不同放牧率下羊草和芦苇可溶性碳水化合物和氮素含量的变化

在松嫩草原羊草草地上通过小区围栏放牧，对不同放牧率下羊草和芦苇可溶性碳水化合物和氮素含量的变化进行了分析。结果表明，羊草和芦苇在生长季初期茎基部的可溶性碳水化合物含量最低，分别为7．12％和3．95％，随着季节推移逐渐增加；叶片可溶性碳水化合物含量随季节推移的变化不大；羊草返青比芦苇早，从而造成5月份实验开始时两种禾草茎基部和叶片可溶性碳水化合物的差异；一定程度的放牧(本实验条件下为P4和P5小区)有利于牧草可溶性碳水化合物的提高，促进牧草再生氮素含量在生长季初期最大，随季节推移逐渐降低，与其物候期相一致；适当放牧能够刺激根对土壤中氮素的吸收，使其向地上部分转移，提高牧草的营养价值。

Variations of water-soluble carbohydrate and nitrogen contents in Leymus chinensis and Phragm ites comm unis under different stocking rate

The variations of the contents of water soluble carbohydrate and nitrogen in L. chinensis and Ph. communis under different stocking rates were studied by fencing grazing experiment on L. chinensis grassland. The results indicated that the water soluble carbohydrate content in the base stem of L. chinensis and Ph. communis was the lowest (7.12% and 3.95%, respectively) at the beginning of growth period, and then increased gradually with seasons. There was no significant variation in the content of leaf water soluble carbohydrate in the grasses. L.chinensis germinated earlier than Ph.communis , resulted in the difference between the water soluble carbohydrate content in the base stem and the leaf of the grasses at the beginning of the experiment in May. Proper stocking rates were favorable for the increase of water soluble carbohydrate content, and could accelerate the regrowth capability of the herbage. The nitrogen content was the highest at the beginning of growth period, and then decreased gradually with seasons, which was accorded with their phenology. Proper stocking rates could stimulate the assimilation of nitrogen in soil, and bring it to the ground, which improved the nutrition value of the herbage.