The response of leaf gas exchange to environmental factors of a dominant tree species, Endospermum chinense in tropical regeneration forest

LUO TuShou, LI YiDe, CHEN DeXiang, CHEN BuFeng,LIN MingXian (Rresearch Iinstitute of Tropical Forestry, CAF, Guangzhou, 510520).  

To investigate how will leaf gas change of species response to environmental factors during the succession of tropical regeneration forest, we choose the dominant tree species, Endospermum chinense Benth as our study case. Leaf gas change characteristics and its responses were measured with Li6400 portable photosynthesis system (LiCor Inc.,USA) in Jianfengling, Hainan Island. Netphotosynthesis, stomatal conductance and transpiration are all exhibited a bimodal diurnal pattern and the first peak is reached during the time of 8:00~10:00; the other subpeak is reached at 14:00. There is a noon break of photosynthesis during 12:00~13:00 due to the absence of irradiance and the closure of part stomata. Although photosynthetic rate is affected by the interaction of such environmental factors and how much this interaction is still to be studied, there is a strong linear relationship between the net photosynthetic rate(Pn) and stomatal conductance (Gs), transpiration rate (E), photosynthetic photon flux density (PPFD), air temperature (Ta) and leaf temperature. No evident relation is found between Pn and intercellular CO2 concentration (Ci), atmospheric CO2 concentration (Ca) and relative humidity (RH) and no strong limitation of such factors contributed to photosynthesis. The light response experiment of Endospermum chinense shows the characteristics of high light saturation point(LSP) with 1683μmol/(m2·s) and low light compensation point (LCP)with 15~25μmol/(m2·s). The shortterm response of leaves to CO2 enrichment resulted in decreasing of stomatal conductance, transpiration and increasing of Pn. Doubled growth concentration of CO2 can enhance Pn by 70%, water use efficiency(WUE) by 78% and decrease transpiration by 443%. Endospermum chinense has a high daily average Pn of 640±017μmolCO2/(m2·s) and daily maximum Pn of 1160μmolCO2/(m2·s), which testified its fastgrowing characteristics.

【Fund】： 国家林业局热带林业研究重点实验室开放基金资助项目(1999);; 海南尖峰岭热带林生态系统定位研究站资助项目(2001-08)~~
【CateGory Index】： Q945.1

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