漫溢干扰过程中微地形对幼苗定居的影响

Effects of the microhabitats on the seedling emergence during the flooding disturbance

通过对比漫溢干扰后边坡、坡中和坡底幼苗的物种组成、密度、幼苗周边的环境条件及土壤种子库的差异来分析漫溢干扰过程中,微地形对幼苗定居的影响。结果表明:(1)微地形对幼苗物种组成和生物多样性指数的影响很大。漫溢干扰后,位于边坡、坡中和坡底幼苗的Simpson多样性指数和Mcintosh均匀度指数在0.01的水平上差异极显著,Margalef丰富度指数在0.05的水平上差异显著。(2)微地形对土壤盐分含量影响很大。方差分析的结果表明,除HCO-3和K+外,边坡、坡中和坡底的pH值、CO23-、SO24-、Ca2+和Mg2+各指标在0.01的水平上差异极显著;全盐、总盐、Cl-和Na+各指标均在0.05的水平上差异显著。(3)微地形通过改变幼苗定居的环境条件,进而影响幼苗库的物种组成、密度和生物多样性指数。微地形中,幼苗库的各种生态指标均小于对应的土壤种子库的生态指标,从坡底到坡中到边坡,除单位面积上的植被密度外,土壤种子库和幼苗库的各项生态指标的变化趋势均不同。

The Tarim River is the longest continental river in China and charactered by its fragile ecosystem in the word. The ecological processes of the Tarim River basin have undergone great changes due to the irrational human activities over the past 50 years, especially in the lower reaches of Tarim River. Therefore, the ecological water conveyance project （EWCP） has been implemented since 2000. The EWCP is an emergency plan for conserving the natural vegetation, controlling the desertification and improving the environment in the lower reaches of Tarim River. It transfers water from the Bosten Lake, to Daxihaizi Reservoir, and finally to Taitema Lake along the water channel. There have been 12 times of watering to the lower Tarim River during the period from 2000 to 2011. After the EWCP, the natural vegetation has obvious response to the water condition change. The studies on the soil seed bank in the region are very important to restoring the degraded ecosystem in lower reaches. Soil seed bank is the potential plant population or plant community. It plays an important role in occurrence, succession, and recovery process of vegetation. The germinated species and germinated seed number in soil seed bankdetermine the species composition and species number of seedlings in a certain degree. Meanwhile, the topography condition in the study areas is also an important factor on influencing germination ability of soil seed bank. Micro- topography impacts the seedling species composition and distribution pattern through the spatial differences in germination ability of soil seed bank, light, water and salt conditions. This paper takes the EWCP as a case study to analyze the effects of micro-topography on the seedling emergence during the flooding disturbance by the method of variance analysis. The species composition, seedling density, environmental condition and soil seed bank in three micro-topography type of the side slope, hillside and base of slope are compared after river flooding disturbance. The study results revealed that ： （ 1 ） Species composition and diversity indices of the seedling were significantly influenced by different types of the micro- topography. After overflowing disturbance, Simpson index and Mcintosh index of seedling species in three types of micro- topography are aloes highly significant at the level of 0.01, and Margalef index is significantly different at the level of 0.05. （2） There is also a great effect on soil salt in the different micro-topography. The variance analysis showed that： except for the HCO3- and K＋, the value of pH, CO3^2-, SO4^2-, Ca2＋ and Mg2＋ in three types of micro-topography are all significantly different at the level of 0.01, and the value to total salt, soluble salt, Cl- and Na＋ are significantly different at the level of 0.05. （3） Micro-topography can affect the species composition, density and diversity indices of the seedling by changing the resided seedling＇s microhabitat. Under the condition of the micro-topography, the seedling bank were less than those in the soil seed bank. From the base slope, the values of the ecological indicators in hillside slope to side slope, the changing trends of the ecological indicators were different between the soil seed bank and seedling bank expect for the indicator of the vegetative density.. The results can better reveal the impact mechanism of river flooding on compose and construction of the plant community, which has an important significance on the degraded ecosystem restoration. Furthermore, the results have a practical reference on protecting and recovering of the natural vegetation in the study region after river flooding interference.