不同密度杉木人工林林下植被发育与演替的定位研究

从 198 6年起,在江西分宜县中国林科院亚热带林业实验中心上村林场,用间伐方式对 8～9年生的杉木人工林进行林分密度的调整,每公顷分别为 30 0 0、2 5 0 0、2 0 0 0及 15 0 0株;郁闭度分别为 0.9、0.7及 0.6。设置固定样地 6个,每年以固定样方调查植物,观测林下植被发育情况,共进行 13a。结果表明,凡经间伐并郁闭度在 0.7以下的林分林下植被均迅速发育且良好,间伐 8～10 a后林下植被覆盖度可达 80 %～90 %,形成三层垂直结构,干生物量可达 4～5 t·hm-2;未经间伐或郁闭度恢复较快的样地,林下植被的良好发育推迟到 2 0年生以后。通过间伐适当调整密度是促进林下植被发育的有效方法,造林密度为 2 5 0 0～30 0 0株·hm-2的一般林分,10年生以后林分密度应保持为 15 0 0～2 0 0 0株·hm-2,郁闭度保持为 0.6、0.7即可取得较好的效果。杉木人工林林下植被以蕨类植物为主。

A Long-term Study on Development and Succession of Undergrowth Vegetations in Chinese Fir (Cunninghamia lanceolata) Plantations with Different Density

In 1986,a study was initiated on the 8 or 9 year old Cunninghamia lanceolata plantations with different retained density after thinning at the Shangcun Forest Farm of the Experimental Center for Subtropical Forestry under the Chinese Academy of Forestry (CAF), which is located in Fenyi County of Jiangxi Province. Six sample plots were set up in the Chinese fir plantations with stand density of 3 000 trees·hm-2, 2 400 trees·hm-2and 1 500 trees·hm-2and with the canopy density of 0.9,0.7 and 0.6 respectively. The annual investigation has been made for 13 years on the development of undergrowth vegetation in the sample plots. The results showed that the undergrowth vegetation developed rapidly and flourished in the plantations with canopy density ≤0.7 the coverage of undergrowth vegetation had reached 80%～90%,with the total amount of undergrowth biomass of 4 or 5 t·hm-2and three storey stand structure was formed in these plantations 8 to 10 years after thinning. But,in the plantations with high density,the undergrowth vegetation started developing only when the plantation grew up to 20 years old. Therefore,reasonable thinning of the plantation can be an effective way for well development of undergrowth vegetation Generally,when the plantation with initial planting density of 2 500～3 000 trees·hm-2grows up to 10 years old,the reasonable retained stand density should be 1 500～2 000 trees·hm-2and the canopy density should be 0.6～0.7 after thinning. The results also showed that the main undergrowth plant species are fernery in Cunninghamia lanceolata plantations