Surprising roles of climate in regulating flowering phenology in a subtropical ecosystem

Abstract

Climate-driven changes in phenology have widespread effects on ecological interactions and species' abundances. Most predictions of changes in phenology and the consequences for ecology and conservation are based on research in temperate systems. Climate-driven changes in phenology are largely undocumented in subtropical regions, which host much of the world's biodiversity. Factors important to regulating phenology in temperate systems (e.g. winter chilling requirements) are likely weak or absent in subtropical ecosystems; plant phenology in these regions could respond to climate differently than in the temperate zone. Here we examine flowering phenology data for 105 plant species based on herbarium specimens and photographs from 1911 to 2015 in the southern subtropical Nanling region in south China. Temperatures in this region warmed 0.3°C over the 105-year study period, and most plant species flowered earlier over time, although species varied substantially in the magnitude of phenological response to warming temperatures. Spring flowering times advanced in response to warming temperatures in late summer and early autumn and in early spring, with late summer and early autumn temperatures having almost twice as strong an effect on spring flowering times as early spring temperatures (−4.7 versus −2.5 days °C −1 ). This strong effect of late summer and early autumn temperatures is very different from temperate systems and has substantial implications for anticipating future changes in phenology. The temperatures in late summer and early autumn may affect spring phenology by accelerating bud formation or initial growth. Warming January temperature delayed summer flowering and advanced winter flowering. Increases in precipitation during April to June also tended to delay summer flowering. Autumn flowering species showed inconsistent responses to warming. These results highlight important differences between climate-driven changes in phenology in temperate and subtropical areas. Understanding these differences will be important in understanding the effects of climate change on vegetation phenology and ecosystem processes.

Proximate cues of flowering in a subtropical rain forest

“…Our findings add to the growing evidence that warming and chilling temperatures together determine flowering times in subtropical forests (Chen et al., 2017; Du et al., 2019; Song et al., 2021; Von Holle et al., 2010; Wang, Dai, et al., 2015). The divergent responses to spring/summer and fall/winter temperatures would affect the sensitivity to temperature fluctuations in plant species (Cook et al., 2012), leading to differences in interannual variation in flowering times among species.…”

“…Our results were consistent with a short‐term study in Fushan, which suggested that warmer temperatures in early spring might advance the flowering times of subtropical trees (Wang et al., 2014). Several recent studies also emphasize the importance of spring temperature in structuring spring phenology in subtropical ecosystems (Chen et al., 2017; Park & Schwartz, 2015; Song et al., 2021; Von Holle et al., 2010; Wang, Dai, et al., 2015). The flowering times of several early‐spring flowering species were related to warm temperatures in the previous summer ( N d for mean temperature ≥ 175 days in Table 3).…”

“…The flowering times of several early‐spring flowering species were related to warm temperatures in the previous summer ( N d for mean temperature ≥ 175 days in Table 3). This result suggests that summer temperatures could promote flower bud initiation or development and thus influence the timing of anthesis during the next year (Salazar‐García et al., 1998; Song et al., 2021).…”

“…Previous phenological studies suggested that interannual variation in temperature may alter flowering times in subtropical plant communities (Chen et al., 2017; Pan et al., 2017; Park & Schwartz, 2015; Song et al., 2021; Von Holle et al., 2010; Wang, Lin, et al., 2015). However, due to limited monitoring time or the sparseness of herbarium records, no conclusive evidence has been provided.…”

China's subtropical deciduous plants are more sensitive to climate change than evergreen plants by flowering phenology

“…According to the continuity and integrity of data, the manual records of flowering phenology, including FFD, PFD, and EFD, were selected from the two observation periods (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014). FD (flowering duration) is the length of time between EFD and FFD (Du, Yang, et al, 2019;Song et al, 2021;Wang et al, 2019;Zhang et al, 2015). The data for the years 1996 to 2003 were not included because no data was recorded during this period due to missing observations, and as such post-2014 data are not publicly available at present.…”