Effects of varying amounts of oil spillage on grassland community of abandoned cropland in loess hilly region

Chinese. 为定量反映落地原油对草地植物群落的影响,选择黄土丘陵区撂荒草地进行野外石油污染模拟试验。试验共设5个处理水平,4个重复,周期为11个月。结果表明：随着浇油量的增加,石油对群落的影响逐渐增大,表现为群落的返青时间推迟,返青系数下降,返青系数与浇油厚度呈极显著负相关;浇油厚度为4.3和5.8 mm时,群落盖度降低、植株数减少且在整个生长季增加缓慢,群落物种丰富度指数和Shannon-wiener多样性指数显著低于对照组;不同种群对石油污染的响应不同,达乌里胡枝子（Lespedeza daurica （Laxm.） Schindl.）和阿尔泰狗哇花（Heteropappus altaicus （Willd.） Novopokr.）8月生长系数有相似趋势,都在1.4 mm浇油厚度时达到最大值0.697和0.612,随着浇油厚度的继续增加,二者的生长系数迅速下降;冰草（Agropyron cristatum （L.） Gaertn.）8月生长系数与浇油厚度呈显著负相关。

English. Loess Hilly Region is one of the areas where ecological environment is frail and it is also an important energy base of China and massive oil exploitation activities have been carried out in that area causing impacts on the environment. In order to illustrate the effect of oil spillage on grasslands vegetation, an ll-month field experiment of oil pollution simulation was conducted in an abandoned cropland in Loess Hilly Region of northern Shaanxi Province. The crude oil was applied at 0.0, 0.7, 1.4, 4.3, and 5.8 mm of thickness and each treatment level was replicated four times. The results show that the impacts of oil spillage on plant community increased gradually with the increased quantity of crud oil applied. The germination time of plant species in community was delayed and the germination indices of oil polluted communities decreased. There was a significant negative correlation between the germination indices and thicknes- ses of oil spillage; at 4.3 and 5.8 mm, the community coverage and plant number showed reduction and the species richness and Shannon-wiener index were significantly lower than that of the control. The response of different population to oil spillage was different, the growth indices of Lespedeza daurica （Laxm.） Schindl. and Heteropappus altaicus （Willd.） Novopokr. in August changed in similar trends and reached to the maximal values of 0. 697 and 0. 612 at 1.4 mm treatment, respectively, but decreased rapidly under ted in August plied. the treatments with between the growth higher amount of oil application. A significant negative correlation exisindices of Agropyron cristaturn （L.） Gaertn. and the amount of oil applied.