Li Weibin, Zhang Hongxia, Wang Wenzhi, Zhang Peipei, Ward Nicholas D, Norwood Matt, Myers-Pigg Allison, Zhao Chuanyan, Leff Riley, Yabusaki Steve, Waichler Scott, Bailey Vanessa L, McDowell Nate G
State Key Laboratory of Grassland and Agro-ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China.
Atmospheric Sciences & Global Change Division, Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
Tree Physiol. 2021 Dec 4;41(12):2326-2340. doi: 10.1093/treephys/tpab073.
Increasing seawater exposure is causing mortality of coastal forests, yet the physiological response associated with seawater-induced tree mortality, particularly in non-halophytes, is poorly understood. We investigated the shifts in carbon and nitrogen (N) metabolism of mature Sitka-spruce trees that were dying after an ecosystem-scale manipulation of tidal seawater exposure. Soil porewater salinity and foliar ion concentrations increased after seawater exposure and were strongly correlated with the percentage of live foliated crown (PLFC; e.g., crown 'greenness', a measure of progression to death). Co-occurring with decreasing PLFC was decreasing photosynthetic capacity, N-investment into photosynthesis, N-resorption efficiency and non-structural carbohydrate (soluble sugars and starch) concentrations, with the starch reserves depleted to near zero when PLFC dropped below 5%. Combined with declining PLFC, these changes subsequently decreased total carbon gain and thus exacerbated the carbon starvation process. This study suggests that an impairment in carbon and N metabolism during the mortality process after seawater exposure is associated with the process of carbon starvation, and provides critical knowledge necessary to predict sea-level rise impacts on coastal forests.
海水暴露增加正导致沿海森林死亡，但与海水诱导树木死亡相关的生理反应，尤其是在非盐生植物中，目前了解甚少。我们研究了在生态系统尺度上对潮汐海水暴露进行操纵后濒死的成熟西加云杉树碳和氮（N）代谢的变化。海水暴露后土壤孔隙水盐度和叶片离子浓度增加，且与活叶树冠百分比（PLFC；例如树冠“绿度”，一种死亡进程的度量）密切相关。随着PLFC降低，光合能力、对光合作用的氮投入、氮再吸收效率和非结构性碳水化合物（可溶性糖和淀粉）浓度均下降，当PLFC降至5%以下时，淀粉储备耗尽至接近零。这些变化与PLFC下降相结合，随后降低了总碳增益，从而加剧了碳饥饿过程。本研究表明，海水暴露后死亡过程中碳和氮代谢的损害与碳饥饿过程相关，并提供了预测海平面上升对沿海森林影响所需的关键知识。
