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Controls on Soil Solution Chemistry in a Subalpine Forest in North‐Central Colorado
Author(s) -
Arthur M. A.,
Fahey T. J.
Publication year - 1993
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1993.03615995005700040040x
Subject(s) - abies lasiocarpa , snowmelt , subalpine forest , soil water , environmental science , hydrology (agriculture) , lysimeter , alpine climate , watershed , picea engelmannii , environmental chemistry , ecology , surface runoff , chemistry , ecosystem , geology , soil science , montane ecology , biology , machine learning , computer science , geotechnical engineering
High‐elevation ecosystems in the western USA are potentially susceptible to increased inputs of strong acids. A long‐term research project was established to identify the processes controlling surface water chemistry and to evaluate the sensitivity of Loch Vale Watershed in Rocky Mountain National Park, Colorado, to acid precipitation. Using lysimeters, we estimated the concentration and flux of major solutes in the Oie and B horizons in an old‐grown Englemann spruce ( Picea engelmannii Parry ex Engelm.) and subalpine fir [ Abies lasiocarpa (Hook.) Nutt.] forest, and in an adjacent site disturbed by a snow avalanche. In the forested site, most solutes were highly concentrated in soil solutions during the initial stages of snowmelt, and concentrations declined rapidly to low levels in the first 4 to 6 wk of snowmelt. Surface water chemistry in Loch Vale Watershed is controlled principally by mineral weathering. During the early stages of snowmelt, however, the flushing of solutes, especially N, S, and C, from forest soils (which comprise only 6% of the study area) exerts an important influence. Rates of cationic denudation per unit area were 3.5 times higher in the forest (131 µmol c m −2 yr −1 ) than in the whole watershed (38 µmol c m −2 yr −1 ) probably because of H + exudation from roots during nutrient uptake and the generation of organic acids in the forest soils. Rates of N mineralization and nitrification as well as concentrations of NO 3 in the soil solution were higher in the second year after forest disturbance from a snow avalanche than immediately following the disturbance, indicating a delayed nitrification response. Significant amounts of NH 4 and NO 3 were temporarily stored in extractable forms in the soil during the first year after the disturbance. Although precipitation inputs and theoretical mineral weathering can explain the total annual solute flux from Loch Vale Watershed, the effects of forest soil solutes may be important during the initial stages of snowmelt and following large‐scale disturbance.