A stochastic model for daily subsurface CO sub(2) concentration and related soil respiration

• Published in: Advances in water resources Vol. 31; no. 7; pp. 987 - 994
• Main Authors: Daly, E, Oishi, A C, Porporato, A, Katul, G G
• Format: Journal Article
• Language: English
• Published: 01.07.2008
• ISSN: 0309-1708
• DOI: 10.1016/j.advwatres.2008.04.001

Near-surface soil CO sub(2) gas-phase concentration (C) and concomitant incident rainfall (P sub(i)) and through-fall (P sub(t)) depths were collected at different locations in a temperate pine forest every 30min during the 2005 and 2006 growing seasons (and then averaged to the daily timescale). At the daily scale, C temporal variations were well described by a sequence of monotonically decreasing functions interrupted by large positive jumps induced by rainfall events. A stochastic model was developed to link rainfall statistics responsible for these jumps to near-surface C dynamics. The model accounted for the effect of daily rainfall variability, both in terms of timing and amount of water, and permitted an analytical derivation of the C probability density function (pdf) using the parameters of the rainfall pdf. Given the observed positive correlation between daily C and soil CO sub(2) fluxes to the atmosphere (F sub(s)), the effects of various rainfall regimes on the statistics of F sub(s) can be deduced from the behavior of C under different climatic conditions. The predictions from this analytical model are consistent with flux measurements reported in manipulative experiments that varied rainfall amount and frequency.