| Popis: |
Although riparian zones can remove nitrate (N03") from groundwater, the interaction between vegetation type, subsurface patches of elevated organic matter, and N03removal rates is still uncertain. The goal of my study was to examine the effects of vegetation type on groundwater N03removal rates in poorly drained riparian subsoils with four treatments, two "forested" and two "suburban" treatments. I also examined the variability in N03removal rates between riparian sites and the relationship between patches of elevated organic matter in the subsoil and groundwater N03removal rates. My study was based on a mesocosm approach to simulate N03dynamics in the shallow groundwater. These mesocosms were obtained from paired forested and suburban (mowed vegetation dominated by non-woody species) vegetated areas at two different sites. Intact horizontal mesocosms (15 cm diam., 40 cm long PVC cores) were extracted from fine to medium textured sands. The soils were derived from stratified glacial drift and were classified as Typic humaquepts or Umbric endoaquods. At each site, I obtained mesocosms from at least 35 cm below the dormant season water table depth. These mesocosms were placed in a controlled environmental chamber and continuously dosed with bromide and N03amended groundwater for 71 days. Mass balance calculations were completed to determine the rate of groundwater N03--N removal from each saturated mesocosm. There was no significant difference in groundwater N03removal rates between forested and suburban vegetated areas within sites. However, there were significant |
