Response of CO2 efflux from forest and annual crop as a function of water retention capacity and the addition of nitrogen

Abstract

The carbon dioxide (CO2) efflux from various terrestrial ecosystems under various moisture contents provides a good understanding of the carbon cycle. The aim of this study was to evaluate the impact of extreme moisture content in the presence and absence of nitrogen (N) fertilizer application on CO2 efflux (ECO2) from forest and annual crop soils. The clay (forest (F ) soil) and sandy loam (annual crop (AC) soil) with or without Rhodic Ferrasol (FR-ro) N fertilizer application were incubated under increasing concentrations of water corresponding to 40-700% of the water retention capacity (WRC). Even with the same classification, the two soils presented particular chemical and physical characteristics, probably due to the conversion of the forest area to agriculture in the AC soil. In all assays, the most ECO2 was found at 24 h soil incubation period. After 24 h of incubation, ECO2 diminished, and the decreased ECO2 was found in annual crop AC 200 1 (incubated for 1728 h in 60, 80, 100, 150, 200, 300, 500 and 700 % WRC) soil. The effect of WRC varied between soils during all incubation periods. The highest ECO2 was found in annual crop AC(200) (incubated for 144 h in 50, 75, 100, 150 and 200 % WRC) and AC(700) (incubated for 144 h in 60, 100, 150, 200, 300 and 700 % WRC) soils with 100% and 60% WRC, respectively. No effect on microbial respiratory activity by the N addition in the soil was found. In waterlogged soils or soils subject to the increased amount of water contents, incubation time and moisture concentration are two important factors that influence ECO2.