Giuseppe Scarascia Mugnozza

Estimation of leaf area index with the Li-Cor LAI 2000 in deciduous forests

Abstract The present study has been performed in Italy, in stands of the main broad-leaved forest species. Thinned and unthinned stands of Quercus cerris L. (6.3% of total area covered by deciduous species in Italy), Castanea sativa L., (8.5%) and Fagus sylvatica L. (12.6%) were selected from 15 permanent plots. LAI data have been collected during the 3 years (1993–1995), using both direct (littertraps) and indirect methods (LAI-2000 Plant Canopy Analyzer, PCA, Li-Cor, Lincoln, NE, USA). LAI estimation by litter collection (LAI LT , 3.2–7.6 m 2 m −2 ) was in the range of values reported for deciduous forest, while the PCA method generally underestimated the LAI (LAI PCA , 1.8–5.8 m 2 m −2 ). Average underestimation was 26.5%, being similar to other reports. The underestimation was higher in thinned (29.1%±14.7%) than in unthinned (22.2%±12.2%) stands and in stands characterised by a LAI LT >5 m 2 m −2 . On the contrary, in stands with LAI LT 2 m −2 , PCA estimates were closer to littertraps ones (−11%±9.6%). On the average, LAI LT was 4.51±0.92 m 2 m −2 and 5.86±0.11 m 2 m −2 , for thinned and unthinned stands, respectively. Also PCA was able to estimate this difference, arriving at 3.14±0.70 m 2 m −2 (thinned stands) and 4.47±0.61 m 2 m −2 (unthinned stands). With both methods, the difference between the two stand types was strongly significant. Although LAI PCA values were always below LAI LT , the correlation between the two data sets was linear and significant. When recalculated omitting the reading of the external PCA ring, the correlation between LAI LT and LAI PCA improved, and the underestimation of LAI PCA was within 12%. Woody area index (WAI) was evaluated with the PCA during the leafless period. The instrument was able to show the difference between thinned (0.55±0.09) and unthinned stands (0.80±0.19). Similar to other studies, the subtraction of WAI from LAI PCA values increased the underestimation of LAI LT . The agreement between the two methods for LAI estimation was satisfactory. Nevertheless, the underestimation by the PCA method must be taken into account. Over different years and stands, the variability of underestimation was not marked, pointing to a reliable use of PCA in different conditions, as, for example, the comparison of thinned and unthinned stands and in measuring temporal and spatial variations of LAI. The overlapping of leaves, the presence of gaps within the canopy and light at the horizon level seem to be some of the important variables that influence LAI estimation by the PCA. Further corrections of the data can improve substantially the performance of the PCA and produce reliable LAI estimates even though the collection of direct reference measurements is strongly recommended to know exactly LAI, in order to assess instrument performance in a given site.

Functional genomics to discover genes for salt tolerance in annual and perennial plants

With the progress in plant genomics, more and more information is being gained about genes that respond to different stresses. Microarray analyses of transcriptome regulation under salt stress have uncovered the complex gene networks involved in mechanisms of sensing, signaling, and short-term response. Most of this knowledge has been derived from shock-stress experiments conducted on one genotype under laboratory conditions, but the long-term acclimation to salt stress has been addressed by only few studies. The genes responsible for the variability of salt tolerance could be valuable resources in breeding programs but they are difficult to identify in typical microarray experiments. The genes revealed by transcriptome analyses of salt-stressed plants are often common to other stresses and other species and do not explain the heritable variation. Comparative genomics is based on the comparison of genotypes differing in pheno-typical behavior and is a promising approach to identify genes that control the heritable genetic variation of salt tolerance.

Climate Change Impacts on Forests and Forest Products in the Mediterranean Area

The Mediterranean Region is defined according to its biogeography and bioclimate. Climate is characterized by mild winters and hot, dry summer. Biodiversity is rich and landscape patterns are complex. Mediterranean forests have historically been subjected to numerous threats (forest fires, over-exploitation, deforestation, degradation), that are today accentuated under climate and land use changes. In this respect, the Mediterranean area appears among the most vulnerable areas to global change. Forest area in the region has increased by 10% between 1990 and 2000. Roundwood nowadays represents 60% and woodfuel 40% of total wood products (125 Mm3). Sometime non-wood forest products and services are more important as they represent 60–70% of total economic value (133 € ha−1) of Mediterranean forests. There are already evidences of impacts of recent climate change on ecophysiology, productivity, dieback and distribution of Mediterranean forests and these impacts will become worse in the future, particularly for increased evaporative demand and repeated extreme events. An interdisciplinary research agenda, integrated with monitoring networks and projection models is needed to provide information at all levels of decision making and to implement a framework of dynamic and adaptive management planning.