Willow phenological modelling at different altitudes in central Italy

In order to estimate the impact of climate change on the phenological parameters and to compare them with the historical record, a decision support system (DSS) has been applied employing a Phenological Modelling Platform. Biological observations of two willow species (Salix acutifolia and smithiana Willd) in 3 gardens at different altitudes located in Central Italy were utilized to identify suitable phenological models related to four main vegetative phase timings (BBCH11, BBCH91, BBCH 94, BBCH95), and male full flowering (BBCH 65) clearly identifiable in these species. The present investigation identifies the best phenological models for the main phenophases allowing their practical application as real-time monitoring and plant development prediction tools. Sigmoid model revealed high performances in simulating spring vegetative phases, BBCH11 (First leaves unfolded), and BBCH91 (Shoot and foliage growth completed). Salix acutifolia Willd. development appeared to be more related to temperature amount interpreted by phenological models in comparison to Salix smithiana Willd. above all during spring (BBCH11 and 91), probably due to a different grade of phenotypic plasticity between the 2 considered species.

“Green pointillism”: detecting the within-population variability of budburst in temperate deciduous trees with phenological cameras

Phenological cameras have been used over a decade for identifying plant phenological markers (budburst, leaf senescence) and more generally the greenness dynamics of forest canopies. The analysis is usually carried out over the full camera field of view, with no particular analysis of the variability of phenological markers among trees.Here we show that images produced by phenological cameras can be used to quantify the within-population variability of budburst (WPVbb) in temperate deciduous forests. Using 7 site-years of image analyses, we report a strong correlation (r²=0.97) between the WPVbb determined with a phenological camera and its quantification through ground observation.We show that WPVbb varies strongly (by a factor of 4) from year to year in a given population, and that those variations are linked with temperature conditions during the budburst period, with colder springs associated to a higher differentiation of budburst (higher WPVbb) among trees.Deploying our approach at the continental scale, i.e. throughout phenological cameras networks, would improve the understanding of the spatial (across populations) and temporal (across years) variations of WPVbb, which have strong implications on forest functioning, tree fitness and phenological modelling.

Fine tuning of hormonal signaling is linked to dormancy status in sweet cherry flower buds

ABSTRACTIn temperate trees, optimal timing and quality of flowering directly depend on adequate winter dormancy progression, regulated by a combination of chilling and warm temperatures. Physiological, genetic and functional genomic studies have shown that hormones play a key role in bud dormancy establishment, maintenance and release. We combined physiological, transcriptional analyses, quantification of abscisic acid (ABA) and gibberellins (GAs), and modelling to further investigate how these signaling pathways are associated with dormancy progression in the flower buds of two sweet cherry cultivars.Our results demonstrated that GA-associated pathways have distinct functions and may be differentially related with dormancy. In addition, ABA levels rise at the onset of dormancy, associated with enhanced expression of ABA biosynthesis PavNCED genes, and decreased prior to dormancy release. Following the observations that ABA levels are correlated with dormancy depth, we identified PavUG71B6, a sweet cherry UDP-GLYCOSYLTRANSFERASE gene that up-regulates active catabolism of ABA to ABA-GE and may be associated with low ABA content in the early cultivar. Subsequently, we modelled ABA content and dormancy behavior in three cultivars based on the expression of a small set of genes regulating ABA levels. These results strongly suggest the central role of ABA pathway in the control of dormancy progression and open up new perspectives for the development of molecular-based phenological modelling.

An appraisal of cereal crop phenology modelling

A review of responses of phenological development of cereal crops, primarily corn (Zea mays L.), wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), to environmental conditions was conducted. Examples of how these studies have been used to model phenological development on the basis of weather data were given.It was concluded that the development rate of most species is a sigmoidal rather than a linear function of temperature. Consequently, phenological models assuming a linear relationship (e.g., degree–days) are inappropriate. Another consequence of the way plants respond to temperature is that the most precise phenological models will require use of temperature data over relatively short periods (e.g., 3 h), rather than just a daily mean temperature. Several suggestions regarding the ways standard climatological station data may be used in such phenological modelling are made.Phenological response to photoperiod was also reviewed, and methods of modelling this response were proposed. Key words: Phenology, temperature, photoperiod, modelling