热带雨林冠层树木和藤本之间光合作用特征参数比较

 丰富的藤本是热带雨林的一个典型特征,但对藤本丰富发育的原因众说纷纭.季节性干旱假说认为干旱条件下藤本具有更强的光合作用而产生竞争优势.但是,由于热带雨林树木高大,冠层浓密,对叶片光合能力的测定往往选取幼苗,或采用离体方式,而且采样过程中极难采集到冠上的阳生叶片.这些局限性降低了前期研究结果的可信度.有鉴于此,我们选择干湿季分明的热带季节雨林为研究对象,在旱季的中期,通过在热带雨林中搭建的大型冠层监测平台,原位测定了热带季节雨林代表乔木绒毛番龙眼成年株及其上缠绕的典型藤本扁担藤的光合特性.结果表明:木本绒毛番龙眼的最大羧化速率(V_cmax)、电子传输速率(J_max)、最大光合速率(A_max)和表观量子效率(AQY)方面皆较藤本植物扁担藤高,但是木本植物的暗呼吸则明显低于藤本植物.据此推测,旱季中期木本植物净碳吸收和物质积累明显优于藤本植物.这些结果与前期离体或幼苗测定的结果相反,暗示回答该问题还需要进一步的深入探讨.

Comparison on photosynthesis parameters of canopy trees and lianas in a tropical rain forest,Xishuangbanna,China

High diversity and density of lianas is a typical property of tropical rain forest.However,the mechanism of high diversity and density of lianas in tropical rain forest is still under active debate.The dry season hypothesis suggested that lianas exerted higher photosynthesis during dry period than woody species,and thus had the competition advantages with woody species.Nevertheless,none of photosynthesis measurement in the field work was in situ and only the seedlings or the understory leaves was collected.It subsequently reduced the credibility of the data for answer the above mentioned question.Thus,we carried out a field work in a tropical rain forest with strongly seasonal of water during the middle of dry season.Our in situ measurement was inconsistent with previous studies and showed that photosynthesis of woody species was higher than lianas in that period.The further data also showed that woody species can take more carbon for dry matter production than lianas.This study implicated that further ecosystem level field work should be carried out before we confirmed the dry season hypothesis.