中文摘要：

为了探讨不同保留密度的华北落叶松人工林枯落物水文作用,于2015年5月在宁夏六盘山选择了15个已间伐时间8年的中龄（31年）华北落叶松人工纯林样地,测量了各样地内枯落物的蓄积量、厚度,并用室内浸泡法对枯落物的持水量和吸水速率进行测定。研究表明：枯落物层的厚度、蓄积量、持水能力在不同林分密度中均存在较大差异。按林分密度由小到大排列（800、1 000、1 200、1 600、1 800株/hm2）,枯落物蓄积量分别为12.53、14.91、17.67、19.71、18.42 t/hm2,密度1 600株/hm2的林分枯落物厚度和蓄积量最大;枯落物最大持水率分别为176.78%,171.89%,182.52%,184.58%,169.60%,最大持水量分别为22.15、25.63、32.25、36.38、31.24 t/hm2,密度1 600株/hm2的林分枯落物最大持水率和最大持水量最高;各密度枯落物持水量与浸水时间均呈明显的对数函数关系（R2〉0.89）,吸水速率与浸水时间呈明显的幂函数关系（R2〉0.88）;各密度林分枯落物的有效拦蓄量在12.50～21.33 t/hm2之间,密度1 600株/hm2的枯落物拦蓄能力最强。结果表明：在本文研究的华北落叶松人工林生长情况和林龄条件下,林分密度为1 600株/hm2左右时枯落物水文功能最强,但不能低于1 200株/hm2,以避免枯落物水文功能的急剧降低。结合本地区华北落叶松中龄人工林的密度对其他生态服务功能影响的研究结果,建议林分合理密度为1 200～1 600株/hm2。

英文摘要：

To explore the impacts of stand density on the hydrological functions of litter layer,we chose fifteen thinned stands of 31-year-old Larix principis-rupprechtii forest in May of 2015,in Liupan Mountains of Ningxia,China. The thickness and storage of litter of these stands were surveyed,and the water-holding capacity and water absorption rate of litter were measured by soaking method. It showed that there was an obvious difference among stand densities for all the parameters describing the hydrological functions of litter,including the thickness,the storage and the water-holding capacity of litter. According to the stand density gradient of 800,1 000,1 200,1 600,and 1 800 trees / ha,the litter storage was 12. 53,14. 91,17. 67,19. 71,and 18. 42 t / ha,showing a maximum of litter thickness and storage in the stand with density of 1 600 trees / ha; the water-holding ratio of litter was 176. 78%,171. 89%,182. 52%,184. 58% and 169. 60%,and the corresponding water-holding capacity was 22. 15,25. 63,32. 25,36. 38 and 31. 24 t / ha respectively,showing the maximum water-holding ratio and water-holding capacity in the stand with density of 1 600 trees / ha. Water-holding capacity of litter had a logarithmic relationship with soaking time（ R2〉 0. 89）,and water absorption rate showed a power function with soaking time（ R2〉 0. 88）. The modified water-interception capacity was 12. 50- 21. 33 t / ha,showing a maximum of water-interception capacity in the stand with density of 1 600 trees / ha. The results showed that,under the given conditions of tree growth and tree age in this study,the hydrological functions of litter reached their maximums at the stand density of 1 600 trees / ha. Moreover,the stand density should not be lower than 1 200 trees / ha,in order to avoid a sharp reduction of the hydrological functions of litter. Taking into account the variation of other ecological services with stand density of middle-aged plantation of L.principis-rupprechtii in the same area,it is recommended to maintain the ratio