Temporal variations in methane emissions from emergent aquatic macrophytes in two boreonemoral lakes.

Per Milberg,Lina Törnqvist,David Bastviken,Lars M Westerberg

doi:10.1093/aobpla/plx029

Abstract

Methane (CH4) emissions via emergent aquatic macrophytes can contribute substantially to the global CH4 balance. We addressed temporal variability in CH4 flux by using the static chamber approach to quantify fluxes from plots dominated by two species considered to differ in flux transport mechanisms (Phragmites australis, Carex rostrata). Temporal variability in daily mean emissions from early June to early October was substantial. The variable that best explained this variation was air temperature. Regular and consistent diel changes were absent and therefore less relevant to include when estimating or modelling CH4 emissions. Methane emissions per m2 from nearby plots were similar for Phragmites australis and Carex rostrata indicating that CH4 production in the system influenced emissions more than the species identity. This study indicates that previously observed diel patterns and species-effects on emissions require further evaluation to support improved local and regional CH4 flux assessments.

Highlights

Methane (CH4) impacts the global energy balance and climate, has substantially higher global warming potential than carbon dioxide (CO2) per kg in a 100-year perspective, and accounts for some 20 % of radiative forcing (Myhre et al 2013)
The vegetation along the lake margin is dominated by Phragmites australis, and different species of Carex, including C. rostrata in the shallower parts, with smaller contributions of Equisetum fluviatile and Typha latifolia, while Nymphaea alba is present at deeper water down to $2 m depth
There were no differences in these CH4 emissions between P. australis and C. rostrata within the same lake (Fig. 3)

Summary

Introduction

Methane (CH4) impacts the global energy balance and climate, has substantially higher global warming potential than carbon dioxide (CO2) per kg in a 100-year perspective, and accounts for some 20 % of radiative forcing (Myhre et al 2013). The fluxes of dissolved CH4 from surface waters are often smaller than flux pathways by which CH4 can ‘escape’ oxidation, such as ebullition (flux by bubbles from sediments) and flux through rooted emergent aquatic macrophytes (Joabsson et al 1999; Bastviken 2009). Such plants have well-developed arenchema in their stems and underground rhizomes that transport oxygen to roots (Laanbroek 2010).

Methods

Results

Discussion

Conclusion