Plant phenology and species‐specific traits control plant CH₄ emissions in a northern boreal fen

Abstract

Summary Aerenchymatic transport is an important mechanism through which plants affect methane (CH4) emissions from peatlands. Controlling environmental factors and the effects of plant phenology remain, however, uncertain. We identified factors controlling seasonal CH4 flux rate and investigated transport efficiency (flux rate per unit of rhizospheric porewater CH4 concentration). We measured CH4 fluxes through individual shoots of Carex rostrata, Menyanthes trifoliata, Betula nana and Salix lapponum throughout growing seasons in 2020 and 2021 and Equisetum fluviatile and Comarum palustre in high summer 2021 along with water‐table level, peat temperature and porewater CH4 concentration. CH4 flux rate of C. rostrata was related to plant phenology and peat temperature. Flux rates of M. trifoliata and shrubs B. nana and S. lapponum were insensitive to the investigated environmental variables. In high summer, flux rate and efficiency were highest for C. rostrata (6.86 mg m−2 h−1 and 0.36 mg m−2 h−1 (μmol l−1)−1, respectively). Menyanthes trifoliata showed a high flux rate, but limited efficiency. Low flux rates and efficiency were detected for the remaining species. Knowledge of the species‐specific CH4 flux rate and their different responses to plant phenology and environmental factors can significantly improve the estimation of ecosystem‐scale CH4 dynamics in boreal peatlands.

CH4transport in wetland plants under controlled environmental conditions – untangling the impacts of phenology

“…Mesocosms of Carex rostrata , Menyanthes trifoliata , Betula nana and Salix lapponum were collected at Lompolojänkkä(67.99 °N, 24.21°E), a northern boreal fen (Ge et al ., 2023) located in Finnish Lapland. The plants were collected in growing seasons 2020 ( C. rostrata and B. nana ) and 2021 ( M. trifoliata and S. lapponum ).…”

“…Plant-mediated CH 4 transport allows soil-produced CH 4 to bypass oxidation in oxic surface peat and thus is a crucial mechanism increasing the total ecosystem CH 4 emissions both in open wetlands and woody ecosystems (Shannon et al ., 1996; Pangala et al ., 2017; Barba et al ., 2019; Ge et al ., 2023; Machacova et al ., 2023). Environmental factors such as soil water table level (WTL), temperature and porewater CH 4 concentration ([CH 4 ] pw ) have been regarded as important controls on ecosystem CH 4 emissions from wetlands (Joabsson & Christensen, 2001; Lai et al ., 2014a).…”

“…(2014) reported that increasing WTL lead to high CH 4 emissions by Carex rostrata , while Ge et al ., (2023) observed no such correlation with the same species. Similarly, [CH 4 ] pw has been found to positively influence plant-mediated CH 4 emission (Aulakh et al ., 2000; Ding et al ., 2005), while no such effect was observed in our earlier study where plant-mediated CH 4 flux (fCH4p) was measured from common boreal peatland plants with different morphological traits (Ge et al . (2023)).…”

“…Recent studies suggest that environmental controls are less important than species-level differences (Korrensalo et al, 2021) and seasonality (Ge et al ., 2023) in determining plant-mediated CH4 transport. It seems evident that species-specific plant morphology and phenology (the development and senescence over the growing season) can affect the CH4 transport.…”

“…Phenology may affect CH 4 transport through changes in plant biomass (Koelbener et al ., 2010), root length (Noyce, 2009) and permeability (Henneberg et al ., 2012), aerenchyma size (Fagerstedt, 1992), stomatal conductance (Morrissey et al ., 1993), and stimulation of rhizospheric CH 4 production (Lai et al ., 2014b) and oxidation (Kankaala et al ., 2005). The seasonal variability of plant-mediated CH4 flux may also differ between plant species (Ge et al, 2023). However, most previous studies have been conducted in the field, where abiotic conditions typically correlate with phenological changes in plants.…”