A deepened water table increases the vulnerability of peat mosses to periodic drought

Here we address the combined impact of multiple stressors that are becoming more common with climate change. To study the combined effects of a lower water table (WT) and increased frequency of drought periods on the resistance and resilience of peatlands, we conducted a mesocosm experiment. This study evaluated how the photosynthesis of lawn Sphagnum mosses responds to and recovers from an experimental periodic drought after exposure to the stresses of a deep or deepened WT (naturally dry and 17-year-long water level drawdown in fen and bog environments. We aimed to quantify if deep WTs 1) support acclimation to drought, or 2) increase the base-level physiological stress of mosses, or 3) exacerbate the impact of periodic drought. There was no evidence of acclimation in mosses from drier environments; periodic drought decreased the photosynthesis of all Sphagnum mosses. Water level drawdown decreased the photosynthesis of bog-originating mosses before periodic drought, indicating that t..., 96 cores of peatland surface cores (mesocosms) covered by Sphagnum mosses were harvested from the Lakkasuo mire complex in Southern Finland in the spring of 2018 and transported to a greenhouse where an experimental periodic drought was applied. A 17-year water level drawdown experiment (established in 2001) was applied in Lakkasuo in a rich fen and bog. In each peatland type, mesocosms were harvested from intermediately wet surfaces (lawns) from three areas with different water table histories: wet pristine, experimental water level drawdown, and naturally dry, making a total of six subsites where mesocosms originated from. Two Sphagnum species were selected from each subsite, with one species being characteristic of the subsite it was selected from and the other species common across all subsites from a given peatland type. After transporting to a greenhouse where the mesocosm water table and environmental conditions were controlled, mesocosms were allowed to acclimate to conditions f..., , # A deepened water table increases the vulnerability of peat mosses to periodic drought

[https://doi.org/10.5061/dryad.02v6wwqb8](https://doi.org/10.5061/dryad.02v6wwqb8)

## Description of the data and file structure

This dataset consists of four files, each containing different types of data relating to the peatland surface cores (\"mesocosms\") used for this experiment. The abbreviations and variable names used in the data are listed below the file descriptions.

1. mesocoms_CO2_exchange_trait.csv contains data on mesocosm traits and photosynthesis CO2 fluxes that were used for non-linear mixed-effects models in R. This is the data file used in the R-script included in this article's supplementary material.
2. mesocosm_eventData.xlsx contains information on the mesocosm collection location and time. These data are not used for analyses.
3. mesocosm_CO2_exchange.csv contains data related to the closed-chamber photosynthesis measurements conducted on mesocosms throughout the experim...