MAIN PURPOSE: Ecophysiological research, biogeochemistry, hydrology.
ECOSYSTEM TYPE: Evergreen oak, Buxus sempervirens, Juniperus oxycedrus.
EXPERIMENTAL TREATMENTS: Throughfall exclusion, rainfall exclusion, thinning.
LOCALISATION: 43.74851149886269 3.6133575439453125
FACILITIES: The site is located on a flat area 35 km North-West of Montpellier. The forest is dominated by the overstorey evergreen tree Quercus ilex (80% cover) managed as a coppice for centuries with the last clear-cut performed in 1942. Mean annual precipitation is 883mm with 75% rainfall between September and April. However, because of the large fraction of rocks and stones in the soil profile, available water averages only 150mm.
Long-term 30% throughfall exclusion and thinning experiments started in 2003. A two layer footbridge (40m long) allows an easy access to the canopy. In 2007, a new and unique manipulative experiment was designed to simulate the effect of extreme droughts on the functioning and the vulnerability of this ecosystem. A mobile rainfall shelter was installed above the canopy in order to simulate 100% rain exclusion during different seasons. This last experiment is now on standby. Measurements recorded include soil and organ-level gas exchange; tree transpiration; above-ground and belowground biomass; phenology; functional traits; litterfall; regeneration; organs, soil and litter biochemistry; VOC emission; dry and wet nitrogen deposition; ectomycorhizal communities. The site also includes an eddy-flux tower that continuously monitors atmosphere-vegetation exchange of CO2, water and energy since 1998. In 2003, the eddy flux tower was upgraded to be part of the ICOS project. A large number of papers have already been published from research at the site and an important database is already available for the users. In 2013, the site was electrified.
● Martin-StPaul, N. K., Limousin, J.-M., Vogt-Schilb, H., Rodríguez-Calcerrada, J., Rambal, S., Longepierre, D. and Misson, L. (2013) The temporal response to drought in a Mediterranean evergreen tree: comparing a regional precipitation gradient and a throughfall exclusion experiment. Global Change Biology. doi: 10.1111/gcb.12215.
● Perez-Ramos, I. M., J. Rodriguez-Calcerrada, J. M. Ourcival and S. Rambal (2013). Quercus ilex recruitment in a drier world: A multi-stage demographic approach. Perspectives in Plant Ecology Evolution and Systematics 15(2): 106–117.
TA PROJECTS: Xylem CO2 fluxes derived from wood respiration in drought-stressed trees (ResStress)
TA User (visit): Roberto Salomon Moreno, Forest Genetics and Ecophysiology Reserch Group, Technical University of Madrid, Spain (February, 2015 – 05 days)
Project Description: Mediterranean forests are expected to suffer more intense droughts based on climate change predictions. Reduced water availability limits stem respiration (RS) in Mediterranean forests (Rodríguez-Calcerrada et al., 2014) at the same time that autotrophic respiration acclimation in the long-term mitigates reductions in carbon use efficiency (Rambal et al., 2014). To accurately estimate RS, commonly assumed as the radial CO2 efflux to the atmosphere (EA), internal CO2 fluxes through xylem (FT) need to be taken into account since the transpiration stream transports a portion of locally respired CO2 upwards (Teskey et al., 2008). Under water stress conditions, FT decreases due to inhibited respiration rates and reduced resistance to radial CO2 diffusion because of the limited stem water content (Salomón et al., in prep.). Rainfall manipulation experiments provide excellent scenarios to investigate the role of water availability on FT and its interaction with EA in order to better understand and model the acclimation to drought of autotrophic respiration.
The objective of this project is to assess of how water deficit jointly affects FT and EA to accurately estimate RS in Mediterranean coppices of Quercus ilex in South France and Quercus pyrenaica in the Iberian Peninsula. Furthermore, this project would strengthen the relationship between the Forest Genetics and Ecophysiology Research Group (Technical University of Madrid, Spain) and the Research Group “Dynamique réactionnelle des ecosystèmes, Analyses spatiale et Modélisation” from the Centre of Functional and Evolutionary Ecology (CNRS, France).
Long-term drought manipulation effects on tree biochemistry (ChemisTree)
TA User (visit): Jesus Rodriguez-Calcerrada, School of Forest Engineering, Technical University of Madrid, Spain (February, 2015 – 05 days)
Project Description: Precipitation manipulation experiments are an effective way to assess drought impact on tree and ecosystem functions while minimizing confounding factors. Current researches on tree acclimation to drought using such experiments have mostly focused on structural (e.g. Martin-StPaul et al. 2013) and functional changes (e.g. Rodriguez-Calcerrada et al. 2014), while overlooking the biochemical changes induced by recurrently increased drought. These biochemical changes concern in particular the tree reserves of non-structural carbohydrates (NSC), which have a demonstrated importance for subsequent tree growth and survival to extreme drought events (McDowell 2011). They also concern the nutrient concentration and stoichiometry (Nitrogen, Phosphorus, and Potassium) in tree tissues, which subsequently affects photosynthesis and growth. The overarching aim of this project is to assess experimental possibilities for studying long-term precipitation manipulation (>10 years) impact on tree biochemistry while strengthening up the scientific relationship between the Forest Genetics and Ecophysiology Research Group (Technical University of Madrid, Spain) and the Research Group “Dynamique réactionnelle des ecosystèmes, Analyses spatiale et Modélisation” from the Centre of Functional and Evolutionary Ecology (CNRS, France). More specifically, the visit of Jesús Rodríguez Calcerrada will have the following objectives: 1) assess the sampling methodology for biochemical analyses at the TA (Puéchabon, with a long-term experimental manipulation of throughfall), 2) share experience and protocols for nutrient and NSC content analyses, and 3) discuss previously acquired data and prepare research articles.
Holm oak phenology and relationships with acorn production (ACOPHEN).
TA User (visit): Maria Dolores Carbonero, Institute of Agricultural and Fishing Research and Education (IFAPA), (June, 2014 - 57 days).
Project Description: Despite the influence of the acorn production to support livestock, wildlife and tree regeneration, little is known about their evolution over time and its relationships with meteorology or endogenous factors such as trade-offs between vegetative growth, phenology and masting. It is therefore very difficult to establish in what way the acorn crops will oscillate over the years. The objectives of this project are: determining the relationships between production of female flowers and acorns with meteorology, phenology, male flowering, vegetative shoot growth and nutritional status of the leaves. The experiment will be undertaken in southern Spain holm oaks located in a pasture farm in the province of Córdoba (University of Córdoba and Institute of Agricultural and Fishing Research and Education-IFAPA) and in the oak forest of Puechabon station, 35 km north of Montpellier (CEFE/CNRS). Data collection and analysis in Puechabon will be held on May 5th to August 18th, 2014, coinciding with Tthe stay of Maria Dolores Muñoz Carbonero (IFAPA). We will analyze the correlations of female flowers and fruits in July with (a) phenology, (b) the intensity of male flowering, (c ) growth and thickness of the shoot in which the flowers are located, (d) the number of leaves of the shoot in which the flowers are located and (e) the chemical composition of the leaves of the shoot in which the flowers are located.