Emergy analysis of chicken breeding modes under low-efficient Pinus massoniana forests

Pinus massoniana forest is a typical low-efficient vegetation type in eroded red-soil areas. Ecological breeding of chicken under forest is a new mode that includes traditional raising chicken under forest and grass planting underneath. This model can reduce soil erosion in P. massoniana forests and improve economic performance. To evaluate ecological and economic benefits of ecological breeding of chicken under P. massoniana forest, this paper used emergy analysis method to evaluate self-sufficiency, investment value, net emergy output, environmental load rate, sustainable development index and emergy feedback rate of traditional chicken breeding mode (CK) and ecological chicken breeding mode (ECB) under P. massoniana forests in Tongba Village, Sanzhou Town and Changting County. The results showed that self-sufficiency, investment value, net emergy output, environmental load rate, sustainable development index, and emergy feedback rate of CK were respectively 0.860, 0.166, 2.125, 3.380, 0.629 and 0.026. Then those of ECB were respectively 0.400, 1.510, 0.870, 1.370, 0.635 and 0.290. The values of investment and sustainable development indexes of ECB increased respectively by 1.344 and 0.006 over those of CK, showing stronger economic vitality. The self-sufficiency and environmental load rate of ECB reduced respectively by 0.460 and 2.010 compared with CK, showing lower environment stress. Net emergy output was lower by 1.255 units and emergy feedback rate higher by 0.264 units over CK. Input-output ratio of CK was 0.30, and that of ECB was 0.53, resulting in high emergy self-sufficiency. Net energy output rate and environmental load of ECB were lower than those under CK, while emergy investment rate and sustainable development index were higher. In general, ecological chicken breeding under forest had stronger economic vitality and lower environment stress, and consequently, was consistent with the trend of economic development in vulnerable forest areas. Poor soil structure in soil erosion areas limited the functions of chemical fertilizer in the circulatory system. This led to low net emergy output and emergy feedback rate. This result was indicative for the optimization of forestry economy modes.