Modelling the critical role of cold acclimation for vegetation survival during extreme winter weather

Abstract

A climate model is an idealized representation of the Earth. Climate models are under constant improvement as they serve as tools for decision making. The land surface is the most uncertain part of the carbon cycle in climate models. Land models also tend to overestimate the amount of vegetation at high latitudes.

The aim of this thesis is to study and improve the representation in models of vegetation survival in cold regions of the world. In the Community Terrestrial System Model (CTSM), we introduced the capacity of plants to acclimate to cold temperatures during winter. The level of cold acclimation was used to reduce water flow through plant organs and to improve predictions of freezing mortality.

We observe that the reduction of water flow in cold acclimated plants benefits growth by preventing dehydration during winter, but this may be a disadvantage when the simultaneous reduction of photosynthesis is too large. Instead of frost damage to plants when temperature drops below a fixed threshold, plants now receive frost damage when temperature drops below the cold acclimation level, which varies among plants, locations, and time. The changes to the model are significant improvements for the modelling of vegetation in cold environments.