Print PageBiological studies on terpenoid compounds focus on the biochemistry of the plants that emit them and the interaction of those compounds within their ecological niche. Atmospheric studies focus mainly on the identification and quantification of the compounds and their impacts on the chemistry of the atmosphere.
One chemical group that stands out from the groups of compounds that are studied by both disciplines are monoterpenes. The emissions of terpenes to the atmosphere play a major role in the chemistry of the lower atmosphere (troposphere) .These emissions are regulated by plant biochemistry, plant physiology, and by environmental factors like radiation and temperature. Monoterpene emissions increase with temperature but not always with light levels. In nature, terpenes act as a plant defensive mechanism against herbivores.
The objective of this work is to address the relevance of landscape structure on terpenoid emissions, using Pinus ponderosa (Ponderosa Pine) as the study species. Pinus ponderosa is a tree species that can form forests with different densities. It is known to possess different monoterpenes in their tissues and it is also known be an important terpenoid emitter. Ponderosa Pine will provide the opportunity to study landscape structure as a factor that could affect terpenoid emissions. The main questions are: 1) What are the factors that have the major influence on Ponderosa Pine emissions: Light or Temperature? 2) Does landscape structure affect terpenoid emissions (dense vs. not-dense forest)?
This study was carried out at the Manitou Experimental Forest (Lat. 38°6'0" N, Long. 105°5'30" W) during the summer of 2009. The site is representative of a Montane ecosystem dominated by Ponderosa Pine. The emissions of monoterpenes from Ponderosa Pine were determined using a dynamic plant enclosure system constructed from Teflon. Monoterpene emissions were adsorbed in a Carbotrap-TENAX cartridge and were analyzed using thermal desorption and GC-FID. Two branches from the same tree were measured each day, one branch in the sun and one in the shade. Emissions were measured over the course of 30 minutes three times per day. PAR and temperature were measured continuously throughout the day as well
Results/Conclusions
Preliminary results show that there is a significant difference on Ponderosa Pine emissions between sun and shaded branches. Statistical analysis shows that PAR has a stronger relationship with the emissions than temperature does.
