Natural wetlands tend to exhibit high levels of soil microhabitat spatial variability, especially in open systems such as headwater complexes.  Since the 18^th century, however, wetlands have been altered due to their position in a matrix of human-induced land changes. In recent years investigations have shown that surrounding land use can lead to hydrologic modification, accelerated sedimentation, and shifts in vegetative and invertebrate community composition.  Less is understood about how these disturbances affect the spatial variability of soils and their microbial processes.  The objective of this study is to characterize variability in the soil microhabitat at two spatial scales within eight headwater wetlands, four that are surrounded by a matrix of land uses and four located in intact forested landscapes. Soil samples were collected from forty-five 1m² sampling blocks within each 40 m² site, on four sampling dates between August of 2006 and 2007. Additional soil cores were collected at 32 random points within six 1m² plots in June 2008. Soils are being analyzed for organic horizon depth, moisture, pH, and an extractable fraction of organic matter.  Variables are being extracted from geostatistical semivariogram models and, along with descriptive statistics, are being compared among dates and between levels of disturbance.

Results/Conclusions

Results show that disturbed sites lack a significant soil organic horizon, while forested sites have high variblity in the depth of their organic horizons. Coefficients of variation for soil moisture and pH are generally higher in forested sites across scales.  Although variation in pH remains constant across dates, the level of significance varies across dates for soil mositure, with larger differences between disturbance levels during summer months.  Over all the comparisons made thus far, one disturbed site is more variable than the others, acting more like a forested site.  We suggest that this might be related to differences in the degree of soil legacy effects from past land use. In summary, results indicate a lower level of variablity in microbial habitat parameters at disturbed sites, compared to sites with intact forested landcapes, a difference that could significantly impact the key microbial processes that these headwater systems provide.