Late winter CO2 efflux measurements at treeline near the Agashashok River, Alaska, 2017-2019

The position of the Arctic treeline is an important regulator of surface energy budgets, carbon cycling and subsistence resources in high latitude environments. It has long been thought that temperature exerts a direct control on growth of treeline trees and the position of the treeline. However, our recent work on white spruce in the Arctic suggests that indirect effects of temperature on tree access to soil nutrients may be of equal or greater importance. Our recent results provide correlative evidence of the importance of winter snow depth as a driver of tree growth. The aim of this project was to experimentally isolate the importance of snow depth and soil nutrient availability and examine the consequences for microbial processes, tree growth and treeline advance. This dataset contains measurements of carbon dioxide (CO2) efflux from soils to the atmosphere that were made using the diffusion gradient method near the drip line of treeline white spruce in late March of 2017-2019. Measurements were made in three treeline ecotones that differ in soil hydrology (Hydric, Mesic and Xeric). Each each site consists of 8 control trees and 8 trees treated with individual snowfences (7.5 meters (m) long, 1.5 m tall).