Chilling rather than photoperiod controls budburst for gymnosperm species in subtropical China

Abstract

Aims The mechanisms regulating spring phenology have been extensively studied in angiosperm species. However, given that gymnosperms and angiosperms diverged 300 million years ago, phenology may be triggered by different cues in gymnosperm species. The regulatory mechanisms of phenology in subtropical regions remain largely unknown. In combination, it remains untested whether subtropical gymnosperm species have chilling requirements and are photosensitive. Methods We conducted a climate chamber experiment with three chilling and three photoperiod treatments to investigate budburst during an 8-week forcing period. We tested whether budburst of eight gymnosperms species (Cryptomeria japonica, Cunninghamia lanceolata, Cupressus funebris, Ginkgo biloba, Metasequoia glyptostroboides, Pinus massoniana, Pseudolarix amabilis, and Podocarpus macrophyllus) was photoperiod sensitive or has strong chilling requirements and whether photoperiod or chilling was more important for advancing budburst. Important Findings Chilling advanced budburst and increased the percentage of budburst for gymnosperm species. Gymnosperm species required moderate chilling days to advance budburst. Interestingly, the forcing requirement for gymnosperm species was higher than that for angiosperms in the same forest, suggesting that gymnosperms may need more cumulative forcing to initiate budburst than do angiosperms. Compared to temperate gymnosperm species in Germany (194-600 °C days), the subtropical species studied here had a much higher forcing requirement (814-1150 °C days). The effects of photoperiod were minor, suggesting that chilling outweighs photoperiod in advancing budburst of gymnosperm species in this subtropical region. These results reveal that increased winter temperatures with continued global warming may impact not only angiosperms but also gymnosperms, leading to their delayed spring budburst.

Extending the Cultivation Area of Pecan (Carya illinoinensis) Toward the South in Southeastern Subtropical China May Cause Increased Cold Damage

“…Our experimental findings confirm that seedlings of the subtropical pecan grown in southeastern China also evince these traits. This is in line with recent studies, which show that several subtropical tree species have a rest period and a chilling requirement ( Du et al, 2019 ; Song et al, 2020 ; Pan et al, 2021 ; Zhang et al, 2021a , b ). The novelty and scarcity of these findings in the case of subtropical trees are in striking contrast with the case of boreal and temperate trees, where the existence of these traits has already been known for a 100 years ( Coville, 1920 ; Jewaria et al, 2021 ).…”

“…For the structure of the overall model, refer to Supplementary Figure 1. (Du et al, 2019;Song et al, 2020;Pan et al, 2021;Zhang et al, 2021a,b). The novelty and scarcity of these findings in the case of subtropical trees are in striking contrast with the case of boreal and temperate trees, where the existence of these traits has already been known for a 100 years (Coville, 1920;Jewaria et al, 2021).…”

“…These models address the developmental phenomena taking place during periods of rest and quiescence with explicit state variables ( Hänninen, 2016 ; Chuine and Régnière, 2017 ). Recently, it has been shown experimentally that subtropical trees also show a rest period and chilling requirement ( Du et al, 2019 ; Song et al, 2020 ; Jewaria et al, 2021 ; Pan et al, 2021 ; Zhang et al, 2021a , b ). The first process-based models of spring phenology have been published for subtropical trees ( Chen et al, 2017 ; Zhang et al, 2021c ).…”

Important role of precipitation in controlling a more uniform spring phenology in the Qinba Mountains, China

“…In this study, we found a decreased WT and a slightly increased ST below 500 m in the QB from 2001 to 2011, which somewhat provides more sufficient accumulation of chilling and forcing for the onset of spring phenology (Fu et al, 2015a;Ettinger et al, 2020;Pan et al, 2022). However, the SOS in this region was delayed (Figure 4D).…”

Spatial Difference of Interactive Effect Between Temperature and Daylength on Ginkgo Budburst

“…The daylength effect is species-specific ( Basler and Körner, 2012 ; Zohner and Renner, 2015 ), and previous experimental studies found a wide range of responses from being insensitive to daylength to showing no budburst at all under short days ( Zohner and Renner, 2015 ; Zohner et al, 2016 ). These studies mostly focused on inter-specific comparisons within angiosperms, while population-level studies that also involve gymnosperms are scarce (but see Kumar and Sati, 2016 ; Pan et al, 2021 ; Wu et al, 2022b ).…”