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Harvard Forest REU Symposium Abstract 2009
- Title: Response of nitrate reductase enzyme activity to soil warming in sapling and canopy trees
- Author: Noelia I Aponte (University of Puerto Rico)
- Abstract:
Increased net nitrogen mineralization and nitrification with warming has been recorded in an ongoing soil warming experiment at Harvard Forest. This has resulted in an increased in the amount of nitrogen available to trees in the heated plot. Trees that posses nitrate reductase enzyme activity are capable of absorbing and reducing nitrates. Species with high nitrate reductase enzyme activity could have an advantage in environments with increased nitrate availability. The present study investigated the relative levels of nitrate reductase enzyme activity among the canopy dominate and understory tree species to examine which species are more readily accessing nitrate than others. We also determined the effects of warming on the nitrate reductase activity of the different species in both the understory and overstory. The results of this study will further enhance the understanding of the nitrogen cycle. Leaf tissues of red maple, white ash and oak trees in the overstory and red maple, sugar maple, oak and black birch trees in the understory were assayed for in vivo nitrate reductase enzyme activity. Determination of the nitrate reductase enzyme activity was done via a colorimetric assay and the enzyme activity was quantified based on the NO2- concentration found in the leaf tissues. Higher levels of nitrate reductase enzyme activity were measured in the leaves of oaks and black birch trees suggesting that nitrate assimilation was significant in these species. Understory black birch had the overall highest nitrate reductase activity. Warming had varying effects on nitrate reductase activity dependant on species. Black birch increased in nitrate reductase activity with warming, while oak trees decreased in activity.
- Research Category: Soil Carbon and Nitrogen Dynamics
