重要值的改进及其在羊草群落分类中的应用

Amending of importance value and its application on classification of Leymus chinensis communities

对重要值进行了改进 ,首次提出了理论平均重要值(theoreticalmeanimportancevalue,TMIV)、简化重要值(simpleimportancevalue,SIV)和样地指数 (sampleplotindex ,SPI)的概念。即 ,理论平均重要值是指随物种数目变化样地内各种植物理论上的平均重要值。简化重要值是指理论平均重要值乘以某一植物的生物量与样地内所有植物的平均生物量的比值或者乘以某一植物的体积(盖度乘以高度 )与样地内所有植物的平均体积的比值。样地指数是指简化重要值乘以某一植物的生物量与所有样地中该植物的平均生物量的比值或者乘以某一植物的体积与所有样地中该植物的平均体积的比值。相对重要值而言 ,简化重要值减少了野外工作量。而样地指数既反映了物种在样地内所占有的优势 ,又反映了物种在样地间所占有的优势 ,使得不同样地的重要值更具可比性。文中用重要值、简化重要值和样地指数三个指标进行羊草群落的聚类分析 ,结果表明 ,简化重要值可用于植物群落的数量分类 ,样地指数比重要值更适宜用于植物群落的数量分类。

Importance value (IV) was amended, and concepts of theoretical mean importance value (TMIV), simple importance value (SIV) and sample plot index (SPI) were given in the present study. Here, they are defined as follow: TMIV is the mean importance value that is calculated theoretically as species number changes in the sample plot. SIV is that the TMIV multiples the ratio of biomass of a plant to average biomass of all plants in same plot or multiples the ratio of volume (coverage multiplying height) of a plant to average volume of all plants in same plot. SPI is that the SIV multiples the ratio of biomass of a plant to average biomass of same plant in all plots or multiples the ratio of volume of a plant to average volume of same plant in all plots. Relatively, to use the SIV can save workload in field compared with the IV, while the SPI can reflect the occupied dominance of a plant not only compared with other plants within a sample plot but also compared with same plant among all sample plots, which makes the IVs of different sample plots have reasonable comparability. Three indices (IV, SIV and SPI) were used in classifying the communities of Leymus chinensis by cluster analysis, and the results indicated that the SIV can be acted as an index and the SPI as a more suitable index in the quantitative classification of plant communities compared with the IV.