黄淮海平原两种不同林龄杨树防护林对麦田土壤水分及蒸散的影响

Effect of two different aged poplar shelterbelt on evapotranspiration and soil water of wheat field in Huang-Huai-Hai Plain of China

通过观测黄淮海平原黑龙港流域12 a和24 a林龄、长500 m、宽250 m的杨树防护林网内农田及旷野(CK)农田土壤水分和蒸散量,分析了防护林水分效应的年代变化特征,结果表明:在小麦拔节-乳熟期间,对比CK,12 a和24 a林龄防护林可使0～200 cm土层土壤贮水量分别提高7.8%,1.9%,可使小麦蒸散量分别降低19.1%,25.0%.12 a林龄时,在距离林带0～10 m范围内的土壤贮水量低于CK(简称负效应区),该范围外的土壤贮水量则高于CK(简称正效应区),24 a林龄时在距离林带0～15 m范围内为负效应区、此范围外为正效应区.在上述2种林龄期,防护农田内小麦蒸散量随距林带距离的变化均呈抛物线状分布趋势.在0～2H(H为树高)范围内,防护林对小麦蒸散的降低作用尤为显著,故对因树木根系吸水所导致的林带附近农田土壤水分下降的状况具有重要的缓解作用.

In this study, the evapotranspiration and soil water were observed in the wheat field protected by poplar shelterbelt which was 500 m long and 250 m wide and in the open （CK） during wheat jointing-early ripeness period in Heilonggang basin of Huang-Huai-Hai Plain when the trees were 12- year and 24-year old respectively, and historical variations of water effects of the shelterbelt were evaluated. The results suggested that： 12-year and 24-year aged shelterbelt increased soil water storage in 0-200 cm layer by 7.8% , 1.9% respectively, and reduced evapotranspiration by 19.1% , 25.0% respectively; In the field protected by 12-year aged shelterbelt, soil water decreased in soil 0 - 10.0 m from the shelterbelt, which was called negative water effects zone （NWEZ） comparing with CK, and raised in the other zone called PWEZ happened in soil 0 - 15 positive water effects zone （PWEZ）. And by 24-year aged shelterbelt, 0 m from the shelterbelt; Evapotranspiration variation with the distance from the shelterbelt demonstrated parabolic curve trend at the above tree aged stage, and significantly decreased in 0-2. OH compared with CK （H： the tree height）, that helped ease soil water stress posed by tree root＇s uptaking water nearby shelterbelt.