Climate and Management Implications for Surface Soil C and N Properties and Important Soil Processes: A Soil Health Perspective.

Surface soils comprise a critical interface which influences soil health through their role in nutrient cycling and decomposition, soil structure and water infiltration, and erosion potential.  Furthermore, certain soil biogeochemical processes are critical to soil productivity and environmentally significant, and thus an important component of a soil health assessment.  In this study we tested multiple surface soil C and N properties and processes across the inland Pacific Northwest (PNW) to assess the influence of climate and management on surface soil health, and to gain greater understanding of the relationship between soil properties and processes.  Both active and passive pools of C and N were measured along with laboratory based potential and basal denitrification ( PDR/BDR) and potential nitrogen mineralization (PNM).  In short, mean annual precipitation and temperature were found to be the main drivers of soil C and N properties and processes, and both the hydrolysable and non-hydrolysable fractions were sensitive to these climate factors.  Permanganate oxidizeable carbon (POXC) is an easily measured soil property and displayed sensitivity to soil organic matter (SOM) stabilization and was coupled with 24 hour Cmin, another easily measured soil property, to provide complimentary information regarding the influence of tillage and cropping intensity on surface soil health. Multiple soil C and N properties also displayed a significant positive correlation with PNM and PDR, and to a lesser extent BDR.  An integration of climate variables along with management variables had varying levels of success in explaining variation in these soil processes, but represent that on a regional basis, easily measured variables can provide insight into harder to measure processes that have implications from a soil and environmental health perspective.