species,season,and (grazing) intensity. The main ingestion behaviour towards L. chinensis was top-removal and defoliation,and towards P. communis ,top-removal and stem-pulling. Before August, L. chinensis top-removal rate decreased with increasing grazing intensity and season change,but showed opposite trends after August. The defoliation rate chiefly increased and then decreased with increasing grazing intensity and over the season change. The stem-pulling rate increased with increase in grazing intensity,and was highest in June and lowest in September. Generally,the proportion of untouched L. chinensis increased with reduction in grazing intensity and during the later stage of the growth season. For P. communis, the top-removal rate decreased and then increased as time progressed. In June,the stem-pulling rate decreased with reduction of (grazing) intensity,but in other months chiefly showed the opposite trend. Looking at the complete growing season,the stem-pulling rate was at maximum at the beginning of June. The defoliation rate was negatively correlated with the other two ingestion behaviour types aforementioned. Before July,the proportion of P. communis untouched increased with reduction in grazing intensity,but after July,it was lower under moderate grazing intensity than under light or heavy grazing intensities. During the growing season,under grazing disturbance,the proportion of P. communis untouched reached the maximum in August.