黄土丘陵区沙棘人工林发育过程中物种多样性及种间关联变化

根据野外调查资料，分析了不同发育阶段沙棘人工群落物种多样性及种间关联的变化特征.结果表明,群落各层及总体物种多样性基本呈“S”形波动变化.在不同发育阶段的沙棘群落中，物种丰富度和多样性指数均呈现草本层＞灌木层的趋势.灌木层物种多样性指数在撂荒地中较低，随群落发育逐渐增加，灌木层物种均匀度指数在13年生的沙棘林中较高；草本层多样性指数在3年生的人工林中较高，在8年生的人工林中较低，在25年生的人工林中较高.人工沙棘林中种间关联正负绝对值基本呈抛物线形变化，13年生左右显著程度和联结强度较弱，群落内物种间物种替代速度缓慢，竞争较少，群落组成和结构相对稳定.在沙棘人工林的经营和管理上，应是13年生以前以保护为主，到25年生时进行适度择伐，抚育萌生幼苗，促进种群更新发育.

Impact of oil shale waste slag on plant growth and benefits of limestone amendment

Because of the high acidity, low nutrients content, aluminum toxicity and potential heavy metals pollution, oil shale waste slag has negative effects on the normal growth of plants. A pot experiment with Tristania conferta, Schima wallichii, Vetiveria zizanioides and Paspalum notaturn showed that after eight months growth on oil shale waste slag, the biomass of T. conferta, S. wallichii, P. notatum and V. zizanioides was decreased by 43.5%, 55.0%, 68.4% and 88.6%, respectively, compared with the control. The amendment of limestone increased the biomass of T. conferta by 3.1%, but that of S. wallichii, P. notatum and V. zizanioides was still decreased by 32. 0%, 31.1% and 60. 4%, respectively. There was a synergistic effect between acid stress and A1 toxicity. Limestone amendment had better effects on mitigating the impact of oil shale waste slag, but the effects differed with different plant species.