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キーワード:
alpine tundra; methane; trace gas
Nitrous-oxide flux; atmospheric methane; spatial variation;
forest soils; consumption; temperature; responses; oxidation;
emission; water
要旨:
We measured CH4 fluxes from three major plant communities characteristic of alpine tundra in the Colorado Front Range. Plant communities in this ecosystem are determined by soil moisture regimes induced by winter snowpack distribution. Spatial patterns of CH4 flux during the snow-free season corresponded roughly with these plant communities. In Carex- dominated meadows, which receive the most moisture from snowmelt, net CH4 production occurred. However, CH4 production in one Carex site (seasonal mean = +8.45 mg CH4 m(-2) d(-1)) was significantly larger than in the other Carex sites (seasonal means = -0.06 and +0.05 mg CH4 m(-2) d(-1)). This high CH4 flux may have resulted from shallower snowpack during the winter. In Acomastylis meadows, which have an intermediate moisture regime, CH4 oxidation dominated (seasonal mean = -0.43 mg CH4 m(-2) d(-1)). In the windswept Kobresia meadow plant community, which receive the least amount of moisture from snowmelt, only CH4 oxidation was observed (seasonal mean = - 0.77 mg CH4 m(-2) d(-1)). Methane fluxes correlated with a different set of environmental factors within each plant community. In the Carex plant community, CH4 emission was limited by soil temperature. In the Acomastylis meadows, CH4 oxidation rates correlated positively with soil temperature and negatively with soil moisture. In the Kobresia community, CH4 oxidation was stimulated by precipitation. Thus, both snow-free season CH4 fluxes and the controls on those CH4 fluxes were related to the plant communities determined by winter snowpack.We measured CH4 fluxes from three major plant communities characteristic of alpine tundra in the Colorado Front Range. Plant communities in this ecosystem are determined by soil moisture regimes induced by winter snowpack distribution. Spatial patterns of CH4 flux during the snow-free season corresponded roughly with these plant communities. In Carex-dominated meadows, which receive the most moisture from snowmelt, net CH4 production occurred. However, CH4 production in one Carex site (seasonal mean = +8.45 mg CH4 m(-2) d(-1)) was significantly larger than in the other Carex sites (seasonal means = -0.06 and +0.05 mg CH4 m(-2) d(-1)). This high CH4 flux may have resulted from shallower snowpack during the winter. In Acomastylis meadows, which have an intermediate moisture regime, CH4 oxidation dominated (seasonal mean = -0.43 mg CH4 m(-2) d(-1)). In the windswept Kobresia meadow plant community, which receive the least amount of moisture from snowmelt, only CH4 oxidation was observed (seasonal mean = - 0.77 mg CH4 m(-2) d(-1)). Methane fluxes correlated with a different set of environmental factors within each plant community. In the Carex plant community, CH4 emission was limited by soil temperature. In the Acomastylis meadows, CH4 oxidation rates correlated positively with soil temperature and negatively with soil moisture. In the Kobresia community, CH4 oxidation was stimulated by precipitation. Thus, both snow-free season CH4 fluxes and the controls on those CH4 fluxes were related to the plant communities determined by winter snowpack.
