Báo cáo lâm nghiệp: Variation of stomatal resistance with leaf age in Quercus petraea: effect on the soil-water balance of an oak forest

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Báo cáo lâm nghiệp: "Variation of stomatal resistance with leaf age in Quercus petraea: effect on the soil-water balance of an oak forest"Variation of stomatal resistance with leaf agein Quercus petraea: effect on the soil-water balanceof an oak forestJ. Nizinski, D. Morand B. SaugierLaboratoired’Ecologie V6g6tale, CNRS URA121, Bitiment 362, Universit6 de Paris-Sud, 91405Orsay Cedex, France electron micro-Introduction abaxial epidermis (scanning scope).In deciduous forests, evapotranspirationfollows variations in the leaf area index Observations related to the soil-water(LAI). It is thus expected to reach a maxi- balancemum in spring when the LAI reaches aplateau and when the soil water supply is Fig. 1 shows the strong decrease in sto-adequate. From a detailed study of the matal resistance with leaf age, expressedsoil-water balance over 3 yr, we found as the ratio of actual leaf area to its maxi-that evapotranspiration reached a maxi- mal area. All these values were obtainedmum nearly 1 mo after the leaf area index at high light intensity and ample water(Nizinski and Saugier, 1988; 1989a, b). supply. This curve is repeated in Fig. 2b,We thus decided to study the effect of leaf which shows a further decrease in stoma-age on stomatal resistance and on the tal resistance after full leaf developmentmorphology of the leaf epidermis. (Fig. 2a). The decrease in stomatal resis- tance led to a progressive increase in the ratio of real transpiration to potential (Pen- man) evaporation (TlETP) from 0 at budMaterials and Methods burst to about 0.5 at the end of leaf growth and to 0.8 at the end of June.Study site: 2 stands of Q. petraea (Matt.) Liebl.in the Fontainebleau forest (1981-1983) and onthe Orsay campus (1987); soil-water balance Morphology of leaf epidermismeasurements: rain gauges, stemflow collars,neutron probe; stomatal resistance (Delta T Mk- electron of the leaf Scanning microscopy3 porometer) in the middle of the day; leaf size epidermis revealed: 1) young leaves have(Delta T area meter) and the observation of thestomates that have not achieved their References covered with adevelopment. They are Nizinski J. & Saugier B. (1988) A model of leafdense net of hairs (Fig. 3, 1a and 2a); and development for a mature Quer budding2) as the leaf matures, all stomates end cus forest. J. Appl. Ecol. 25, 643-652their development and hairs progressively Nizinski J. & Saugier B. (1989a) Dynamique de 1’eau sous chênaie (Quercus petraea (Matt.)disappear (Fig. 3, 1b and 2b). The decrea- Liebl.) en foret de Fontainebleau. Ann. Sci.se in epidermal resistance after the leaf For. 46, 173-186has reached its full size may thus be attri- Nizinski J. & Saugier B. (1989b) A model ofbuted to both stomatal development and a transpiration and soil-water balance for a ma-decrease in boundary layer resistance. ture oak forest. Agric. For. Meteorol. in press