黄土高原植被演替不同阶段植物系数的变化与适应性评价

用4年长期定位试验资料,利用植物系数、蒸散量、土壤含水量和土壤水分对植物的有效性等指标,研究了黄土高原植被群落不同演替阶段(草本群落→灌木群落→早期森林群落→顶级群落)的耗水特性与生态适应性。结果表明:不同演替阶段,群落实际蒸散量主要受降水控制,群落间差异不显著(P＞0.05);土壤含水量是早期森林群落明显高于其它群落,草本群落明显高于灌木群落(P＜0.05);植物系数是灌木群落＞草本群落＞乔木群落,而顶级群落大于早期森林群落;土壤水分对植物的有效性是早期森林和顶级群落明显高于草本和灌木群落(P＜0.05)。因此,进行植被建设不但要考虑植物系数还要考虑土壤水分对不同植物的有效性。

Plant Coefficient Variation and Adaptability Evaluation of Different Succession Communities on the Loess Plateau

Many studies has been taken on calculating the vegetation ecological water requirement using plant coefficient(K_p)and potential evapotranspiration(PET),while attention is rarely paid to restriction of soil water deficit and very little information is available on K_p of different communities especially on the Loess Plateau. According to the succession sequence of vegetation in Ziwuling forest region of the Loess Plateau, herbaceous community, shrub community, early forest community and climax forest community were selected to investigate the water consumption and ecological adaptability of different succession stage, considering the soil water stress simultaneously. Using the data getting from long-term experiments in situ, plant coefficients of different communities were calculated in this study, the actual evapotranspiration(ET_a)and mean soil water contents during the growing stage for five representative communities were compared, and the impacts of soil water change on water absorption of plant roots and soil water availability were analyzed.The results showed that,in different succession stages of vegetation,ET_a of communities was mainly influenced by precipitation, with no notable distinction among different communities(P＞0.05); soil water content of the early stage of forest community was significantly higher than other communities, and that of the herbaceous community was clearly higher than the two shrub communities(P＜0.05); the plant coefficients of the shrub communities were the highest, that of herbaceous community was the second and that of climax community was higher than early stage of forest community; the two forest communities had significantly higher soil water availability than the herbaceous and shrub communities (P＜0.05),which might consume more soil water and aggravate the drought of soil.Therefore, not only the plant coefficients but also the soil water availability should be considered in vegetation construction. And the soil water restriction factor should not be ignored in the calculation of vegetation ecological water requirement and the adaptability evaluation.