The contribution of instream wood to streambed organic matter controls on microbial metabolic activity

Microbial metabolic activity (MMA) in streambeds drives greenhouse gas (GHG) production and nutrient turnover. Previous research has identified that the quantity and quality of organic matter (OM) are important controls on MMA. Instream wood may make a significant contribution to the total OM content of the streambed, especially in forested streams, but it has typically been ignored or explicitly omitted in previous research. By means of an incubation experiment, we investigate the impact of streambed wood on MMA, GHG production and nutrient turnover rates. By using three geologies (sandstone, chalk and limestone) and allowing temperatures to fluctuate with environmental conditions, we observe these impacts under a range of typical scenarios. These results could have implications for estimates of GHG emissions from streams and inform catchment management, for example the impacts of direct installation of instream wood in river restoration or the indirect input as a result of riparian planting.