PARENT SESSION
Oral Session #24: Forests: Carbon allocation, carbon budgets. Presiding: C. Reid.
Tuesday, August 7, 2001. 8:00 AM to 11:15 AM. Hall of Ideas F.

Root and "root-free" soil respiration response to soil temperature in Alaskan Black spruce forests.

Vogel, Jason¹, Valentine, David¹, ¹

ABSTRACT- Black spruce forests are ubiquitous throughout North American taiga and often overlay large stores of soil carbon. Near Fairbanks Alaska, topographic variation results in yearly average temperature differences that mimic latitudinal gradients. We located 3 black spruce sites, one of which is part of the Bonanza Creek Long-Term Ecological Research forest, that are similar in stand characteristics but differ in seasonal thaw timing and depth. Because root respiration and decomposition are both directly related to temperature, the relative response of these soil respiration components to temperature change may well determine ecosystem carbon balance. We measured soil respiration inside and outside areas of root exclusion to determine the relative amounts of carbon respired from heterotrophic microbes and derived from "roots" (including exudate and senesced root decomposition). From mid-June to late August 2000, the proportion of respiration derived from "roots" was greatest at the warmest site (62%) than the two colder sites (33%). Total soil respiration in the coldest site had the highest temperature sensitivity and lowest y-intercept (p<0.05). Soil temperature ranged from 2 to 18C and soil respiration 2.5 to 22 umol m-2 s-1. Soil moisture had no discernible influence on soil respiration. Root-free soil respiration response to temperature was consistent across sites, suggesting that root respiration accounted for most of the inter-site variation in temperature sensitivity.

KEY WORDS: soil, respiration, carbon, root