Possible Increase of Vegetation Exposure to Spring Frost under Climate Change in Switzerland

Ondřej Lhotka,Stefan Brönnimann

doi:10.3390/atmos11040391

Abstract

We assessed future changes in spring frost risk for the Aare river catchment that comprises the Swiss Plateau, the most important agricultural region of Switzerland. An ensemble of 15 bias-corrected regional climate model (RCM) simulations from the EXAR data set forced by the RCP 4.5 and RCP 8.5 concentration pathways were analysed for two future periods. Correlating actual meteorological observations and Swiss phenological spring index, we proposed and tested an RCM-compatible methodology (based on temperature data only) for estimating a start of spring and severity of frost events. In the historical climate, a significant advancement in start of spring was observed and frost events were more frequent in those years in which spring started sooner. In 2021–2050, spring is projected to start eight (twelve) days earlier, considering the RCP 4.5 (8.5) scenario. Substantial changes were simulated for the 2070–2099 period under RCP 8.5, when the total severity of frost events was projected to be increased by a factor of 2.1 compared to the historical climate. The study revealed the possible future increase of vegetation exposure to spring frost in Switzerland and that this phenomenon is noticeable even in the near future under the ‘low concentration’ RCP 4.5 scenario.

Highlights

Late spring frost poses a major threat for vegetation’s development and may result in considerable environmental and economic losses [1,2]
A warm start of spring 2017 was followed by an incursion of cold Arctic air into Western and Central Europe, which seriously harmed prematurely grown vegetation [3]
The method was calibrated in 1951–2014 using the Swiss spring index constructed from phenological in-situ observation [34]; it is possible that the relationship between temperature characteristics in spring and timing of vegetation’s development would be changed in the future climate [36] because this link is probably not linear [37]

Summary

Introduction

Late spring frost poses a major threat for vegetation’s development and may result in considerable environmental and economic losses [1,2]. Jeong et al [5], a growing season for temperate vegetation over the Northern Hemisphere has been starting earlier, the mean trend being about 2 days per decade in the 1982–2008 period. Menzel et al [6] concluded that the average trend of spring/summer phenophase dates was −2.5 days per decade in Europe (phenophases tend to occur sooner). It should be noted, that these changes are species- and region-dependent [7,8]. According to Kolářová et al [9], who analysed 18 common tree species in Central Europe, the largest advancements in spring phenophases were observed for shorter-lived, early-successional species (e.g., Prunus spinosa or Robinia pseudoacacia).

Objectives

Discussion

Conclusion