State Key Laboratory of Grassland Agro-ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, Engineering Research Center of Grassland Industry, Ministry of Education, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China.
College of Water Sciences, Beijing Normal University, Beijing, China.
Glob Chang Biol. 2021 Jun;27(12):2905-2913. doi: 10.1111/gcb.15586. Epub 2021 Mar 17.
Plant phenology is highly sensitive to climate change, and shifts in autumnal foliar senescence are critical for plant productivity and nutrient cycling. Global warming has delayed the timing of foliar senescence, but the response of autumnal foliar senescence to nonuniform seasonal warming remains poorly understood, with experimental evidence in trees especially scarce. We therefore conducted a field experiment on seasonally asymmetric warming on 2-year-old larch (Larix principis-rupprechtii) seedlings in two hydrologically contrasting years (wet 2018 and dry 2019). Autumnal and year-round warming significantly delayed the timing of foliar senescence by 6 and 7 d in 2018, the wet year, with corresponding temperature sensitivities of 6.73 ± 1.47 and 8.26 ± 1.00 d/°C, respectively. Interestingly, the dates of senescence did not change across the warming treatments in 2019, the dry year. However, there was no significant effect of summer warming on the timing of foliar senescence neither in the wet nor dry year. The delayed autumnal foliar senescence was responsible for an increase in biomass only in the wet year, 2018. In contrast, summer warming, but not autumnal warming, increased the mortality of the seedlings in both 2018 and 2019. These results suggest that the hydrological conditions substantially modify the response of autumnal phenology and growth to seasonal warming. Autumnal warming increases growth, whereas summer warming could cause carbon starvation/hydraulic failure, reduce growth, and lead to higher mortality. Our results suggest that the functioning, ecosystem services, and sustainability of forests in the future depend on the strength and pattern of nonuniform seasonal warming. This study can inspire new research in phenology and tree growth in experiments with asymmetric warming.
植物物候对气候变化高度敏感，秋季叶片衰老的变化对植物生产力和养分循环至关重要。全球变暖已经延迟了叶片衰老的时间，但秋季叶片衰老对非均匀季节变暖的响应仍知之甚少，特别是在树木方面的实验证据很少。因此，我们在两个水文条件不同的年份（湿润的 2018 年和干旱的 2019 年）对 2 年生落叶松（Larix principis-rupprechtii）幼苗进行了季节性非均匀增温的田间实验。在湿润的 2018 年，秋季和全年增温分别使叶片衰老的时间推迟了 6 和 7 天，相应的温度敏感性分别为 6.73±1.47 和 8.26±1.00°C。有趣的是，在干旱的 2019 年，变暖处理并没有改变叶片衰老的时间。然而，无论是在湿润年还是干旱年，夏季增温都没有显著影响叶片衰老的时间。秋季叶片衰老的延迟仅在湿润的 2018 年增加了生物量。相反，夏季增温，而不是秋季增温，增加了 2018 年和 2019 年幼苗的死亡率。这些结果表明，水文条件极大地改变了秋季物候和生长对季节性增温的响应。秋季增温增加了生长，而夏季增温可能导致碳饥饿/水力衰竭，减少生长，并导致更高的死亡率。我们的结果表明，未来森林的功能、生态系统服务和可持续性取决于非均匀季节性增温的强度和模式。本研究可以启发在具有非均匀增温实验中进行物候和树木生长的新研究。
