Protocol Problems in Building the Alaska Carbon Database.

There is increased demand for soil carbon data in Alaska. Carbon data from various sources are constantly cited or used as estimates. Based on our examination of data from 292 pedons (excluding Arctic Alaska) the following problems were encountered:  (1) 83% of the pedons lack some horizon bulk density measurements. (2) 47% of the pedons have OC measured by dichromate oxidation which produced results 25% higher than that from TOC by ignition. (3) 20% of the pedons are missing OC and BD data on the surface organic horizons. (4) Some OC values were estimated from loss on ignition (LOI) and using the traditional conversion factor of 0.58, whereas in Alaska the factor is nearly 0.49. (5). In about 12% of the pedons the rock fragment contents were missing even though the texture modifiers were gravelly or very gravelly. (6) 3% of the pedons with missing depth increment. (7). Some Gelisol pedons lack ice content estimation.  Except item 5, 6 and 7, regression equations were developed based on parent material, drainage class, and comparable methodology to extrapolate the missing data. In addition, older supplementary data available or about 3% of the pedons sampled prior to 1990 were georeferenced by section, township, and range instead of GPS. Thus latitudes and longitudes were reestablished by plotting on geological maps.