青海高寒区不同密度白桦林枯落物水文效应

目的定量研究青海高寒区不同密度白桦林枯落物的水文效应，为该区白桦林的营造、配置及水文功能管理等提供理论依据。方法于2016年7—8月对青海省大通县宝库林区进行了调查。每种密度白桦林选择3块样地，林龄均为22~24年, 测定了5种密度(225、500、688、900、1 220株/hm2)白桦林的枯落物厚度、蓄积量、最大持水率等指标，并用浸泡法来研究枯落物持水量与浸水时间的关系、吸水速率与浸水时间的关系。结果5种林分密度的枯落物厚度、蓄积量、持水能力有明显差异:(1)5种密度林分(按225、500、688、900、1 220株/hm2排序)枯落物厚度分别为4.51、4.64、5.30、6.10、5.35 cm，枯落物蓄积量分别为11.22、13.54、15.33、17.86、15.86 t/hm2，最大持水率分别为227.91%、214.40%、215.44%、236.81%、221.70%。(2)枯落物最大持水量、有效拦蓄量排序均为900株/hm2>1 220株/hm2>688株/hm2>500株/hm2>225株/hm2。(3)枯落物持水量和浸泡时间的关系与对数函数拟合较好，回归系数R2达0.90以上，吸水速率和浸泡时间的关系与幂函数拟合较好，回归系数R2达0.99以上。结论林分密度在900株/hm2时，枯落物蓄积量、最大持水量、有效拦蓄量均达到最大，枯落物水源涵养作用达到最优。所以从枯落物的水文效应角度来考虑，密度为900株/hm2时，枯落物的水文效应最佳。 

Hydrological effects of litter of Betula platyphylla forest with different densities in alpine region,Qinghai of northwestern China

Objective] In order to quantitatively study the hydrological effects of different densities of Betula platyphylla in Qinghai alpine region and to provide theoretical basis for the afforestation, allocation and management of the hydrological effects of local Betula platyphylla forest. Method ] The investigation was carried out in July and August of 2016 in Baoku Forest Area of Datong County, Qinghai Province of northwestern China. Three Betula platyphylla plots were selected for each density, and the stand age was 22 - 24 years. The litter thickness, storage, maximum water-holding rate and other indexes of five different densities of Betula platyphylla forest were measured. The relationship between the water-holding capacity of litter and soaking time, the relationship between water absorption rate and soaking time were studied by soaking method. Result] There were significant differences in the litter thickness, storage and water-holding capacity among the five kinds of stand density. (1) As to the 5 density stand ordered as 225, 500, 688, 900, 1220 tree / ha, the litter thickness was 4. 51, 4. 64, 5. 30, 6. 10 and 5. 35 cm, respectively; the litter storage was 11. 22, 13. 54, 15. 33, 17. 86 and 15. 86 t/ ha. The maximum water-holding rate of litter was 227. 91％ , 214. 40％ , 215. 44％ , 236. 81％ and 221. 70％ , respectively. (2) The maximum water-holding capacity and the effective water-interception capacity of litter were both in the order of 900 tree / ha > 1220 tree / ha > 688 tree / ha > 500 tree / ha > 225 tree / ha, respectively. (3) The relationship between the water-holding capacity and soaking time of litter was fitted well with the logarithmic function and the regression coefficient R2 was over 0. 90. The relationship between water absorption rate and soaking time had the power function and the regression coefficient R2 was over 0. 99. Conclusion] The litter storage, maximum water-holding capacity and effective water-interception capacity reached the maximum at the stand density of 900 tree / ha. The effects of water conservation on litter were optimal in the stand with density of 900 tree / ha. Therefore, from the perspective of the hydrological effect of litter, the density was 900 tree / ha, and the hydrological effect of litter is the best.