Báo cáo khoa học: Environmental and endogenous controls on leaf- and stand-level water conductance in a Scots pine plantation Neils Sturm Barbara Köstner Wolfram a John D.

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: " Environmental and endogenous controls on leaf- and stand-level water conductance in a Scots pine plantation Neils Sturm Barbara Köstner Wolfram a John D...
Nội dung trích xuất từ tài liệu:
Báo cáo khoa học: " Environmental and endogenous controls on leaf- and stand-level water conductance in a Scots pine plantation Neils Sturm Barbara Köstner Wolfram a John D. " Original article Environmental and endogenous controls on leaf- and stand-level water conductance in a Scots pine plantation Hartung Neils Sturm Barbara Köstner Wolfram a John D. Tenhunen a of Plant Ecology II, Bayreuth Institute for Terrestrial Ecosystem Research, Department University of Bayreuth, 95440 Bayreuth, Germany Julius-von-Sachs-Institut b für Biowissenschaften der Universität Würzburg, Lehrstuhl für Botanik I, Mittlerer Dallenbergweg 64, 97082 Würzburg, Germany (Received 12 March 1997; accepted 31 July 1997)Abstract - Measurements of leaf level gas exchange and conductance, tree transpiration viasapflow monitoring, soil moisture and water extraction, predawn water potential, and xylemabscisic acid (ABA) concentration were carried out over the course of the 1993 and 1994 sum-mer seasons at the Hartheim Pinus sylvestris plantation on the Upper Rhein Plain, Germany.Periodic leaf level conductance determinations with porometry established a maximum valueof ca 280 mmol m s (13.6 mm s Half maximal conductance was attained at 40 μmol m -2-1 ). -1 -2-1sand 90 % of light saturation occurred at ca 500 μmol m s PPFD. Conductance decreased -2 -1strongly with increases in vapor pressure deficit above 10 hPa, while the temperature optimumwas 22 °C at light saturation. Strong restrictions on maximum conductance at both leaf and standlevels were apparent below a soil moisture content of 16 volume percent. Although less strongly,conductance also decreased with initial drying of the upper soil layers and decreases in predawnwater potential from -0.4 to -0.6 MPa. In this range of water potential change, xylem ABAincreased to between 200 and 500 nmol L Thus, an immediate leaf-level reaction to the onset . -1of summer weather conditions is observed, i.e. leaf conductance and water use decrease. Wehypothesize that ABA functions as a key control on water balance, transmitting informationabout soil water status and endogenously modifying canopy response in order to budget water andavoid extensive cavitation damage in most years. Transpiration potential of the stand was reducedby thinning during autumn 1993 in approximate proportion to changes in leaf area index andsapwood area. Simultaneous observations of sapflow and conductance have allowed us to viewthe effects of leaf conductance on whole plant water use, while thinning revealed the effects ofstand level phenomena on conductance regulation. (© Inra/Elsevier, Paris.)conductance / transpiration / abscisic acid / drought / Pinus sylvestris* Correspondence and reprintsTel: (49) 921 55 5620; fax: (49) 921 55 5799; e-mail: john.tenhunen@bitoek.uni-bayreuth.deRésumé - Contrôle environnemental et endogène de la conductance stomatique et du cou- plantation de pins sylvestres. Des mesures de l’échange du gaz et de la conduc-vert dans unetance stomatique de l’eau, de la transpiration par deux méthodes de mesure du flux de sève, del’humidité du sol et de l’extraction de l’eau du sol, du potentiel hydrique foliaire de base et de laconcentration en acide absissique (ABA) dans l’aubier ont été réalisées au cours des étés 1993 et1994 dans une plantation de pins sylvestres dans la plaine rhénane au sud-ouest de l’Allemagne,près du village de Hartheim. Les mesures périodiques de la conductance stomatique ont montréune valeur maximale de 280 mmol m s (13,6 mm s Le demi-maximum de la conduc- -2-1 ). -1tance stomatique était atteint pour un rayonnement de 40 μmol m s et la conductance était éta- -2 -1blie à 90 % du maximum lors d’une exposition à 500 μmol m sLa conductance était dimi- -2 -1 .nuée rapidement dès que le déficit de saturation de l’air dépassait 10 hPa. L’optimum de laconductance était atteint pour une température de 22 °C, en condition de lumière saturante. ...