关键词: 河狸, 啃伐对策, 食物堆, 河谷林

Abstract: Three species of willow——Salix turanica, S. caspica and S. triandraconstitute the principal foraging species for the beaver in Xinjiang. Investigations were designed to study the beaver's foraging strategy in fall in theBurgan River Reserve of Xinjiang. As predicted, beavers foraged fewer treesat increasing distance from the river's edge or the food cache and were moreselective to different size of trees. Beavers tended to cut farther in upperreaches than in lower reaches. Trees near the food cache were seldom cut.Trees in the 2.5-4.5cm category were preferred. As the distance from thecentral place increased, beavers tended to cut trees of 3.5-4.5cm in diame-ter. Large and small trees tended to be selected at any distances. It was notedthat the beaver usually cut in a spotty or "block cutting" way, producingdecided"foraging places". The cut density was correlated directly with thestand density. On the other hand, the rate of available trees cut was inverselycorrelated with the stand density. The oimum range for beaver's cutting was within 15m from the shore and between 40-120m from the food cache.When beavers cut away almost all the trees with no selectivity within reachof their activities, cut the largest trees heavily, or shift their winter burrowfrequently (1-2 years), it means that it is hard to carry the standing quan-tity of beavers for the habitat. Human activities were the primary factorswhich made the degeneration of the woods. Prohibitting from felling trees andgrazing is the key step in the beaver's conservation.

Key words: Beaver (Castor fiber L.), Foraging strategy, Food cache, Standing quantity, Conservation