冀西北山地华北落叶松和白桦林下枯落物水文特征

目的]探讨冀西北山区不同人工林枯落物持水特性的差异,为该地区森林水文循环和森林开发管理提供基础依据。方法]以冀西北张家口市崇礼山区的华北落叶松、白桦人工林为研究对象,在林下设置标准样地,测定枯落物层厚度和蓄积量,通过室内浸泡法测定持水特征。结果]华北落叶松和白桦林下枯落物层厚度分别为4.2,3.4cm,枯落物蓄积量为10.90,4.92t/hm2;浸泡24h后华北落叶松枯落物(未分解层和半分解层)总持水量为4 228.5g/kg,白桦枯落物(未分解层和半分解层)总持水量为5 208.6g/kg,二者的有效拦蓄量分别为14.06,8.85t/hm2。在整个持水过程中,华北落叶松、白桦林下枯落物持水量、吸水速率与浸水时间的变化规律基本一致,均在前4h内持水作用较强,4~8h后逐渐变缓,10h后其持水量基本达到饱和;枯落物持水量与浸水时间存在对数曲线关系,而吸水速率与浸泡时间存在幂函数关系。结论]森林枯落物层发挥水文功能由持水能力和蓄积量共同决定,在森林经营管理过程中应充分考虑包括树种组成和搭配、林分密度等因子的影响。

Hydrological Effects of Larix Principis-rupprechtii and Betula Platyphylla Forest Litters in Northwest Mountain of Hebei Province

Objective] The differences in litter water-holding characteristics of different plantation types were investigated to provide scientific basis for understanding the forest hydrological cycles and its management in study area.Methods] Larix principis-rupprechtii and Betula platyphylla plantations in Chongli mountain of Zhangjiakou City were chosen in this study. We established standard plots under the two forest types. The depth and storage of the litter layer were measured and water-holding characteristics of litter were measured using immersion method.Results] The litter was as thick as 4.2 cm and 3.4 cm and the total litter volume was 10.90 t/hm²and 4.92 t/hm² in the L. principis-rupprechtii and B. platyphylla plantations, respectively. The maximum water holding capacity(measured after 24 h immersion) of litter layer in L. principis-rupprechtii and B. platyphylla were 4 228.5 g/kg and 5 208.6 g/kg, and the corresponding effective water holding capacity were 14.06 t/hm² and 8.85 t/hm², respectively. During the whole water holding process, the water holding capacity, absorption and the immersed time change with same trend, they were superior to the rest of time in the first 4 hours and the water holding capacity reached saturation after 10 h immersion. In addition, the relationship between litter water holding capacity and immersed time followed a logarithmic curve, and that between the water absorption rate and immersed time was fitted well with a power function.Conclusion] Hydrological function of forest litter is regulated by both litter storage and water-holding capacity. Some factors, such as species composition and stand density, should be considered in forest management.