Road Dust Alters Extracellular Enzyme Activities in Tussock Tundra Soils, Alaska, U.S.A.

Moorhead, D; Linkins, A; Everett, K

Dust from gravel roads affects soil physical-chemical characteristics, microclimate, and plant communities of tussock tundra ecosystems in northern Alaska, U.S.A. We found that activities of extracellular enzymes associated with cellulose decay and phosphorus mineralization in soils were inversely proportional to dust loading along the Dalton Highway, Alaska. Overall, endocellulase, exocellulase, and phosphatase activities within 5 m of this gravel road were reduced by 88, 74, and 45%, respectively, of activity levels at 500 m. Detailed examinations of soil components showed that phosphatase enzyme activities were displaced from organic matter complexes by dust inputs and became adsorbed onto mineral materials. This decreased the rate of enzyme-mediated reactions. Mathematical models incorporating these reduced levels of enzyme activities projected substantial reductions in carbon (from cellulose) and phosphorus mineralization. Moreover, reduced carbon utilization by decomposer microbiota, resulting from slower cellulose decay, also decreased microbial immobilization of nitrogen, thus increasing simulated net nitrogen mineralization. Such changes in soil nutrient dynamics would be expected to affect the structure of plant communities, as has been reported for vegetation adjacent to the Dalton Highway. However, concurrent changes in other environmental characteristics of the soil environment near this road (e.g., drainage) limit our ability to establish causal relationships.

Road Dust Alters Extracellular Enzyme Activities in Tussock Tundra Soils, Alaska, U.S.A.

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