Remote sensing of photosynthetic processes by photochemical reflectance index (PRI)

The Photochemical Reflectance Index (PRI) has been proposed as a tool for the estimation of leaf and canopy light-use efficiency and photosynthesis from remote-sensing data. The application of the index is based on more than fifteen years of spectroscopic studies at the leaf level, which support it with a sound physiological basis. In the present study, the correlation between PRI and instantaneous light-use efficiency was estimated across a range of vegetation types in the San Rossore Regional Park, a CHRIS-Proba core site. The relationship was also tested over an entire season for a pine forest in the Park, where carbon fluxes have been monitored by eddy-covariance over the last five years. Seasonal changes in photosynthetic potential were also monitored at the site, in order to test the correlation with PRI reported in the literature. In September 2004, estimates of canopy PRI from CHRIS images were compared with leaf-level measurements from 13 plots corresponding to different vegetation types. The results were used to extrapolate leaf-level information to the entire scene

Physiological and structural changes in response to altered precipitation regimes in a Mediterranean macchia ecosystem.

Significant decrease in precipitation up to 15–20% has been observed in the Mediterranean area in the last two decades as a consequence of climate change. To simulate an analogous scenario, the precipitation regime was altered in replicated experimental plots in a Mediterranean macchia dominated by Arbutus unedo L. species. Two different levels of soil water content (SWC) were obtained during the summer: a mean value of 7% was obtained in water-depleted (D) plots by a partial (-20%) rain exclusion treatment using rain gutters; while a mean value of 14% in SWC was obtained in watered (W) plots supplying water by a sprinkler net. The physiological and structural changes were investigated over the course of two consecutive years by measurement of water potential, gas exchange leaf carbon isotopes, leaf pigments and growth. Apart from short-term responses, mainly related to the elastic response of stomatal conductance to soil water, a more long-lasting and significant acclimation to water availability was observed as a result of the increase in hydraulic resistance in the soil–plant continuum, which persisted even after the return to full water availability during the fall and winter. This response involved the permanent down-regulation of stomatal conductance and photosynthesis, accumulation of photo-protective pigments, as well as a reduction in shoot growth, leaf area index and an increase in shoot-bearing flowers in D plots. This acclimation response prevented the onset of any runaway damage thereby reducing the forest vulnerability to drought. Furthermore, the imposed drought induced a slight increase or no change in intrinsic water-use efficiency (WUEint), as a result of the parallel increase in stomatal and non-stomatal limitations; conversely integrated WUE (i.e., estimated from leaf carbon isotopes) was not affected by drought

Physiological and structural changes in response to altered precipitation regimes in a Mediterranean macchia ecosystem

Significant decrease in precipitation up to 15-20% has been observed in the Mediterranean area in the last two decades as a consequence of climate change. To simulate an analogous scenario, the precipitation regime was altered in replicated experimental plots in a Mediterranean macchia dominated by Arbutus unedo L. species. Two different levels of soil water content (SWC) were obtained during the summer: a mean value of 7% was obtained in water-depleted (D) plots by a partial (-20%) rain exclusion treatment using rain gutters; while a mean value of 14% in SWC was obtained in watered (W) plots supplying water by a sprinkler net. The physiological and structural changes were investigated over the course of two consecutive years by measurement of water potential, gas exchange leaf carbon isotopes, leaf pigments and growth. Apart from short-term responses, mainly related to the elastic response of stomatal conductance to soil water, a more long-lasting and significant acclimation to water availability was observed as a result of the increase in hydraulic resistance in the soil-plant continuum, which persisted even after the return to full water availability during the fall and winter. This response involved the permanent down-regulation of stomatal conductance and photosynthesis, accumulation of photo-protective pigments, as well as a reduction in shoot growth, leaf area index and an increase in shoot-bearing flowers in D plots. This acclimation response prevented the onset of any run-away damage thereby reducing the forest vulnerability to drought. Furthermore, the imposed drought induced a slight increase or no change in intrinsic water-use efficiency (WUE(int)), as a result of the parallel increase in stomatal and non-stomatal limitations; conversely integrated WUE (i.e., estimated from leaf carbon isotopes) was not affected by drought

Quale ruolo per l\u2019arboricoltura da legno italiana nel protocollo di Kyoto? Indicazioni da una \u201cKyoto forest\u201d della pianura emiliana

The carbon balance of an afforested area in the Emilia-Romagna floodplain has been monitored for a 4-year period. Detailed measurements covering both above- and below-ground components of biomass production and accumulation were complemented by eddy-covariance measurements at the ecosystem level. Experimental results have been extrapolated in time by means of a process-based ecosystem model, so as to better assess the potential role of afforestation towards the carbon-reduction goals of the Kyoto Protoc