残落物混合分解对杨树-农作物复合系统土壤碳氮矿化的影响

采用室内培养的方法研究杨-麦、杨-花生等不同复合经营模式下,杨树叶与农作物秸秆混合后对土壤碳、氮矿化及土壤微生物量的影响。结果表明:(1)单一模式中,花生叶处理的有机碳矿化累积量最大,花生茎秆、杨树叶处理次之,小麦秸秆处理最低。混合处理有机碳矿化累积量依次为杨树叶-花生叶>杨树叶-花生茎秆>杨树叶-小麦秸秆,且培养结束时,混合物表现出明显的促进作用;(2)土壤微生物量碳、氮与各残落物氮含量、C/N比存在显著的相关性;(3)杨树叶、小麦秸秆及其混合物处理的土壤矿质态氮含量均低于对照,而添加花生叶、花生茎秆以及它们与杨树叶的混合物使矿质态氮含量高于对照。试验说明杨-麦、杨-花生复合模式均能有效提高土壤微生物的生物量,调节碳的动态及氮的供应,而选择种植含氮量高的农作物更有利于促进残落物分解和养分归还,这对深入研究林-农复合系统的模式筛选、结构优化及可持续经营具有一定的现实意义。

Effects of Mixed Residues on Carbon and Nitrogen Mineralization in the Soil of Poplar-Crops Agroforestry System

In the agroforestry system,the mixture of the forest litter and crop straw residues is different in chemical compositions and physical structure from single component,and plays a key role in ecosystem carbon and nutrient cycle.The agroforestry models of poplar-peanut and poplar-wheat,which are the typical agroforestry models in northern Jiangsu province,were chosen to study the impacts of mixed residues on carbon and nitrogen mineralization,microbial biomass carbon and nitrogen in the soil.The soils for the experiment were collected from Siyang county of northern Jiangsu province.The main results were as follows:(1)The cumulated carbon mineralization displayed in the order of H>HJ,Y >M >CK for single residue treatments,while it was ranged as Y-H >Y-HJ >Y-M in mixed residue treatments.At the end of incubation,the mixture of the forest litter and crop straw residues demonstrated significant stimulation on the cumulated carbon mineralization.(2)A significant correlation was observed among contents of nitrogen in litters,carbon-nitrogen ratio and microbial biomass carbon and nitrogen in the soil.In mixed residue treatments,the microbial biomass carbon and nitrogen in the soil was higher in treatment of Y-H with lower carbon-nitrogen ratio,and was lower in treament of Y-M with higher carbon-nitrogen ratio.(3)When poplar leaf litter(Y),wheat straw residue(M) and their mixture(Y-M) were added to the soil,the contents of mineral nitrogen was significantly smaller than the control.However,when peanut leaf residue(H),peanut stalk residue(HJ),and their mixed residues with the poplar leaf litter(Y-H,Y-HJ) were added,the contents of mineral nitrogen in soil increased significantly.Results from this study suggested that the mixture of the poplar leaf litter and crop straw residues,particularly in crops with a higher nitrogen level,could regulate carbon dynamic and nitrogen supply.Such a study can provide important information for selecting model,optiming structure and sustainable development of the agroforestry system.