Sensitivity analysis of tree phenology models reveals increasing sensitivity of their predictions to winter chilling temperature and photoperiod with warming climate

Abstract

The phenology of plants is a major driver of agro-ecosystem processes and biosphere feedbacks to the climate system. Phenology models are classically used in ecology and agronomy to project future phenological changes. With our increasing understanding of the environmental cues affecting bud development, phenology models also increase in complexity. But, we expect these cues, and the underlying physiological processes, to have varying influence on bud break date predictions depending on the specific weather patterns in winter and spring. Here, we evaluated the parameter sensitivity of state-of-the-art process-based phenology models that have been widely used to predict forest tree species phenology. We used sensitivity analysis to compare the behavior of models with increasing complexity under specific climatic conditions. We thus assessed whether the influence of the parameters and modeled processes on predictions varies with winter and spring temperatures. We found that the prediction of the bud break date was mainly affected by the response to forcing temperature under current climatic conditions. However, the impact of the parameters driving the response to chilling temperatures and to photoperiod on the prediction of the models increased with warmer winter and spring temperatures. Interaction effects between parameters played an important role on the prediction of models, especially for the most complex models, but did not affect the relative influence of parameters on bud break dates. Our results highlighted that a stronger focus should be given to the characterization of the reaction norms to both forcing and chilling temperature to predict accurately bud break dates in a larger range of climatic conditions and evaluate the evolutionary potential of phenological traits with climate change.

Comparing Apple and Pear Phenology and Model Performance: What Seven Decades of Observations Reveal

“…Although some authors assume linear relationships between temperature and phenology [11,44], hints for antagonistic effects could be detected at our study site, revealing non-linear correlations (Figure 3), similar to findings for other temperate regions [42,45,46]. It also appeared that the relative influence of temperatures during chilling increases with the average temperature of a location [34].…”

“…Segmenting 68 years of phenological observations into contrasting segments allowed to compare flowering under relatively cold and mild dormancy periods for apple and pear. The determining phase for changed bloom timing was the forcing phase (January to April), with a significant negative relationship between temperature and the DOY of flowering, which has also been reported for other temperate regions [13,42]. Effects of a warm and a cold year compared to a typical year have been studied for mountainous forest trees [43] with similar results regarding the magnitude of the effect of warming during the winter and spring months.…”

Where is the optimum? Predicting the variation of selection along climatic gradients and the adaptive value of plasticity. A case study on tree phenology

“…We varied one parameter of the bud growth reaction norm, previously identified as the main driver of the budburst date variation (Gauzere et al. ; Fig. 1A), to obtain (1) different average budburst dates over the 1960–2012 period in a biological credible range ( z ), and (2) the resulting average reproductive success over that same period for a tree with that reaction norm (Fig.…”

Climate change reshapes the drivers of false spring risk across European trees

“…Of the four climatic and geographic factors we examined, the effects of mean spring temperature and distance from the coast remained relatively stable compared with elevation and NAO, suggesting stability in some factors over time. This is perhaps not surprising as climate change is shifting critical spring temperatures – and ultimately the environmental drivers of phenology (Gauzere et al ., 2019) – and reshaping the temporal and spatial dynamics of how climate affects budburst, leafout and freezing temperatures. Yet it does suggest that despite evidence that climate change has greater impacts on sites further from the coast (Harrington & Gould, 2015), warming does not restructure the effect of distance from the coast on false spring risk.…”

“…With recent warming the importance of varying climatic factors on phenology has shifted (e.g. Cook & Wolkovich, 2016; Gauzere et al ., 2019), which could in turn impact false spring risk. The importance of elevation, for example, may decline with warming.…”