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Creators/Authors contains: "Crawford, Daniel"

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  1. ; ; ; ; ; ; ; (, Science)
    Climate-induced northward advance of boreal forest is expected to lessen albedo, alter carbon stocks, and replace tundra, but where and when this advance will occur remains largely unknown. Using data from 19 sites across 22 degrees of longitude along the tree line of northern Alaska, we show a stronger temporal correlation of tree ring growth with open water uncovered by retreating Arctic sea ice than with air temperature. Spatially, our results suggest that tree growth, recruitment, and range expansion are causally linked to open water through associated warmer temperatures, deeper snowpacks, and improved nutrient availability. We apply a meta-analysis to 82 circumarctic sites, finding that proportionally more tree lines have advanced where proximal to ongoing sea ice loss. Taken together, these findings underpin how and where changing sea ice conditions facilitate high-latitude forest advance. 
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  2. ; ; (, NSF Arctic Data Center)
    Tree-ring widths from 1576 white spruce trees growing at 78 treelines distributed across 19 research sites along a longitudinal gradient in the Brooks Range of northern Alaska. The general purpose of the sampling was to examine west-east variation in white spruce growth responses to changes in climate. Trees were sampled at both high ("alpine") and low elevation treelines ("arctic"). Increment cores were collected in August and September of 2022 as low as possible on each tree (~25 centimeter height). Trees indicated with an "f" were treated with NPK (nitrogen, phosphorus, potassium) fertilizer in June of 2019 and June of 2021. 
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