Municipal wastewater effects on nitrogen cycling in a mature hardwood forest

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:5642934

Kim, D Y

Land disposal of municipal wastewater is considered ecologically acceptable and cost effective. The success of land treatment systems, however, requires proper functioning of all ecosystem components. The impact of municipal wastewater irrigation on the structure and function of an Appalachian hardwood forest in Virginia was investigated. Four irrigation rates (17.5, 35, 70, and 140 cm yr[sup [minus]1]) were applied in this hardwood forest, and their effects on forest nutrient cycling were monitored for two years. Tree growth, seedling reproduction, tree mortality, species diversity, and N sequestering by vegetation were not changed significantly. Herbaceous ground cover increased due to irrigation, except for the 140 cm yr[sup [minus]1] treatment where the heavy spray caused physical damage to the cover. Depending on the rate applied, the mature hardwood forest system sequestered only [minus]3.4 to 8.2 kg N ha yr[sup [minus]1] in the aboveground biomass. Therefore, the fate of added N to the system became a function of N transformation processes in the soil. Nitrogen mineralization and nitrification increased as irrigation increased. Denitrification rates were not affected by irrigation; the process of denitrification did not constitute a significant N output from the forest system. The additional soil nitrate (NO[sub 3][sup [minus]]) was left to leach because of the low assimilation by the plant/soil system and the low denitrification rate. Nitrogen storage decreased in the forest floor due to the increase in litter decomposition, and increased in the surface soil due to the increase in microbial N assimilation. Total soil N increased on the low irrigation sites and decreased on the high irrigation sites, indicating that high rates of irrigation stimulated N loss from the soil by enhancing soil N transformations. The health of the forest ecosystem was not adversely affected during this period, but the forest did not serve as a net sink for N.

• Research Organization: Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Chemistry
• OSTI ID: 5642934
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320604 -- Energy Conservation
Consumption
& Utilization-- Municipalities & Community Systems-- Municipal Waste Management-- (1980-)
54 ENVIRONMENTAL SCIENCES
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
BIOLOGICAL EFFECTS
BIOMASS
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
DENITRIFICATION
DISSOLUTION
ELEMENTS
ENERGY SOURCES
FORESTS
GROUND COVER
GROWTH
HYDROGEN COMPOUNDS
IRRIGATION
LEACHING
LIQUID WASTES
MINERALIZATION
MORTALITY
MUNICIPAL WASTES
NITRIFICATION
NITROGEN
NITROGEN COMPOUNDS
NITROGEN CYCLE
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PLANT GROWTH
RENEWABLE ENERGY SOURCES
REPRODUCTION
SEPARATION PROCESSES
SPECIES DIVERSITY
WASTE PRODUCT UTILIZATION
WASTE WATER
WASTES
WATER