Isoprene emission from tropical forest canopy leaves

We screened 51 species of trees and vines for isoprene emission by using a tower crane to gain access to the top of the canopy in a semideciduous fore st in the Republic of Panama. Of the species screened, 15 emitted isoprene at rates greater than 0.8 nmol m(-2) s(-1). We measured the influence of li ght and temperature on emissions. The species-dependent emission rates at 3 03 K and 1000 mu mol m(-2) s(-1 o)f incident photosynthetically active radi ation ranged from 9 to 43 nmol m(-2) s(-1) with coefficients of variation o f about 20%. Isoprene emission showed a hyperbolic response to light intens ity and an exponential response to temperature. We modified an existing alg orithm developed for temperate plants to fit the temperature response of th ese tropical species. We suggest a new algorithm to fit the light response of isoprene emission. The new and modified algorithms are compared to the a lgorithms developed for temperate plants that are used in global models of isoprene emission. Both sets of algorithms also are compared to additional validation data collected in Panama and to published data on isoprene emiss ion from a tropical dry forest in Puerto Rico. Our comparisons suggest that algorithms developed for temperate plants can significantly underestimate isoprene emissions from tropical forests at high-light and high-temperature levels.