Global CO2 fertilization of Sphagnum peat mosses via suppression of photorespiration during the twentieth century

Henrik Serk,Klaus-Holger Knorr,Ina Ehlers,Mats B Nilsson,Tim Moore,Verónica Pancotto,Wiebke Münchberger,Elisabet Bohlin,Samantha Grover,Karsten Kalbitz,Julie Talbot,Carolina Olid,Thomas Wieloch,Xianwei Wang,Juul Limpens,Jürgen Schleucher

doi:10.1038/s41598-021-02953-1

Abstract

Natural peatlands contribute significantly to global carbon sequestration and storage of biomass, most of which derives from Sphagnum peat mosses. Atmospheric CO2 levels have increased dramatically during the twentieth century, from 280 to > 400 ppm, which has affected plant carbon dynamics. Net carbon assimilation is strongly reduced by photorespiration, a process that depends on the CO2 to O2 ratio. Here we investigate the response of the photorespiration to photosynthesis ratio in Sphagnum mosses to recent CO2 increases by comparing deuterium isotopomers of historical and contemporary Sphagnum tissues collected from 36 peat cores from five continents. Rising CO2 levels generally suppressed photorespiration relative to photosynthesis but the magnitude of suppression depended on the current water table depth. By estimating the changes in water table depth, temperature, and precipitation during the twentieth century, we excluded potential effects of these climate parameters on the observed isotopomer responses. Further, we showed that the photorespiration to photosynthesis ratio varied between Sphagnum subgenera, indicating differences in their photosynthetic capacity. The global suppression of photorespiration in Sphagnum suggests an increased net primary production potential in response to the ongoing rise in atmospheric CO2, in particular for mire structures with intermediate water table depths.

Highlights

Natural peatlands contribute significantly to global carbon sequestration and storage of biomass, most of which derives from Sphagnum peat mosses
Multiple observations indicate that recent increases in atmospheric C O2 have affected peat C accumulation rates: (i) the variation in acrotelm peat accumulation was mainly driven by photosynthesis[9], (ii) peat C accumulation in Alaskan mires increased about threefold during the twentieth century[10], and (iii) the variation in net ecosystem exchange between mires was mainly controlled by differences in leaf area index[11]
Global changes in the photorespiration to photosynthesis ratio during the twentieth century were assessed by comparing the D 6S/D6R ratios of modern and ≥ 100 years old Sphagnum tissues

Summary

Introduction

Natural peatlands contribute significantly to global carbon sequestration and storage of biomass, most of which derives from Sphagnum peat mosses. We investigate the response of the photorespiration to photosynthesis ratio in Sphagnum mosses to recent CO2 increases by comparing deuterium isotopomers of historical and contemporary Sphagnum tissues collected from 36 peat cores from five continents. The global suppression of photorespiration in Sphagnum suggests an increased net primary production potential in response to the ongoing rise in atmospheric CO2, in particular for mire structures with intermediate water table depths. We recently experimentally investigated the response of the photorespiration to photosynthesis ratio (i.e. the D6S/D6R ratio) to the recent increase in atmospheric C O2 levels from 280 to 400 ppm and the dependence of this response on selected climate variables including temperature, water table (WT) depth, and light intensity[27]. Sphagnum photosynthetic C fluxes are expected to vary with species and microhabitat[29,30,31,32]

Objectives

Methods

Results

Discussion

Conclusion