紫色土坡耕地C、N与微生物C、N变化及其耦合特征

Changes and coupling of C and N in hillslope cropland of purple soil and microbial biomass

以紫色土坡耕地为研究对象,综合探讨不同坡度变化下植被/裸地小区以及长期不同施肥处理下紫色土坡耕地土壤C、N与微生物C、N变化及其耦合特征.结果表明：植被覆盖小区总有机碳（TOC）变化为49.0~63.9 g·kg-1,裸地TOC变化为47.4~50.8 g·kg-1,并随坡度增加逐渐下降;植被小区微生物碳（MBC）为0.9~3.45 g·kg-1,而裸地小区MBC仅为0.1~0.68 g·kg-1.不同施肥处理下坡耕地土壤TOC为57.0~64.5 g·kg-1,施加有机肥处理土壤的TOC含量高于其他施肥方式.植被小区总氮（TN）为2.6~4.2 g·kg-1,裸地小区TN含量为1.6~5.5 g·kg-1,植被小区微生物氮（MBN）高于裸地小区;不同施肥处理下TN含量随土层深度增加呈显著下降,有机肥和秸秆与化肥配施相比单一施加氮肥对土壤MBN的增加更为显著.有机肥及其与化肥配施下土壤C/N比为10~17,而秸秆及其与化肥配施土壤C/N比为8~13,单施氮肥为12左右,增施有机肥和秸秆还田有利于保持土壤C/N的稳定提高;同时,施肥有利于提高微生物熵,增加土壤中活性有机碳的比例;紫色土坡耕地MBC和TN具有显著的耦合特征（R2=0.66）.

The aim of this paper is to discuss the changes and coupling of C and N in the hillslope cropland of purple soil and microbial biomass under different gradient for planted and bare plot and long-term fertilization treatment. The results show that the range of TOC in planted plot is 49. 0~ 63. 9 g·kg-1and in bare plot is 47. 4 ~ 50. 8 g·kg-1,both of which decrease with increasing gradients. The range of MBC in planted plot is 0.9 ~3.45 g·kg-1,while in bare plot is only0.1 ~0.68 g·kg-1. The range of TOC under different fertilization treatment is 57. 0 ~ 64. 5 g·kg-1,and the TOC is significantly higher under application of organic fertilizer than other fertilizer. The TN in planted plot is 2. 6 ~ 4. 2 g·kg-1and in bare plot is 1. 6 ~ 5. 5g·kg-1. Meanwhile,the MBN is higher in planted plot than in bare plot. The TN under different fertilization treatment significantly decreases withincreasing soil depth,and the increase on MBN under organic fertilizer and straw combined with chemical fertilizer is notable. The ratio of C and N under combination of organic and chemical fertilizers is between 10 and 17,under combination of straw and chemical fertilizer is between 8 and 13,and under single application of N is 12. Increase in organic fertilizer and straw return would be helpful for maintaining and enhancing soil C /N. Meanwhile,fertilization treatment would be helpful for increasing microbe entropy and enhancing the proportion of active soil organic C to TOC. The coupling between MBC and TN in the hillslope cropland of purple soil is notable,with R2coefficient of 0. 66.