不同放牧情景下黑河上游亚高山草甸人工降雨截留特征

Artificial rainfall interception characteristics in alpine meadows under diferent grazing scenarios in the upper reach of Heihe River

采用人工降雨实验方法研究了黑河上游天老池小流域对放牧以及禁牧情况下亚高山草甸草地的人工降雨截留过程,并用简易浸泡法测定了草地冠层最大持水能力.结果显示:放牧干扰显著改变了亚高山草甸草地地表植被冠层特征和物种组成,放牧草地与禁牧草地相比下冠层盖度、生物量和冠层株高分别减少了9%,55%,19.2 cm,草地截留特征受不同冠层结构的影响产生一定差异.在一个给定降雨强度下,草地冠层截留量先呈线性增加,穿透雨出现后呈现指数增长,其中禁牧草地出现穿透雨的人工降雨量为1.80 mm,放牧草地的为1.10 mm.草地截留量随降雨强度的增加呈现先增加后减少的变化,在0.7～0.8 mm/min降雨强度级别下截留量最大,草地截留率与降雨强度具有负幂函数关系.研究区草地冠层截留量较大,使用人工降雨法在降雨强度级别为0.7～0.8 mm/min下实测得到草地最大截留容量,禁牧草地的为6.50 mm,放牧草地的为5.17 mm.在降雨强度为<0.3 mm/min时(研究区主要降雨强度),实测禁牧草地饱和截留量为1.95 mm,放牧草地的为1.29 mm.使用简易浸泡法测得禁牧草地截留容量为0.92 mm,放牧草地的为0.65 mm.

The interception data from two categories of grazing scenario meadows (the grazing meadows and the grazing prohibition meadows) were collected under the artificial raining experiment with a different rainfall intensity and using a simple absorbent method to estimate the water storage capacity of these alpine meadows in Tianlaochi catchment in the upper reach of Heihe River. The results showed that disturbance of grazing had significantly changed the canopy characteristics and the species of subalpine meadow vegetation. Compared with the grazing-prohibition meadow, the canopy coverage, biomass and plant height of the grazing meadows decreased by 9%, 55% and 19.2 cm respectively. Influence by different canopy structures and characteristics, the interception characteristics of the different grazing scenario meadows showed certain differences. With a steadfast rainfall intensity, the interception processes of the alpine meadows were linearly increasing at first and, after the appearance of through fall (when the rainfall reached a value of 1.80 mm for the grazing prohibition and 1.10 mm for the grazing meadows), the interception presented an exponential increase. The relationship between the canopy interception ratio and interception rainfall in alpine meadows can be represented by a power function. The canopy interception of the alpine meadow in our study area could reach a high value. At the 0.7～0.8 mm/min rainfall intensity, the maximum rates of canopy interceptions (canopy storage capacity) for the grazing prohibition and grazing meadows were 6.50 mm and 5.17 mm. At the 0.3 mm/min rainfall intensity, which was similar to the realistic rainfall condition, the canopy interceptions for the grazing prohibition and grazing meadows were 1.95 mm and 1.29 mm. The canopy storage capacity measured by the simple storage absorbent method for the grazing prohibition and grazing meadows were 0.92 mm and 0.65 mm.