• Vadeboncoeur, Matthew A.
  University of New Hampshire
  
• Hamburg, Steven P.
  Environmental Defense Fund
  
• Blum, Joel D.
  University of Michigan
  
• Pennino, Michael J.
  University of Maryland
  
• Yanai, Ruth D.
  SUNY College of Environmental Science and Forestry
  
• Johnson, Chris E.
  Syracuse University
  

Many important questions in ecosystem science require estimates of stocks of soil carbon and nutrients.   Quantitative soil pits provide direct measurements of total soil mass and elemental content in depth‐based samples representative of large volumes, bypassing potential errors associated with independently measuring soil bulk density, rock volume, and elemental concentrations.  The method also allows relatively unbiased sampling of other belowground carbon and nutrient stocks, including roots, coarse organic fragments, and rocks.  We present a comprehensive methodology for sampling these pools with quantitative pits and assess their accuracy, precision, effort, and sampling intensity as compared to other methods.  At 14 forested sites in New Hampshire, non‐soil belowground pools (which other methods may omit, double‐count, or undercount) accounted for upwards of 25% of total belowground N and C stocks: coarse material accounted for 4% and 1% of C and N in the O horizon; roots were 11% and 4% of C and N in the O horizon and 10% and 3% of C and N in the B horizon; and soil adhering to rocks represented 5% of total B‐horizon C and N.  The top 50 cm of the C horizon contained the equivalent of 17% of B‐horizon C and N.  Sampling procedures should be carefully designed to avoid treating these important pools inconsistently.  Quantitative soil pits have fewer sources of systematic error than coring methods; the main disadvantage is that because they are time‐consuming and create a larger zone of disturbance, fewer observations can be made than with cores.