红壤坡地水力侵蚀下土壤有机碳迁移分布规律及流失过程模拟研究

发布时间：2018-11-22 17:33

【摘要】：土壤侵蚀是我国严重的环境问题之一,它不仅引起水土流失,造成土壤养分含量减少,导致土地生产力下降,使土地资源遭受严重破坏,而且由其引起的土壤有机碳(soil organic carbon,SOC)迁移流失,对SOC固定和区域碳循环产生极大影响,进而改变全球气候状况。南方红壤丘陵区是水力侵蚀严重的地区,由土壤侵蚀造成的SOC迁移再分布是生态环境研究的热点问题。本研究通过在2 m(宽)×5 m(长)野外径流小区进行的模拟降雨试验获得数据,试验共设计6场降雨,翻耕4场降雨(100,80,40和30 mm/h),免耕2场降雨(80和30 mm/h),分析小区尺度水力侵蚀影响下径流、泥沙、SOC迁移流失特征及其相互之间的关系和降雨前后SOC坡面与剖面分布差异,以探究水力侵蚀对SOC迁移再分布的影响,同时结合坡面输沙模型与SOC流失计算理论对SOC流失过程进行模拟。研究结果表明:(1)模拟降雨后,表层SOC坡面分布格局发生了显著变化,坡中SOC含量减少,坡下SOC含量增加。同时,水力侵蚀改变SOC的剖面分布格局,SOC发生垂向迁移,表层0~20 cm SOC含量减少,深层20~40 cm SOC含量增加。雨强和耕作方式影响SOC的再分布,雨强越大,SOC再分布越显著。翻耕方式下SOC再分布比免耕方式下明显。(2)坡面产流过程对泥沙态有机碳流失过程具有明显影响,除大雨强条件下泥沙态有机碳流失速率在10~30 min呈现短时间峰值外,各径流小区泥沙态有机碳流失过程与坡面产流过程总体变化趋势基本一致,均表现为产流开始后,其流失率随降雨历时延长而增加,而后逐步趋于平稳,但坡面产流过程对径流有机碳流失过程无明显影响;坡面径流率大小影响SOC流失,坡面径流率变化能解释80%SOC流失的变化,坡面径流率与SOC流失呈线性正相关关系,且坡面径流率对泥沙态有机碳流失的影响比其对径流有机碳流失的影响更明显。泥沙态有机碳含量与泥沙流失量之间呈显著立方拟合关系(除大雨强翻耕与小雨强免耕);泥沙态有机碳流失量与泥沙流失量呈显著线性相关关系。(3)坡面SOC流失模型能够有效地应用于南方红壤丘陵区次降雨过程中坡面SOC流失的模拟中,且具有较好模拟效果,SOC流失率模拟平均误差在30%左右,决定系数在0.85以上;同时模拟结果表明泥沙和SOC流失过程在坡面径流侵蚀影响下呈现波动状态,表现为产流开始后10 min泥沙和SOC流失呈增加趋势,其后在波动中逐渐趋于平稳;通过比较翻耕和免耕条件坡面径流输沙和SOC流失模型,结果表明,翻耕导致的泥沙和SOC流失率大于免耕。
[Abstract]:Soil erosion is one of the serious environmental problems in China. It not only causes soil and water loss, but also results in the decrease of soil nutrient content, the decrease of land productivity and the serious destruction of land resources. The soil organic carbon (soil organic carbon,) caused by soil erosion is also caused by soil erosion. SOC) transport loss has a great impact on SOC fixation and regional carbon cycle, thus changing the global climate. The red soil hilly region in southern China is a region with serious hydraulic erosion. The SOC migration and redistribution caused by soil erosion is a hot issue in the study of ecological environment. In this study, the simulated rainfall data were obtained in a 2 m (wide) 脳 5 m (long) field runoff plot. A total of 6 rainfall events were designed, 4 tilling rainfall (40 and 30 mm/h) and 2 no-tillage rainfall (80 and 30 mm/h) were designed. The characteristics of runoff, sediment, SOC transport and loss under the influence of hydraulic erosion on plot scale and their relationship with each other, and the distribution difference of SOC slope and profile before and after rainfall were analyzed in order to explore the influence of hydraulic erosion on the redistribution of SOC migration. At the same time, combined with slope sediment transport model and SOC loss calculation theory, the process of SOC loss is simulated. The results showed that: (1) after simulated rainfall, the distribution pattern of surface SOC slope changed significantly, the SOC content in the slope decreased and the SOC content in the slope increased. At the same time, hydraulic erosion changed the profile distribution pattern of SOC, the vertical migration of SOC occurred, the content of 20 cm SOC in surface layer decreased, and the content of 20 cm SOC in deep layer increased. The redistribution of SOC was influenced by rain intensity and tillage method. The higher the rain intensity was, the more significant the redistribution of SOC was. The redistribution of SOC in tillage was more obvious than that in no-tillage. (2) the runoff process on the slope had a significant effect on the loss process of sediment organic carbon, except for the short peak value of sediment organic carbon loss rate at 1030 min under the condition of heavy rain. The process of sediment organic carbon loss in each runoff plot is basically consistent with the overall change trend of runoff production on the slope, which shows that the loss rate increases with the increase of rainfall duration after the beginning of runoff production, and then tends to steady gradually. However, runoff production on the slope has no obvious effect on the loss of organic carbon from runoff. The magnitude of slope runoff rate affects SOC loss, the variation of slope runoff rate can explain the change of 80%SOC loss, and the slope runoff rate has a linear positive correlation with SOC loss. The effect of slope runoff rate on sediment organic carbon loss is more obvious than that on runoff organic carbon loss. There was a significant cubic fitting relationship between sediment organic carbon content and sediment loss (except heavy tillage in heavy rain and no-tillage in light rain). There is a significant linear correlation between sediment organic carbon loss and sediment loss. (3) the slope SOC loss model can be effectively applied to the simulation of SOC loss on the slope in the red soil hilly region of southern China, and has a good simulation effect. The simulated average error of SOC loss rate is about 30%, and the determining coefficient is more than 0.85; At the same time, the simulation results show that the process of sediment and SOC loss is fluctuating under the influence of runoff erosion on the slope, which shows that the sediment and SOC loss increase at 10 min after the beginning of runoff production, and then tend to steady gradually in the fluctuation. The sediment and SOC loss rates caused by tillage were higher than that of no-tillage by comparing runoff sediment transport and SOC loss model with no-tillage conditions.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S157

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