Chemistry and microbial activity of forest and pasture riparian-zone soils along three Pacific Northwest streams

Throughout the United States, agricultural practices are responsible for large quantities of nutrients entering lakes and streams. Previous studies have shown that forested riparian areas can filter nutrients from surface runoff and groundwater that may potentially contaminate lakes and streams. This study examined seasonal differences in soil chemistry and soil microorganisms in paired mixed-forest riparian and pasture systems, the aim being to gain understanding of the sequestering of N and P. The forest soils retained higher levels of organic C and N, mineralizable N, extractable P, and fungal biomass, and had higher respiration rates than pasture soils. These findings suggest that forested riparian zones have a greater capacity than pasture soils to sequester C and retain nutrients. In past studies, fungal biomass has been shown to be less than bacterial biomass in grassland soils, but in this study, fungal biomass was greater than bacterial biomass throughout the year in both forest and pasture soils.