陕北黄土高原杜松疏林草原初步研究

PRELIMINARY STUDIES ON THE JUNIPERUS RIGIDA OPEN WOOD IN THE LOESS PLATEAU OF NORTHERN SHAANXI PROVINCE

陕北长城沿线以南至延安以北为森林草原地带(图1)。疏林草原是森林草原植物群落分类最高单位,旱中生和中旱生草本植物组成的草甸草原上稀疏分布着一些旱中生矮乔木,乔木盖度不超过20％,更多情况下不超过5％,对群落内环境不起明显作用。灌木多为旱中生,优势度很小。杜松(Juniperus rigida)疏林草原是陕北黄土高原上森林草原地带重要类型之一,为“三北”防护林建设工程的自然样板和遵循的自然规律。

The Juniperus rigida open wood is the initial plant community on bare area of forest-steppe zone in the Loess Plateau of northern Shaanxi Province. There are two succession periods: xeromorphic steppe plants are dominant in the earlier period, such as Stipa sp, Festuca ovina, Thymus mongolicua and Atemisia frigida, etc.; xero-mesophytes are dominant in the later period, such as Atemisia giraidii, A, gmelinii and Lespedeza davurica, etc. Since soil condition is improved by the plant communty of earlier period, the plants of later period are developing, which is accompanied by soil change from drought to mesophytezation, so the fundamental driving force of the succession is a dynamic of edaphic internal cause succession under the action of plant communities.