Reply to comment by Gracz on “Wetland drying and succession across the Kenai Peninsula Lowlands, south-central Alaska”Appears in the Can. J. For. Res. 35: 1931–1941.

Abstract

Gracz (2011, Can. J. For. Res. 41: 425–428) proposes that the Good Friday earthquake of 1964 caused falling lake levels and drying wetlands on Alaska’s Northern Kenai Lowlands (NKL). His hypothesis states that the earthquake increased hydraulic conductivity by fracturing a leaky confining layer, accelerating drainage of surface water into regional aquifers. We counter that a single model of draining does not apply across the heterogeneity of geomorphology and soils on the NKL. In particular, the NKL’s glacial history precludes uniform application of a subsurface hydrologic model for lake draining and the nature of peat-based wetlands precludes its application to wetland drying. Instead, small, yet cumulative, climatic reductions in moisture surplus explain both observed lake level declines and vegetation changes. Moreover, and unlike a climatic hypothesis, a seismic hypothesis fails to explain lake drying elsewhere in Alaska. Although it is likely that the earthquake influenced some hydrologic features in the NKL, it is unlikely that a single hydrologic model based on a simple mechanical cause, e.g., downward drainage, adequately explains the changes observed across the whole NKL. Conversely, we maintain that the uniformity of the vegetation response seen across different landscapes, including wetlands, forests, and alpine areas, throughout the state of Alaska strongly supports a climatic hypothesis.