Effects of forest chicken complex system with different densities on topsoil and understory vegetation in karst mountains

As one of the innovative agricultural modes of Compound Management of Forest and Poultry, forests ecological chicken brood has high ecological and economic benefits. However, in pursuit of maximum economic benefits, farmers often ignore ecological environmental protection, resulting in a negative impact on karst region with fragile ecological environment. Therefore, this study analyzed the effects of 600 chickens / hm2 (T1), 1200 chickens / hm2 (T2) and 2400 chickens / hm2 (T3) on the surface soil and vegetation under the forest, and comprehensively considered the ecological and economic value to determine the reasonable poultry-raising density of under-forest economy in karst mountain area. After four months of poultry-raising experiment, the results showed that：1) Under T1 and T2 poultry-raising conditions, saturated hydraulic conductivity and maximum moisture capacity of the soil increased, but the change of soil bulk density and porosity is not obvious. Under T3 condition, the saturated hydraulic conductivity and porosity of soil decreased, and the soil appeared obvious hardening phenomenon. 2) The contents of soil total nitrogen and soil organic carbon in all conditions increased compared with those before poultry-raising, with the largest increment at T2 condition, increased by 69.0% and 89.3% respectively. The contents of total phosphorus and total potassium in soil increased with the poultry-raising density, which increased by 29.3 % and 36.8 % respectively under T3. 3) The biomass of herbaceous vegetation decreased by more than 95% under all conditions. Four months after stopping poultry-raising, the biomass of herbaceous vegetation in T1 T2 and T3 conditions recovered to 41.2%, 3.5% and 1.5% of that before poultry-raising, respectively. 4) The chicken raising income of T1, T2 and T3 conditions were 72000, 144000 and 288000 RMB per hectare respectively. Based on the above results, the density of forests ecological chicken brood in karst mountainous area should be controlled within 600 chickens / hm2, and the forbidden grazing area and rotational grazing area should be divided, which can improve soil quality and protect vegetation diversity, take into account economic and ecological benefits, and achieve sustainable green development of mountain agriculture.