Development of an instantaneous puff model: (1) Dispersion of an insect pheromone plume in conifer canopies and (2) Advection of carbon dioxide within a canopy during nocturnal drainage flows.

摘要

The overall goals of this work are to improve our understanding and ability to model the transport and dispersion of gases within a forest canopy and to develop a useful, relatively simple dispersion model to treat transport and dispersion within a canopy. Two areas of application are the transport of pheromones released from bark beetle infestations and the measurement and modeling of CO2 fluxes within and above a forest during nighttime drainage flows.; The summer flight behavior of Ips pini in response to its aggregate pheromone was studied in a northern Michigan pine forest from 2002 through 2004. Peak seasonal flight occurred in July and late September with a diurnal peak occurring between 4 PM and 8 PM. Ips pini significantly preferred to fly above 1.3 m (2002). Bi-hourly average temperature was found to significantly affect bi-hourly Ips pini trap catch, but not fully explain the variation in catch.; Assessment of sulfur hexafluoride (SF6) tracer concentrations and Ips pini behavioral response to a synthetic aggregation pheromone source showed that distance from the source, but not direction, to have a significant affect on trap catch. Attraction to unbaited traps increased at estimated pheromone concentrations greater than 0.02 mug m-3. SF6 was found to be a suitable pheromone surrogate for Ips pini.; A three-dimensional Lagrangian puff model was developed to simulate instantaneous transport and dispersion within a forest canopy. The puff model simulated the dilution of SF6, used as pheromone surrogate, within a factor of two of the observations 53%--90% of the time at distances from 5 m to 30 m from the source. Additionally, the model simulated the instantaneous sharp peaks and narrow widths common in pheromone plume behavior.; To address uncertainties in the measurement of Net Ecosystem Exchange of carbon for a forest, the model was applied to simulate transport and dispersion of CO2 at the Niwot Ridge AmeriFlux site (Colorado). SF6 tracer data and CO2 vertical profiles, collected at upslope and downslope mass-balance towers, were used to evaluate the model. Model performance was acceptable with simulated nighttime horizontal flux within 20% of the observed horizontal flux.