Thermal time models for estimating plant phenological development under climate

Abstract

Accurate prediction of plant phenology is a key requirement for plant development models. The prediction of crop yield and quality from meteorological data can be improved by quantifying heat and moisture conditions during specified phenological phases. The analysis of long-term time series of spring phenology for different deciduous trees species supplies with the important information how the timing of leaf unfolding is related to spring temperatures and crop phenological development. The objective of this study was to investigate the timing of phenological phases of deciduous trees (silver birch, small-leaved lime, Norway maple and common oak) using thermal time as a key parameter and compare observed as well projected data with the phenological changes of winter wheat and spring barley under ongoing and future climate change conditions. Thermal time (growing degree days) was evaluated used more precise degree days approach. The projection of climatic parameters was conducted using the data of three Global Circulation Models under the optimistic scenario (RCP 2.6) and the pessimistic scenario (RCP 8.5). It was shown that plants react to climate changes in a similar way. High correlation between the dates of winter wheat regrowth after dormancy and birch leaf unfolding was detected. The advancement of these spring phenological phases along with climate warming is also very similar and equals approximately 12 days over the last six decades. The regrowth phase of winter wheat occurs almost 20 days earlier than leaf unfolding of this early season tree, indicating significantly lower thermal accumulation requirement in order to start the spring vegetation of winter wheat.