Responses of ethylene and methane consumption to temperature and pH in temperate volcanic forest soils

摘要

There is limited knowledge about the consumption and interaction of methane (CH) and ethylene (CH) in forest soils under disturbances of temperature and acidification. Temperate volcanic forest topsoils (0-5 cm) sampled under different tree species (e.g. Pinus sylvestris, Cryptomeria japonica and Quercus serrata) were used to study the capacities for CH and CH consumption and their sensitivity to temperature and pH. We also studied the responses of soil nitrogen (N) transformations to temperature and relationships to consumption of both CH and CH. The CH consumption rates increased with temperature up to 35oC, whereas the optimum temperature for CH consumption rates was approximately 25oC. Both Q values and activation energies for CH consumption rates over the range 5 to 25oC were larger than corresponding values for CH consumption rates. The rates of nitrous oxide (NO) and nitric oxide (NO) evolution and net N mineralization in the soils increased exponentially with temperature up to 35oC, with relatively large Q values and activation energies for NO evolution. In these forest topsoils, rates of CH and CH consumption at pH < 4.0 were negligible, and the pH optimum for both consumptions varied from 5.5 to 6.2. Most of the tested forest soils had an optimum pH for CH and CH consumption that was above natural pH values, which indicated that soil acidification would inhibit CH and CH consumption in situ. There was a high rate of net CH evolution from forest soils acidified experimentally to pH < 4.0, particularly from Cryptomeria japonica forest soil, and 67% of the variation in CH evolution rates could be accounted for by the increase in soil water-soluble organic carbon concentrations. Previous studies have shown that addition of CH in headspace gases can inhibit atmospheric CH consumption in such forest soils. Hence, the evolution of CH from temperate volcanic forest soils at decreasing pH can exacerbate inhibition of the soil atmospheric CH consumption in situ.