Ētude critique de faisabilité sur: la comparabilité des nonnées météorologiques "RENECOFOR" avec celles de Météo France, l'estimation de la réserve utile en eau du sol et le calcul des en eau du sol et le calcul des volumes d'eau drainée en vue du calcul de bilans minéraux sur les placettes du sous-réseau CATAENAT

Fontainebleau

2008

107 S. + 165 S. Annex

Bandaufführung

978-2-84207-323-7

149936

The first part of this report focuses on comparative studies carried out on data from the forest meteorological sub-network and from the National Weather Service weather staions located the closest to the RENECOFOR sites. Seven different parameters were studied: precipitation, minimum temperatures, maximum temperatures, global solar radiation, relative air humidity, wind velocity and potential evapotranspiration (PET). global analyses as well as plotspecific analyses were made for each parameter using daily, monthly and sometimes annual time scales. Correlations between the two data sets were calculated, and deviations were specified. The second part of this report gives detailed information on the steps taken to obtain estimates for available water reserve for each plot and each soil horizon. Available water depends on three major factors: i) the amount of coarse fragments in the soil; ii) maximum rooting depths; and iii) volumetric soil water content, which corresponds to the difference between water content at field capacity (saturation of soil micropores) and water content at permanent wilting point, both of which depend on soil texture, soil bulk density (indicative of structure), amount of organic matter, etc. The third part of this report concerns calculations of daily water balance and drained water. Unsurprisingly, the amount of drained water is closely related to precipitation; however, there are strong variations from year to year and from plot to plot. For all plots over the 5-year period, the average amount of drained water corresponded to 42 % of the annual precipitation. Drained water volumes ranged from 20 % for plot SP 05 to 55 % for plot DOU 17. In the Aigoual beech forest (HET 30) where mean annual precipitation is 2,000 m per year, drained water values corresponded to more than 80 % of the annual precipitation. Drained water, always expressed as a percentage of precipitation volumes, can vary considerably from one year to the next at the plot level. The widest variations were observed for plot SP 11 (drained water volumes between 18 % and 52 %) and PS 44 (13 % to 42 %); the smallest variations were on HET 30 (78 to 86 %), PS 67a (25 to 35 %) and SP 25 (49 to 59 %).