Improving assessments of tropospheric ozone injury to Mediterranean montane conifer forests in California (USA) and Catalonia (Spain) with GIS models related to plant water relations

摘要

The impacts of tropospheric ozone on conifer health in the Sierra Nevada of California, USA, and the Pyrenees of Catalonia, Spain, were measured using field assessments and GIS variables of landscape gradients related to plant water relations, stomatal conductance and hence to ozone uptake. Measurements related to ozone injury included visible chlorotic mottling, needle retention, needle length, and crown depth, which together compose the Ozone Injury Index (OH). The OH values observed in Catalonia were similar to those in California, but Oil alone correlated poorly to ambient ozone in all sites. Combining ambient ozone with CIS variables related to landscape variability of plant hydrological status, derived from stepwise regressions, produced models with R~2 = 0.35, p = 0.016 in Catalonia, R~2 = 0.36, p < 0.001 in Yosemite and R~2 = 0.33, p = 0.007 in Sequoia/Kings Canyon National Parks in California. Individual OH components in Catalonia were modeled with improved success compared to the original full Oil, in particular visible chlorotic mottling (R~2 = 0.60, p < 0.001). The results show that ozone is negatively impacting forest health in California and Catalonia and also that modeling ozone injury improves by including GIS variables related to plant water relations.