从径向生长量分析红松幼树生长光需求

该文调查了20年前在辽东山区次生林林冠下栽植红松幼苗而长成的群落，分析了红松在群落中的地位，检测林冠下栽植红松的成效，并以基盘分析20年期间红松径向生长规律，从而探讨首次透光伐的适宜时间。结果表明:20年后红松植株高均小于4 m，大于3 m的植株仅占13.9%，平均高为1.8 m，树高年平均增长量为0.078 m/a；大部分红松仍位于灌木层，这说明在无法保证光照的环境中红松生长十分缓慢，应实行透光伐。红松径向生长规律为:先有一个2～3年的缓慢生长过程，随后加速增长并持续一段时间，然后锐减并稳定在一个极低值；林冠下栽植红松后4～12年是红松快速生长时期，这9年期间平均径向生长量为3.06 mm/a；第8年平均径向生长量达到最大值，为3.45 mm/a；第13年红松径向生长量急剧下降，在1.32～1.83 mm/a之间。根据受压判断公式测得在12年后应进行首次透光伐。 

Light requirement of Pinus koraiensis saplings from radial stem growth

In 1986,selective cutting of a secondary forest in montane zone of eastern Liaoning Province was carried out in order to plant three years old seedlings of Pinus koraiensis.In september 2004,the authors surveyed the forest to study the status of P.koraiensis and,in 2005 and 2006,checked the radial stem growth to find out the suitable time for the first release cutting.Results were showed as the followings: 20 years after selective cutting,all P.koraiensis plants were still lower than 4 m,only 13.9% individuals were higher than 3 m,the average height was only 1.8 m, and the yearly height growth was only 0.078 m.These results showed that P.koraiensis grew very slowly and still situated on the shrub layer.A release cutting should have been carried out early to supply sunshine for P.koraiensis forests.P.koraiensis's radial stem growth had an evident law,ie after a 2-3 years period of slow growth,P.koraiensis accelerated the radial stem growth and kept the quick growth for a duration.Later,the growth sharply reduced to the extreme and kept the minimum value till now.The rapid growth period appeared during 1990 to 1998 when the average radial stem growth reached 3.06 mm/year.In 1992,the radial stem growth of P.koraiensis attained at the highest of 3.45 mm/year.Since 1999,the radial stem growth of P.koraiensis reduced sharply to 1.32-1.83 mm/year till now.The analysis of P.koraiensis' radial stem growth implies that the first release cutting should be carried out about 12 years after planting P. koraiensis seedlings.