近自然化改造对杉木人工林物种多样性的影响

在广西凭祥市热林中心青山实验场设置杉木人工林近自然化改造样地,进行3种间伐强度处理(75%、55%、35%),均匀套种4种阔叶树。改造5年后,研究不同间伐强度近自然经营对群落组成、物种多样性和林分生长状况的影响。结果表明:近自然化改造5年后,乔、灌、草3层的物种数明显增加,灌草层的优势种有所变化,但各间伐处理的优势物种大致相同;各间伐处理的灌木层物种多样性指数无显著差异;改造后各处理草本层物种多样性指数均高于未改造的纯林,各处理草本层的Simpon指数和均匀度指数均显著高于改造前的纯林。杉木胸径随间伐强度的增大而增加且差异显著,但各处理间树高无显著差异;套种的4种阔叶树的胸径、树高随间伐强度的增大而增加,大叶栎、红椎的胸径、树高生长量在不同间伐处理林分中有显著差异;高间伐强度改造的杉木人工林适合套种阳性树种大叶栎、米老排和中性树种红椎,中等间伐强度改造的杉木人工林适合套种耐阴性树种润楠。

Effect of Close-to-Nature Management on Species Diversity in a Cunninghamia lanceolata Plantation

The study was conducted in a Cunninghamia lanceolata stand under close-to-nature management, with three different thinning densities (75%, 55%, and 35%) and three repetitions, in the Experimental Center of Tropical Forestry, Pingxiang, Guangxi. Four broad-leaved species Castanopsis hystrix, Mytilaria laosensis, Castanopsis fissa and Machilus pingii were randomly inter-planted into the Cunninghamia lanceolata stand. The impact of close-to-nature management with different thinning densities on community composition, species diversity and growth status were studied. The results showed that after five years of the close-to-nature management, the number of species in tree layer, shrub layer and herb layer highly increased. The dominant species in shrub layer and herb layer varied before and after thinning operation, but they were mostly the same in different thinning intensities. In the shrub layer, there was no significant difference in diversity indexes between the thinning stands and the unthinned pure stands. In the herb layer, the diversity indexes in the thinning stands were higher than that of the unthinned pure stands, while the Simpson index and Pielous evenness index were significantly higher than the pure stand. The average DBH of Cunninghamia lanceolata was significantly increased with the thinning intensities, but no significant difference was found in tree height. The DBH and height of the broad-leaved trees grew as the thinning density increasing. Significant differences were found in the DBH and height of Castanopsis fissa and Castanopsis hystrix in different thinning intensities. Intolerant species such as Castanopsis fissa and Mytilaria laosensis, as well as neutral species Castanopsis hystrix were good for inter-planted in high thinning intensity during close-to-nature management in Cunninghamia lanceolata plantation, while the shade tolerant species like Machilus pingii performed better in medium thinning stands.