桉树工业人工林植物物种多样性及动态研究

以定位监测与时空互代相结合的方法，于1998—2003年，从不同连栽代数、层次的物种丰富度、均匀度和物种多样性指数等方面对桉树工业人工林群落的物种多样性及动态进行了研究。 结果表明:①从1998—2003年，第1代林分出现的物种数为78种，第2代林分只有39种，第2代林分出现的物种数比第1代减少了50%；以达到主伐时的林分监测结果比较，第2代林分的物种丰富度、Shannon_Wiener指数和Simpson指数分别比第1代林分下降39.39%、17.76%和5.45%。 ②在1个经营周期（6 a）内，桉树工业人工林的物种丰富度呈先快速增加，后稍下降，再增加的“S型”变化；Shannon_Wiener指数和Simpson指数呈先快后慢的逐渐递增趋势；由于在1个经营周期内，物种的恢复总是达不到原有（第1代）的水平，因此，连栽和短轮伐期经营必然导致物种多样性的降低。 ③灌木层的物种丰富度和多样性指数普遍高于草本层，连栽具有降低灌木层物种丰富度和多样性指数，提高草本层物种丰富度和多样性指数的作用。 

Plant diversity and dynamics in industrial plantations of eucalyptus

The species richness, evenness and species diversity of plants in industrial plantations of eucalyptus were studied during 6 years from 1998 to 2003, using the methods of !time specific" and !fixed position monitoring". The main results are as follows: 1) Seventy_eight species of plants appeared in the first generation stand and 39 species in the second from 1998 to 2003. The species number in the second generation stand was 50% lower than that of the first. The species richness, Shannon_Wiener index and Simpson index of the second generation stand decreased by 39.39%, 17.76% and 5.45% compared with those of the first. 2) The species richness of the industrial plantations of eucalyptus showed a !S_type" change from 1998 to 2003, and Shannon_Wiener index and Simpson index both increased with the increase of stand age, but the early increase speed was faster than the later one. The continuous cropping and short_term management will reduce the diversity because the species recovery cannot reach the primary diversity level in a management period. 3) The species richness and species diversity index of shrub layer are obviously higher than those of herb layer. But continuous cropping has effects on reducing species richness and species diversity index of shrub layer and improving those of herb layer.