设置6块样地对河北省张北地区杨树林分枯稍的原因进行了调查,结果表明样地Ⅱ和样地Ⅳ内,枯稍程度与树高的相关性在0.05的水平上均达到了显著相关,而枯稍与胸径的相关性在样地Ⅱ内达到了显著相关,在样地Ⅳ内相关性不显著;被调查的6块样地有5块样地土壤剖面中存在钙积层,它阻碍了根系向下生长,杨树在该土壤条件下不能继续正常生长,是杨树枯稍的一个重要原因;杨树林龄过大,树势较弱,地下水紧缺以及虫害危害对枯稍也有影响。我们认为,在更新整地时,挖穿钙积层更有利于林分生长;选择造林树种时,尝试用采伐周期更长、适生性更好的樟子松和榆树造林,或可取得更佳的生态效益;该地区应做好森林防虫工作,并严格控制农业生产用水。
To understand the reasons for poplar degeneration with different degrees in Zhangbei,we investigated the poplar forest stands.Results suggest that in plot Ⅱ and plot Ⅳ,the top dry degree had significant correlation with tree height in a certain level.But when the top dry degree and the diameter at breast height had significant correlation in plot Ⅱ,there was no significant correlation in plot Ⅳ.In all the 6 plots investigated,5 had tepetate in their soil profiles.The tepetate kept root system from growing in soil,it was a main top dry factor.As the forest age was too old and underground water was decreasing sharply,the trees were really weak,which were easily attacked by insects.
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