Soil respiration within riparian buffers and adjacent crop fields

We quantified rates of soil respiration among sites within an agricultural landscape in central Iowa, USA. The study was conducted in riparian cool-se ason grass buffers, in re-established multispecies (switchgrass + poplar) r iparian buffers and in adjacent crop (maize and soybean) fields. The object ives were to determine the variability in soil respiration among buffer typ es and crop fields within a riparian landscape, and to identify those facto rs correlating with the observed differences. Soil respiration was measured approximately monthly over a two-year period using the soda-lime technique . Mean daily soil respiration across all treatments ranged from 0.14 to 8.3 g C m(-2) d(-1). There were no significant differences between cool-season grass buffers and re-established forest buffers, but respiration rates ben eath switchgrass were significantly lower than those beneath cool-season gr ass. Soil respiration was significantly greater in both buffer systems than in the cropped fields. Seasonal changes in soil respiration were strongly related to temperature changes. Over all sites, soil temperature and soil m oisture together accounted for 69% of the seasonal variability in soil resp iration. Annual soil respiration rates correlated strongly with soil organi c carbon (R = 0.75, P < 0.001) and fine root (<2 mm) biomass (R = 0.85, P < 0.001). Annual soil respiration rates averaged 1140 g C m(-2) for poplar, 1185 g C m(-2) for cool-season grass, 1020 g C m(-2) for switchgrass, 750 g C m(-2) for soybean and 740 g C m(-2) for corn. Overall, vegetated buffers had significantly higher soil respiration rates than did adjacent crop fie lds, indicating greater soil biological activity within the buffers.