Controls on methane emissions from Alnus glutinosa saplings

Abstract

SummaryRecent studies have confirmed significant tree-mediated methane emissions in wetlands; however, conditions and processes controlling such emissions are unclear. Here we identify factors that control the emission of methane from Alnus glutinosa.Methane fluxes from the soil surface, tree stem surfaces, leaf surfaces and whole mesocosms, pore water methane concentrations and physiological factors (assimilation rate, stomatal conductance and transpiration) were measured from 4-yr old A. glutinosa trees grown under two artificially controlled water-table positions.Up to 64% of methane emitted from the high water-table mesocosms was transported to the atmosphere through A. glutinosa. Stem emissions from 2 to 22 cm above the soil surface accounted for up to 42% of total tree-mediated methane emissions. Methane emissions were not detected from leaves and no relationship existed between leaf surface area and rates of tree-mediated methane emissions. Tree stem methane flux strength was controlled by the amount of methane dissolved in pore water and the density of stem lenticels.Our data show that stem surfaces dominate methane egress from A. glutinosa, suggesting that leaf area index is not a suitable approach for scaling tree-mediated methane emissions from all types of forested wetland.

Mechanisms of methane transport through <i>Populus trichocarpa</i>

“…The value can be interpreted to indicate two or more mechanisms of transport, possibly some combination of movement through membrane barriers, bulk flow, and diffusion. However, although gas transport through aerenchyma is usually assumed to be diffusive (Chanton, 2005;Garnet et al, 2005;Machacova et al, 2013;Pangala et al, 2014), this work strongly suggests that molecular …”

“…Although a large amount of CH 4 has been shown to come through emergent wetland plants (Shannon et al, 1996), physiological correlations for tree emission of CH 4 have been studied very little and the role that woody vegetation has in wetland emission of CH 4 is still poorly understood (Vann 25 and Megonigal, 2003;Terazawa et al, 2007). It should be mentioned that more recently, Pangala et al (2014) did find a strong correlation between lenticel density and CH 4 flux from stems in the tree species Alnus glutinosa. It is clear from the data here that temperature and flux, δ .…”

“…Although it has been suggested that the developmental stage of a tree may play a role in the ability of a tree to transport CH 4 (Pangala et al, 2014), the specific CH 4 transport mechanisms themselves are not expected to be altered by more mature tree growth. Therefore, the mechanisms described here should be applicable qualitatively to more 20 mature trees, even though there may be quantitative shifts in CH 4 flux.…”

“…It has been proposed that CH 4 can be transported through these structures (Rusch and Rennenberg, 1998). Gas transport through plant tissues is usually suggested to be diffusive in current literature, whether for emergent aquatic plants (Chanton, 2005) or upland or riparian trees (Machacova et al, 2013;Pangala et al, 2014).…”

Effect of waterlogging on boreal forest tree seedlings during dormancy and early growing season

“…Hypertrophic lenticels are considered as entry points of oxygen from shoot to root (Armstrong 1968;Hook et al 1971). There is also evidence that hypertrophic lenticels serve as excretory sites to eliminate potentially toxic compounds such as ethanol, acetaldehyde and ethylene which result from anaerobic metabolism in the roots (Pangala et al 2014).…”