【作者】 孙建光；

【导师】 李保国；

【作者基本信息】 中国农业大学 ， 土壤学， 2004， 博士

【摘要】 青海共和盆地地处青藏高原的东北缘，属于高寒干旱和半干旱气候区。近年来，由于环境变化和人口剧增，青海共和盆地的荒漠化问题已日益严重。为了做到对本区的水土资源的可持续利用、防治本区的荒漠化和保护龙羊峡水库，所以基于DEM和已有的气象、水文长短期观测和实测数据，首先构建了青海共和盆地降雨、径流、蒸散和区域水分平衡的分布式模型；进一步在此基础上，构建了青海共和盆地草地生产力的模型和基于作物水分耗散与放牧因子校正的青海共和盆地草地生产力模型；利用草地载畜能力和现有牲畜量以及社会经济因子等统计数据，结合实地调查，分析了青海共和盆地草地生产力、物种构成、生境变化和荒漠化成因及其内在驱动因子，并对草地可持续利用做了评价。研究的主要结论如下： 1．在青海共和盆地，近50年的年降雨量序列是平稳的、无周期，其时空变化与径流、蒸发、潜在蒸散和土壤水分的关系表明，气候干燥和严重的荒漠化不是由于降雨量减少直接引起，龙羊峡水库对共和盆地年降雨量变化没有影响；但是年气温序列是非平稳的，茶卡、恰卜恰和贵南的年气温平均每年升高0.0247、0.0422和0.0272℃，且气温升高2℃，年潜在蒸散增加57mm，盆地内气候逐渐变干燥，但影响比较小；由于历年潜在蒸散序列是平稳的，因此气候变化对盆地的作物潜在蒸散的影响在研究期内是较小的。 2．在青海共和盆地，降雨产流主要在山区和水域附近，而且雨季产流占总径流量的90％；盆地降雨的总产流量为7.08亿m~3，丰水年为9.06亿m~3，枯水年为5.66亿m~3，因此径流量受降雨量年变率的影响很大。尤其枯水年径流量的减少可能成为影响盆地荒漠化的原因之一。 3．在青海共和盆地，历年潜在蒸散平均974mm，各月潜在蒸散与降雨和温度之间是很好的正相关，所以雨热同季有利于作物生长：年潜在蒸散的空间分布范围从485—1174mm，平均1027mm，而且年潜在蒸散空间分布与降雨和坡度是负相关，与温度和大气外层辐射正相关，因此水分和温度的是影响作物水分耗散的重要因子，决定了共和盆地植被的气候生产力。 在共和盆地，牧草的年蒸散量从95-680mm，平均494mm，它的总量为80.4亿m~3，比年降雨量高27.6亿m~3，其中山地约为9.1亿m~3，低于降雨量6.5亿m~3，滩地约为52.9亿m~3，较降雨量高25.1亿m~3，河谷约为18.8亿m~3，较降雨量高10.2亿m~3；牧草的年实际蒸散量为41.7亿m~3，较年降雨量低10.3亿m~3，其中山地约为7.3亿m~3，低于降雨量8.3亿m~3，滩地约为25.2亿m~3，低于降雨量1.6亿m~3，河谷约为9.1亿m~3，高于降水量0.5亿m~3。如果考虑径流，降雨在山地基本能满足牧草生长的水分需求，在河谷滩地不能满足牧草最大生长，但仅在河谷降雨可能不能满足牧草实际水分耗散。 共和盆地牧草的生态需水量约为77.7亿m~3，生态耗水量约为40.1亿m~3，生态最低需水量和耗水量分别为11.6和5.6亿m~3。目前正常年份牧草的生态耗水量能够基本满足，所以共和草地退化和荒漠化需要进一步分析。 4．基于水分平衡模型，青海共和盆地土壤水分在黄河以西的乌兰县茶卡、共和县沙珠玉和黄河谷地及部分滩地降雨不能满足牧草实际蒸散的水分需求，其中茶卡盆地缺50-300mm，沙珠玉和恰卜恰河谷、滩地0-100mm，而河卡和贵南降水能够满足牧草实际水分需求，存在0-150mm的水分盈余，塔拉滩、木格滩土壤水分基本平衡或略有盈余，山区土壤水分是略有盈余，基本上平衡的。盆地的河谷滩地不能满足牧草蒸散的水分需求，山地略有亏缺，基本平衡。 5.在共和盆地，6一9月的累积NDVI值与年降雨量的空间分布之间是正相关，与年潜在蒸散和高程是负相关;草地生物量和降雨量之间也是正相关，与年潜在蒸散也是负相关，因此盆地内水分的时空分异是决定草地生产力的关键因子之一:另一方面，草地的光温生产潜力15.3比a，约为光合生产潜力的53%，而且在山区约为44%，滩地约为54%，河谷约为58%，所以温度应当是限制牧草生产能力的一个重要的因子，尤其在山区。 共和盆地牧草的气候生产潜力约6.6比a，约为光温生产潜力的43%，光合生产潜力的23%;而且河谷、滩地牧草的气候生产潜力分别约为光温生产潜力的34%和41%，山地约为69%，水分对牧草的气候生产潜力影响在河谷和滩地要大于山地，尤其是草原化荒漠和荒漠化草原气候生产力相对较低;共和盆地的实际等级草地生产力是气候生产力的1巧一1/12;经过作物水分需求和放牧的校正，草地生产力平均2.2比a，约为气候生产力的33.3%，已基本接近草地实际的生产力;作物水分需求和放牧对共和盆地草地生产力有很大影响，而且放牧已成为草地生产力降低和草地退化的重要原因之一。 6.依据青海共和盆地围栏内外草地生物量的调查，未封育草场的生物量是封育草场的57.7%，而且沙生和荒漠植被入侵，使未封育草场优势物种生物量降低;过牧会造成草地退化和环境恶化，围栏封育有利于草地恢复;依据社会经济统计资料，不合理的土地利用使共和盆地的草地退化，而且人口增长及其外部效应是内在驱动因子;共和盆地草地可持续利用的综合指数从33一39，平均38，草地是不可持续利?更多还原

