DOI: 10.5061/dryad.zpc866thq
title: Data from: Seasonal acclimation of photosynthetic thermal tolerances in six woody tropical species along a thermal gradient

description: 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 °C). Between seasons, there were significant overall
 increases in the thermal tolerances of three species (i.e., higher thermal
 tolerances in the hotter dry season), suggesting that leaf megathermy is
 prominent in these species. Also, three species acclimated their thermal
 tolerances to microsite-level differences in seasonal temperature maxima,
 suggesting closer fidelity between leaf and air temperatures (i.e.,
 limited homeothermy) for these species. Our results show that
 some woody species from the moist Amazon can acclimate their thermal
 tolerances over short time scales, although acclimation is likely
 insufficient to overcome thermal stress during extreme temperature events.
 Some species may therefore be more sensitive to heatwaves than others,
 which could impact survival and composition of tropical lowland forests
 into the future.
description: 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
 (n<sub>trees</sub> = 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
 (F<sub>v</sub>/F<sub>m</sub>) on leaf discs 24
 hours after being treated in 15-minute temperature-controlled water baths
 (n<sub>temperatures</sub> = 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 functioning).
 Associated seasonal air temperature maxima for each sampled
 individual were obtained by interpolating the seasonal maximum air
 temperature recorded by 13 TOMST TMS-4 dataloggers deployed across the
 study site with a clear Landsat image taken in each respective season.
 Interpolation was done with linear regression between the TOMST
 dataloggers and Landsat imagery to continuously predict seasonal maximum
 air temperature across the study site. Please see
 associated publication for further details.
description: # 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