降雨与植被变化对川中丘陵区典型小流域侵蚀产沙的影响

第17卷　第4期2019年8月

中国水土保持科学

Science of Soil and Water Conservation

Vol.17　No.4Aug.2019

降雨与植被变化对川中丘陵区典型小流域侵蚀产沙的影响

付　滟1,郑江坤1†,任雨之1,王文武1,曾倩婷1,向明辉2,陈　鑫2,张云奇1,赵　鹏1

(1.四川农业大学林学院,水土保持与荒漠化防治四川省高校重点实验室,611130,成都;

2.遂宁水土保持试验站,629006,四川遂宁)

摘要:为了解年和次降雨尺度下植被变化对解家湾小流域侵蚀产沙的影响,运用RUSLE 模型计算小流域降雨侵蚀力,采用双累积曲线法和分离判别法分析侵蚀产沙变化的成因㊂根据植被调整和双累积曲线变化,分为农作物种植期(1986 1989)㊁经果林种植期(1990 2008)和搁荒期(2009 2016);以农作物种植期为基准期,经果林种植期侵蚀产沙量减少了80.24%,其中植被和降雨的贡献率分别为78%和22%,经果林使冠层覆盖增加,根系固土能力增强,并且梯田梗坎可减少产沙㊂以经果林种植期为基准期,搁荒期侵蚀产沙量增加79.52%,其中植被和降雨的贡献率分别为88%和12%,搁荒期引起的排水不畅会导致梯田梗坎大量溃坏,增加产沙量㊂流域产沙与植被覆盖大小和梯田埂坎是否完善有直接关系㊂植被覆盖在一定的降雨侵蚀力区间内减沙作用明显,但超过临界值时,植被减沙作用变弱㊂增加乔灌层㊁布设水土保持工程并进行有效田间管护可明显减少侵蚀产沙㊂关键词:梯田工程;植被变化;双累积曲线;输沙模数;川中丘陵区中图分类号:S157.1

文献标志码:A

文章编号:2096⁃2673(2019)04⁃0067⁃08

DOI :10.16843/j.sswc.2019.04.009

收稿日期:20180903　修回日期:20181023

项目名称:水利部公益性行业科研专项 水土保持生态效应监测与评价技术研究”(201501045);中国博士后科学基金面上项

目 四川紫色土土壤有机碳流失机理及对碳储量的影响”(2012M511938);国家自然科学基金 华北土石山区典型林分坡地径流形成机制研究”(41601028), 近50a 沂蒙山区大型水库泥沙来源及其对流域环境演变的响应”

(41671277)

第一作者简介:付滟(1997 ),女,本科生㊂主要研究方向:土壤侵蚀与水土保持㊂E⁃mail:1016521383@

†通信作者简介:郑江坤(1982 ),男,博士,副教授㊂主要研究方向:生态水文和水土保持㊂E⁃mail:jiangkunzheng@

Effects of rainfall and vegetation change on soil erosion and sediment yield

in typical small watershed in hilly area of central Sichuan Basin

FU Yan 1,ZHENG Jiangkun 1,REN Yuzhi 1,WANG Wenwu 1,ZEN Qianting 1,XIANG Minghui 2,

CHENG Xin 2,ZHANG Yunqi 1,ZHAO Peng 1

(1.Key Laboratory of Soil and Water Conservation &Desertification Combating of Sichuan Provincial Colleges and Universities,College of Forestry,Sichuan Agricultural University,611130,Chengdu,China;

2.Water and Soil Conservation Experiment Station of Suining City,629006,Suining,Sichuan,China)Abstract :[Background ]It is found that vegetation plays an important role in soil and water conservation.This paper is to understand the effect of vegetation change on soil erosion and sediment

yield in Xiejiawan watershed,a small watershed in hilly area of central Sichuan Basin,under annual and individual rainfall scales.[Methods ]Based on the data of rainfall and sediment yield of Xiejiawan watershed over 30years,RUSLE model was used to calculate the rainfall erosivity of the small bined Land⁃Use and Land⁃Cover Change (LUCC)with soil and water conservation engineering adjustment,the causes of soil erosion and sediment yield were quantitatively evaluated by the double

