A Review of Methods Used to Measure Treeline Migration and Their Application

Abstract

Treelines define the upper limits of where trees are capable of growing. These exist at high elevations across many of the world’s mountain ranges and at high latitudes across much of Russia and Canada. With climate change causing more favourable conditions for tree-expansion in many areas, these boundaries are moving to higher elevations and latitudes in many places. In this study we look at four of the more common methods used to track and monitor treeline changes, specifically dendrochronology, measurements of tree-diameter, repeat vegetation transects, and the use of photographs and remotely sensed imagery. We break down the various methods and discuss their reliability under various conditions. There are a few key parameters that determine the suitability of a method to measure treeline change, such as the accessibility of the study site, the availability of historical data such as photographs, notes or maps, the size of the area to be studied, and if the drivers of migration are of interest. Dendrochronology provides the most exact data and is the only methodology that enables correlation of treeline movements with climate change. However, using remote sensed data and repeat photographs is a quicker approach that allows larger areas to be studied. We highlight that no method is consistently superior but that the optimum method is largely site and scale dependent.

Keywords: dendrochronology, method selection, repeat photography, treeline migration, treerings, vegetation transect, vegetation chang