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The Impact of Nitrification on Soil Acidification and Cation Leaching in a Red Alder Ecosystem
Author(s) -
Van Miegroet H.,
Cole D. W.
Publication year - 1984
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1984.00472425001300040015x
Subject(s) - alder , leaching (pedology) , nitrification , soil acidification , chemistry , acid neutralizing capacity , cation exchange capacity , environmental chemistry , ecosystem , soil ph , environmental science , soil water , agronomy , ecology , soil science , nitrogen , biology , organic chemistry , acid deposition
The objectives of this study were to investigate the impacts of internal nitrification on soil and soil solution acidity and on the rate of nutrient export through NO 3 − mediated leaching. This was achieved by comparing soil chemical properties and soil solution composition within a naturally N‐rich red alder ( Alnus rubra Bong.) ecosystem to those of an adjacent Douglas‐fir [ Pseudotsuga menziesil (Mirbel) Franco] forest where soil N levels were significantly lower and no measurable HNO 3 production could be observed. In the red alder system, where > 100 kg ha −1 yr −1 of N were added through symbiotic N 2 fixation, the net annual NO 3 − leaching past the 40‐cm soil depth amounted to 3460 mol charges ha −1 , and NO 3 − concentrations in the solutions collected below 40 cm periodically exceeded drinking water standards of 10 mg L −1 . The H + and NO 3 − release was most pronounced in the forest floor and top 10 cm of the soil under alder occupancy and caused significant acidification of percolating solutions. Less than 1% of the total H + input from internal (nitrification) and external (atmospheric) sources leached below the 40‐cm depth, which was indicative for the strong buffering capacity of this particular soil. The cation displacement reactions involved in this pH buffering caused a 15% decline in base saturation and a significant acidification of the upper part of the soil profile. The presence of large amounts of mobile NO 3 − in solution triggered accelerated cation leaching, causing a selective redistribution of primarily exchangeable Ca 2+ from the A to the B horizon. These field studies lead us to conclude that the rate and the selectivity of NO 3 − mediated leaching in a red alder system could significantly lower the exchangeable cation pool in the rooting zone or cause nutrient imbalance, if a site is managed for repeated rotations of red alder.