Emergy-based Analysis For The Development Of Agro-ecosystem In Shanxi Province

Agro-ecosystem is a basic system for human living. Analyzing its structure and function and evaluating the value of the environmental resource and making a quantity research on it are of advantage to reinforce the nation's knowledge and awareness of agricultural environmental resource, and valuable to the sustainable development of ecosystem and human society. Shanxi province is a model province in the Loess Plateau. It lies in the transition zone of half-drought agriculture to drought agriculture, and is actualizing area of six large environmental projects such as San-bei fence forest project, etc. With much population, natural vegetation in the six large basins in Shanxi has been replaced by farming. The agro-ecosystem in Shanxi is very frail for short of water and gravely erosion of topsoil. Studying the running state and efficiency of Shanxi agro-ecosystem and disclosing developmental rule and trend of the system and disclosing correlation between human being and environment in the special area are of great value to evaluating and utilizing agricultural resource in the yellow loess tableland scientifically and reasonably and to establishing and carrying out the sustainable and developmental policies on agricultural economy.Based on the theory and methodology of emergy, this thesis systematically evaluated the input-output condition, running efficiency and environmental loading of agro-ecosystem in Shanxi Province, and disclosed its basic developmental trend, and compared on difference of three type area, and disclosed structure and developmental advantage of planting, stockbreeding, forestry and fishing within the system, and evaluated sustainable development state. The main results showed that:(1) Total environmental emergy and renewable organic emergy of Sanxi agro-ecosystem account for 81% in total emergy input. The system is still in traditional agricultural phase which mainly depend on environmental resource and manpower. Comparing with national and international level, the emergy input level is low (EIR 1.53). Using efficiency for environmental resource is also low. Agro-ecosystem is under developed comparatively.(2) Main body of agriculture in Shanxi province is stockbreeding and planting. The proportion of forestry and fishing are very small. Maize and wheat are main crop among planting, and have advantage compared with sundry, vegetable and fruit. Emergy yield efficiency of the system is low. There is emergy deficit in the system. Compared with Gansu (1.26), Chongqin (3.67) and Liaonin (2.89), emergy yield ratio (EYR) of agricultural system in Shanxi is low (0.96), it means the emergy yield of Shanxi agricultural system only can keep simple reproduction.(3) From 1980 to 2006, the running efficiency of agro-ecosystem in Shanxi province has been improved a lot. On one hand, the proportion of labor emergy and industry emergy trends to rationalization. It means that laggard handwork production mode is being replaced by advanced industrialization way. On the other hand, planting emergy proportion decreases from 75.98% to 40.71%, and stockbreeding emergy proportion increases from 20.45% to 55.66%. The structure change is a result of regulating agricultural structure, and also is the reason that the efficiency of system has been improved. Its EYR increases from 0.36 to 0.96, it means that emergy yield of agro-ecosystem in Shanxi province is improved continually, and is transferring from emergy deficit to emergy equation.(4) From 1980 to 2006, since stockbreeding emergy increases rapidly from 6.81E+21sej to 5.21E+22sej, increased 665%, it drive emergy yield heighten enhance largely. After life level increasing and scale of stockbreeding enlarging, stockbreeding will continue to play a role of engine in the system. Planting emergy yield presents a small fluctuation, degree increased was small. The planting looks like be restricted by some threshold value. Planting emergy will present a small fluctuation continually without a large agro-technical progress. Acreage which has forest occupy 53.36% in total woodland area, so forestry emergy will increase continually under the policy of reverting farmland to forests. Since fish-breeding only fit in bank of the Yellow River and other few areas, fishing emergy yield will be small under limit of natural condition.(5) Developmental trend of structure of planting: Emergy yield of maize, which has been increasing continually from 1980 to 2006, and accounts for 39% of planting emergy in 2006, promotes planting emergy greatly. Oil-plant emergy yield influence planting emergy most. Emergy yield of wheat, sundry grains and cotton wave small. Emergy yield of sundry grains (include millet, sundry wheat, bean and kaoliang, etc.) decline much. Tubers emergy is calm in the past 27 years. Emergy yield of vegetable and fruit show good rising trend.(6) The results of comparing emergy of different eco-economic areas showed that: Agro-ecosystem in the excellent area, for example Wanrong County, mainly depended on manpower, whose emergy proportion reached 70.62%. With fertility soil and numerous populations, agricultural production in the area belongs to labor-coarctation type. Agro-ecosystem in the bad area, for example Wanrong County, depended on environmental resource most; its emergy self-support ratio arrived to 27.06%, whose characteristic of agriculture was coarse management. Cooperation of labor emergy (Labor emergy ratio 51.67%) and industry supplemental emergy (industry supplemental emergy ratio 27.64%) was better in the middling type region, the total emergy yield was higher, and so did its EYR (1.25), shown a higher agricultural productive efficiency. Planting of excellent area had advantage (planting emergy ratio 61.14%). Stockbreeding in the middling area had advantage (stockbreeding emergy ratio 61.40%). Total emergy yield in the bad area was too small and had no advantage.EYR of three type areas, the excellent, the middling and the bad one, were 0.70, 1.25 and 0.93 in turn. EYR in the middling area was the biggest of all, exceeded 1, that means the agro-ecosystem in the middling area had emergy surplus, whose competition strength was better. Environmental loading ratio (ELR) of three type areas, the excellent, the middling and the bad one were 9.33, 5.79 and 2.80 in turn. The index of excellent area was the highest of all. That means the pressure brought to bear to environment in the middling area was the biggest of all. Contrarily, emergy-based sustainability index (ESI) was 0.06, 0.22 and 0.33 in turn. The index of excellent area was the lowest of all, whose sustainability was worst.(7) ESI of whole agro-ecosystem in Shanxi province was 0.12 in 2006, which was less than 1 largely, that means the system was consumption one. Agricultural environmental resource in Shanxi province is small (renewable environmental emergy ratio 11.28%), population is numerous; more manpower was ploughed into agro-ecosystem (labor emergy ratio 61%). However, because agricultural condition is worse, together with lack of agro-technology, overmany devotion of labor emergy did not bring on elevation of emergy yield, so developmental state of the system is not sustainable. Furthermore, the sustainability of the system also suffer pressure from exasperate entironment.(8) The sustainability of agro-ecosystem in Shanxi province has been rising under some measures such as reverting farmland to forest, transferring labor force from agriculture to industry and service, increasing agro-technology and so on. From 1980 to 2006, forestland increased from 1605kha to 3757kha, renewable environmental emergy increased from 9.47E+21sej to 1.26E+22sej, agricultural laborer reduced from 7.03×10~6 person to 6.40×10~6 person so that labor emergy decreased 9%, unrenewable supplemental emergy went up from 1.11E+22sej to 2.17E+22sej, increased 143%. All of previous factor result that: ELR decreased from 9.87 to 7.83, EYR increased from 0.36 to 0.96, ESI increased from 0.04 to 0.12.