Estimating Soil Nitrogen and Carbon Pools in a Northern Hardwood Forest Ecosystem

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Abstract
An intensive soil sampling design was evaluated to determine what resolution could be obtained in N and C pool size estimates in a northern hardwood forest soil. Pits of measured volume were excavated by horizon in the forest floor and in three depth strata in the mineral soil. Future comparisons should be able to detect differences in N and C pool sizes ranging from 8 to 25% of the observed mean values depending upon the element and depth strata. Future sampling should detect changes of 230 and 130 kg N ha−1 in the forest floor (combined O horizons) and 0‐ to 10‐cm stratum in the mineral soil respectively. Similarly, changes of 5.9 and 2.4 Mg C ha−1 should be detectable for forest floor and 0 to 10 cm pools respectively. Soil N content for the forest floor was 1300 kg N ha−1. For the mineral soil depth strata (0–10 cm, 10–20 cm, 20 cm to the bottom of the B horizon), N contents were 1600, 1200 and 3100 kg N ha−1 respectively. Total solum N content was estimated to be 7200 kg N ha−1. Soil C contents for the combined O horizons, 0‐ to 10‐, 10‐ to 20‐ and ≥ 20‐cm strata were 30, 32, 27 and 73 Mg C ha−1 respectively. The total solum C content was estimated to be 160 Mg C ha−1. Concentrations of soil N and C were positively correlated with elevation over the 240 m range studied, but soil pools of N and C were not correlated with elevation or soil mapping unit.