All the resultant activities have tended, on balance, to reduce tree cover and increase grassland.
总的来说，所有由此产生的活动都趋向于减少树木覆盖，增加草地。
2
When surface cover of natural grassland reaches 90%, the benefits for grass reducing surface runoff is above 90% and not any erosion occurs.
当草地地面覆盖达90%时，草被拦蓄径流效益达90%以上，而基本上无侵蚀发生。
3
The results are as follows:1)With increased time of free grazing, the ground cover of the grassland and the production ability gradually descend, the plant species gradually reduces.