中国水土保持科学2019年cumulative curve method and the separation discriminant method during different periods in the small watershed.[Results]1)During1986-2016,rainfall and erosive rainfall in Xiejiawan watershed occurred mainly in June,July and August which accounted for80%of that in all the year.Therefore,soil and water conservation projects should be strengthened in summer.2)Interannual variability of rainfall and erosive rainfall were not obvious during1986-2016,meanwhile,annual mean sediment modulus during1990-2008was obviously less than the values during1986-1989and2009-2016.Soil erosion and sediment yield decreased dramatically when LUCC changed from farmland to orchard.The soil and water conservation engineering measures were destroyed seriously when the forest land was abandoned, resulting in the amount of soil erosion increased at initial stage of abandoned period and decreased gradually after the restoration of understory herbs at later stage of abandoned period.According to LUCC and the trend of double cumulative curve,the time period was divided into crop period(1986-1989), orchard period(1990-2008)and abandoned period(2009-2016).3)Taking crop period as the base period,the contribution rates of vegetation and rainfall on sediment reduction were78%and22%, respectively when crop was transformed into orchard,which indicated that planting orchard effectively reduced the sediment transport modulus in the small watershed.This was mainly due to the increase of canopy coverage enhanced soil consolidation capacity of roots,and the strengthened repair and management of terrace ridges.4)Taking orchard period as the base period,the contribution rates of vegetation change and rainfall on sediment increase were88%and12%,respectively in abandoned period.As the results of lacking land management and drainage,terrace ridges were damaged a lot, which increased sediment yield.Furthermore,sediment yield was positively correlated with rainfall during crop period.Sediment yield was directly related to vegetation coverage and the improvement of terrace ridge measures during orchard period and abandoned period.The sediment reduction effect of vegetation coverage was obvious in a certain range of rainfall erosivity.When the vegetation coverage exceeded the critical value,the sediment reduction effect of vegetation became weaker.[Conclusions]When other conditions remain unchanged,soil erosion and sediment yield is reduced significantly by increasing surface coverage.It plays an important guiding role in soil and water conservation in purple soil watershed by increasing tree and shrub layer,laying soil and water conservation projects,and effective field management.

Keywords:terrace project;vegetation change;double cumulative curve;sediment transport modulus; hilly area of central Sichuan basin

土壤侵蚀不仅造成土壤养分流失,还加剧地下水污染和湖泊等水体的富营养化㊂影响土壤侵蚀的因素包括降雨㊁地形地貌㊁土壤㊁植被覆盖等[1],对同一流域而言,其地形地貌和土壤性质是长期地质作用的产物,短期内变化较小,因而降雨和植被覆盖成为影响土壤侵蚀的关键[2]㊂降雨因素中,降雨量[34]㊁降雨历时[4]和降雨强度[45]都是流域产沙的主控因子㊂森林植被具有多层截持作用,减流减沙效果明显,具有较强的涵养水源和保持水土功能[6],增加和恢复地表植被,可降低土壤的侵蚀速率[78]㊂

尽管许多学者已在年尺度[6]和次降雨[910]尺度下研究小流域侵蚀产沙特征,但川中丘陵区年尺度和次降雨尺度下的土壤侵蚀规律研究较少㊂笔者通过分析小流域年尺度和次降雨尺度的产沙规律及其成因,可为该区土壤侵蚀防控提供一定参考㊂

1　研究区概况

解家湾小流域位于嘉陵江中下游重点治理区的四川省遂宁市安居区㊂流域集雨面积6.89hm2,平均纵比降29.2‰,海拔最低280m,最高331.6m,属典型盆中丘陵地貌㊂土壤为侏罗系遂宁组岩层发育而成的紫色土,土壤松散,抗冲刷和抗蚀能力均弱㊂主要农作物为玉米(Zea mays)㊁番薯(Ipomoea bata⁃tas)㊁普通小麦(Triticum aestivum)㊁蚕豆(Vicia fa⁃ba),主要经果林为柑橘(Citrus reticulata)㊁桃

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