Variability of nitrogen and carbon in surface soils of six forest types in the Oregon Cascades

Soil samples were collected from sites typical of six forest habitattypes in the western Oregon Cascades to determine the variabilityIn total N, C, and mineralizable N. Within each type, 20 samplesof surface soil (0-15 cm deep) were removed from around the outsideperimeter of a 0.25-ha plot. Averages of 23, 28, and 70 samples wereneeded to estimate the population mean of total N, C, and miner-alizable N, respectively, with an accuracy of ± 10% at a 95% prob-ability. Variability was not reduced by reporting data on the basisof mass per area rather than concentration, but the method of re-porting data affected the relative ranking of sites. Within-site var-iability was not generally related to microsite differences in slope orcoarse fragment content.
Additingal Index Words: soil sampling, soil variability, mineral-izable N, habitat types.