| Popis: |
Plant shoots can emit methane (CH4) which is produced by an unknown aerobic, non-enzymatic process within the plant. Only a few publications report shoot CH4 fluxes outside a laboratory setting, and those of boreal trees come to contradictory results (Machacova et al., 2016; Sundqvist et al., 2012). Resolving the CH4 fluxes of boreal trees is needed in order to understand the role of boreal forests in the global methane budget.We conducted shoot chamber measurements on Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) between April and May 2019, to find out if the shoots of boreal conifer trees are a source of aerobic CH4 during the early growing season. The experiment was done with potted 2-3 year old nursery saplings in a common garden experiment, to enable regular measurements over a period of six weeks. CH4 fluxes were measured 2-3 times per day, on two days per week from seven saplings (four P. sylvestris and three P. abies, respectively). We also conducted two around the clock campaigns where we measured the saplings hourly throughout the day and night. The CH4 and carbon dioxide (CO2) exchange were quantified with a portable LGR online greenhouse gas analyser connected in closed loop to custom-made, transparent shoot chambers. Photosynthetically active radiation (PAR) was measured concurrently with a PP Systems EGM-4 monitor.Our measurements show emissions of CH4 from both tree species, ranging from 0.25 to 7.64 and -0.45 to 6.42 g-1 needle dry weight h-1 (inter-quartile range) from P. sylvestris and P. abies shoots, respectively. The shoot CH4 emissions from both species correlated positively with PAR. During the around the clock measurements the emissions showed a diurnal pattern. Our experiment demonstrates that the shoots of both P. sylvestris and P. abies can be a source of CH4 in the spring and that the source process is likely driven by solar irradiation. ReferencesMachacova, K., Bäck, J., Vanhatalo, A. et al. 2016. Pinus sylvestris as a missing source of nitrous oxide and methane in boreal forest. Scientific Reports, 6(September 2015), 1–8.Sundqvist, E., Crill, P., Mlder, M. et al. 2012. Atmospheric methane removal by boreal plants. Geophysical Research Letters, 39(21), 10–15. |
