细柄阿丁枫和米槠细根寿命影响因素

Abstract

Fine roots production and turnover is a significant component of the carbon cycle in forest ecosystems.Fine root survivorship was monitored by minirhizotrons during two successive years in two subtropical evergreen broadleaved forests(Altingia grlilipes,ALG;and,Castanopsis carlesii,CAC) in Wanmulin Natural Reserve,Jian-ou,Fujian province.Root longevity was estimated by the Kaplan-Meier method and differences among single factors,including fine root diameter(d0.3 mm,0.3d0.6 mm,0.6d1 mm),order(first order,higher order),year of birth(2007,2008),season of birth(spring,summer,autumn,winter),soil depth(0D20 cm,20D40 cm),and number of neighbor root(N5,5N10,10N),were tested by the Log-rank test.Cox proportional hazards regression analysis was also applied to assess the relative effects of these factors on root survivorship.Mean and median fine root longevity of ALG were(286±8) d and(184±9) d,respectively,while CAC′s were(261±10) d and(212±8) d.When considering the individual factor alone,root longevity were significantly affected by season of birth,root diameter,order,and number of neighbor root(P0.01 for all cases) in both two forests;year of birth had significant effect only in CAC(P0.01) and soil depth had significant effect only in ALG(P0.01).Mean fine root longevity of ALG in summer was(204±14) d,which was respectively lower than in spring(290±11) d,autumn(307±13) d and winter(263±25) d.Mean fine root longevity of CAC in summer and winter were(164±20) d and(156±16) d,respectively,which were significantly lower than in spring(269±15) d and autumn(346±17) d.With the increase of fine root diameter,median fine root longevity increased significantly in ALG(P0.01);while in CAC,median fine root longevity increased from d0.3 mm diameter to 0.3d0.6 mm diameter,and showed little change with further increase in diameter(P0.05).With the increase of root order,mean fine root longevity of ALG and CAC were increased significantly(P0.01).Mean fine root of ALG′s first order and higher order were(267±8) d and(559±32) d,respectively,While CAC′s were(247±10) d and(425±41) d.The number of fine root in ALG and CAC was decreased with root order increased.With the addition of number of neighbor root,mean fine root longevity of ALG and CAC were increased significantly(P0.01).Furthermore,mean fine root longevity of ALG in 0N5,5N10 and 10N was(226±9) d,(309±15) d and(467±21) d,respectively.While CAC's was(246±11) d,(290±25) d and(438±45) d.Cox proportional hazards regression showed that in both two forests year of birth had no significant effects on root longevity(P0.05).According to the size of impact on root longevity,these factors can be ranked as: root order,season of birth,root diameter,and number of neighbor root.Soil depth had the weakest effect in ALG while had no effect in CAC(P0.05).