样点数量对林区土壤水分动态测定精度的影响

Effect 6f Number of Sampling Points on the Estimating Precision of Dynamic State of Forest Soil AYater on Loess Plateau

为了保证土壤水分动态的测定精度对森林土壤水分变异性进行了研究,以合理确定样点数。结果表明,森林土壤水分的变异主要来源于林地土壤条件的变化及树冠对降雨的不均匀截留,且随季节而变化。在研究地区,土壤水分的变异系数在6～20％,要使土壤水分动态的测定精度高于0.90,测定重量含水量及容重的样点数须分别不少于10个及8个。对林木分布不均或土壤条件变化较大的林地,土壤水分变异系数更大,所需的样点数也更多。

The number of sampling points on variation of forest soil were determined for given estimating precisions of dynamic state of forest soil water. The results showed that the variation of forest soil water was caused mainly by variations of forest soil conditions and uneven interception of rainfall by tree crowns that, varies with seasons. In forest region of loess plateau, the variation coefficient of so:l water was 6 to 20%. The estimating precision of dynamic state of soil water could be higher than 0.90 only when sampling points for measuring weight soil water content and volume weight of soil were no less than 10 and 8 separati vely. As the variation coefficient of soil water was greater on uneven distributed forest land or where its soil conditions varied more orominently, more sampling points were required to satisfy the given estimating precision.