Research On Field CH₄ Flux And Related Microbes Under Simulated Climate

Global climate change is a global concern,and is a topic of intense international research efforts in order to combat and adapt to climate change.Air temperature changes naturally daily and seasonally as the earth rotates on its own axis and around the sun.Soil moisture also varies widely in response to changes in rainfall.All of these make it more difficult to predict global climate change impacts.In this research project,small glasshouses or shelters（1 m×2 m×1 m）were used to give higher temperature and drier soil conditions to simulate climate change impact.32 small glasshouses that can control air temperature and soil moisture inside were built.Air temperature in the small glasshouses were controlled to be higher than ambient temperature by 3-5 ℃,and soil moisture in the glasshouses were controlled to be lower than that outside the glasshouses by about 10%of field capacity.Four hundred kilogram urea-N was applied to half of the plots with or without shelter to study the impact of nitrogen（N）fertilizer application on methane（CH₄）flux under the simulated climatic conditions for 259 days.The simulated warmer and drier conditions inside the shelters affected the nitrogen transformation rates in the soil and maintained higher NH4+ and NO3-concentrations than those without the shelter.Urea increased soil respiration as soil CO2 flux was increased.The higher temperatures and drier soil conditions inside the shelters prolonged the elevated soil CO2 fluxes following urea application.Urea provides substrate to soil microbes as thus increasing soil respiration.Urea application did not change soil CH₄ flux significantly,however.Higher air temperature and drier soil moisture conditions created by the shelter decreased soil CH₄ flux briefly at the beginning of the experiment.Soil methanogens and methanotrophs gene copy numbers were not significantly affected by the temperature and soil moisture conditions inside the shelters nor by the urea application.Soil methanogens mcrA gene copy numbers ranged from 8.0×105 to 8.15×105 per gram dry soil.Soil methanotrophs pmoA gene copy numbers ranged from 2.5×104 to 7.5×104 per gram dry soil.