Richard Joffre

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The dehesas of the southwestern Iberian Peninsula are 'man-made' ecosystems characterised by a savannah-like physiognomy. The trees are viewed as an integrated part of the system, and as a result are planted, managed, and regularly pruned. Palynological and historical evidence of the manipulation of initial ecosystems by man to obtain a savannah-like(More)
Land use and climate changes induce shifts in plant functional diversity and community structure, thereby modifying ecosystem processes. This is particularly true for litter decomposition, an essential process in the biogeochemical cycles of carbon and nutrients. In this study, we asked whether changes in functional traits of living leaves in response to(More)
Freezing sensitivity of leaves and xylem was examined in four co-occurring Mediterranean oaks (Quercus spp.) grown in a common garden to determine whether freezing responses of leaves and xylem were coordinated and could be predicted by leaf lifespan. Freezing-induced embolism and loss of photosynthetic function were measured after overnight exposure to a(More)
A multidisciplinary team undertook a six-year investigation on the agro-ecological and socio-economic aspects of the dehesa system in the Sierra Norte area, a part of the Sierra Morena of the Sevilla Province, Western Andalusia, Spain. This paper summarizes its findings on the various agro-ecological features of the system and evaluates the system's(More)
In this study, sun leaf carbon isotope composition (δ13C) of two co-occurring woody Mediterranean species (Quercus pubescens Willd., a deciduous oak, and Q. ilex L., an evergreen one) was investigated on four sites with different water availability. The total range of δ13C values was 4.4 and 3.1‰ for Q. pubescens and Q. ilex respectively. The intra-site(More)
Remobilization of internal resources is an important mechanism enabling plants to be partly independent of external nutrient availability. We assessed resource remobilization during the growing period in woody and foliar tissues of leafy branches of mature evergreen Mediterranean oak (Quercus ilex L.) at three field sites. We compared nonstructural(More)
The aim of this study was to produce calibration equations between near-infrared reflectance (NIR) spectra and the concentrations of carbon, nitrogen, and phosphorus in heterogeneous material: from living needles to litter in Pinus halepensis stands subjected to prescribed burnings. The aim was to determine whether calibrations should be conducted within(More)
We investigated growth, leaf monoterpene emission, gas exchange, leaf structure and leaf chemical composition of 1-year-old Quercus ilex L. seedlings grown in ambient (350 microl l(-1)) and elevated (700 microl l(-1)) CO2 concentrations ([CO2]). Monoterpene emission and gas exchange were determined at constant temperature and irradiance (25 degrees C and(More)
Soil nitrogen can alter storage and remobilization of carbon and nitrogen in forest trees and affect growth responses to elevated carbon dioxide concentration ([CO(2)]). We investigated these effects in oak saplings (Quercus robur L.) exposed for two years to ambient or twice ambient [CO(2)] in combination with low- (LN, 0.6 mmol N l(-1)) or high-nitrogen(More)
The effect of an extended drought (from 1992 to 1995) on water relations was assessed on evergreen oak (Quercus ilex L.) in a dehesa ecosystem (Seville, Southern Spain). Diurnal and seasonal transpiration patterns were analysed at leaf (porometry) and whole-tree level (sap flow), focusing on the relationship between tree transpiration rates (Et) and(More)