Zhang Xueping

EFFECTS OF SOIL FAUNA ON LITTER DECOMPOSITION

Forest litter is the physical makeup part of forest ecosystem. The rate of decomposition of forest litter is low in temperate and cool temperate zones. There is important significance to search and utilize the function of soil animals, in order to probe the material circulation and energy flow in forest ecosystem. We selected three kinds of mesh bag with different mesh size, in which, large pore mesh bag is large enough to permit the activities of all kinds of soil animals, medium mesh bag is designed to exclude the function of soil macrofauna, while small mesh bag is small enough to exclude the effects of any kind of soil animals as far as possible. The decomposition time is three years. The studying results show that: the decomposing speed of the bags with big meshes, under functions of all kinds of soil animals, faster than the bags with medium meshes, under functions of medium and small soil animals, as well as the bags with small meshes that excluding all possibility of functions of soil animals; in the process of decomposition of litter, relationship of the litter lost weight with number of soil animals is not obvious clearly; the degree of functions of soil animals to soft litter higher than hard litter; according to the analysis of diversity index, no regular changes will happen to the diversity of soil animals as the time of decomposing samples lengthen.

Emergy Analysis and Assessment of Sustainability on the Agro-ecosystem in Heilongjiang Province: As a Case of Xinglong Town

Agriculture is the foundation of national economic development. Agricultural sustainable development is an important part of the social-economic sustainable development and a key historical task of building new socialist countryside in our country. Xinglong town is a typical representation of black cultivated land in Heilongjiang Province. This study presents an ecological analysis of the agro ecosystems of Xing long town for the period from 2005 to 2009, on the basis of Odums well known concept of emergy in ecological economy. The results indicated that : there was an increasing trend in the total emergy input from 2005 to 2009, among which, purchased supplemented energy accounted for 69.4%, of which chemical fertilizer accounted for a larger proportion. And the proportion of environmental resource was 20.1%and that of renewable organic energy value were 6.8%. Depending on the purchased supplemental energy made the agro ecosystem withstand greater pressure on the environment and the environment load ratio of five-year growth. The net emergy yield ratio was higher than national average and showed a decreasing trend. The environment sustainable index £¨ESI£© was 1.41, which indicated there had greater potential for sustainable development on the agro ecosystem in Xing long town, and showed a declining trend also. The variation of the indices was an obvious indicator for the transformation of agriculture in Xinglong town from traditional to modern pattern and the development of agro ecosystems need to be further improved.