PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Root respiration and biomass in the forest floor and surface mineral soil of northern hardwood forests receiving chronic N additions.

Burton, Andrew^*,1, Culclasure, John, ¹ Michigan Technological University, Houghton, MI

ABSTRACT- Previous research has found decreased soil respiration rates in response to chronic N additions in northern hardwood forsts in Michigan, but has not been able to provide a full mechanistic explanation. One possible mechanism is a reduction in the relative proportion of root biomass located in the forest floor under chronic N additions, since it is presumed that fine roots in the forest floor have inherently greater respiration rates than those in the surface mineral soil. By looking at the forest floor and surface mineral soil separately, which had not been done previously, this study hoped to better understand at least part of the decreased soil respiration puzzle. As predicted, respiration rates for fine roots (< 1 mm) in the forest floor were significantly greater than rates for fine roots in the surface mineral soil, corresponding to greater fine root N concentrations in forest floor roots. Fine root biomass was lower, but not significantly so, in the forest floor of the N-amended plots compared to the control plots. This trend is in the hypothesized direction needed to explain at least a portion of the reduced soil respiration in the N-amended plots. Root biomass measurements of forest floor and surface mineral soil at three additional sites receiving the same treatments will used to determine if the trend observed at this site occurs consistently and explains a portion of the reduction in soil CO₂ efflux resulting from chronic N additions.

Key words: chronic N deposition, root biomass, soil and root respiration, Acer saccharum