温性典型草原羊草光合特性对模拟放牧因素分解的响应

Responses of photosynthetic characteristics of Leymus chinensis in temperate typical steppe to component factors of simulated grazing

放牧是一种复合胁迫,包括采食、践踏、粪尿返还等因素。为明晰放牧对草原影响的过程与机制,通过刈割、人工模拟踩踏、人工粪尿添加来模拟家畜放牧过程,以羊草为例,研究了株高、盖度、干重以及羊草叶片的光合特性对放牧分解因子的响应。结果表明,采食及包含采食因子的处理显著降低了羊草的盖度、高度及干重,但提升了羊草叶片的净光合速率(P_(n))、蒸腾速率(T_(r))、气孔导度(G_(s))、胞间CO_(2)浓度(C_(i)),降低了羊草叶片的水分利用效率(WUE)。羊草株高与羊草叶片净光合速率、气孔导度、胞间CO_(2)浓度、蒸腾速率显著负相关,与水分利用效率显著正相关;土壤含水量与气孔导度、胞间CO_(2)浓度、蒸腾速率显著正相关。相对而言,践踏和粪便以及它们的交互作用对羊草的影响比采食弱。综合可得,家畜的采食是放牧对温性典型草原羊草光合特性影响的主要因子。

Grazing is a compound stress,including factors such as feeding,trampling,and dung and urine return.In order to clarify the separate impacts on grassland of the components of grazing,this study simulated the process of livestock grazing by mowing,artificial simulated trampling,and artificial manure addition.Using Leymus chinensis as a model plant,the responses of plant height,vegetation cover,dry weight and photosynthetic characteristics of L.chinensis leaves to components of the grazing process were studied.It was found that feeding and treatments containing feeding factors significantly reduced the cover,height and dry weight of L.chinensis,but increased the net photosynthetic rate,transpiration rate,stomatal conductance,and intercellular CO_(2) concentration,but reduced the water use efficiency of L.chinensis leaves.L.chinensis plant height was significantly negatively correlated with net photosynthetic rate,stomatal conductance,intercellular CO_(2) concentration,and transpiration rate,and significantly positively correlated with water use efficiency.Soil water content,stomatal conductance,intercellular CO_(2) concentration and transpiration rate were significantly positively correlated.Relatively speaking,trampling and feces and their interaction have a weaker effect on L.chinensis than herbage consumption.Overall,defoliation through livestock feeding is the main factor affecting the photosynthetic characteristics of L.chinensis in temperate typical steppe.