Assessment of oak forest condition based on leaf biochemical variables and chlorophyll fluorescence.

Pedunculate oak forests (Quercus robur L.) in the Ticino Regional Park, Italy, are declining as a result of insect attacks, summer droughts and air pollution. The assessment and monitoring of forest condition can provide a basis for managing and conserving forest ecosystems and thereby avoid loss of valuable natural resources. Currently, most forest assessments are limited to ground-based visual evaluations that are local and subjective. It is therefore difficult to compare data collected by different crews or to define reliable trends over years. We examined vegetation variables that can be quantitatively estimated by remote observations and, thus, are suitable for objective monitoring over extended forested areas. We found that total chlorophyll (Chl) concentration is the most suitable variable for assessing pedunculate oak decline. It is highly correlated with visual assessments of discoloration. Furthermore, Chl concentration can be accurately estimated from leaf optical properties, making it feasible to map Chl concentration at the canopy level from satellite and airborne remote observations.