MEASURING NUTRIENT AVAILABILITY IN ARCTIC SOILS USING ION-EXCHANGE RESINS - A FIELD-TEST

We tested the suitability of ion exchange resin (IER) bags for in situ measurement of nutrient availability in arctic ecosystems where nutrient mineralization rates are exceptionally low. We deployed IER bags for 2 to 44 wk in a variety of ecosystem types on the North Slope of Alaska and compared N and P accumulation on the resins to several other measures of plant-available N and P, including net N mineralization rates measured using in situ soil incubations. We also tested various factors that could affect nutrient accumulation on IER to optimize the performance of IER. Long deployment times gave lower estimates of nutrient availability than did a series of shorter deployments. Nitrate and phosphate were desorbed in the field when resins were preloaded with these nutrients, but NH4+ was not. Neither the amount of resin nor the small soil disturbance associated with its placement appeared to affect nutrient accumulation rates on IER. Nutrient accumulations on IER did not correlate well with other measures of NH4+, NO3-, and phosphate availability. However, landscape differences in N vs. P availability ascertained from resins corresponded well with N/P ratios in soils and soil solutions and with results from factorial fertilizer experiments. Seasonal patterns of nutrient availability determined by resins were also consistent with plant uptake data.