Biomass distributions in dwarf tree, krummholz, and tundra vegetation in the alpine treeline ecotone

Abstract

Alpine treeline ecotones are expected to respond to climate change with shifts in biomass patterns and carbon dynamics; however, the nature of these shifts and the current structure of carbon storage at treeline remain poorly understood. Biomass at treeline sites in Glacier National Park (GNP), Montana was measured in different aboveground carbon pools. Notably large proportions of biomass were recorded in compartments of dead material (~64% in upright tree cover, ~82% in krummholz). The storage of proportionally so much carbon in dead material complicates predictions of alpine treeline response to climate change, given the expectation of increased respiration losses through decomposition in a warmer climate. Although conventional belief holds that treeline advance will result in sequestration of carbon as tundra is replaced by trees, carbon release by decomposition may deviate from this expectation. This work represents a descriptive study that highlights the importance of conducting similar work at broader spatial scales and in more varied locations to further determine the magnitude and extent of its implications.