小滦河谷地土壤侵蚀速率的定量测算

Quantitative Estimation of Soil Erosion Rate in Xiaoluanhe River Valley

野外调查和地貌学、生物学分析表明,发生水土流失的坡面上生长的独树或树丛定点记录了坡面水土流失的全过程,可以作为定量测算坡面侵蚀速率的标志。因坡面侵蚀而悬空的树干基部高出当前地面的垂直距离,即为其生长期间坡面侵蚀的厚度;而树木的年轮记录提供了时间尺度。据此,测算出河北省承德市小滦河谷地无成片森林覆盖的亚黏土坡面,在1681～2010年期间的平均侵蚀速率为2.1 mm/a;而有冲沟发育的风沙土坡面,在1961～2010年期间的平均侵蚀速率达24.0 mm/a。

The results of field investigation and geomorphology, biology analysis showed that grove or tree alone growing on the soil and water loss slope could be used for quantitative estimation of slope surface erosion rate. The vertical distance from current slope surface to the impending trunk base was the erosion thickness of slope surface during their growth period. And tree growth ring provided a time scale. Accordingly, the measure of an average erosion rate on clay slope surface without for- est cover in Xiaoluanhe River valley, Chengde city, Hebei province in 1681~2010 was calculated as 2.1 mm/a; and on the sand clay slop surface developed from gaily, the average erosion rate in 1961~2010 was 24 mm/a.