乌兰布和沙漠东北部沙区人工林土壤钾素特征研究

通过对乌兰布和沙漠东北部沙区不同林地土壤样品的测定与分析,研究了林地土壤各形态钾素含量、相关性和垂直分异特征。结果显示:表层各形态钾素在各林地内呈不均衡分布。造林对表层土壤钾素具有不同程度的积累效应,特别是二白杨、小美旱以及固氮树种花棒、沙棘和沙枣;林地全钾含量中,各形态钾素所占比例不同,但平均97%以上的钾素植物难以直接利用;缓效钾是有效钾素非常重要的潜在给源。各林地有效性钾、速效钾和缓效钾含量绝大部分表层(0-20cm)高于下层(20-40cm),矿物钾和全钾主要决定于土壤母质,层次间差异很小。在干旱条件下,林地土壤含水量较高的树种以及固氮树种更有利于有效钾素的提升。各形态钾素间存在着不同程度的转化关系;有机质、CEC明显影响着各形态钾素的含量、转化及其有效性。整体而言,乔木提升有效性钾、速效钾和缓效钾含量稍优于灌木,但差异很小。因此,在沙区干旱条件下,建议推广对土壤质量提高和生态环境改善更具潜力的固氮沙生灌木。

Soil Potassium Characteristics on Planted Forest in the Northeast Sandy Area of Ulanbuh Desert

Through determining and analyzing soil samples of different forestlands in the northeast sandy area of Ulanbuh desert, characteristics on contents, correlations and vertical distribution of soil various potassium were studied. The results showed that the contents of various potassium of topsoil(0-20 cm) were imbalanced. Afforestation had accumulation effects on various potassium of topsoil in varying degrees, especially Populus gansuensis C., Populus simonii × (Populus pyrarnidalis + Salix matsudana) cv. Poplaris and nitrogen fixation trees (Hedysarum scoparium Fisch. , Hippophae rhamnoides L. and Elaeagnus angustifolia L.). The proportion of various potassium accounting for total potassium(TK) content were different,but more than 97% of the TK were difficult to be directly used by plants. Slowly available potassium(SAK)were very important potential sources of available potassium(AK). The contents of AK, readily available potassium(RAK) and SAK of topsoil(0-20 era) were mostly higher than the subsoil(20-40 cm), and the contents of mineral potassium(MK) and TK depended mainly on soil parent material, and their differences in layers were very small. Under drought conditions, tree species of higher soil water content and nitrogen fixation trees were more beneficial to improvement of AK and RAK. There were conversion relationships among various potassium in varying degrees. Soil organic matter and cation exchange capacity(CEC) influenced obviously on the contents, transformations and effectiveness of various potassium. On the whole, the tree, enhancing contents of AK, RAK and SAK, was slightly better than the shrub, but small differences. Thus, in drought sandy area, sandy shrubs of nitrogen fixation with the potential for enhancing soil quality and improving eco-environment should be extended widely.