利用强度对沙地植被恢复能力的影响

Effect of utilization intensities on restoration capacity of sandy vegetation

在腾格里沙漠南缘,以两种植被恢复状态良好的封育沙地为研究对象,进行不同利用强度试验,通过一个生长季的监测,研究了封育沙地群落物种多样性和生物量的变化,结果表明:(1)两种封育沙地灌木层各处理的优势种均为沙蒿(Artemisia arenaria DC.)或猪毛蒿(Artemisia scoparia Waldst.et Kit.),其重要值在0.47～0.75之间。植物群落的物种组成因不同的封育措施而异,在同一封育措施下利用强度对群落的物种组成无显著影响。(2)两种封育沙地灌木层的多样性指数和均匀度指数均表现为天然封育沙地>半刈割沙地>全刈割沙地,即随利用强度增加,两封育沙地灌木层群落多样性指数和均匀度指数均呈减少趋势,表明随利用强度的增加,使沙地植被所处的环境异质性增加,促使沙地植被向不同方向发展;但在不同的封育措施区利用强度对草本层多样性指数和均匀度指数的影响不同。(3)相同封育措施不同利用强度群落的相似性指数均很高,最大值可达到2,但不同封育措施各利用强度的相似指数均小于0.3。群落的相似性指数主要受封育措施影响,而利用强度对其影响不大。(4)两种封育沙地全刈割处理的地上生物量均显著小于半刈割处理和对照组,而对照组和半刈割处理之间无显著差异,表明随利用强度的增加,封育沙地群落地上生物量显著减少;而适度降低盖度,群落地上部分生物量变化不大。

The study area is located at the south edge of the Tengger Desert, where the annual average temperature is 8.2℃, the extremely maximum and minimum temperatures are 36.6℃ and - 27.3℃, respectively. The an- nual sunshine duration is about 2 725.7 hours; and the annual precipitation and evaporation are 184.8 mm and 3 038.5mm, respectively; the average wind speed is 3.5 m/s, while the highest 21.7 m/s; days with 〉 8 - scale＇s wind are 27.9 and days with sandstorm are 21.9 in a year; groundwater table is 80 m; soil types are mostly grey brown desert soil and sierozem. In this paper, cutting is a main utilization type which exerts on species in the management of fencing sandy land ecosystem, and it has important effect on the restoration process of sand ecosystem. In order to accurately reflect the variation in structure and function of ecosystem and the correlation of ecosys- tem situation with different utilization intensities under the condition of fragile oasis - desert ecotone, fencing sandy land is a style of vegetation restoration at the south edge of the Tengger Desert, where vegetation restoration growth is under favorable state. The experiment was conducted under different utilization intensities to estimate the change in biodiversity and biomass by once investigation after one-growing-season. The results showed as follows ： （ 1 ） the dominant species of different treatment was Artemisia arenaria DC. or Artemisia scoparia Waldst. et Kit. and their important values were in the range of 0.47 - 0.75 for two fencing land sands. The species composition of vegetation community was different with different fencing; the influence of different utilization intensities on species composi- tion of vegetation community was not significant for the same fencing methods. （2） Both the diversity index and the evenness index of shrub layer for the two fencing sandy land were expressed as following quantity order： natural fencing sandy land＇s indexes 〉 semi-cutting sandy land＇s ones 〉 cutting sandy land＇s ones, namely that both of the indexes were in a decreasing trend with the increasing in human utilization. It illustrated that the increasing of human utilization made the increasing in environment heterogeneity, thus leaded the sandy land vegetation to different directions. However, the impact of human utilization on the diversity index and evenness index of herb layer was shown the differences in different plots which had different fencing methods. （3） Similar indexes of the plots with the same fencing methods and different human utilization are high, the maximum reached 2; By contrast, similar indexes of the plots with the different fencing methods on each level of human utilization were smaller than 0.3. Therefore, the similar index of community was mainly affected by different fencing methods, and the human utilization has little effect on it. （4） The above-ground biomass of cutting treatment was significantly less than that of semi-cutting treatment and CK in two fencing sand lands, but CK had no significant difference with semi-cutting treatment, it showed that the above-ground biomass decreased significantly with increased utilization intensities in fencing sand land community; But the change in above-ground biomass was little when its coverage reduced favorably.