耕作方式对华北冬小麦田土壤微生物生物量碳分布特征的影响

摘要

土壤微生物生物量碳(SMBC)反映了土壤有机碳(SOC)情况,其值大小代表了土壤肥力的高低,研究不同耕作方式SMBC的变化特征及其影响因素具有重要意义.试验于2001年在中国科学院栾城农业生态系统实验站开始,试验设置翻耕(CT)、旋耕(RT)、免耕(NT)三个处理.利用熏蒸提取-容量分析法研究了不同耕作处理2007-2008年冬小麦生育期的SMBC分布特征及影响因素.结果表明SMBC具有时空变化特征:在冬小麦生育期中,各SMBC处理均随着时间波动起伏,并在小麦返青期和扬花期达到峰值;空间分布上SMBC含量随土壤深度的增加而降低.不同耕作处理间差异显著,0～5cm 土层SMBC以NT最高,CT最低;5～10cm土层RT与CT相当,NT最低;10～20 cm土层以CT最高,NT最低;20～30cm各处理均较低,NT亦为最低.对不同处理SMBC层化率分析显示:NT具有明显的表层富集现象;RT处理0～10 cm SMBC分布均匀;CT处理0～20 cm SMBC分布均匀.对SMBC的影响因素分析表明:土壤有机碳是SMBC空间分布的主要影响因素,二者呈显著正相关.而土壤温度和土壤含水量是影响SMBC季节变化的主要外界因素.%Soil microbial biomass carbon (SMBC), an important indicator of soil fertility, is closely related to soil organic carbon (SOC) content. A field experiment was conducted to characterize the influences of tillage practices on SMBC. The study was established at the Luancheng Agro-Ecosystem Experimental Station in 2001 with three tillage practices under winter wheat: conventional tillage (CT), rotary tillage (RT), and no-tillage (NT). Soil samples were collected in the 2007-2008 crop seasons and fumigation-extraction method was used to measure SMBC under the tillage treatments. In winter wheat growing period, SMBC showed significant temporal and spatial variations. The peaks of SMBC were observed at the re-greening and blooming stages. SMBC content decreased with increasing soil depth. The highest and lowest SMBC values in the 0 ～ 5 cm appeared in the NT and CT treatments, respectively. In the 5 ～ 10 cm soil layer, the RT and CT treatments had equivalent SMBC contents, which were greater than that of the NT treatment. In the 10 ～ 20 cm soil layer, the highest and lowest SMBC values appeared in the CT and NT treatments,respectively. At soil depth greater than 20 cm, each treatment had low SMBC values. Significant SMBC stratification was observed under NT in the 0 ～ 30 layer. On the other hand, homogeneous SMBC concentration appeared in the 0 ～ 10 cm layer under RT and in the 0 ～ 20 cm layer under CT. SMBC concentration in the soil profile was closely related to soil organic carbon content, and soil temperature and water content were the nain environmental factors influencing the temporal changes of SMBC.