Spacial And Temporal Variations Of Soil Carbon, Nitrogen And Water As Affected By An Experimental Forest Fire In The Great Xingan Mountains

October 2009, in the northern Great xin'an mountains wild forest fires were burning test points. The fixed grid method using layout samples, in the fire before and after the nodes were sampled at different time 4 times:before the fire-the day after the fire-after the snow season the following year-after the next rainy season. Carbon-nitrogen-water main line of the three environmental factors of soil analysis experiment under the influence of forest fire soil organic carbon, microbial biomass carbon, nitrogen, carbon and nitrogen ratio, ammonia nitrogen, nitrate nitrogen, ammonium nitrogen/nitrate state nitrogen, soil moisture and other traits of the time change and spatial pattern. The results are as follows:1) The fire can lead to soil organic carbon in small increase and decrease to varying degrees, due to time after the fire intensity and fire to another. Fire cause instant loss of soil organic carbon is only the role of high-intensity fire was significant; in mild fire, the soil organic carbon has instead increased. After snowmelt season and the rainy season, heavy fire continued regional soil organic carbon over a significant reduction; in light of regional soil organic carbon continued to fire small increase. Fire at each time node spatial patterns of soil organic carbon or organic carbon relative rate of change of pattern and pattern of fire intensity levels were associated with greater resistance.2) The fire can lead to significantly lower soil microbial biomass carbon, microbial biomass carbon after burning and fire intensity changes are closely related. Fire caused immediate loss of soil microbial biomass carbon due to fire intensity varies only in the role of high-intensity fire was significant. As life forms, microbial sensitivity to high temperature is much higher than organic carbon, volatile combustion and other physical process, so after severe fire than the microbial biomass carbon in soil organic carbon decline for large. Post-fire spatial patterns of soil microbial biomass carbon and microbial biomass C relative change rate of spatial pattern and fire intensity patterns are highly relevant.3) The fire caused changes in soil nitrogen vary by fire intensity, light, moderate soil nitrogen fire caused a small increase in persistent, severe persistent fire caused minor soil nitrogen reduction. Node at each time after burning (especially after the snow melt or after the rainy season) and spatial pattern of soil total nitrogen and total relative change rate of fire intensity pattern of spatial distribution and inter-relationships are with a certain degree, that high-intensity fire area mainly as soil minor loss of total nitrogen and post real-time continuous slight decrease of mild to moderate burn area mainly for the sustainability of soil nitrogen modest rise.4)Coexistence of soil nitrogen and organic carbon in organic matter, so the change between the two great relevance. Mild to moderate burning the soil organic carbon and nitrogen have sustained a slight increasing trend, in which the relative increase in total nitrogen than the larger organic carbon; fire caused severe soil organic carbon and total nitrogen decreased continuously, in which organic carbon The decline in total nitrogen than for large. Of carbon and nitrogen of these two important and interrelated environmental elements, whether mild, moderate or severe burning fire, will lead to different levels of relative "nitrogen-rich carbon reduction" results, all the soil C/N different a decline.5) The fire could lead to a significant increase of soil ammonium nitrogen, ammonium nitrogen changes in soil and fire intensity, but the performance at different times very different. Ammonium nitrogen immediately after the fire was erratic minor changes, the average did not change significantly; through the snowmelt season for late spring soil burned at high temperature, although the supply may be adequate carbon source (death of fine roots), microbial nitrogen still very significant accumulation of net mineralization, soil ammonium generally significantly higher in mild fire was significantly greater than the regional average growth rate of severe burn area; at this time due to seasonal factors of soil ammonium nitrogen, micro-topography, fire and fire intensity factor, and many other control, fire and fire intensity factors can be shown highlighted. Summer, due to leaching, regeneration of vegetation or the absorption of residual vegetation, soil microbial community gradually recovered, and possible re-absorption of ammonia volatilization loss and other reasons, burned soil ammonium nitrogen declined significantly compared with the late spring, but was still significantly higher than its value before the fire, and was significantly higher than the same period of the surrounding woodland was burned; then set fire to the universality of factors can significantly affect the performance of it, but fire intensity factors due to other factors become obvious interference. Spatial patterns of soil ammonium spatial pattern of fire intensity and the correlation was only in the following year in late spring when the rest of the time are not obvious.6) The performance of soil nitrate at different time nodes in different directions and degrees of change. The lowest soil nitrate before the fire, weak digestion. Changes in soil N after fire intensity and fire, but the performance at different times very different. Fire immediately after the light is relatively small change in soil nitrate, the average did not change significantly; moderate and severe fire immediately after the relatively significant increase in soil nitrate. Experienced snow quarters burned soil temperature and pH values are higher, the relative accumulation of nitrogen was of microbial nitrification and nitrate increased significantly in general relativity, and increases with increasing fire intensity. Summer because leaching, regeneration of vegetation or the absorption of residual vegetation, soil microbial communities to recover gradually re-absorption and other reasons, and spring soil nitrate decreased significantly compared; In addition, nitrate burned at this time control than the surrounding unburned forest land is 1 order of magnitude, indicating that nitrification was of fire. Each time the node after fire spatial pattern of soil nitrate or nitrate content of the relative rate of change of pattern and pattern of fire intensity were shown between the different degrees of relevance.7) Great xin'an mountains region in cold, acidic soil environment is not conducive to nitrification, nitrification generally weak, soil available nitrogen to ammonium nitrogen predominant. Ammonium nitrogen in soil after fire/N for the overall performance continues to decrease reached a significant level. Ammonium nitrogen in soil after fire/N decreased significantly large have immediate and severe burning down more obvious areas. Through the snow or rain season, the ammonium nitrogen/nitrate ratio generally decreased steadily, and ultimately reduce the degree of intensity with the fire intensified. Despite the relative increase of N is large, but the absolute increase is limited, so the soil after burning ammonium/nitrate ratio decreased significantly, to what extent changes in the plant's "Nitrogen habitat" needs further study.8) significant impact on fire and the temporal and spatial variation of soil moisture. Fire caused the immediate loss of soil moisture levels increase with the fire fueled. Soil moisture as affected by precipitation-driven character, in the spring dry season burning of superposition effects are still significant, burned surface temperature (charcoal absorbs solar radiation), re-burned out organic seal protection, increased soil moisture evaporation loss, drought exacerbated the degree level with the fire, soil moisture spatial pattern and fire intensity pattern of a close relationship between, and will inevitably affect the pattern of vegetation renewal or regeneration. Summer season, soil moisture affected by climate change led the Trail wet season fire effects on soil moisture levels become obvious. After the fire of different intensity of soil carbon, nitrogen, water, space and time of each index a comprehensive analysis of reasons for the changes. Carbon, nitrogen, water, soil environment are important elements of the three, the forest fire of its spatial and temporal variation under the influence study of fire effects for the conduct of the quantitative evaluation of Great xin'an mountains important.