We selected 30 (half-mature), 40 (near-mature), 50 (mature) years old Pinus tabuliformis plantations, respective-ly, to make thinning treatment according to the intensities of low, medium, heavy and control with the cutting percents of (30.4%-35.7%), (42.9%-45.4%), (55.8%-58.8%) and 0%.The investigation was conducted to investigate the response of the undergrowth vegetation of P.tabuliformis plantation at different stand ages to different thinning after two years thinning.At the beginning (within two years), the undergrowth shrub and herb species increase along with the en-hancing thinning intensity.The heavy intensity thinning increases the number of meso-xerophytes and mesophytes vegeta-tion, and decrease xero-mesophytes plants.It also raises the number of the dominant species of the undergrowth vegetation and enhances the coverage and density of the undergrowth with the increasing intensities .And the vegetation layer vertical structure became much clearer.The diversity index of the shrub and herb species wad is improved, Shannon-Wiener index is more sensitive to its effect, and the biomass of the undergrowth vegetation layer is increased with the thinning enhan-cing.Thinning has significant effects on the development of the undergrowth vegetation of P.tabuliformis plantation and the heavy thinning intensity (55.8%-58.8%) is more favorable among the short-term effects.%分别选取中龄林（30 a）、近熟林（40 a）和成熟林（50 a）的油松人工林按株数量进行弱度（30．4％～35．7％）、中度（42．9％～45．4％）和强度（55．8％～58．8％）间伐并设置对照（0）处理，研究间伐后2 a间各林龄油松人工林下植被对不同间伐强度的响应情况。结果表明：间伐初期（2 a内），林下灌木、草本物种数均随间伐强度的增强而增多，强度间伐使林下旱中生植物减少，中旱生、中生植物增多；间伐增加了油松林下植被层优势种数量，林下植物密度、总盖度随间伐强度增强而增大，植被层垂直结构分化更加明显；间伐提高了林下灌木、草本层生物多样性指数，Shannon-Wiener指数对间伐效果表现更为敏感，林下植被层生物量随间伐强度增强而增加。间伐对油松人工林林下植被发育的影响是显著的，短期影响效果为强度间伐能够良好的促进林下植被发育。
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