Báo cáo lâm nghiệp: Environmental control of CO assimilation rate and leaf 2 conductance in two species of the tropical rain forest of French Guiana (Jacaranda copaia D. Don and Eperua falcata Aubl.)

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Environmental control of CO assimilation rate and leaf 2 conductance in two species of the tropical rain forest of French Guiana (Jacaranda copaia D. Don and Eperua falcata Aubl.)...
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Báo cáo lâm nghiệp: "Environmental control of CO assimilation rate and leaf 2 conductance in two species of the tropical rain forest of French Guiana (Jacaranda copaia D. Don and Eperua falcata Aubl.)"Environmental control of CO assimilation rate and leaf 2conductance in two species of the tropical rain forest ofFrench Guiana (Jacaranda copaia D. Don and Eperuafalcata Aubl.) J.M. Guehl 21R. Huc1 Station de Recherches Forestières, INRA, BP 709, 97387 Kourou Cedex, andLaboratoire2 de Bioclimatologie-Ecophysiologie, Station de Sylviculture et Production, INRA,Centre de 54280 Seichamps, France Nancy, Champenoux, in French Guiana (53° W, 5.2° N) with 2200 mmIntroduction average annual rainfall. Total rainfall over the experimental period (1 September-15 OctoberThe potential environmental limitations to 1987) amounted to 67.8 mm, extreme air tem-forest tree production under subequatorial peratures were 20 (night) and 34°C (day) and average potential evapotranspiration was 4.0climatic conditions are not well under- mm!d-!. The mean height of the studied treesstood. Despite important annual precipita- was 3.6 m (J. copaia) and 2.4 m (E. falcata). Intion, drought in the atmosphere and in the situ C0 assimilation rate (A) and leaf conduc- 2soil is likely to play a limiting role, tance (g) were determined by means of a port-because: 1) significant climatic water defi- able gas-exchange measurement system (Li- Cor 6200; LI-COR, Lincoln, NE, U.S.A.). Prior tocits occur during the dry seasons; and 2) the measurements reported here, the within-the rain forest species do not seem to tree variability of gas exchange was assessedhave evolved efficient adaptative features and was shown to be related to the position ofagainst drought (Doley et al., 1987). The the whorls on the main orthotropic stem in J.present study was aimed at comparing the copaia and to the position of the leaves on theC0 assimilation and stomatal conduc- plagiotropic branches in E. falcata. The data2 hereafter refer to the zone of maximum A andtance behavior under natural conditions g. Leaf water potential values were determinedduring the dry season in artifical 3 yr old with a Scholander pressure bomb.stands of J. copaia, a long living pioneerspecies occurring in open sites, and of E.falcata, a common species of the matureforest canopy. Results and Discussion The 2 species exhibited fundamentally dif- ferent patterns of daily courses of A vsMaterials and Methods photosynthetic photon flux density U as ) p is shown for a typical cloudless day in theThe study was performed at an experimentalsite of the Centre Technique Forestier Tropical beginning of the dry season in Fig. 1. Withthe exception of leaflet 12, E. falcata was diurnal changes in A in the J. copaia leaf-characterized by daily changes in A being lets were clearly related to the changesin close relationship with those in /p, while of leaf-to-air water vapor pressure dif-J. copaia exhibited a diurnal pattern with a ference (Aw), these latter being closelyclear depression of A during the after- associated with the variations of leaf tem- Midday depression entirely perature (Fig. 3). It is not possible here to cannotnoon.be taken into account by the concurrent disentangle the possibly colimiting effects of dw and hig temperatures on A. But itstomatal closure, since in the J. copaia h lleaflets, A decreased at constant, or even is worth noting that, in a similar situation,slig ...