# Local Adaptation for Seasonal Cold Tolerance in a High‐Elevation Conifer Species, Subalpine Larch (Larix lyallii Parl.)

## TL;DR

This study shows that subalpine larch populations from colder areas are better adapted to extreme cold, which is important for their conservation as their habitat shrinks due to climate change.

## Contribution

The study provides the first evidence of local adaptation in cold tolerance for subalpine larch.

## Key findings

- Populations from colder sites with shorter frost-free periods showed higher cold tolerance.
- Cold tolerance differences were most pronounced in spring and autumn.
- Climate variables like frost-free period length predict cold injury in subalpine larch.

## Abstract

Subalpine larch (
Larix lyallii
Parl.) is a deciduous conifer that only grows at treeline in the Cascade Range and Rocky Mountains of western North America. This habitat is shrinking due to climate change but subalpine larch is unlikely to migrate or adapt in situ and is therefore at risk of maladaptation and eventual extirpation. Future conservation efforts should be informed by an understanding of local adaptation in key traits. In this study, cold tolerance was assessed for 18 populations of subalpine larch from the Canadian portion of the species range that are grafted ex situ at the Kalamalka Forestry Centre in Vernon, BC. Electrolyte leakage was measured after stem tissue was subjected to artificial freezing tests at a range of subzero temperatures (−10°C to −40°C) over 2 years and three seasons (winter, spring, and autumn). Adaptive clines in cold tolerance were observed, providing the first evidence of local adaptation in this species. Temperature‐associated climate variables such as the length of the frost‐free period (FFP), the Julian date for the end of the frost‐free period, and mean coldest month temperature were significant predictors of cold injury at −40°C in all three seasons. Populations from colder sites with a shorter FFP were found to have significantly higher cold tolerance in all three seasons, with the biggest differences observed in spring and autumn. Future management strategies should prioritize the conservation of adaptive variation in cold tolerance.