Relationships between CO2 evolution from soil, substrate temperature, and substrate moisture in four mature forest types in interior Alaska

Abstract

A soda lime technique was used to measure CO2 evolution at the soil surface in four mature forest types (aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), black spruce (Picea mariana (Mill.) B.S.P.), and white spruce (P. glauca (Moench) Voss)) in interior Alaska. Surface temperature, 15-cm depth temperature and soil moisture were measured concurrently with CO2 evolution. Accumulated CO2 evolution ranged from 1315-1654 g CO2 .cntdot. m-12 for the period May 1-Sept. 30 in 1981 and 1982 in the four stands. Data were used to develop 3-dimensional response surfaces and test mathematical models of respiration in relation to substrate temperature and moisture. GRESP, a biologically based model, provided a fairly accurate simulation of the seasonal course of respiration as a function of substrate temperature and moisture. In an attempt to better define the observed response surface trends, a best-fit equation model, BRESP, was formulated. BRESP includes the moisture portion of the GRESP equation, and an altered temperature equation which more adequately defines the upper and lower thresholds of respiration in relation to substrate temperature. GRESP and BRESP each produced similar r2 values; however, higher order polynomial equations gave a better-fit model. The weakest area of all models for simulating seasonal trends was during the periods of peak respiration in June.