Hubei Enshi Tujia Farmers Ecosystem Structure And Function Studies

The agro-ecosystem is a compound ecosystem of natural ecosystem and artificial ecosystem. The study on the structure and function of agro-ecosystem is very important for improving agricultural production and agricultural sustainable development. As a kind of agro-ecosysytem, fanner household ecosystem is common in the western region and minority area of China and it has the important research significance.In this study, taking forty Tujia minority peasant households habituated in three typical villages in mountainous area which located in the southwest of Hubei province as an example, and adopting the method by literature study combined with field investigation, the structure and function characteristics of different agro-ecosystems were elementarily studied. The results showed as bellow:(1) On the basis of cluster analysis to economic input and output, the agroculture modes of forty peasant households were classified into three kinds:Plant-Livestock mode (PL), Plant-Livestock-Marsh gas-Fruiter mode (PLMF) and Plant-Livestock-Marsh gas-Fishery/Vegetable cultivation mode (PLMFV). The result was perfectly coincided with the local actual situation and reflected the structure adjustment direction of the household agro-ecosystems in research area.(2) Through analyzing the diversity of constituent and structure in different agro-ecosystems, the results showed that the constituent and structure of farmer household ecosystem were crop and livestock, which was the traditional mode of agro-ecosystem in area of Tujia nationality. Based on the crop and livestock, the new mode of farmer household ecosystem was built. For the given three modes, the structure of agro-ecosystem become more perfect and the efficiency become higher with the additing of a new link in the original mode of agro-ecosystem. The order of structure rationality and efficiency in agro-ecosystem from high to low was PLMFV, PLMF, PL(3) Black box-mode was adopted to study the cycling and balance of nutrients in household agro-ecosystems. The results showed that the average amount of N surplus and P surplus was respectively high to53.0%and62.5%in three modes of agro-ecosystems, and the average amount of K deficit was12.7%. About the total nutrient circulation, the internal circulation efficiency became higher with the increase of structure diversity.The proportion of nutrient coming from organic fertilizer was higher and the degree of sysetem relying on outside lower in household agro-ecosystems.(4) The method of emergy analysis was adopted to research the energy characteristics of household agro-ecosystem. On the basis of analyzing the emergy input and output in subsystem of three modes,three kinds of energy flow model were constructed.By establishing emergy index system combined with comprehensive evaluation to three agro-ecosystem modes,the results showed that the energy input-output ratio in farmer household agro-ecosystem followed by PLMFV>PLMF>PL. The proportion of organic energy in the agro-ecosystem improved and the ratio of output to input rose with the increase of components in agro-ecosystem. It was proved that the emergy using efficiency would be improved in the use of multi-stage recycle of organic compounds in the agro-ecosystem.