Response of vegetation and carbon fluxes to brown lemming herbivory in northern Alaska

[摘要] The warming of the Arctic is affecting the carbon cycle of tundraecosystems. Most research on carbon fluxes from Arctic tundra ecosystems hasfocused on abiotic environmental controls (e.g., temperature, rainfall, orradiation). However, Arctic tundra vegetation, and therefore the carbonbalance of these ecosystems, can be substantially impacted by herbivory. Inthis study we tested how vegetation consumption by brown lemmings ( Lemmus trimucronatus ) canimpact carbon exchange of a wet-sedge tundra ecosystem near Utqiaġvik,Alaska during the summer and the recovery of vegetation during the followingsummer. We placed brown lemmings in individual enclosure plots and testedthe impact of lemmings' herbivory on carbon dioxide (CO 2 ) fluxes, methane(CH 4 ) fluxes, and the normalized difference vegetation index (NDVI)immediately after lemming removal and during the following growing season.During the first summer of the experiment, lemmings' herbivory reduced plantbiomass (as shown by the decrease in the NDVI) and decreased net CO 2 uptake while not significantly impacting CH 4 emissions. CH 4 emissions were likely not significantly affected due to CH 4 beingproduced deeper in the soil and escaping from the stem bases of the vascularplants. The summer following the lemming treatments, NDVI and net CO 2 fluxes returned to magnitudes similar to those observed before the start ofthe experiment, suggesting a complete recovery of the vegetation and atransitory nature of the impact of lemming herbivory. Overall, lemmingherbivory has short-term but substantial effects on carbon sequestration byvegetation and might contribute to the considerable interannual variabilityin CO 2 fluxes from tundra ecosystems.

[学科分类] 大气科学