Seasonal acclimation of photosynthetic thermal tolerances in six woody tropical species along a thermal gradient

Extreme heat events are becoming increasingly common, and the short-term acclimation of photosynthesis will have a large impact on plant performance. Trees in lowland tropical forests, which are hypothesized to have limited abilities to tolerate rising temperatures, may need to rely on short term acclimation of their more plastic traits, like photosynthetic thermal tolerance, to persist in the face of increasingly variable climates. Here we investigated seasonal acclimation of thermal tolerances in plant species of the moist Amazon. Specifically, we measured the photosynthetic thermal tolerances of six common woody Amazonian species at the beginning and at the end of the dry season to determine the species’ abilities to acclimate to intra-annual changes to climate. In addition, we used the natural thermal gradient present at our research site to test the acclimation of individual plants to maximum air temperatures not currently observed elsewhere in the moist lowland Amazon (up to ~43 °..., We collected individual-level photosynthetic thermal tolerance data for six woody species of the lowland Amazon (Boiling River, Huánuco Department, Peru) following the methods described in the associated manuscript. We remeasured the same individuals (ntrees = 8-12 per species) at the beginning and end of the local dry season (in June and October, respectively) to test for seasonal acclimation of thermal tolerance. To measure thermal tolerance, we recorded the maximum quantum efficiency of photosystem II (Fv/Fm) on leaf discs 24 hours after being treated in 15-minute temperature-controlled water baths (ntemperatures = 9). We then fit a four-parameter logistic regression to each individual in each season and calculated thermal tolerance metrics of interest: T5 (5% decline in photosystem II functioning), T50 (50% decline in photosystem II functioning), T95 (95% decline in photosystem II funcitoning), DW (difference between T95 and T5), and Tcrit (initial decline in photosystem II function..., , # Seasonal acclimation of photosynthetic thermal tolerances in six woody tropical species along a thermal gradient. [https://doi.org/10.5061/dryad.zpc866thq](https://doi.org/10.5061/dryad.zpc866thq) ## Description of the data and file structure Data include photosynthetic thermal tolerance data for six woody species in the lowland Amazon (Boiling River, Huánuco Department, Peru) measured at the beginning and end of the local dry season (June and October, respectively). Seasonal temperature maxima are also included. ### Files and variables #### File: KullbergFeeley\_FunctionalEcology\_2024.xlsx **Description:** * Sheet 0: README * Sheet 1: RawFluorescence -- raw FvFm data at each water bath temperature for all sampled individuals in both seasons * Sheet2: ThermalTolerances and SiteTemps -- sampled tree locations, seasonal micro-site air temperature maxima, and calculated thermal tolerance metrics (T5, T50, T95, DW, and Tcrit) for both seasons极端高温事件愈发频发，光合作用的短期驯化将对植物性能产生显著影响。此前假说认为，低地热带森林的树木耐受气温升高的能力有限，因此可能需要依赖光合热耐受性（photosynthetic thermal tolerance）这类可塑性更强的性状的短期驯化，才能在日益多变的气候中存续。 本研究针对湿润亚马逊地区的植物物种，调查了其热耐受性的季节驯化过程。具体而言，我们于旱季初期与末期，测定了亚马逊地区6种常见木本植物的光合热耐受性，以明确各物种响应气候年内变化的驯化能力。此外，我们依托研究站点自然存在的温度梯度，探究了单个植株对当前湿润低地亚马逊其他区域尚未观测到的最高气温（最高约43℃）的驯化情况。 我们依照相关论文中描述的方法，收集了秘鲁瓦努科省（Huánuco Department）沸腾河流域低地亚马逊6种木本植物的个体水平光合热耐受性数据。我们于当地旱季初期（6月）与末期（10月），对同一批植株（每个物种植株数为8-12株）进行了重测，以此检验热耐受性的季节驯化效应。热耐受性测定方法为：将叶盘置于控温水浴中处理15分钟后，24小时内记录光系统II（Photosystem II）的最大量子效率（Fv/Fm），共设置9个温度梯度。随后我们针对每个季节的每个个体拟合四参数逻辑斯蒂回归（four-parameter logistic regression）模型，并计算了目标热耐受性指标：T5（光系统II功能下降5%时的温度）、T50（光系统II功能下降50%时的温度）、T95（光系统II功能下降95%时的温度）、DW（T95与T5的差值）以及Tcrit（光系统II功能初始下降时的温度）。 本研究的主题为《沿温度梯度的6种热带木本植物光合热耐受性的季节驯化》，相关数据集的DOI为：https://doi.org/10.5061/dryad.zpc866thq ## 数据与文件结构说明 本数据集包含低地亚马逊地区6种木本植物的光合热耐受性数据，采样点位于秘鲁瓦努科省沸腾河流域，测定时间为当地旱季初期与末期（分别为6月与10月），同时包含季节最高气温数据。 ### 文件与变量 #### 文件：KullbergFeeley_FunctionalEcology_2024.xlsx **说明：** - 工作表0：README（说明文档） - 工作表1：RawFluorescence——两个季节所有采样个体在各水浴温度下的原始Fv/Fm数据 - 工作表2：ThermalTolerances and SiteTemps——采样树木的位置信息、各季节微生境空气最高气温，以及两个季节的计算得到的热耐受性指标（T5、T50、T95、DW与Tcrit）