【Abstract】 Gonghe Basin is located in the north eastern part of Qinghai-Tibeten Plateau, belong to arid and semi-arid climate region. Because of the environmental change and population rise, the issue of desertification becomes very serious in Gonghe Basin, Qinghai. In order to maintain the sustainable use of land and water resource, to protect the land from desertification and to make Longyangxia reservoir safe, firstly, the spatially disturbed model has been established in which includes DEM-based precipitation and runoff, regional transpiration and regional water balance modules in Gonghe. Secondly, the model of grassland climate potential productivity and the model of grassland productivity modified by plant water demand and stocking intensity factors has been constructed in Gonghe. According to the carrying capacity and the actual amount of animals on the grassland, coupled with actual grassland investigation, and by using social-economic data, the grassland productivity, species composition, biotope and the cause of desertification has been analyzed. Finally, the evaluation of grassland sustainable use has been performed. The main research results are as follows:1. Annual precipitation series about 50 years is stable and no period; further, the climate drying and desertification aren’t caused directly by the decrease of precipitation during the period of the research according to the relational analysis among precipitation temporal-spatial change, runoff, evaporation, potential evapotranspiration and soil water; Longyangxia reservoir which was built in 1986 doesn’t have influence on precipitation up to now; but annual temperature series in Gonghe is unstable, having a linear upward trend, and it increases about 0.0247,0.0422 and 0.0272C per year, and temperature rise must be having an influence on desertification, but there is a very little temperature change , so that the effect is very small; annual potential evapotranspiration series is stable too, so climate change has little influence on plant water consumption.2. The runoff has been created in mountain and waters or neighboring regions, and it is 90 percent of the total in rainy season; the total amount of precipitation is 7.08X109m3 in accordance with real amount, about 6.46 X 109m3or so, and it is 9.06 X 109m3in the rainy years, 5.66 X 109m3 in the drying years. There is 3.46 X 109m3 difference between them. So precipitation has a great influence on runoff. Especially, river retreat in drying year becomes one of the main causes of desertification because of the decrease of runoff.3. Temporally, annual potential evapotranspiration is from 882 to 107 lmm, with a mean value of 974mm at Qiabuqia; and it is positively correlational to precipitation and temperature, so it is beneficial for plant growth because precipitation and heat ocurs at the same growth period.; spatially, annual potential evapotranspiration is from 485mm to 1174mm, with a mean value of 1027mm, and it’s spatial distribution is negatively correlational to precipitation and slope, whereas positively correlational to temperature and extra solar radiation, therefore the spatio-temporal difference of water become the key factors to plant growth and plant climate potential productivity.The grass evapotranspiration is from 95 to 680mm in space, 494mm on average; and it’s total amount is 80.4 X 109 m3, which is 27.6 X 109 m3 higher than annual precipitation; grass evapotranspiration is 9.1 X 109 m3, which is 15.6 X 109 m3 lower than annual precipitation, there is a balance between water demand and supply with annual runoff included in the mountainous area; it is 52.9X 109m3, which is 25.1 X 109m3 less than annual precipitation in the terrace; it is 18.8X 109m3,10.2X109m3 less than annual precipitation in the valley, water becomes a main limiting factors for plant growth..The grass actual evapotranspiration is from 75 to 331mm in space, 255mm on average; and it’s total amount is 41.7X 109m3, which is 10.3X 109m3 lower than annual precipitation; it is 7.3X 109m\ which is 15.6X更多还原