蔗区小流域泥沙有机碳入河负荷的时空变化特征及其影响因素

Factors Influencing Spatial and Temporal Characteristics of Organic Carbon Loading to Rivers From Sediment in Small Watersheds in Sugarcane Areas

[目的]针对广西红壤区典型小流域坡耕地甘蔗土壤有机碳流失问题,探究其流失时空特征和影响因素,解析流域泥沙有机碳在甘蔗不同生长时期入河负荷时空变化,为揭示自然降雨侵蚀下土壤有机碳流失的影响机制提供科学依据。[方法]试验区位于广西壮族自治区崇左市扶绥县客兰水库水源区那辣小流域,流域分为下游子流域(S 1)和上游子流域(S_(2),S_(3))。利用无人机技术和径流泥沙自动监测—采样系统对甘蔗4个生长时期(苗期、分蘖期、伸长期和成熟期)入河泥沙有机碳及植被覆盖度等进行监测,并利用皮尔逊相关分析,确定入河泥沙有机碳与降雨径流、植被覆盖度和施肥等影响因素的关系。[结果]①甘蔗苗期的流域泥沙有机碳入河负荷占整个生长期总流失量的61.1%,显著高于其他生长期,其特征为苗期(5.1 kg/hm^(2))>成熟期(1.6 kg/hm^(2))>伸长期(1.4 kg/hm^(2))>分蘖期(0.3 kg/hm^(2))。②流域降雨径流和植被覆盖度与泥沙有机碳入河负荷呈极显著相关,分别解释了泥沙有机碳入河负荷生长期变化的45%和54%;而流域施肥和土壤容重与泥沙有机碳入河负荷呈显著相关,分别解释了泥沙有机碳入河负荷生长期变化的79%和36%。[结论]流域入河泥沙有机碳流失变化主要是由降雨径流、植被覆盖度、施肥和土壤容重所引起。在蔗区小流域,通过增加植被覆盖以减少地表径流的冲刷及调控施肥时间,对降低土壤有机碳流失具有重要作用。

[Objective]The spatial and temporal characteristics and influencing factors of soil organic carbon loss from sugarcane in a typical small watershed in the red soil area of Guangxi Zhuang Autonomous Region were determined,and the spatial and temporal changes of organic carbon from watershed sediment entering the river during different growth periods of sugarcane were analyzed in order to identify the factors influencing soil organic carbon loss under natural rainfall erosion.[Methods]The experimental area was located in the Nala sub-basin of the water source area of Kailan Reservoir at Fusui County,Chongzuo City,Guangxi Zhuang Autonomous Region.The watershed was divided into the lower sub-basin(S 1)and the upper sub-basins(S_(2)and S_(3)).The organic carbon of incoming sediment and vegetation cover were monitored during four growth periods(seedling,tillering,elongation,and maturity)of sugarcane using UAV technology and an automatic runoff sediment monitoring-sampling system.Pearson correlation analysis was used to determine the relationship between organic carbon of incoming sediment and influencing factors such as rainfall runoff,vegetation cover,and fertilizer application.[Results]①The organic carbon load of sediment into the river during the seedling stage of sugarcane accounted for 61.1%of the total loss during the entire growing season,and this value was significantly greater than values observed in the other growing periods.Organic carbon load followed the order of seedling stage(5.1 kg/hm^(2))>maturity stage(1.6 kg/hm^(2))>elongation stage(1.4 kg/hm^(2))>tillering stage(0.3 kg/hm^(2));②rainfall runoff and vegetation cover were significantly correlated with organic carbon loss from incoming sediment,explaining 45%and 54%,respectively,of the variation in organic carbon loss from incoming sediment during the growing season.Fertilizer application and soil bulk density were significantly correlated with organic carbon loss from incoming sediment in the watershed,explaining 79%and 36%,respectively,of the variation in organic carbon loss from incoming sediment during the growing season.[Conclusion]Studies have shown that organic carbon loss from watershed sediments is mainly influenced by rainfall runoff,vegetation cover,fertilizer application,and soil bulk density.In small watersheds in sugarcane areas,increasing vegetation cover to reduce surface runoff and regulating the timing of fertilizer application can play an important role in reducing soil organic carbon loss.