Mitchell Zimmerman; Dana Chadwick; Kathleen Grant; Corey Lawrence
Soil organic carbon (SOC) holds a significant portion of terrestrial carbon stores, and studies have found that the stability of this carbon stock could be dependent on soil manganese (Mn) limiting microbial decomposition processes. The purpose of this study is to determine if the positive relationship between Mn availability in soil and the rate of decomposition of organic matter identified in past studies has any discernible influence on the SOC concentration in soil samples collected across sites with various vegetation and geology types in the Upper East River Watershed in Colorado. The samples were collected from 437 sites containing multiple conifer species, quaking aspen stands, riparian shrubs, and diverse meadows. In total, 487 samples were collected and processed to determine the SOC and Mn content of the fresh leaves, litter, soil, and roots. When comparing Mn and SOC levels across different vegetation types, we found conifer systems to have a significantly higher litter, foliar, and root Mn than the meadow, broadleaf, and shrub systems, and significantly higher SOC than every other vegetation type except wet meadow. Linear regression of SOC vs Mn found a slight positive relationship between the two, but had an insignificant p-value at the p = 0.05 level. In conifer systems, a statistically significant positive relationship was found, and in wet and mesic meadow systems we saw convincing negative relationships, both with significant p-values. In other words, the results were inconsistent across vegetation systems. Our findings imply, despite evidence that Mn is a convincing predictor of decomposition rates and long-term carbon sequestration in the soil, that it is difficult to use such knowledge to predict soil and topographic features in practice and that findings may not be transferable from boreal to temperate montane systems.