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