【摘要】：土壤侵蝕是我國(guó)嚴(yán)重的環(huán)境問(wèn)題之一,它不僅引起水土流失,造成土壤養(yǎng)分含量減少,導(dǎo)致土地生產(chǎn)力下降,使土地資源遭受?chē)?yán)重破壞,而且由其引起的土壤有機(jī)碳(soil organic carbon,SOC)遷移流失,對(duì)SOC固定和區(qū)域碳循環(huán)產(chǎn)生極大影響,進(jìn)而改變?nèi)驓夂驙顩r。南方紅壤丘陵區(qū)是水力侵蝕嚴(yán)重的地區(qū),由土壤侵蝕造成的SOC遷移再分布是生態(tài)環(huán)境研究的熱點(diǎn)問(wèn)題。本研究通過(guò)在2 m(寬)×5 m(長(zhǎng))野外徑流小區(qū)進(jìn)行的模擬降雨試驗(yàn)獲得數(shù)據(jù),試驗(yàn)共設(shè)計(jì)6場(chǎng)降雨,翻耕4場(chǎng)降雨(100,80,40和30 mm/h),免耕2場(chǎng)降雨(80和30 mm/h),分析小區(qū)尺度水力侵蝕影響下徑流、泥沙、SOC遷移流失特征及其相互之間的關(guān)系和降雨前后SOC坡面與剖面分布差異,以探究水力侵蝕對(duì)SOC遷移再分布的影響,同時(shí)結(jié)合坡面輸沙模型與SOC流失計(jì)算理論對(duì)SOC流失過(guò)程進(jìn)行模擬。研究結(jié)果表明:(1)模擬降雨后,表層SOC坡面分布格局發(fā)生了顯著變化,坡中SOC含量減少,坡下SOC含量增加。同時(shí),水力侵蝕改變SOC的剖面分布格局,SOC發(fā)生垂向遷移,表層0~20 cm SOC含量減少,深層20~40 cm SOC含量增加。雨強(qiáng)和耕作方式影響SOC的再分布,雨強(qiáng)越大,SOC再分布越顯著。翻耕方式下SOC再分布比免耕方式下明顯。(2)坡面產(chǎn)流過(guò)程對(duì)泥沙態(tài)有機(jī)碳流失過(guò)程具有明顯影響,除大雨強(qiáng)條件下泥沙態(tài)有機(jī)碳流失速率在10~30 min呈現(xiàn)短時(shí)間峰值外,各徑流小區(qū)泥沙態(tài)有機(jī)碳流失過(guò)程與坡面產(chǎn)流過(guò)程總體變化趨勢(shì)基本一致,均表現(xiàn)為產(chǎn)流開(kāi)始后,其流失率隨降雨歷時(shí)延長(zhǎng)而增加,而后逐步趨于平穩(wěn),但坡面產(chǎn)流過(guò)程對(duì)徑流有機(jī)碳流失過(guò)程無(wú)明顯影響;坡面徑流率大小影響SOC流失,坡面徑流率變化能解釋80%SOC流失的變化,坡面徑流率與SOC流失呈線性正相關(guān)關(guān)系,且坡面徑流率對(duì)泥沙態(tài)有機(jī)碳流失的影響比其對(duì)徑流有機(jī)碳流失的影響更明顯。泥沙態(tài)有機(jī)碳含量與泥沙流失量之間呈顯著立方擬合關(guān)系(除大雨強(qiáng)翻耕與小雨強(qiáng)免耕);泥沙態(tài)有機(jī)碳流失量與泥沙流失量呈顯著線性相關(guān)關(guān)系。(3)坡面SOC流失模型能夠有效地應(yīng)用于南方紅壤丘陵區(qū)次降雨過(guò)程中坡面SOC流失的模擬中,且具有較好模擬效果,SOC流失率模擬平均誤差在30%左右,決定系數(shù)在0.85以上;同時(shí)模擬結(jié)果表明泥沙和SOC流失過(guò)程在坡面徑流侵蝕影響下呈現(xiàn)波動(dòng)狀態(tài),表現(xiàn)為產(chǎn)流開(kāi)始后10 min泥沙和SOC流失呈增加趨勢(shì),其后在波動(dòng)中逐漸趨于平穩(wěn);通過(guò)比較翻耕和免耕條件坡面徑流輸沙和SOC流失模型,結(jié)果表明,翻耕導(dǎo)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.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：S157

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