Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, 723 Xingke Road, Tianhe District, Guangzhou 510650, China; University of Chinese Academy of Sciences, 19(A) Yuquan Road, Shijingshan District, Beijing 100049, China.
MOE Key Laboratory of Biosystems Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou 310000, China.
Sci Total Environ. 2023 Aug 15;886:163951. doi: 10.1016/j.scitotenv.2023.163951. Epub 2023 May 9.
Arid and semi-arid forests are important carbon sinks, with implications for the global carbon balance. However, the impacts of climate warming on the growth of arid and semi-arid forest tree species and ecosystem carbon sink dynamics remain uncertain because the effects of the complex interactions between precipitation and temperature on xylem phenology are not clearly understood. Here, we monitored xylem formation over two years in two dominant tree species (Siberian larch, Larix sibirica Ledeb.; Siberian spruce, Picea obovata Ledeb.) along the arid and semi-arid southern Altai Mountains of Central Asia. We determined that temperature interaction with precipitation plays a key role in regulating xylem phenology of these two species, with differences between species. Under rising mean annual temperatures, the growth of L. sibirica advanced as the onset of xylem formation was not limited by early season water availability. However, the earlier cessation of cell enlargement, likely due to legacy effects, compensated for such advancement. In contrast, water stress constrained the advancement of xylem formation under rising temperatures in P. obovata. Nevertheless, water stress was seemingly relieved later in the growing season and consequently did not lead to the earlier cessation of xylem formation. Our results demonstrate that precipitation drives species-specific response to rising temperatures and thus is a key driver of growing season length and carbon sink dynamics in arid and semi-arid forests under climate warming. Integrating the effects of temperature and precipitation on xylem phenology in climate models may improve estimates of climate-carbon feedback in arid and semi-arid forests under future warming scenarios.
干旱和半干旱森林是重要的碳汇，对全球碳平衡有重要影响。然而，气候变暖对干旱和半干旱森林树种生长和生态系统碳汇动态的影响尚不确定，因为降水和温度的复杂相互作用对木质部物候的影响尚不清楚。在这里，我们在中亚干旱和半干旱南阿尔泰山的两个主要树种（西伯利亚落叶松、Larix sibirica Ledeb.；西伯利亚云杉、Picea obovata Ledeb.）中监测了两年的木质部形成。我们确定温度与降水的相互作用在调节这两个物种的木质部物候方面起着关键作用，而且物种之间存在差异。在年平均气温升高的情况下，L. sibirica 的生长提前，因为木质部形成的开始不受早期水分供应的限制。然而，细胞扩大的早期停止，可能由于遗留效应，补偿了这种提前。相比之下，在气温上升的情况下，水胁迫限制了 P. obovata 木质部形成的提前。然而，水胁迫在生长季节后期似乎得到缓解，因此不会导致木质部形成的早期停止。我们的研究结果表明，降水驱动了物种对气温升高的特定响应，因此是气候变暖下干旱和半干旱森林生长季节长度和碳汇动态的关键驱动因素。在气候模型中整合温度和降水对木质部物候的影响，可能会提高未来变暖情景下干旱和半干旱森林气候-碳反馈的估计。
