Impact of nitrification on soil acidification and cation leaching in a red alder ecosystem

Journal Article · · J. Environ. Qual.; (United States)

OSTI ID:5830717

Van Miegroet, H; Cole, D W

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/sub 3//sup -/ 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 menziesii (Mirbel) Franco) forest where soil N levels were significantly lower and no measurable HNO/sub 3/ production could be observed. In the red alder system, where > 100 kg ha/sup -1/ yr/sup -1/ of N were added through symbiotic N/sub 2/ fixation, the net annual NO/sub 3//sup -/ leaching past the 40-cm soil depth amounted to 3460 mol charges ha/sup -1/, and NO/sub 3//sup -/ concentrations in the solutions collected below 40 cm periodically exceeded drinking water standards of 10 mg L/sup -1/. The H/sup +/ and NO/sub 3//sup -/ 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/sup +/ 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/sub 3//sup -/ in solution triggered accelerated cation leaching, causing a selective redistribution of primarily exchangeable Ca/sup 2/ from the A to the B horizon. These field studies lead us to conclude that the rate and the selectivity of NO/sub 3//sup -/ 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.

• Research Organization: Univ. of Washington, Seattle
• OSTI ID: 5830717
• Journal Information: J. Environ. Qual.; (United States), Journal Name: J. Environ. Qual.; (United States) Vol. 13:4; ISSN JEVQA
• Country of Publication: United States
• Language: English

Related Subjects

510200* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACIDIFICATION
CALCIUM IONS
CATIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
DISSOLUTION
ECOLOGICAL CONCENTRATION
ECOSYSTEMS
ELEMENTS
ENVIRONMENTAL TRANSPORT
FORESTS
HYDROGEN COMPOUNDS
HYDROGEN IONS
HYDROGEN IONS 1 PLUS
INORGANIC ACIDS
ION EXCHANGE
IONS
LEACHING
MASS TRANSFER
NITRATES
NITRIC ACID
NITRIFICATION
NITROGEN
NITROGEN COMPOUNDS
NITROGEN FIXATION
NONMETALS
OXYGEN COMPOUNDS
SEPARATION PROCESSES
SOILS
TERRESTRIAL ECOSYSTEMS