ABSTRACT
Predicting ozone-induced reduction of carbon sequestration of forests under elevated tropospheric ozone concentrations requires robust mechanistic leaf-level models, scaled up to whole tree and stand level. As ozone effects depend on genotype, the ability to predict these effects on forest carbon cycling via competitive response between genotypes will also be required. This study tests a process-based model that predicts the relative effects of ozone on the photosynthetic rate and growth of an ozone-sensitive aspen clone, as a first step in simulating the competitive response of genotypes to atmospheric and climate change. The resulting composite model simulated the relative above ground growth response of ozone-sensitive aspen clone 259 exposed to square wave variation in ozone concentration. This included a greater effect on stem diameter than on stem height, earlier leaf abscission, and reduced stem and leaf dry matter production at the end of the growing season. Further development of the model to reduce predictive uncertainty is discussed.
Subject(s)
Air Pollutants/pharmacology , Ozone/pharmacology , Plant Leaves/drug effects , Plant Stems/drug effects , Salicaceae/drug effects , Algorithms , Biomass , Carbon/metabolism , Climate , Ecosystem , Forestry , Models, Biological , Photosynthesis/drug effects , Photosynthesis/physiology , Plant Leaves/growth & development , Plant Leaves/metabolism , Plant Stems/growth & development , Plant Stems/metabolism , Salicaceae/genetics , Salicaceae/growth & development , Salicaceae/metabolismABSTRACT
The ECOPHYS model is an ecophysiological growth process model of juvenile poplar clones growing under near optimal conditions. The theoretical basis for the ECOPHYS model is that (1) individual leaves drive and control growth; (2) the microenvironment at the leaf exerts primary control of photosynthetic rates; (3) leaf orientation is a major determinant of that microenvironment, (4) photosynthates produced by leaves are allocated among meristematic and respiratory sinks: and (5) the plant's genome and microenvironment regulate photosynthate allocation. The major driving variables are solar radiation, temperature, and clonal morphological and physiological factors. The user can interact or override any or all of the input variables to examine the effects of such changes on photosynthetic production and growth. Verification and sensitivity analyses of ECOPHYS are presented and discussed. The use of ECOPHYS as a research tool is illustrated with several examples. Model potential and limitations are discussed.
