Emergy Analysis Of Agroforestry Ecosystems In Purple Soil Area

The basic situation of purple soil area was a large population density and little farmland for every person on an average. The agroforestry ecosystem,as a model of reasonable exploitation and utilization of the land resource,was an important method to solve the ecological environment problem and an effective approach to achieve sustainanble development in purple soil area. This paper took the agroforestry ecosystem in purple soil area as the research objective. The major contents were classifying agroforestry models,analyzing strcture characteristics,and using emergy analysis method to make valuation and comparative on different agroforestry systems. The main coclusions of the study were as follows:(1)The agroforestry ecosystem in purple soil area can be classified as terrace agroforestry system,slopingfield agroforestry system,gully bottom agroforestry system,and courtyard agroforestry system. The vertical structure of agroforestry included double layer construction,three layer construction,and multilayer construction. The horizontal structure included strip intercropping,peripheral planting,belt mixing,block mixing,and block inlaying and so on.(2)The energy input structures were similar in the three agroforestry systems. The ratio of non-renewable environment resource to non-renewable resource were 8.21%~8.42% for pear tree -crop intercropping system,11.25%~11.80% for walnut-crop intercropping system,and 13.19%~14.60% for shaddock-crop intercropping system. This result showed that soil and water conservation take an important role in agroforestry ecosystem in purple soil area.(3)There were a great deal of the emergy input of labor and fertilizer in the three agroforestry ecosystem. The ratio of labor emergy to oganic supplemental emergy were 51.66%~69.69% for pear tree-crop intercropping system,52.68%~68.27% for walnut-crop intercropping system,and 49.18%~72.39% for shaddock-crop intercropping system. The ration of fertilizer emergy to inorganic supplemental emergy were 99.41%~ 99.51%,98.06%~98.87%,and 98.71%~98.84%,respectively. The human labor was the main power. The level of science and technology is backward. Meanwhile,excessive use of fertilizer is not beneficial for the long-time develop of agroforestry ecosystem at the local.(4)There was a higher economic development level in agroforestry ecosystem in purple soil area. The shaddock-crop intercropping system had the highest net emergy yield ratio and the most advantageous in price competition. The pear tree-crop intercropping system had the highest emergy investment ratio. The emergy self-suifficiency ratio of these three agroforestry ecosystems were all small,and it was illustrated that the production was hugely influenced by market and the self-development power was weak. The agroforestry ecosystem in purple soil area was friendly to the environment. The walnut-crop intercropping system had the lowest environment load ration and showed the most potential in development. The agroforestry ecosystem in purple soil area was growing and relatively vigorous. The development of it was sustainable. The shaddock-crop intercropping system had the highest emergy sustainable indices.(5)The pear-rape-corn model,walnut-rape-corn model,and shaddock-rape-corn model were the best model in each agroforestry ecosystem at present,and it was embodied particularly in the highest production efficiency,the most advantageous in price-competition,the smallest influence from market,the most powerful in self-development,and had sustainable development potential in to some extent. The pear-wheat-sweet potato model,walnut-wheat-sweet potato model,and shaddock-wheat-sweet potato model had the most develop potential in each agroforestry ecosystem , because of the lowest renewable environment resource utilization and the smallest environment load.(6)The agricultural eco-economic system in Chenjiawan was in the stage of traditional agriculture. The living standard of the local people was low. The agriculture production was less stressful for the whole environment ecosystem. The agricultural eco-economic system had a higher production efficiency,but economically underdeveloped.