坡耕地水土保持措施下黑土有机碳演变研究

Soil erosion has been the dominant factor of the sloping farmland induced the decrease of soil quality and productivity in the Mollisols region of Northeast China. The soil and water loss was greatly declined by the control of soil erosion, but the effect of soil and water conservation on the soil quality and productivity was/is a slow and long term process. Up to now, the systematic and scientific data was scarce to reveal the long-term effects, which couldn’t convincingly support the management of soil and water conservation. In this study, the average surface erosion modulus in a typical sloping farmland will be determined by 137Cs technique, and the SOC variation of 12-year between the year of 2004 and 2016 will be observed in 13 sloping farmland. The SOC variation after 10 years of soil erosion control will be compared in a typical sloping farmland. The 11-year SOC changes between the year of 2005 and 2016 will be cleared in Tongshuang small watershed by soil survey, and the SOC evolvement of 35-year will be figured out combined 137Cs technique. Our objectives are (1) to confirmed the soil loss and SOC spatial variation in the whole slope farmland; (2) to determine the SOC evolvement after 10-year soil erosion control in the field scale;(3) to figure out the SOC evolvement after 35-year soil erosion control in small watershed scale; (4) to analyze the actuating mechanism for SOC evolvement, and make sure the critical conditions SOC increased. The managements of soil and water conservation should be supported by the evaluation of the long-term SOC evolvement under soil erosion control in the Mollisols region of Northeast China.

水土流失已成为黑土坡耕地土壤质量退化和生产力下降的主要诱因，实施水土保持措施后水土流失显著降低，其对黑土质量和生产力的作用是一个缓慢长期的过程，目前该作用过程和效果缺乏系统科学数据，未能对黑土区水土保持建设提供有力支撑。本研究在已有的10年研究基础上，采用典型坡耕地调查测定、137Cs示踪技术、野外水土流失监测等方法，研究揭示黑土坡耕地（1）顺坡垄作坡耕地水土流失及土壤有机碳空间演变；（2）田块尺度水土保持实施10年全坡面土壤有机碳空间演变；（3）小流域尺度水土保持实施35年不同坡位不同水保措施下的土壤有机碳演变；（4）土壤有机碳演变的驱动机制及其恢复的临界条件。科学评价水土保持保土对农田黑土有机碳恢复功效，旨在为东北黑土区水土流失综合治理提供科技支撑。

水土流失已成为黑土坡耕地土壤质量退化和生产力下降的主要诱因，实施水土保持措施后 水土流失显著降低，其对黑土质量和生产力的作用是一个缓慢长期的过程，目前该作用过程和 效果缺乏系统科学数据，未能对黑土区水土保持建设提供有力支撑。本研究在已有的10年研究基础上，采用典型坡耕地调查测定、137Cs示踪技术、野外水土流失监测等方法，研究揭示黑土坡耕地（1）顺坡垄作坡耕地水土流失及土壤有机碳空间演变；（2）田块尺度水土保持实施 10年全坡面土壤有机碳空间演变；（3）小流域尺度水土保持实施35年不同坡位不同水保措施下的土壤有机碳演变。结果表明（1）13个1.5-13度典型坡面土壤SOM整体发生着降低，平均降低了3.01 g·kg-1，即降低6.77%，年平均下降0.56%，以2-5度SOM下降幅度最大。3.4度顺坡垄作坡耕地平均侵蚀速率为2481.57 t·km-2·a-1，坡上、坡中和坡下土壤有机质含量均下降，年均下降速率分别为0.50%、0.62%和0.17%，即顺坡垄作导致全坡面耕层土壤质量下降。（2）典型坡耕地变顺坡为等高垄作10年，SOM含量增加了2.61 g·kg-1，增加了8.4%，年均增长率为0.84%，以沉积最为严重的坡脚西侧增加最多25.1%，但土壤TN含量减少了0.04 g·kg-1，降低了2.8%，说明等高改垄虽然土壤碳缓慢增加，但土壤氮却出现了亏缺，需增施氮肥。（3）典型小流域实施水土保持11年内SOM由39.0 g/kg增加为41.3g/kg，年均增长速率为5.4‰。而实施水土保持前水土流失严重，SOM含量为34.4 g/kg，较垦前下降了42.7%，年均下降速率为15.8‰，实施水土保持措施后26年SOM含量增加了20.1%。本研究定量地揭示了顺坡垄作水土流失导致SOM下降速率、等高改垄提升SOM含量的速率、小流域尺度全面实施水土保持土壤增碳速率，对土壤侵蚀危害土壤质量以及水土保持对农田黑土有机碳恢复功效开展的科学评价，为东北黑土区水土流失综合治理提供科技支撑。