Elemental Mobility through Small Tundra Watersheds

Abstract

Tundra plants and soils may constrain ecosystem response to climate change. To understand these constraints requires integrated studies of biogeochemical cycling in tundra ecosystems. This paper summarizes a 4-yr irrigation-fertilization experiment designed to evaluate elemental mobility through small tundra watersheds and examines the “leaky ecosystem-nutrient hypothesis.” The irrigation treatment increased elemental mobility of Fe and Mn, possibly due to reducing conditions caused by waterlogging. Ammonium and NO₃ concentrations remained above background levels for four field seasons following application of a slow-release NPK fertilizer. Sharp peaks and valleys in NH₄ and NO₃ concentrations over the four seasons suggest slow fertilizer solubilization due to low temperatures and mixing of waters of variable composition. Fertilizer P showed limited mobility. Soil solutions were saturated with respect to gibbsite suggesting that a gibbsite-like mineral may control Al solubility in these arctic soils. Comparisons of elemental concentrations among tundra ecosystems indicate that weathering rates are highly individualistic, depending critically on soil parent material. Furthermore, tundra ecosystems are leaky with respect to nutrients, which may have ramifications well beyond the disturbance both with respect to time and space, and bears attention in assessing the future response of tundra ecosystems.