Physical injury stimulates aerobic methane emissions from terrestrial plants

Z.-P Wang,J.-Q Zheng,X.-G Han,J Gulledge,L.-H Li,W Liu

doi:10.5194/bg-6-615-2009

Abstract

Abstract. Physical injury is common in terrestrial plants as a result of grazing, harvesting, trampling, and extreme weather events. Previous studies demonstrated enhanced emission of non-microbial CH4 under aerobic conditions from plant tissues when they were exposed to increasing UV radiation and temperature. Since physical injury is also a form of environmental stress, we sought to determine whether it would also affect CH4 emissions from plants. Physical injury (cutting) stimulated CH4 emission from fresh twigs of Artemisia species under aerobic conditions. More cutting resulted in more CH4 emissions. Hypoxia also enhanced CH4 emission from both uncut and cut Artemisia frigida twigs. Physical injury typically results in cell wall degradation, which may either stimulate formation of reactive oxygen species (ROS) or decrease scavenging of them. Increased ROS activity might explain increased CH4 emission in response to physical injury and other forms of stress. There were significant differences in CH4 emissions among 10 species of Artemisia, with some species emitting no detectable CH4 under any circumstances. Consequently, CH4 emissions may be species-dependent and therefore difficult to estimate in nature based on total plant biomass. Our results and those of previous studies suggest that a variety of environmental stresses stimulate CH4 emission from a wide variety of plant species. Global change processes, including climate change, depletion of stratospheric ozone, increasing ground-level ozone, spread of plant pests, and land-use changes, could cause more stress in plants on a global scale, potentially stimulating more CH4 emission globally.

Highlights

Methane (CH4) is an important atmospheric trace gas, contributing to global warming and atmospheric redox chemistry
We examined the effect of physical injury and hypoxia on CH4 emissions from 10 species of the Artemisia genus sampled from the grasslands of Inner Mongolia
We examined the effect of physical injury on CH4 emission rates from all Artemisia species we found in the Xilin River basin (10 species total)

Summary

Introduction

Methane (CH4) is an important atmospheric trace gas, contributing to global warming and atmospheric redox chemistry. A recent study (Keppler et al, 2006) reported aerobic CH4 emission from plants by an unrecognized, non-microbial mechanism, a result that has been controversial (Schiermeier, 2006; Dueck and van der Werf, 2008). Six independent studies (Keppler et al, 2008; McLeod et al, 2008; Vigano et al, 2008; Wang et al, 2008; Bruggemann et al, 2009; Messenger et al, 2009) did detect CH4 emission from plant tissues/compounds under aerobic conditions in the laboratory. Several studies used isotope signature analysis to confirm that the CH4 originated directly from plant tissues/compounds rather than from microbial methanogenesis (Keppler et al, 2008; Wang et al, 2008; Bruggemann et al, 2009). Keppler et al (2006) initially estimated aerobic CH4 emission by plants to be in the range of 62–236 Tg CH4 y−1, Published by Copernicus Publications on behalf of the European Geosciences Union

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