塔里木河上游不同森林类型枯落物的持水特性

Water-holding Characteristics of Litter Under Different Forest Types in the Upper Reaches of Tarim River

对塔里木河上游4种森林类型(灰胡杨杜梨混交林、灰胡杨林、胡杨林、柽柳灌木林)林下枯落物蓄积量调查分析和持水特性进行研究。结果表明:(1)不同森林类型林下枯落物半分解层蓄积量、最大持水量、最大拦蓄量、有效拦蓄量与有效拦蓄深均大于未分解层。(2)枯落物总蓄积量、最大持水量、最大拦蓄量、有效拦蓄量与有效拦蓄深大小顺序为灰胡杨林>柽柳林>胡杨林>混交林,灰胡杨林各指标分别为5.45t/hm2,7.83t/hm2,10.63t/hm2,8.73t/hm2,0.87mm,其持水蓄水能力最强。(3)不同森林类型林下枯落物持水量、吸水速率与浸水时间的动态变化规律基本相似。枯落物持水量随浸泡时间延长而增长,在水中浸泡16h时,其持水量基本达到最大值;未分解层和半分解层吸水速率在0.5h最快,随时间延长吸水速率逐渐减缓,10h后明显减缓,未分解层和半分解层吸水速率基本趋向一致。在枯落物持水作用较强的前2h内,吸水速率最快的为柽柳林,其次为灰胡杨林。(4)未分解层和半分解层持水率同浸泡时间呈显著对数关系(Y=aln t+b),吸水速率与浸泡时间呈显著幂函数关系(V=ktn)。综上所述,塔里木荒漠区灰胡杨林表现出较好的水土保持与涵养水源能力,建议在今后森林经营中选择灰胡杨为造林树种,并采取适当的森林健康调节措施,以充分发挥森林的水源涵养功能。

Water-holding characteristic of litter could be obtained after survey and analysis, and studied the process of water-holding capacity of litter in the 4 typical forests （mixed wood, Populus pruinosa forest, Populus euphratica forest and shrub forest） in the upper reaches of Tarim river. The result showed as the following. （1）The litter amount, maximum water-holding capacity, maximum retaining amount, effective retaining amount and effective retain depth of half-decomposed litter were higher than that of non-decomposed litter. （2）The total litter storages, maximum water-holding capacity, maximum retaining amount, effective retaining amount and effective retain depth in the 4 different forests were Populus pruinosa forest 〉shrub forest 〉Populus euphratica forest 〉mixed wood, the order of each index of litter in Populus pruinosa forest was 5.45 t/hm2 , 7.83 t/hm2 , 10.63 t/hm2 , 8.73 t/hm2 , 0.87 mm which showed Populus pruinosa forest had the largest ability of water-holding capacity. （3）The dynamic changes in water-holding capacity, water-absorbent rate and time of forest litters under different forest types were basically similar. The water holding capacity of litter increased with extension of water immersion and being immersed in water for 16 h, the forest litter usually reached its maximum water-holding capacity and the water holding capacity had no longer significant changes with further increase in soaking time. In the initial 2 h, the water-absorbent rate of non-decomposed and half-decomposed litter was fastest, in 2 - 8 h after immersion, the rate rapidly decreased, 10 h later, the rate of decline slowed down significantly, and the water-absorbent rates of the two kinds of litters converged. In the initial 2 h of water retention capacity of litter, shrub forest had the largest water absorption rate, mixed forest had the lowest water absorption rate. （4） The relationships between water-holding rate and immersion time of whether half-decomposed or non-decomposed litter in 4 different forest types were significantly fitted by Logarithmic equation（Y=aln t＋b）. The relationships between water absorption speed rate and soaking time were described by power function （V = ktn ）. In short, the Populus pruinosa forest showed the best water and soil conservation ability than the other forests in Tarim desert area. Consequently, Populus pruinosa should be planted as first-class tree species in future forest optimization management in order to perform better in water conservation.