Connection between Biodiversity Development and Ability of Water and Soil Conservation of Abandoned Land in the Western Qinling-Bashan Mountains
|Keywords||Ecological Restoration Biodiversity Soil and Water Conservation the Western QinLing-Bashan Mountains|
Changjiang mid-up-river region is the biological barrier of the Changjiang River drainage. The local and mid-down-river area’s healthy development of economy and society, ecological safe, bedload problem and biodiversity protecting when the Three Gorges Projct is completed are connection with the terrestrial ecosystem stability on the region. According to investigation, slope plough, barren hills and slopes, sparse young forest are the main erosion land use type in the middle and upper reaches of the Changjiang River. Under exerting the nature’s self-restoration ability, it can achieve renewing plants, soil and water conservation, exerting ecosystem service ability. This region have the self-restoration ability because that most of the Changjiang River drainage locates in the east-Asia tropic monsoon region, with superior nature condition, and annual rainfall about 800～1100mm, flush prcipitation, and various kinds of plants, so it is in favor of ecosystem’s self-restoration.Ecological restoration project on abandoned land is the pivot work in soil and water loss area. The Jia Lingjiang River, which is an anabranch of Changjiang River, on its upriver drainage, has a regional significance in ecological restoration project. The growth of plant biodiversity and the good results of soil and water conservation are what the ecological restoration project wants. Ecological restoration research in the Western Qinling-Bashan Mountains where is basin of Qinling Mountain’s drape zone, valley and having good entironment, is underway. It is important to find the connection between biodiversity development and ability of water and soil conservation of Abandoned Land on theory and practice of ecological restoration work in the Changjiang River drainage.This paper carrys on the forth phase of "Chang Zhi" project which is a ecological soil and water conservation restoration project in LiangDang. The abandoned land situated on LiangDang, which is chosen from several samples of ecological restoration project and based on the remote sensing （RS） pictures’ study. The results: （1） Choose a sample land in the region, that is 106°9.6’—106°10.5’ E, 33°54.1’—33°54.5 ’ N, by studying the remote sensing （RS） ersatz color pictures of 4（R） : 5（G） : 3（B） which come from Landsat-5 and its scale is 1:500,000. In this region, the natural vegetation cover was 72.81% . According to study by geography information system （GIS） technology, we chosed a sample land which was abandoned from 7 years ago, that was located between the northern mountains and the middle valley. The sample land at an elevation of 1,185m its acreage is 20×5m2 and slope is 22°N.（2） In the studying periods: maximum plant richness indxe in the sample land is Rmax=7, minimum plant richness index in the sample land is Rmin=2; plant Simpson diversity index Dmax=0.887 and Dmin=0.203; plant Shannon diversity index H’max=0.668 and H’ min=0.078; plant Margalef richness index Mmax= 10.470 and Mmin=2.701; most Caswell model’s V（N.D.） value is between -2 and +2, they are 0.57575（2002a）, 0.059792（2003a）, 0.300042（2004a） and -0.46242（2005a）.（3） The Shannon diversity indexes distributing pictures are regularized by GIS analysis tools which is more precision than other tools in simulating continuous spacial factors. The Shannon diversity indexes value’s increase in the sapmle land trend from north to south, while it trends equality year after year. And the plant Shannon diversity indexes, which are distributing on higher altitude, are on low level. On the analysis pictures of 2004a and 2005a we can read that the plants’ succession trends slow-down, because of the arbor species’ increase and the equality trend of diversity indexes.Most Caswell model’s V（N.D.） value is between -2 and +2, they are 0.57575（2002a）, 0.059792（2003a）, 0.300042（2004a） and—0.46242（2005a）. Model analysis results show that: habit stability trend neutral to unneutral because of some pression unkown from 2002a to 2004a （—1.902～1.925）. The eighteenth sample’ s Caswell model’s V（N.D.） value is—2.286 and the twenty-second sample’ s Caswell model’s V（N.D.） value is—2.1. They are show that the tow samples have been obviously disturbed and in pression.（4） This paper have studied growth seasons, which is from March to August, to find the connection between precipitation, outflow and bedload on sample in 4 years. In 2005a, sample habit stability trend neutral to unneutral because of the unneutral climate. Analysis result: the sample’ s ability to hold precipitation is increasing and the soil and water conservation ability is boost up, while the number and richness of plant is increasing. But the increasing of sample’ s ability is not linearity, because the intensity and frequency of precipitation in short time are unneutral. The bedload is connection with the outflow, while the outflow is connection with frequency of downfall or continued precipitation more than 3 days. In this study, we found that continued precipitation on low intensity level made more outflow. So the continued precipitation on low intensity level is an ultimate out factor of soil and water loss.（5） The plants element change: the Artemisia A and Artemisia selengensis Turcz. were decreasing in number while the Sophora viciifolia Hance, Robinia pseudoacacia L., Ailanthus altissima （Mill.）swingle and Zanthoxylum bungeanum Maxim., which are young arbor or shrub, were increasing year after year, although plant species richness changed less in the sample land. This kind of decreasing and increasing is good for building up the ability that roots of plants go deep into and hold the soil. The Medicago falcata L. which is a kind of leguminous plant is good for reforming nitrogen environment of oil, but The Medicago falcata L. is poor in number and is unneutrul in the sample land, what made a little change for the oil nutrition environment. That is why the herbage plant species that resisted the lean soil appeared in the sample are the main plant.