三种乡土树种在二种林分改造模式下的生理生态比较

在丘陵荒山先锋树种马占相思林的林窗和均匀间伐50％(简称林冠层下)的2种林分改造模式下，研究了降真香、红椎和火力楠3种乡土树种生长初期的生理生态。结果表明，不管是在冬季或夏季，林窗中比林冠层下有更高的光合有效辐射(PAR)和相对湿度(RH)，并且有较低的气温(Tair)，林窗与林内最主要的差异是PAR的变化。生长在林窗里的植株比林冠层下的叶片小而厚，叶片单位面积干重增加，林窗里的植株叶片有较高的叶绿素含量。冬天，降真香和红椎在林窗里和林冠层下的净光合速率(Pn)日变化曲线都为单峰型，而火力楠在林窗下为双峰型，林冠层下为单峰型。3种树种在林窗里和林冠层下植株的蒸腾速率(Tr)有较相似的日进程，都为单峰型。2种林分改造模式下3种树种叶片气孔导度(GS)的日变化也较相似，与PAR的变化趋势相似，而与RH变化呈相反趋势。冬季。降真香和红椎在林窗的水分利用效率(WUE)比林冠层下稍高，而火力楠在林冠层下则比林窗高．但它们都无显著差异。夏天，3种树种在林窗和林冠层下的Pn与冬天有相似的结果。夏季红椎和降真香在林窗的Tr比林冠层下高，而火力楠在林冠层下的Tr比林窗高。Gs的变化趋势也与PAR相似，与RH变化趋势相反。夏季，降真香和火力楠的WUE在林窗比林冠层下高，但红椎却比林冠层下的低。3个树种中火力楠的WUE最高。3种树种在林窗和林冠层下的wUE都是冬季比夏季高。综合植物各项生理生态指标的分析结果可知，降真香和红椎较适宜种植在林窗里，而火力楠较能适应有一定郁闭度的林冠层下。

Ecophysiological characteristics of three native species used in two forest reconstructing models

It is of importance to utilize native species to reconstruct forest.Three native species of Acronychia pedunculata,Castanopsis hystrix and Michelia macclurei were respectively planted in man-made gaps and under Acacia mangium forest which was cut evenly at fifty percent.Their physiological characteristics such as chlorophyll content,net photosynthetic rate (Pn),transpiration rate (Tr),stamatal conductance (Gs),and water use efficiency (WUE) were measured.The results showed that there were higher photosynthetically active radiation (PAR) and relative humidity (RH) of air,and lower air temperature (T air) in gaps than under forest canopy layer.The leaves of 3 tree species in gaps were smaller and thicker,and the dry mass per unit area and chlorophyll content of leaves were much higher in gaps than under the canopy layer.In winter,the daily changes of Pn of A.pedunculata and C.hystrix showed single-peaked curve model in gaps and under canopy layer,while that of M.macclurei showed bimodal curve model in gaps and single-peaked curve model under canopy layer.The daily changes of Tr in leaves of the 3 species all showed single-peaked curve.Similar tendency in daily Gs of the 3 species in gaps and under canopy layer was shown,which was similar to the daily tendency of PAR and reverse to the RH.The WUE of A.pedunculata and C.hystrix were higher in gaps than those under canopy layer,while that of M.macclurei was reverse with no significant difference.In summer,all the 3 species had similar changes in Pn to that of the winter.The Tr of C.hystrix and A.pedunculata were higher in gaps than under canopy layer,while that of M.macclurei under canopy layer was higher than that in gaps.The tendency of Gs of the 3 species in summer was also similar to that of PAR,and reverse to that of RH.The WUE of A.pedunculata and M.macclurei were higher in gaps than under canopy layer,while that of C.hystrix were reverse.The WUE of M.macclurei was the highest among the 3 species in winter or summer,and that of the 3 species were all higher in winter than in summer.It could be concluded that A.pedunculata and C.hystrix grew better under the canopy layer and M.macclurei grew better in gaps.