青海贵南草原沙漠化影响因子的贡献率

影响因子贡献率是目前沙漠化研究的焦点之一,诸因子对沙漠化发展的贡献和对沙漠化现状的贡献是这一科学问题的两个方面。利用风洞模拟实验和¹³⁷Cs示踪技术,建立了青海贵南现代草原沙漠化多因子方程,分别区分了该区风速变化、植被变化、牲畜践踏(滥牧)、樵采破坏(滥樵)和草地开垦(滥垦)等五个主要影响因子对沙漠化现状及其发展的贡献率。结果表明,牲畜践踏、樵采活动和草地开垦对沙漠化发展的贡献率分别为54.78%、4.66%和40.56%,人类不合理经济活动是近40a来沙漠化发展的根本原因。平均侵蚀风速变化很小,对沙漠化发展的贡献率为零。植被盖度的变化对沙漠化发展具有显著的贡献,但在近几十年来气候变化尚不足于对植被盖度造成明显影响的前提下,对沙漠化的影响作用被进一步归结为人文因子的贡献。沙漠化现状是在自然沙漠化过程的基础上人类不合理经济活动进一步叠加的结果,自然因子和人文因子对当前沙漠化现状的贡献率分别为27.8%和72.2%,人文因子中牲畜践踏、樵采活动和草地开垦对沙漠化现状的贡献率分别为39.55%、3.37%和29.28%。沙漠化影响因子的贡献率因时、因地而异。

Contributing Ratios of Several Factors to the Steppe Desertification in Guinan, Qinhai Province

Contributing ratio of desertification factors is an important issue in the field of desertification study. The ratios to the development of desertification and to the status of desertification are two sides of the scientific issue. Making use of wind tunnel test and ¹³⁷Cs technique, a multi-factor function of modern desertification in steppe area of Guinan County is constructed, in which change of wind speed, vegetation cover, livestock trampling, woodcutting, and grassland cultivation are involved. The results show that contributing ratios of livestock trampling, woodcutting and grassland cultivation to the development of desertification are 54.78%, 4.66%, and 0.56% respectively. That is to say, human unreasonable activities are conclusive cause of the development of desertification since 1960s. Change of average wind speed is very small, hence it has little contribution to the development of desertification. Change of vegetation cover is very important to the development of desertification. Since climatic change had no obvious affects on vegetation cover and humane activities directly led to the decrease of vegetation cover in the latest several years, contribution of vegetation cover's change to the development of desertification is ascribed to humane factors. The status of desertification is a result of climatic change and human unreasonable activities. Climatic change-induced natural desertification is the background, human activities accelerating the process. Contributing ratios of natural and humane factors to the status of desertification are 27.8% and 72.2% respectively. The contributing ratio of each factor changes with time and site.