海拔和坡向对高寒灌丛草甸凋落物水源涵养功能的影响

以康定县折多山高寒山地灌丛草甸凋落物为研究对象,采用室外调查及室内测定结合的方法分析了凋落物蓄积量、持水及失水过程,以期探讨不同海拔和坡向凋落物水源涵养功能的差异。结果表明：（1）研究区凋落物的蓄积量在4.02~4.77 t/hm²波动,均表现出随着海拔的升高而逐渐降低,且半阴坡>半阳坡,海拔对凋落物蓄积量呈极显著影响（P<0.01）;（2）研究区凋落物最大持水量与蓄积量表现出一致的规律,有效拦蓄量最大为3 800 m半阳坡（5.95 t/hm²）,最小为3 800 m半阴坡（2.53 t/hm²）;（3）枯落物持水量与浸水时间关系式为：W_t=aln （t）+b;枯落物吸水速率与浸水时间关系式为：V=ktⁿ;失水量与失水时间呈显著对数关系（R²>0.95,P<0.01）,失水速率与失水时间呈显著幂函数关系（R²>0.99,P<0.01）。可见,该地区灌丛草甸凋落物的水源涵养功能在不同海拔和坡向间有明显分异特征,控制放牧减轻草甸退化和增加该生态系统的物种多样性能有效提高该区凋落物水源涵养功能。

Effects of Altitude and Slope Direction on Water Conservation Function of Litter in Alpine Shrub Meadow

The alpine shrub meadow ecosystem in western Sichuan is of great significance to the water ecological security of the Yangtze River Basin, and its litter layer is one of the important components of the water conservation function in this ecosystem. The alpine shrub meadow litter in Zheduo mountain was chosen as study objective, the field investigation and laboratory analysis were used to study the litter accumulation, water holding and water loss process, in order to explore the difference of water conservation function of litter among different elevations and slope aspects. The results showed that: (1) The litter accumulation in the study area fluctuated between 4.02~4.77 t/hm², all of which showed a gradual decrease with the increase of altitude, and the rule of semi-shadow slope>semi-sun slope. The elevation had the extremely significant impact on litter accumulation (P<0.01); (2) The maximum water holding capacity and volume of litter in the study area showed the same law, the maximum effective storage capacity occurred in semi-sunny slope at 3 800 m (5.95 t/hm²), and the minimum occurred in semi-shady slope at 3 800 m (2.53 t/hm²); (3) The relationship between litter water holding capacity and immersion time was W_t=aln(t)+b; whereas the relationship between litter water absorption rate and immersion time was V=ktⁿ. Water loss amount and water loss time showed a significant logarithmic relationship (R²>0.95, P<0.01), whereas water loss rate and water loss time showed a significant power function relationship (R²>0.99, P<0.01). It could be seen that the water conservation function of shrub-meadow litter in this area had distinct characteristics under different altitudes and slope directions. Controlling grazing to reduce the meadow degradation and increasing the species diversity of this ecosystem could effectively improve the water conservation of litter in this area.