Methane Emissions From Plants Under Aerobic Conditions In Mid-subtropic, China

Plant was generally regarded as "sink" of greenhouse gases, whereas a few researches indicated that terrestrial plants can emit methane under aerobic conditions. This topic on plant methane emissions was still in debate. Study whether the plants can emit methane will help the research of "Source" or "Sink" for greenhouse gases. Forest coverage in the mid-subtropical region of China, especially in Fujian province ranks first in the country, so to find out whether the plants can emit methane will directly influence the methane budget in this region and even the whole world. In this study,60 kinds of plants were selected in mid-subtropical region of China (Fujian Wanmulin natural reserve, Minjiang River estuary, etc.) to determine the methane emission from detached leaves and the whole plants through incubation method. The major results were as follows:No or slight methane emissions were observed for 22 of total 60 plant leaves at normal temperatures (12～18℃), and methane emission rates for the other 38 plant leaves ranged from 0.10 to 0.73 ngCH4·g-1DW·h-1. The order of methane emission rate from plant leaves of different families was:Leguminosae > Magnoliaceae > Lauraceae = Moraceae>Fagaceae. Methane emission rates from leaves of the shrubs, hydrophyte and coniferous trees were higher than those of the arbors, terrestrial plants and broad-leaved trees respectively, but there were no significant differences (P>0.05). The maximum value of methane emission rate from the detached leaves was 2.46 ngCH4g·DW·h-1 when the temperature was 40℃. The methane emission fluxes of the whole plant were very low and most of which were negative values, suggesting a net uptake of methane for these plant types. In addition, we also detected that sunshine, UV radiation, temperature (heating) and physical injury were the important influencing factors on the methane emission.