Study on water metabolism and balance during the period of tree's hibernation

The water metabolism and balance during the period of trees' hibernation were studied. The results show that at the beginning of the period of trees' hibernation , the water content of experimental trees is between 39.36% and 49.86% (Nov.30) ；to Mar.10 of the next year, it drops to 34.05%～41.03%; then it rises up till the middle of March. During this period, the optimum water content is about 35%～50%. But trees are easily hurt by cold condition while water content is beyond 55%，yet trees are very difficult to reproduce while water content is under 25%, and even they would die when water content is under 20%. Within 100 days (from Nov.30 to Mar. 10) of trees' hibernation, the average value of trees' water metabolism changes from -53.1kg to -88.3kg. Trees can utilize 139.5～211.4kg water, and consume 192.6～299.7kg water to sustain trees' water metabolis m negative balance.