The influence of spectral composition on spring and autumn phenology in trees

Abstract

Several recent reviews highlight the molecular mechanisms that underpin phenological responses to temperature and photoperiod; however, these have mostly overlooked the influence of solar radiation and its spectral composition on these processes. For instance, solar radiation in the blue and ultraviolet (UV) regions of the spectrum, as well as the red/far-red (R:FR) ratio, can influence spring and autumn phenology. Solar radiation reaching the Earth changes diurnally and seasonally; however, rising global temperatures, latitudinal range shifts and light pollution are likely to produce novel combinations of phenological cues for tree species. Here, we review the literature on phenological responses to spectral composition. Our objective was to explore the natural variation in spectral composition using radiative transfer models and to reveal any species-specific or ecotype-specific responses relating to latitudinal origin. These responses are likely to be most pronounced at high latitudes where spectral composition varies most throughout the year. For instance, trees from high latitudes tend to be more sensitive to changes in R:FR than those from low latitudes. The effects of blue light and UV radiation on phenology have not been studied as much as those of R:FR, but the limited results available suggest both could be candidate cues affecting autumn leaf colouration and senescence. Failure of more–southern species and ecotypes to adapt and use spectral cues during northwards range shifts could result in mistimed phenology, potentially resulting in frost damage, reduced fitness and limited range expansion. Future areas for research should look to establish how consistently different functional types of tree respond to spectral cues and identify photoreceptor-mediated mechanisms that allow plants to combine information from multiple light cues to coordinate the timing of phenological events. It should then be feasible to consider the synchronous or sequential action of light cues within a hierarchy of environmental factors regulating phenology.

Assessing the effects of artificial light at night on biodiversity across latitude – Current knowledge gaps

“…The search combining "light pollution" OR "artificial light", and restricted to the Agricultural and Biological Sciences section, yielded 233 relevant references. These were three reviews in which artificial lighting was not the main topic (Borniger & Nelson, 2017;Brelsford, Nybakken, Kotilainen, & Robson, 2019;Higuchi, 2010), and one research paper on humans (Martín-Olalla, 2019). In comparison, using the combination of keywords (tropic* OR equat*) and "artificial light", "artificial" AND "light", or "light pollution", we identified 11 references (Bennie, Duffy, et al, 2015;Dorado-Correa, Rodríguez-Rocha, & Brumm, 2016;Erkhert, 1976;Frank, Gabbert, Chaves-Campos, & LaVal, 2019;De Freitas, Bennie, Mantovani, & Gaston, 2017;Gineste et al, 2017;González-Bernal, Greenlees, Brown, & Shine, 2016;Gupta & Pushkala, 2016;Lewanzik & Voigt, 2014;Rivas et al, 2018;Thakurdas et al, 2009).…”

“…A final search using the combination ("artificial light" OR "light pollution") AND "latitud*" yielded 59 hits but only four additional and partly relevant references. These were three reviews in which artificial lighting was not the main topic (Borniger & Nelson, 2017;Brelsford, Nybakken, Kotilainen, & Robson, 2019;Higuchi, 2010), and one research paper on humans (Martín-Olalla, 2019). These figures highlight the publication bias between biomes and the fact that authors do not explicitly consider the biogeographical context.…”

Quantitative genetic architecture of adaptive phenology traits in the deciduous tree, Populus trichocarpa (Torr. and Gray)

“…While both spring and autumn phenology determine growing season and are therefore potentially adaptive, transitions are determined by different cues and therefore may respond to selection in different ways (Singh et al Associate editor: Alison Bentley 2017). Dormancy is broken by changes in temperature at the beginning of spring in many plants (McKown et al 2018a), and therefore bud burst is defined by cues which have significant variation between local environments and successive years (Basler and Körner 2012;Brelsford et al 2019). Growth cessation is generally induced by changes in photoperiod (Fracheboud et al 2009;Lagercrantz 2009;Michelson et al 2017) or associated changes in the light spectrum (Leuchner et al 2007;Brelsford et al 2019), and therefore varies predictably with latitude and consistently between growing seasons (Howe et al 2003).…”

“…Dormancy is broken by changes in temperature at the beginning of spring in many plants (McKown et al 2018a), and therefore bud burst is defined by cues which have significant variation between local environments and successive years (Basler and Körner 2012;Brelsford et al 2019). Growth cessation is generally induced by changes in photoperiod (Fracheboud et al 2009;Lagercrantz 2009;Michelson et al 2017) or associated changes in the light spectrum (Leuchner et al 2007;Brelsford et al 2019), and therefore varies predictably with latitude and consistently between growing seasons (Howe et al 2003). These different characteristics between the triggers of growth and dormancy mean that the adaptation toward the optimal conditions and timing for spring and autumn phenology requires different biological responses.…”

Greater capacity to exploit warming temperatures in northern populations of European beech is partly driven by delayed leaf senescence

“…1). The major drivers of LS have been more difficult to identify (Gallinat et al 2015; Brelsford et al 2019). A recent meta-analysis showed that summer and autumn temperatures, precipitation and photoperiod can all affect LS (Gill et al 2015).…”