Soil CO2 fluxes in Irish agricultural systems

Abstract

Worldwide concern with climate change and its effects on our future environment requires a better understanding and quantification of the processes contributing to it. Studies on the role of soil processes is needed to quantify the large scale surface fluxes of water, heat and greenhouse gases and also to determine the effects of land use and land cover changes. CO2 efflux from soil to atmosphere is an important part of the C cycle in nature. One of the key questions to be addressed is the future dynamics of the greenhouse gas emission and their impact on global warming. The potential increase in CO2 release from the soil caused by future elevated temperature may have a positive feedback effect on the atmospheric CO2 and global change. Soil respiration, one of the major fluxes of global carbon cycling that could significantly slow down or accelerate the increase in atmospheric CO2, with consequent feedbacks to climate change. Soil respiration is influenced by land use, management practices, and environmental conditions. Soil CO2 flux was measured in a cut and grazed pasture and a spring barley field managed under Conventional and reduced tillage at the Oak Park Crop Research Centre, Co. Carlow, Ireland in order to determine the relationship between soil CO2 flux and environmental factors and biomass. Soil CO2 flux increased as the day progressed, and was positively related to above & belowground biomass. Soil C02 efflux averaged 3.25 g CO2-C m-2 day -1 for grassland, compared to 3.52 g C02-C m-2 day -1 for reduced tillage and 3.6 g CO2-C m-2 day -1 for conventional tillage under spring barley crop. However, most of the variation in soil CO2 flux explained by a multiple regression model was attributed to the annual cycles of soil temperature and moisture. Soil CO2 flux did not follow standard Qio relationships. Differences in soil CO2 efflux among treatments could be attributed to differences in SOC and MBC, and plant biomass input suggesting that land use plays a significant role in soil CO2 efflux from respiration.