土地沙漠化作为全球性生态环境问题，长期以来受到国际社会的广泛关注。中国是世界沙化土地分布广、面积大、危害严重的国家之一，青海省地处地球“第三极”的青藏高原，受海拔高、气温低等自然因素的影响，生态环境敏感脆弱，土地沙漠化是本区面临的严重生态问题之一。青海湖盆地-共和盆地沙化土地面积5061.10km²，占全省沙化土地面积的3.6%，是青海省沙化土地重点区，也是沙化土地综合治理的典型区。国家和青海省政府在这里实施了一系列沙化土地治理工程，使青海湖-共和盆地沙区环境得到改善，但在如何科学、有效、多维度评价沙化土地治理成效，突出治沙工作价值方面，还需要深入研究。本研究通过对沙化土地治理成效建立系统、科学的评价评估体系，并从评价评估中发现如何有效提升沙化土地治理的成效和价值，为该区域未来的沙化土地治理工作提供新目标和新路径。

论文选取青海湖-共和盆地沙化土地作为主要研究对象，并以青海湖克土和共和沙珠玉两个典型沙化土地综合治理试验示范区作为具体样地。通过遥感影像解译、植被特征调查、土壤物理性质特征测定、防风固沙效益测定、小气候观测、生态产品价值评估模型模拟，开展了青海湖-共和盆地沙化土地变化及演变特征分析，沙化土地治理及其生态效益、经济效益、综合效益评析，以及沙化土地治理的生态产品价值量化研究，主要结论如下：

（1）构建了1994—2022年青海湖-共和盆地土地利用转化矩阵，摸清了各种土地类型的变化情况，以及沙地的正逆变化，沙地总体呈大幅减少趋势，1994—2022年共减少4403.32km²，主要转移为草地、水域和耕地。对青海湖-共和盆地沙化土地分布、演变及程度变化情况的研究结果显示，沙地变化与沙化土地变化基本吻合，青海湖-共和盆地沙化土地整体呈下降的趋势，从1994年的9073.54km²，降到2022年的5061.10km²，减少4012.44km²。在自然因素和人为因素共同作用下，不同程度的沙化土地都有所减少，极重度沙化土地面积减少27.43km²，重度沙化土地面积减少669.68km²，中度沙化土地面积减少2825.70km²，轻度沙化土地面积减少886.90km²，其他沙化土地面积增加397.26 km²。

（2）研究区沙化土地治理生态效益显著，生物活沙障能够有效提升防风和固沙效益，并对土壤有明显的改良作用，对小气候调节也有促进作用，人工治理对于植被盖度的提升和增加植被生态修复功能都有重要作用。经济效益方面，种植菊芋、燕麦等经济植物治沙能有效增加防沙治沙工作的经济效益，每亩每年能产生经济效益近200元。综合效益方面，根据不同区域选择相适应的防沙治沙技术和模式，对比分析不同治沙措施的效益，结果表明，研究区采用机械和生物措施相结合的沙化土地修复技术综合效益最高。

（3）1994—2020年，青海湖-共和盆地每年产生的生态产品价值量在300亿以上，青海湖-共和盆地荒漠生态系统的年均生态产品价值为51.63万元/km²，转化为乔木森林生态系统，年均生态产品价值能增加247.95万元/km²；转化为灌木森林生态系统，年均生态产品价值能增加199.14万元/km²；转化为草地生态系统，年均生态产品价值能增加37.40万元/km²。计算1994—2022年，由荒漠生态系统转化产生的生态产品价值共计15.71亿元，即沙化土地治理产生的生态产品价值。从生态产品价值的角度，青海湖-共和盆地沙化土地的治理成效显著，对区域整体生态产品价值提升具有重要作用。

