Harvard Forest Research

Organic Nitrogen Production and Turnover in Temperate Forest Soils

Principal Investigator: Adrien Finzi
Boston University: Apr 01 2008 - Aug 30 2010:

Abstract:
Previous research on soil nitrogen (N) availability in the temperate zone has focused on inorganic N cycling, reflecting the assumption that plants are only able to take up inorganic N forms. However, recent studies show that organic N can be taken up by temperate forest trees and that organic forms of N serve as a substrate for mineralization and nitrification (Gallet et al submitted, Finzi and Berthrong 2005). Despite the increasing evidence for the importance of organic N to plant nutrition, research on the processes that control the availability and plant uptake of organic N in temperate forest soils is limited. In light of these unknowns, the goals of this research are (1) to quantify the rate of organic N production and turnover in forest soils influenced solely by one of four tree species, white ash (Fraxinus americana), sugar maple (Acer saccharum), beech (Fagus grandifolia), and hemlock (Tsugas canadensis), (2) to examine seasonal variation in organic N production and turnover, and (3) to determine the effect of soil organic matter (SOM) chemistry and substrate availability on the production and turnover of organic N.
This research will take place in both the Harvard Forest, MA and in the Pisgah State Forest, NH. In the summer of 2007, we established six replicate 8-m radius plots dominated by each tree species. The two forms of organic N we will focus on will be amino acids and amino sugars. In each plot, we will measure the pool sizes and fluxes of organic N and inorganic N throughout the growing season. In the lab, we will perform experiments on the effects of SOM chemistry manipulations on organic N production and turnover.
: