Effects Of Fire Disturbance On Temporal And Spatial Dynamics Of Greenhouse Gas Emissions From Forested Wetlands In Xiaoxing’an Mountains,Northeast China

There are the main distribution area of forested wetlands in Greater, Xiao Xing’an and ChangBai Mountain in china, forest fires are common human and natural phenomena in area, to study the influence of the fire disturbance on forested wetlands regular pattern is significant to understanding of greenhouse gas carbon sinks and management of wetland resources of wetlands in temperate and cold temperate zone.In study, seven major types of wetlands Xiao Xing’an Mountain as the research object along the transitional water environmental gradients, there are Carex schmidtii(C), Betula ovalifolia a Carex schmidtii shrub swamps(G), Alnus sibirica swamp(M), Betula platypHylla swamp(B), Larix gmelinii-Carex schmidtii swamp(LT), Larix gmelinii-moss(LX), and Larix gmelinii SpHagnum spp. Swamp(LN), By using a static opaque chamber and gas chromatography method to simultaneous observation the3main greenhouse gases emission fluxes and the related control factor(temperature and water level) of the unburned and burned disturbance(mild-ground fire, severe-canopy fire) alone forest wetland transition, and researched the extent and mechanism of influence the of seasonal dynamics of emissions, main control factor, spatial distribution pattern, Revealed the regular pattern of temporal dynamics of greenhouse gases emission in wetland after the fire disturbance. The results showed that:(1) Fire disturbance changed the seasonal dynamics, the main control factor and spatial distribution pattern of CH4emissions in marsh.〖The average emission fluxes of the unburned plots and the burned plots are distributed in-0.004±0.019-14.345±2.265and-0.001±0.012～22.373±3.650mg·m-2·h-1.The disturbance of mild fire improves the average emission fluxes of the C, G, M, B, LT by56%-524.7%observably(P<0.05), making the larch mosses swamp translate into the CH4weak emissions source from its weak absorption, severe fire disturbance makes the birch swamp trans turn into CH4weak absorption from its weak emissions.②Temperature is the main controlling factor of the swamp wetland methane emission flux to most of the natural forest.Significant correlation with temperature and water level of wetlands in the high level types. Conversely, the lower level types and the relatively low temperature.After fire disturbance, temperature has significant influence on water level low marsh type, its methane emission flux and temperature of the related degree improved significantly.③The CH4emission peak of each type of unburned and burned forest swamp appeared in summer or autumn,and after fire methane emissions from summer biggest and autumn next, More unburned and burned to spring marsh wetland methane emissions showed a weak absorption. The CH4emission flux along the transition zone water environment gradient showed fall sharply spatial distribution pattern of unburned wetland, and a decreasing spatial after fire(Marsh was strong sources of CH4emission, shrub’s was medium,and5kinds of forest swamp was weak emission sources or absorption sinks,Marsh and shrub swamp were strong emission sources and the former was higher than the latter, Alnus sibirica-Carex schmidtii’s was medium, the other4kinds of forest swamp was the weak emission sources).Temperature was the main factor that the CH4spatial distribution of wetland transition zone emission of fire disturbance in Xiao Xing’an Mountains.(2) Fire disturbance changed the seasonal dynamics, the main control factor and spatial distribution pattern of CO2emissions in marsh.①The average emission fluxes of the unburned and the burned plots are distributed in270.7±85.3～541.6±22.2and212.9±27.43～529.95±58.75mg·m-2·h-1. The disturbance of mild fire reduced the average emission fluxes of the C, M, B, by21.3%～57.4%observably(P<0.05), and improved average emission fluxes of the LT, LN by24.9%～63.7%(P<0.05)observably.②Temperature is the main controlling factor of the swamp wetland carbon dioxide emission flux to C,G,L of the natural forest swap.Other types of swamp wetland CO2emission flux with temperature, water level, has weak related or not. Temperature and water level changed main controlling factors of CO2emission flux of B,LT swamp,and relevant or not with C,G swamp after fire disturbance.Temperature and water level combine affect the CO2emissions flux of LX,LN swap,no matter unburned or burn.③The CO2emission peak of each type of unburned and burned forest swamp appeared in summer(LT swap appeared in autumn), The emission fluxes of CO2had changed in spring and autumn after fire disturbance. The CO2emission fluxes in the unburned wetlands transition showed that "r" spatial distribution pattern type along the transitional water environmental gradients,C swamp was relatively high emission fluxes, the other six swamp showed a decreasing trend after the beginning increase, the maximum emission fluxes was B swamp, LN’s was the lowest. After fire disturbance showed reverse "r" spatial distribution pattern type,LN swamp was relatively high emission fluxes, the other six swamp showed a decreasing trend after the beginning increase, the maximum emission fluxes was LT swamp, C’s was the lowest.The surface temperature and soil temperature of5cm combined impact transition zone swamps CO2emission flux after fire disturbance, temperature is the cause of the spatial distribution pattern was changed.(3) Fire disturbance changes the marsh seasonal dynamics of N2O emissions, the main control factor, and spatial distribution pattern.①The average emission fluxes of the unburned plots and the burned plots were distributed in0.0167±0.0759～0.0869±0.0130,-0.0029±0.0353～0.0630±0.0070mg·m2·h-1. The mild fire disturbance significantly decreased the average emission fluxes of the C, G, M, B, LT, LN swamp by26.7%～99.8%(P<0.05). It made the LX from the N2O emission sources to absorption source. Severe fire disturbance significantly decreased the average emission fluxes of the B and LT by65.7%and67.7%(P<0.05).②Temperature on the influence of forest swamp wetland N2O emission flux was higher than the water level. Various types of unburned and burning sample to the N2O emission flux had no significant correlation with water level, except unburned shrub swamp.Correlation was unburned C, B swamp N2O emission flux and temperature high,lower with LT swap,and no significant correlation to M and LN swap.The N2O emission flux weakened with significant correlation to temperature(LN swamp improve).③The N2O emission peak of each type of unburned forest swamp appeared in spring, weak emission in summer or autumn. The emission peak appeared in spring too,After fire disturbance(B and LX’s translated summer&autumn),seasonal pattern was weak emission in spring and weak absorption in summer&autumn.The N2O emission fluxes in the unburned wetlands transition showed that spatial distribution pattern was plummeted type along the transitional water environmental gradients(C, LT,LN swamp were the relatively high sources of N2O emissions, and G, M, B swamp were the medium emissions, while LX swamp was the relatively lowest). It showed the spatial distribution pattern that transition kinds of wetlands was relatively high in the lower part and relatively lower in the higher part of the wetlands,C, G,M swamp were the relatively high sources of N2O emissions, while B, LT, LX, LN swamp were the relatively lower.(4) Fire disturbance affected to the total emissions and space distribution pattern of CH4, CO2, N2O in growing season wetlands.①The distribution of total CH4emissions of growing season no fire and Fire disturbance plots was-0.15±0.66～447.53±76.69,3.01±0.42-698.03±135.47kg.hm-2.yr-1, fire disturbance change the distribution pattern of its wetland CH4emissions along environmental gradients transitional space from plummeted to a descending pattern type.②The distribution of total CO2emissions of growing season no fire and Fire disturbance plots was8.47±2.66～16.90±0.70,6.64±0.86～15.85±2.09kg.hm-2.yr-1, With the bottom of the marsh transition CO2emission is relatively high, the other type of swamp forest transition zone along the swamp to the direction of water environmental gradient showed single peak type distribution, After fire disturbance, CO2emissions along environmental gradients transitional space from "r" to "N" pattern type。③The distribution of total N2O emissions of growing season no fire and Fire disturbance plots was0.31±0.52～2.70±0.21、0.09±0.13～1.95±0.23kg.hm-2.yr-1,Fire disturbance changed the distribution pattern of its wetland N2O emissions along environmental gradients transitional space(First decreased, then increased again to reduce fluctuations form change to high ends of the central low, Similar "U" shaped distribution).(5) Fire disturbance affected the Global Warming Potential (GWP) and spatial distribution pattern to wetlands. The GWP of growing season no fire and Fire disturbance plots was8.75±2.92～26.65±3.25,8.96±3.13～23.28±4.04t.hm-2.yr-1,And change the distribution pattern of GWP along environmental gradients transitional space(from similar "r" to "W" pattern type). Severe fire disturbance made GWP of B swap significantly lower (22.9%,P<0.05), But decreased smaller than the slight fire disturbance (36.6%),Significantly increased (39.0%, P<0.05) of GWP of LT swap, Greater than the Slight fire disturbance (17.3%).