Effects Of Bird Droppings On Litter Decomposition And Soil Nitrogen Mineralization In Subtropical Evergreen Broad-leaved Forests

Birds are important components of the subtropical evergreen broad-leaved forest ecosystems,however bamboo expansion significantly reduced the species and numbers of birds and reduced the litter decomposition rate and soil N mineralization.N is one of the main elements required for plant growth and the whole process of ecosystem.It was assumed that birds had effects on litter decomposition and soil N mineralization by bird droppings.In order to test this hypothesis,the litter leaf of Castanopsis fargesii,Phyllostachys edulis and Pinus massoniana in broad-leaved forest and the surface soil?0²0 cm?at Mingyue mountain in jiangxi province were selected as the research materials to simulated the bird droppings effects on litter decomposition and soil N mineralization by laboratory experiments,and try to explain influencing mechanism from the perspective of ecological stoichiometry.Our results indicate that:?1?Bird dropping has a certain effect on forest litter decomposition rate,the leaf litter decomposition coefficient k-values of C.fargesii,Ph.edulis,P.massoniana were0.42,0.42,0.20 under no droppings addition?Ck?,0.44,0.53,0.26 under 6 mg g^-1,and 0.70,0.69,0.46 under 12 mg g^-11 respectively.?2?Birds droppings had influence on different types of forest litter,the positive facilitating effect of C.fargesii,Ph.edulis and P.massoniana were 66.7%,64.3%,130%under addition of 12 g^-11 mg droppings,the p.massoniana leaves decomposed at the maximum rate.?3?Bird droppings accelerated subtropical forest N mineralization rate significantly,mainly accelerating ammonification rate.However,the extend of impact on the rate of mineralization was related to droppings content,and showing orderly:0.6 g>0.1 g>CK.?4?Bird droppings changed C:N:P stoichiometric ratio of litter substrate,from1344:31:1 to 1404:37:1 for C.fargesii,from 1461:34:1 to 1101:26:1 for Ph.edulis and from 2966:44:1 to 3010:55:1 for P.massoniana.Reduced C:N and microbes contained in birds droppings could accelerate litter decompsition.Thus,birds droppings directly changed the C:N:P ratio of litter matrix,especially lowering C:N,and led to litter decompose faster.The more the bird droppings added,the faster litter decomposed.Meanwhile the microorganisms?fungi,bacteria,actinomyces?contained in bird droppings could accelerate the decomposition rate and soil mineralization rate at a large extent.