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Puechabon
Puechabon
Site descriptionThis study site is located in the Puéchabon State Forest on a flat area 35 km North-West of Montpellier in the south of France. It is surrounded by large area of dense forests and open forests and shrublands. Vegetation is largely dominated by the overstorey tree Quercus ilex whose percent cover is greater than 80%. The leaf area index is about 2.9 m2 m-2. Mean tree height is about 5.5 m. In 1999, density of resprouted stem was 8500 ± 600 stems per ha. The percentage of stem with DBH < 4 cm was 11% and 46% for DBH > 7 cm. In 2007, density of resprouted stem was 6304 stems per ha. The percentage of stem with DBH < 4 cm is 7% and 56% for DBH > 7 cm. The above-ground biomass is about 11800 g dry matter m-2. Understorey species compose a sparse shrubby layer with Buxus sempervirens, Phyllirea latifolia, Pistacia terebinthus and Juniperus oxycedrus and have likely a small contribution to the whole ecosystem functions. The area has a Mediterranean-type climate. Rainfall occurs during autumn and winter with about 75% between September and April. Mean annual precipitation is 883 mm with a range 550-1549 mm recorded over the previous 16 years. Mean annual temperature over the same period were 13.5 °C respectively. LandusePuéchabon State Forest has been managed as a coppice for centuries and the last clear cut was performed in 1942. Soil & GeologyThis forest grows on hard Jurassic limestone filled with clay soil. Because of the large fraction of rocks and stones in the soil profile available water cumulated over 4.5 m depth averages only 150 mm. Because of this low availability, vegetation undergoes very frequent drought summer stress. MeasurementsFlux towerFlux Measurements (half-hourly)
Atmospheric Measurements
Temperature
Radiation
Others
Manipulation experiments
Treatments within the CARBO-Extreme projectThroughfall exclusion experiment (Exp. 1)In 2003, the throughfall exclusion experiment was set up on four 140m² plots (14 x 10m) situated on a flat area, so that lateral flow of water is negligible:
On the dry and dry-thinned plots, throughfall exclusion was achieved using 14 m long and 0.19 m wide PVC gutters covering 33% of the ground area under the Quercus ilex canopy, with the aim to exclude 33% of throughfall. On the control plot and the thinned plot, identical gutters had been set up upside down so that the albedo and the micro-climate of the forest understorey were the same in all plots. The leaf area index (LAI) was 3.1m² m-² in the controls plots and 1.6 m² m-² in the thinned plots. In the control plot, rainfall partitioning into interception loss, throughfall and stemflow was respectively 30.9%, 56.6% and 12.5% of the total precipitation. Thinning reduced the stem basal area by 33% and the total interception loss by 34.6%. Given the rainfall partitioning, the throughfall exclusion was found to remove 19% of total precipitation, which was confirmed by soil water content measurements. Rainfall exclusion experiment (Exp. 2)In 2007, a rainfall exclusion experiment was established on the site and included 3 plots of 195 m² each (15 m x 13 m, 2 x treatment, 1 x control). The experiment was designed to exclude 100% of rainfall on different forest plots at different periods of the year, without changes in other meteorological variables such as incident radiation, temperature and vapor pressure deficit. Rainfall exclusion was achieved trough a mobile rainfall shelter of 15 m x 13 m standing above the canopy on 60 m long rails. The two exclusion plots were situated at each extremity of the rails, the middle part serving as a parking position for the shelter in the absence of rain. The control plot was situated 20 m aside, in the east direction of the exclusion plots. Two rainfall exclusion treatments were defined
Related projects
Pictures        ContactSerge Rambal ReferencesMisson, L., Rocheteau, A., Rambal, S., Ourcival, J-M., Limousin, J-M., Rodriguez, R. (2009) Functional changes in the control of carbon fluxes after 3 years of increased drought in a Mediterranean evergreen forest? Global Change Biology (in press). Limousin J.-M., Rambal S., Ourcival J.-M., Joffre R. (2009). Reply to comment by Llorens et al. "Modelling rainfall interception in a Mediterranean Quercus ilex ecosystem: lesson from a throughfall exclusion experiment". Journal of Hydrology, 365: 142-143. Limousin J.-M., Rambal S., Ourcival J.-M., Rocheteau A., Joffre R., Rodriguez-Cortina R. (2009). Long-term transpiration change with rainfall decline in a Mediterranean Quercus ilex forest. Global Change Biology,15: 2163-2175. Lavoir A.-V., Staudt M., Schnitzler J. P., Landais D., Massol F., Rocheteau A., Rodriguez R., Zimmer I., Rambal S. (2009). Drought reduced monoterpene emissions from the evergreen Mediterranean oak Quercus ilex: results from a throughfall displacement experiment, Biogeosciences, 6, 1167-1180, 2009. |