黄土丘陵区中龄至成熟油松人工林的水文效应动态

【目的】研究黄土丘陵区中龄至成熟油松人工林的水文效应动态，为当地森林的经营管理提供理论依据。【方法】通过对陕北黄龙山林区典型油松人工林的长期水文定位观测，以采伐上层乔木后自然恢复的灌草地（以下简称“采伐地”）为对照，研究油松林在中龄林-近熟林-成熟林过程中林冠层对降水的再分配、枯落物层对降水的截留率及其对产流与产沙量和土壤储水量等的影响。【结果】从中龄林到成熟林，油松林冠年截留率由17.0%增加到29.7%，其年平均截留率为采伐地灌草层的5倍左右；油松林树干年茎流率平均为2.8%，且与林龄、年降水量关系不明显；油松林枯落物层对降水的年截留率约为9.7%，随林龄变化保持稳定，且与采伐地差异不显著；油松林地多年平均径流深和产沙量分别为1.76 mm/年和1.11 t/(km²·年)，采伐地较油松林地分别高出10.4%和100%；油松林地0～300 cm土层年均土壤储水量为420.1 mm，较采伐地减少139.2 mm，且随林龄增加以1.8 mm/年的速率下降。【结论】油松人工林由中龄林到成熟林的发育过程中，冠层截留降水能力显著增加，年径流深、土壤储水量呈微弱下降趋势，而枯落物层截留率、林地产沙量等则无明显变化；油松林显示出强大的水土保持功能，采伐上层乔木保留地被物层不会导致严重的水土流失；通过合理间伐，可以减轻林地径流深和土壤储水量逐渐减少的不利影响，改善林地水文状况。

Trends of hydrological effects of Pinus tabulaeformis forest from middle age to mature in the Loess Hilly Region

【Objective】Study about the trends of hydrological effects of Pinus tabulaeformis forest in the Loess Hilly Region can support theoretical basis for local forest management.【Method】Based on long-term located observation on hydrological effects of typical planted P.tabulaeformis forest(taking restored shrub-grass vegetation after clear-cutting of forest as control,hereinafter referred as CK or clear-cutting land)in Huanglong of northern Shaanxi,changes of hydrological effects including precipitation redistribution by canopy,water retention by litter,surface runoff and sediment yield,and soil water storage in middle aged to mature planted P.tabulaeformis forest were researched.【Result】From middle aged to mature of P.tabulaeformis forest,the annual interception by canopy increases from 17.0% to 29.7%,and the mean interception rate of canopy of P.tabulaeformis is about 5 times of CK.The mean stem flow rate is 2.8%,and the relationship between age and annual precipitation is not obvious.Annual interception by litter is about 9.7%,which remains stable with forest age and has no significant difference from CK.The surface runoff and sediment yield in P.tabulaeformis forestland are 1.76 mm/a and 1.11 t/(km2·a) respectively and the increment of the runoff and sediment in CK is 10.4% and 100.0% respectively.The mean soil water storage(0-300 cm) in P.tabulaeformis forestland is 420.1 mm(139.2 mm less than the CK) and decreasing in rate of 1.8 mm/a with the age of forest.【Conclusion】In the process of planted P.tabulaeformis forest from middle age to mature,the capacity of canopy interception increases significantly,the surface runoff and water storage in soil are on slow decline,but changes of interception by litter,surface sediment yields are not obvious.The original P.tabulaeformis forest displays the strong soil and water conservation function,and cutting upper arbor trees in P.tabulaeformis forest would not lead to serious soil erosion and whereas rational thinning of forest trees could reduce the harmfulness of dry layer in soil and improve the hydrological environment of forestland.