Long-term changes in duration of vegetation season of winter wheat under climate warming in north Lithuania

Abstract

Appreciable changes in duration of both parts of winter wheat vegetation seasons are defined over investigated 55 years period. An essential delay of emergence phase (13.5 days) and a very slight delay in the beginning of winter dormancy (0.5 day) resulted in the shortening of pre-winter vegetation period by almost two weeks. More essential advancement of green-up after winter dormancy (12 days) than maturity phase (7 days) led to extension of main (post-winter) vegetation season by five days. More essential advancement of maturity than green-up phase and consequently shortening of post-winter vegetation period is foreseen for both analyzed (RCP 2.6 and RCP 8.5) climate change scenarios. According to pessimistic RCP 8.5 scenario advancement of winter wheat maturity phase by almost 30 days and shortening of post-winter vegetation season by 15 days is foreseen for far (2071–2100) projection. Correction of agricultural practice and modification of winter wheat cultivars should be considered as necessary options in order to adopt ongoing climate changes. An essential decrease (33 days) in duration of winter dormancy is projected according to the same scenario, however, taking into account that in higher latitudes climate warming lead to prolonged chilling period and earlier fulfillment of chilling requirements, projected decrease in the duration of winter dormancy period do not pose threat of plant vernalization shortage in the investigated geographical region. The rebirth of phenology is a specific feature of the last decades and recently phenological observations usually are treated as a source of the most sensitive data of plant response to climate change. The objective of this study is to examine climate warming related the long term (1961–2015) changes in duration of both – initial (pre-winter) and main (post-winter ) winter wheat vegetation seasons, and to present projections of future phenological changes. The data of long-term agricultural investigations (1961-2015) which include phenological observations and were performed in Joniškėlis Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry were used for this study. The latest generation of climate change scenarios which are based on the Representative Concentration Pathways (RCPs) approach is used to project annual and monthly temperature for the near (2011–2040), middle (2041–2070) and far (2071–2100) future. This study covers two (optimistic and pessimistic) scenarios for future concentrations of greenhouse gases and future climate conditions simulated by five Global Circulation Models (GCM). Phenological projection is based on thermal accumulation approach, “leave one out” is applied for the cross validation of phenological model.