摘要
为了探究不同放牧制度对草原地表径流和各形态氮流失特征的影响,以及氮流失过程中主要的影响因素,以呼伦贝尔砂质土壤草地为研究对象,分别在实行自由放牧、轮牧、休牧3种放牧制度的草地,调查采集主要植被及土壤特征数据,并进行25.2、44.4、64.8、90 mm·h^−1雨强的降雨模拟实验。结果表明:地表径流与降雨强度和载畜率存在显著正相关,与植被覆盖程度呈负相关。3种放牧草地中,自由放牧草地氮流失最多,轮牧草地次之,休牧草地流失最少。随降雨强度的增加,径流中氮流失量增加显著(P<0.05),而径流中氮浓度增加不显著(P>0.05)。不溶态氮是降雨径流中氮的主要流失形式,在同一放牧草地,高强度的降雨会引起溶解态氮流失比例下降,不溶态氮的流失比例上升。各形态氮流失量的主要影响因素为径流速率、径流量和产流时间。利用简化参数的有效混合深度模型对土壤氮迁移过程进行模拟,不完全混合模型模拟效果优于完全混合模型,模拟精度较高,误差不超过5%。因此,适当的将呼伦贝尔草原自由放牧草地向休牧和轮牧草地转变,将有利于减少土壤氮的损失,可以为放牧制度的选择和管理提供基础信息。
Soil erosion makes an important contribution to damaging and degrading the ecological environment and the loss of nutrients in the soil erosion process results in a decrease in soil fertility.The process and degree of damage from soil and water loss will vary under different grazing systems because of different vegetation coverage rates,as will the types of nitrogen loss.Understanding this information is important to guide the development of adaptable management practices and governance polices for ecological and environmental protection in Steppes.In this study,we chose to research a Steppe ecosystem with a sandy soil in the Hulun Buir Steppes of northern China.We studied three grazing systems:no grazing,rotation grazing,and free grazing.We c ollected soil samples and investigated vegetation growth conditions in all three grazing systems.We used a rainfall simulator to simulate four different rainfall intensities 25.2,44.4,64.8 and 90 mm·h^−1.Each rainfall intensity experiment was replicated in the same grazing pasture three times.In each simulated rainfall experiment,we collected all the runoff to test runoff volume.When the rainfall began,we collected runoff samples every 3 min a total of eight times.We tested runoff,sediments,total nitrogen,nitrate nitrogen and ammoniacal nitrogen for each runoff sample and explored the mechanism of nitrogen loss via rainfall runoff.The results showed that stocking rates had important effects on reducing surface runoff between different grazing systems.Surface runoff was significantly and positively related to rainfall intensity and stocking rate.Under the same rainfall conditions,surface runoff was negatively associated with vegetation coverage.Nitrogen runoff losses were highest from free grazing grassland,followed by rotation grazing grassland.The no grazing grassland had the smallest nitrogen runoff losses.Higher rainfall intensity increased the loss of nitrogen,but no significant correlations were observed between higher rainfall and the nitrogen concentration of runoff.Undissolved nitrogen was the main form of nitrogen in the runoff.In the same grassland,the percentage of dissolved nitrogen in total nitrogen in runoff decreased with higher rainfall,and undissolved nitrogen levels increased.The amounts of nitrogen loss were affected by the different grazing methods;however,grazing methods did not change the underlying rules governing nitrogen runoff losses.Factors including runoff rate,runoff volume,and runoff-yielding time were the main reasons for the various forms of nitrogen runoff losses.We use the effective mixing depth,a mathematical model,to simulate the process of solute transport in soil.The experimental data fit showed that the incomplete mixing model fitted the data better than the complete mixing model.The incomplete mixing model had higher simulated precision,with an error less than 5%.These results could provide important baseline information for choosing grazing methods and grassland management practices and could facilitate the reduction of nitrogen runoff losses and encourage the development of adaptable grazing methods.This study provides essential baseline information for the choice of different grazing methods and management practices.
作者
樊才睿
张成福
史小红
孙标
FAN Cairui;ZHANG Chengfu;SHI Xiaohong;SUN Biao(Jining Normal University,Ulanchab 012000,China;Inner Mongolia Agricultural University,Hohhot 010018,China)
出处
《生态环境学报》
CSCD
北大核心
2020年第5期951-960,共10页
Ecology and Environmental Sciences
基金
国家自然科学基金项目(51779118)
内蒙古自然科学基金博士基金项目(2019BS05027)
内蒙古自治区高校科研项目(NJZY19239)
集宁师范学院博士基金项目(jsbsjj1802)
集宁师范学院科研项目(jsky2018037)。
关键词
放牧制度
人工模拟降雨
总氮
铵态氮
硝态氮
grazing systems
simulated rainfall
total nitrogen
nitrate nitrogen
ammonium nitrogen
