黄土丘陵区沟坡典型植物群落枯落物蓄积量及其持水性能

Litter and its water-holding properties of typical plant communities distributed on gully steep slopes in the loess hilly-gully region

为探讨黄土丘陵区植被恢复后沟坡植物群落枯落物蓄积状况及其水文功能,以纸坊沟小流域沟坡7个典型植物群落为调查对象,采用野外调查、全收获法和室内浸泡的方法,对其枯落物蓄积量、盖度、持水性能进行系统研究。结果表明:枯落物盖度表现为草本群落均值(43. 1%)>灌木群落(39. 8%),且赖草群落显著大于其他植物群落(P <0. 05);枯落物蓄积量表现为灌木群落(486. 94 g/m^2)显著大于草本群落(230. 87 g/m^2)(P <0. 05);枯落物有效拦蓄量灌木群落均值(567. 40 g/m^2)显著大于草本群落(323. 90 g/m^2),柠条群落最大(685. 26 g/m^2),白羊草群落最小(149. 11 g/m^2)。通过对植物群落枯落物持水量与浸泡时间进行分析拟合,得到该时段二者之间的函数关系式U=alnt+b.

[Background] Gully steep slopes is the geomorphic position where soil erosion is the most serious in the Loess Plateau,in which soil and water conservation has always been paid more attention to.The litter layer presents many functions effectively,such as capturing precipitation,regulating surface runoff,and preserving soil and water from erosion. However,compared with hilly slopes,relative few studies have been conducted to quantify the accumulative amount and water-holding capacity of plant litters on gully steep slopes. Moreover,the comparative study of litter on hilly slopes and gully slopes is less. [Methods]To clarify the eco-hydrological functions of plant litters located on gully steep slopes of the loess hilly-gully region,seven typical vegetation communities were selected in Zhifanggou small watershed in Ansai district,Shaanxi province. The accumulative amount of litter was determined by harvesting method. Water-holding capacity and absorption rate was measured by the immersion method.Litter coverage was estimated by sighting estimation. [Results]1) The mean litter accumulation of shrub communities( 486. 94 g/m2) was significantly greater than that of herb communities( 230. 87 g/m2)( P <0. 05). 2) The mean litter coverage of herb communities( 43. 1%) was higher than that of shrub communities( 39. 8%). The litter coverage of Leymus secalinus( Georgi) Tzvel. community was obviously greater than other communities( P < 0. 05). 3) The mean litter effective interception capacity of shrub communities( 567. 4 g/m2) was notably greater than that of herb communities( 323. 9 g/m2)and the largest was in Caragana korshinskii Kom. community( 685. 26 g/m2),while the smallest was in Bothriochloa ischaemum( L.) Keng( 149. 11 g/m2). 4) By analyzing and fitting the water-holding capacity and soaking time of different communities,the relationship between water-holding capacity and soaking time was obtained as: U = alnt + b. [Conclusions] The shrub litter is more effective than herbaceous litter in reducing runoff and conserving soil and water on the gully slopes. The accumulative amount,coverage and effective water-holding capacity of the typical vegetation litters on gully steep slopes were lower than those of hilly slope in the same small watershed. C. Korshinskii Kom. and Hippophae rhamnoides are the better choice for sunny slope to control erosion,L. secalinus( Georgi) Tzvel. is the preferable plant for shadow slope. The results are conducive to assessing the hydrological benefits of litter layer and allocation of soil conservation measures on gully steep slopes in the hilly-gully region.