Soil enzymes are bioactive proteins in soil. And soil is good medium of soil enzymes, not only because the soil pro-vides sorts of catalytic conditions ( such as temperature, water, pH, reactant and so on), but also because soil can prevent soil enzymes from deactivation by combining with them through covalent bond, electrovalent bond or hydrogen bond. About 60 soil enzymes have been found by now, which mainly result from soil microorganisms. Soil enzymes act as an important role in the transforming of plant nutrition elements. The leading function of soil enzymes is taking part in the circulation of nutrition elements, such as C, N, P, S, and so on. Together with soil microorganisms, soil enzymes promote all of the reactions involved soil bio - chemical processes. Therefore, the activities of soil enzymes are universally taken for as characteristic index of soil quality. Chinese scientists began to study soil enzymes in 1960' s, and in 1980, s, along with the development of environmental sciences, the studies of soil enzymes became more and more important. To our knowledge, the studies mainly focused on farmland ecosystem, and some on the relationship of soil enzymes and environmental pollution, few studies have been made on the possible effects of soil enzymes in desert ecosystem, still less using soil enzymes as a way to manage and restore the desert ecosystems.In this study, two kinds of sand samples were collected respectively from the depth I - 5 cm of the representative natural shift dune and fixed dune ( artificial vegetation of higher plant was set up three years before) of Hobq desert, China. Firstly, soil enzyme activities (invertase, protease, urease and alkaline phosphatase) were investigated, and then, desert algae were inoculated onto the surface of shift dune soil in order to study the effects of artificial micro-algae crust on the enzyme activities. Our data showed that the total soil enzyme activities in both dunes were very low when compared with ordinary soil of Inner Mongolia Plateau, and the soil enzyme activities of two dunes were significant difference (p < 0.05 Soil enzyme activities of invertase, protease, urease and alkaline phosphatase were 2.3, 3.3, 3.1 and 21.6 times in the fixed dune than in the shift dune, respectively I which indicated that artificial vegetation of higher plant had notable positive effects on shift dune soil. As for vegetation of lower plant, after 30 days of inoculation Microcoleus vaginatus Gom. and Phormidium tenue (Menegh.) Gom. (0.5 mu g Chl..a/cm(2)) onto the sand surface, obvious algal crust could be seen and after 90 days, soil enzyme activities of invertase, protease, urease and alkaline phosphatase were 1.6-3.6 times, 3.1-6.0 times, 2.8-10.6 times and 29-79 times than the origin values, respectively. The results indicated that the lower plant vegetation (algal crust) was probably more effective than the higher plant vegetation in terms of the changes of soil enzymes. At the present time, controlling desertification becomes a serious problem all over the world, and great efforts have been made to hold back desertification. The present work showed that shift dune and fixed dune have different soil enzyme activities, and demonstrated the ameliorative effect of artificial micro-algae crust on desert soil in the viewpoint of soil enzyme activities. So, our work would be a promising way for desertification control and for soil melioration and colonization of desert areas.
Tang Dong-Shan (xhtds@sohu.com) ; Wang Wei-Bo; Li Dun-Hai; Hu Chun-Xiang; Liu Yong-Ding (liuyd@ihb.ac.cn).Effects of artificial algal crust on soil enzyme activities of Hopq desert, China,Acta Hydrobiologica Sinica,2007,31(3):339-344
