中国农田土壤中有机物料腐解特征的整合分析

Decomposition of Organic Materials in Cropland Soils across China:A Metaanalysis

整合1980年—2013年中国农田土壤有机物料腐解试验的相关文献,分析了华南、华北、西北和东北等典型农业区不同类型有机物料腐解一年后的残留率(h1)及其驱动因子。结果表明,中国不同有机物料h1平均为0.335 g g-1,受到物料类型、区域以及二者交互作用等因素的显著影响。总体上,h1在物料类型上呈绿肥<秸秆<根茬≈有机肥,在区域上呈华南≈华北<西北≈东北。但h1的区域差异因物料类型而异。其中,绿肥、秸秆和根茬的h1均呈华北<华南和东北,而有机肥的h1在各区域间差异不显著。同时,h1的物料类型差异也因区域而异。在湿润半湿润的华南、华北和东北地区,h1均呈根茬>秸秆和绿肥;而在干旱半干旱的西北地区,受水分条件的限制,各物料类型间h1差异不显著。逐步回归结果显示,木质素与氮素含量之比(lignin∶N)是绿肥、秸秆和根茬腐解的首要影响因子,而年均温和干燥指数居于其次,表明农田土壤中植物性有机物料的腐解,物料性质较气候因子占主导。但对于腐解或半腐解状态的有机肥,其腐解已不受气候和物料性质的显著影响。此外,单一气候因子或物料性质对h1变异性的解释率往往不超过15%,气候和物料性质的综合解释率尚低于40%,表明要准确预测农田土壤有机物料的腐解过程,需要更多地重视区域或点位特征(例如,土壤理化和生物学性质等)的影响。

Decomposition of organic materials in cropland soils is critical to recycling of soil carbon（C）and nutrients. We collected data from the 56 published studies during 1980—2013 that have examined the decomposition of organic materials across China. Our objectives were to to quantify the fraction of C remaining after one year’s decomposition（h1）and to investigate the impact of types of organic materials（green manure,straw,root and manure）and agricultural regions（Northeast,Northwest,North and South China）. Overall,h1 ranged from 0.10 to 0.75 g g-1,with an average of 0.335 ± 0.005 g g-1 across China,and was significantly affected by types of organic materials and agricultural regions and their interactions. On the whole,in terms of h1,the four major types of organic materials displayed an order of green manure 〈 straw 〈 root and organic manure,and the regions,an order of South China ≈ North China 〈 Northwest China ≈ Northeast China. However,the regional variation of h1 was also affected by type of organic materials. For instance,h1 of straw,root and green manure were lower in North China than in South and Northeast China,while h1 of organic manure did not differ much between regions. On the other hand,h1 of organic materials also varied with the regions. For example,in humid and semi-humid Northeast,North and South China,h1 of root was higher than that of green manure and straw,while in the arid and semi-arid Northwest China,h1 did not differ much between types of organic materials,because of aridity. Step-wise regression analyses shows that lignin∶N ratio is the major factor regulating decomposition of straw,root and green manure,while mean annual temperature and aridity follows in the effect. However,decomposition of organic manure,which had already been decomposed or semi-decomposed,was not significantly affected by climatic factors,nor by quality（chemical composition）of the organic material. In addition,a singer factor,either of climate or of quality of organic materials,could maximally explain no more than 15% of the variability of h1,and the combination of climatic factors and quality of the organic materials could only explain less than 40% of the variability,which suggests that to predict accurately the decomposition processes of organic materials in cropland,more attention should be paid to impacts of the regional or site-specific characteristics,such as soil physic-chemical and biological properties.