Influence Of Litter, Nitrogen, Moisture And Temperature Condition On CO₂ Emissions From Forest Soils

Forest soil CO2 emissions and carbon-nitrogen cycle of forest ecosystem are affected by increased nitrogen deposition, sustainable global warming, changed of pattern and intensity of precipitation. Although large numbers of studies for temperate forest was carried out by field observation test of nitrogen deposition and hydrothermal conditions change and litter add on forest soil incubation experiment of greenhouse effect, how single and interaction affect of increased atmospheric nitrogen deposition, global warming, pattern change of precipitation and litter decomposition of the regional forest soil net greenhouse gas flux and soil properties is still not clear. Hence, it is particularly important and urgent for us to study soil CO2 fluxes and transformation processes of soil carbon and nitrogen under nitrogen, water and temperature condition and litter applied and the mechanisms involved. This study will be beneficial to provide scientific support for reasonably asssing the changing trends of regional soil carbon sequestration and CO2 fluxes and for the buildup of related models.Packed soil-core incubation experiments were done to study ①the eatlier and later periods of the singular and interactive effects of nitrogenaddition.different litter addition on soil CO2 fluxes and soil properties from a mature broadleaf and Korean pine mixed forest (BKPF) under two water and temperature conditions;②the main mechanisms of soil CO2 fluxes combining with the varation of main soil properties. The results show that:1) The higher temperature and humidity and litter addition promot instantaneous forest soil CO2 emissions and cumulative emissions, and nitrogen suppresses transient emissions and accumulation of soil CO2 emissions under experimental conditions. Fraxinus mandshurica litter plays the most significant role in promoting CO2 cumulative emissions of forest soil while the Pinus koraiensis litter plays the minimum role. There is interaction effect between Nitrogen added, hydrothermal conditions and litter on soil CO2 emissions cumulative.The different species of litter the temperature, humidity, and nitrogen and their interactions effect of forest soil CO2 emission have different significant.2) There is significant positive correlation between forest soil CO2 cumulative emissions and soil microbial nitrogen during erlier incubation.The same result exists in forest soil CO2 cumulative emissions and DOC extracted by K2SO4 during later incubation. Forest soil CO2 Cumulative emissions decreases with the increasing of soil nitrogen availability(P<0.001). There is significant different influence in single factor and interaction effect of temperature, humidity, and nitrogen of soil properties with different species litter.3) High temperature has larger priming effect than low temperature in transient emissions of CO2 induced by litter during the early stage of the interaction (0 to 35 days). Fraxinus mandshurica (FM) on soil CO2 induced by litter stimulation effect is greater than the other litter add processing.Temperature, moisture and litter all promote the forest soil CO2 cumulative emissions induced by litter while nitrogen inhibition. The soil CO2 emissions caused by litter are affected by soil temperature, moisture and nitrogen condition. The promote effect of soil CO2 cumulative emissions of temperature on the litter species is not obvious. The inhibition of nitrogen on transient emissions of CO2 induced by litter and this inhibiting effect is highest in high temperature and moisture. The different species of litter the temperature, humidity, and nitrogen and their interactions effect of forest soil CO2 emission caused by litter have different significant.4) Temperature, moisture and nitrogen addition significantly affected litter added water leaching DOC(P<0.01) there is significant interaction of the temperature and moisture(P<0.01).There is significant interaction effect between nitrogen, temperature and moisture on Water extraction DOC without litter during later incubation. There is significant interaction effect between nitrogen, temperature and moisture on Water extraction DOC with litter during later incubation (P<0.5). There is no significant single and interaction effect on CO2 flux caused by litter between Temperature, moisture and nitrogen addition.