As a global ecological environment problem, land desertification has been widely concerned by the international community for a long time. China is one of the countries with wide distribution, large area and serious harm of desertification land in the world. Qinghai Province is located in the Qinghai-Tibet Plateau, the ' third pole ' of the earth. Affected by natural factors such as high altitude and low temperature, the ecological environment is sensitive and fragile. Land desertification is also one of the serious ecological problems faced by this area. The desertified land area of Qinghai Lake Basin-Gonghe Basin is 5061.10 km2, accounting for 3.6 % of the desertified land area in the province. It is a key area of desertified land in Qinghai Province and a typical area for comprehensive management of desertified land. The state and the Qinghai Provincial Government have implemented a series of desertification land control projects here, so that the environment of the Qinghai Lake-Gonghe Basin sand area has been improved. However, how to scientifically, effectively and multi-dimensionally evaluate the effectiveness of desertification land control and highlight the value of desertification control work still needs further study.

In this paper, the desertification land in Qinghai Lake-Gonghe Basin is selected as the main research area, and the two typical desertification land comprehensive management demonstration areas of Qinghai Lake Ketu and Gonghe Shazhuyu are taken as the specific sample plots. Through the interpretation of rumor images, investigation of vegetation characteristics, determination of soil physical properties, determination of windbreak and sand fixation benefits, microclimate observation, and simulation of ecological product value evaluation model, the changes and evolution characteristics of desertified land in Qinghai Lake-Gonghe Basin were analyzed. Desertified land management and its ecological benefits, economic benefits, and comprehensive benefits were evaluated, and the value of ecological products for desertified land management was quantified. The main conclusions are as follows :

(1) By constructing the land use transformation matrix of Qinghai Lake-Gonghe Basin from 1994 to 2022, the changes of various land types, as well as the whereabouts and sources of sandy land were found out. The sandy land showed a significant reduction trend. From 1994 to 2022, it decreased by 4403.32 km², mainly transferred to grassland, water area and cultivated land. The results of the study on the distribution, evolution and degree change of desertification land in Qinghai Lake-Gonghe Basin show that the change of desertification land is basically consistent with the change of desertification land. The desertification land in Qinghai Lake-Gonghe Basin shows a downward trend as a whole, from 9073.54 km² in 1994 to 5061.10 km² in 2022, a decrease of 4012.44 km². Under the combined action of natural factors and human factors, different degrees of desertification land have been reduced. The area of extremely severe desertification land has decreased by 27.43 km², the area of severe desertification land has decreased by 669.68 km², the area of moderate desertification land has decreased by 2825.70 km², the area of mild desertification land has decreased by 886.90 km², and the area of other desertification land has increased by 397.26 km².

(2) The ecological benefits of desertification land management in the study area are significant. The biological sand barrier can effectively improve the windbreak and sand fixation benefits, and has a significant improvement effect on the soil. It also promotes the regulation of microclimate. Artificial management plays an important role in improving vegetation coverage and increasing vegetation ecological restoration. In terms of economic benefits, planting economic plants such as Jerusalem artichoke and oats can effectively increase the economic benefits of desertification control work, and can generate economic benefits of nearly 200 yuan per mu per year. In terms of comprehensive benefits, the benefits of different sand control measures are compared and analyzed according to the selection of suitable sand control technologies and models in different regions. The results show that the comprehensive benefits of desertification land restoration technology combined with mechanical and biological measures in the study area are the highest.

(3) From 1994 to 2020, the value of ecological products produced by Qinghai Lake-Gonghe Basin is more than 30 billion every year. The average annual ecological product value of desert ecosystem in Qinghai Lake-Gonghe Basin is CNY 516,300 / km², which is transformed into arbor forest ecosystem, and the average annual ecological product value can increase by CNY 2.479,500 / km². Converted into shrub forest ecosystem, the average annual value of ecological products can increase 1.9914 million yuan / km² ; converted into grassland ecosystem, the average annual value of ecological products can increase 374,000 yuan / km². From 1994 to 2022, the value of ecological products generated by the transformation of desert ecosystems totaled 1.571 billion yuan, that is, the value of ecological products generated by desertification land management. From the perspective of ecological product value, the management of desertified land in Qinghai Lake-Gonghe Basin has achieved remarkable results, which plays an important role in improving the overall ecological product value of the region.