共和盆地土地沙漠化因素定量研究

Quantitative research on factors of soil desertification in Gonghe basin

共和盆黄河上游土地沙漠化严重地区,导致青海湖生态环境的恶化,同时还直接威胁龙羊峡水库的正常运转。土地沙漠化面积逐年扩大,严重沙漠化面积以年均0.12万hm2的速度扩展,每年进入龙羊峡水库的流沙量以达313万m3,导致许多牧民搬迁和无家可归。土地沙漠化已经成为共和盆地生态环境恶化的主要问题。选取青海共和盆地从1953到2004年共52a的农牧业人口数量、牲畜数量、耕地面积、降水量和大风日数5个因素进行了分析,借用功效原理、主成分分析原理和数理统计原理构建了评价模型,研究了它们与土地沙漠化的定量关系。结果表明共和盆地土地沙漠化主要是由农牧业人口数量、牲畜数量和耕地面积的增加引起的,权重上分别占到0.4412、0.2582和0.1470,影响系数随时间不断提高,引起社会因素综合影响系数在1994年以前由0增加到0.8105,呈现上升趋势,以后又逐渐下降至2004年的0.7069;降雨量和大风日数对土地沙漠化影响次要的,权重系数只有0.1118和0.0418,影响系数表现为一种不规则的周期性变化,自然因素综合影响系数呈现平稳发展趋势,变化范围在0.0102与0.1381之间。社会因素和自然因素的综合影响系数的变化1994年以前从0.0652增加到0.8974,年均增长1.6%,以后逐年下降至0.7813,年均降低1.2%;同时在综合影响系数的变化趋势线上反映出从1956年以后人类活动对生态环境的影响开始超过自然因素,成为影响共和盆地土地沙漠化的主体因素,1994年达到最高值,以后出现逐年降低的趋势,从20世纪末开始由于退耕还草生态项目的实施,社会因素有了较为明显的降低,但仍然高于自然因素的作用,因此共和盆地土地沙漠化的防治关键与重点是降低人为等社会因素的影响力,应该实施土地沙漠化综合治理工程。

Gonghe basin is a very serious region on soil desertification in the upriver of the Yellow River, which is situated in Gonghe county and Guinan county, Qinghai Province. Soil desertification not only impacts the environment of the Qinghai Lake but also threatens the safety work of the Longyangxia Reservoir. The area of soil desertification is being spread year after year. The area of serious soil desertification is being extended by 1.2 5×10^3hm^2 per year. The Quantity of quicksand that enters into Longyangxia reservoir is about 3.13 ×10^6m^3 from Gonghe basin every year, and forces farmer emigration or homeless. Desertification is the main issue of environment deterioration in Gonghe basin. The paper choose five factors that including farmer population, livestock scalar, plantation area, precipitation and gale days ,and quantificationally study the relationship between those factors and soil desertification. The analyzed data is about 52 years from 1953 to 2004. Appraised function model is constructed by efficacy principle, principal components principle and statistic principle. The research results indicated the main factors of soil desertification are farmer population, livestock scalar and plantation area, and which weight values are 0.4412, 0.2582 and 0. 1470. The effect coefficient （EC） of society factors heightens year by year, and society factor comprehensive effect coefficient （ECE） presents rising trend from 0 to 0. 8105 before 1994, and gradually descends to 0. 7069 in 2004. The sub-reason of desertification is precipitation and gale days, which weight values are only 0. 1118 and 0. 0418, and their effect coefficient （EC） presents a kind of non-ruler periodicity change. Natural factor comprehensive effect coefficient （ECE） takes on slowness fluctuate change trend from 0. 0102 to 0. 1381. Comprehensive effect coefficient rise from 0. 0572 to 0. 8974, and the ratio of increase is 1.6% per year, and falling down 0. 7813 in 2004, and the ratio of decrease is 1.20% per year. At the same time, ECE from society factors is more than natural factors after 1956, it is further proves that society factors is the main body of desertifieation in Gonghe basin after 1965. The maximum of ECE arises in 1994, and presents the descend trend from 1994 to 2004. Society factors are still the main reason of soil desertifieation, though the project of Returning Farmland to Forestry or Pasture is put into practice in the end of 20 century. Hence, the key and emphases measure of prevention soil desertifieation is the force of society factors to environment, and should bring into effect of integrate father project to keep within limits soil desertifieation in Gonghe basin.