郁闭度对柳杉人工林下红豆树幼树生长和矿质营养的影响

Effect of canopy closure on the growth and mineral nutrition of Ormosia hosiei seedlings under Cryptomeria japonica plantation

为探讨红豆树在不同郁闭度林冠下造林的效果,筛选林下更新补植红豆树的最佳郁闭度,在现有柳杉人工林中通过调控设置3个郁闭度L_(1)(0.6)、L_(2)(0.5)、L_(3)(0.4),补植2年生红豆树幼苗,测定其株高、地径、生物量等生长指标和叶片氮、磷、钾等矿质营养含量指标,通过隶属函数进行综合评价。结果表明,不同郁闭度处理下红豆树株高、地径生长差异不显著(P>0.05),株高生长最好的是郁闭度0.5,分别比郁闭度0.6、0.4提高19.27%和11.52%;地径生长最好的是郁闭度0.5,比表现最差的郁闭度0.4高0.06%;不同郁闭度处理,红豆树根、茎、叶、总生物量差异显著(P<0.05),根、叶生物量及总生物量均以郁闭度0.5表现最优;不同处理红豆树叶片氮、磷、钾差异显著(P<0.05),均是郁闭度0.5含量最高。通过隶属函数综合分析表明,红豆树在不同郁闭度下的生长综合表现L_(2)>L_(1)>L_(3),可以认为2年生的红豆树在柳杉林下栽植适宜的郁闭度为0.5。

To investigate the silvicultural effect of Ormosia hosiei under different canopy closure levels,and to determine the optimal canopy closure level for understory regeneration of O.hosiei,three canopy closure levels,i.e.,L_(1)(0.6),L_(2)(0.5)and L_(3)(0.4)were set in the existing Cryptomeria japonica plantation,2-year-old O.hosiei seedlings were planted in the understory,and their growth indexes(height,root collar diameter,biomass)and leaf mineral nutrient contents(nitrogen,phosphorus,potassium)were measured.A comprehensive evaluation was carried out by using the membership function.The results showed that the difference in height and root collar diameter of O.hosiei seedlings was not significant(P>0.05)among different treatments.0.5 canopy closure level had the highest height index,which was 19.27% and 11.52%higher than 0.6 canopy closure level and 0.4 canopy closure level,respectively;0.5 canopy closure level had the highest root collar diameter index,which was 0.06% higher than 0.4 canopy closure level.The root,stem,leaf and total biomass of O.hosiei seedlings differed significantly(P<0.05)among different treatments.The root,leaf and total biomass performed best at 0.5 canopy closure level.The nitrogen,phosphorus and potassium contents of O.hosiei leaves differed significantly(P<0.05)among different treatments,with the highest content at 0.5 canopy closure level.The comprehensive analysis of the membership function showed that the growth of O.hosiei under different canopy closure levels was L_(2)>L_(1)>L_(3).It is concluded that the suitable canopy closure level for 2-year-old O.hosiei seedlings planted under C.japonica plantation is 0.5.