| The greenhouse effect, which is caused by human activities, creates climate change, disrupts ecosystems and is causing increasing concern internationally. Forest fires, and the related disturbance, are a natural component of forest ecosystems. Forest fire, a main disturbance factor in forest ecosystems, is widely recognized as an essential natural process in those ecosystems. Many people have begun to realize that fires not only have physical effects but forest fires may increase in number and become more intense in response to future climatic change, which will influence the carbon cycle in forest ecosystems.Understanding the effect of fire disturbance and the changes it causes to a forest ecosystem’s carbon cycle under the background of climate warming is important in support of attempts to gain a correct understanding of the overall effects of climate warming. Scientists need to formulate reasonable and scientifically-based methods to measure these effects in support of developing a forest fire management strategy. Estimating and displaying forest fire carbon emissions will allow land managers to better manage and understand the vital significance of the forest ecosystem carbon cycle and the function of carbon balance within the ecosystem. Finally, we propose an effective and scientifically-based forest fire management strategy.This paper analyzes the carbon cycle in two typical forests:the boreal forest of Daxing’anling Mountains and the temperate forest of Heilongjiang Province, China. A large number of field studies and extensive sampling were combined with indoor controlled environment experiments and data analysis to determine forest fire carbon and carbonaceous gas emissions at the stand level. This was done using a model to estimate forest fire carbon emissions and to analyze factors affecting emissions. Forest fire carbon and carbonaceous gas emissions were estimated and analyzed for a Heilongjiang Province forest (Daxing’anling boreal forest and Heilongjiang Province temperate forest), including an analysis of the spatial and temporal patterns of forest fires and the climatological factors influencing changes in fire intensity and extent.An optimal path for forest fire management can be determined by combining scientific and reasonable forest fire management strategies with an analysis of carbon and carbonaceous gas emissions from forest fires. The main results follow.1) Forest fire carbon emissions are systematically and quantitatively evaluated. Several field investigation and sampling methods are discussed, including:indoor controlled environment experiments and experimental analysis methods, analysis of forest fire carbon and carbonaceous gas emissions using various methods to determine the parameters to be measured, modeling and measuring of forest fire carbon emissions, stand level analysis used to clarify forest fire carbon emissions estimates and factors affecting emissions, and discussion of the methods used to estimate and inventory forest fire carbonaceous gas emissions.2) A database of actual forest fire carbon emissions was created using the selected parameters. Carbon emissions parameters (per unit area of forest fuel loading, fuel carbon content and combustion efficiency) and the main emission factors were measured for the Daxing’anling boreal forest and Heilongjiang Province temperate forest allowing the establishment of a more comprehensive forest fire emission database.3) Total forest fire carbon emissions for forest fires in the Daxing’anling boreal forest during1965-2010(46years) were estimated to be3.12×107t, or an average of6.79×105t yr-1. Forest fire carbon emissions for various forest types were:Larix-Rhododendron forests,11.79t/hm2; Larix-Ledum forests,7.53t/hm2; Larix-grass forests,11.51t/hm2; Pinus pumila-Larix gmelinii forests,10.85t/hm2; Betula platyphylla forests,5.55t/hm2; Pinus sylvestris var. mongolica forests,4.01t/hm2; Quercus mongolica forests,12.67t/hm2; coniferous forests,18.72t/hm2; broad-leaved forests,11.20t/hm2; coniferous broad-leaved mixed forests,3.06t/hm2. The46-year soil organic carbon emissions from forest fires totaled2.20×107t.4) Levels of emissions of four major carbonaceous gases from forest fires were estimated for the Daxing’anling boreal forest. Forest fire carbonaceous gas [CO2, CO, CH4and non-methane hydrocarbons (NMHC)] emissions in the Daxing’anling boreal forest were estimated to be9.76×107t,9.51×106t,5.46×105t and2.14x105t, respectively, with an annual average of2.12×106t,2.07×105t,1.19×104t and4.65×103t, respectively. Emissions of the four major carbonaceous gases (CO2, CO, CH4, and NMHC, listed respectively below) calculated per unit area for each forest type were:Larix-Rhododendron forests,36.09,4.18,0.22and0.07t/hm2; Larix-Ledum forests,23.94,2.35,0.10and0.05t/hm2; Larix-grass forests,36.35,4.09,0.24and0.08t/hm2; P. pumila-L. gmelinii forests,34.59,3.09,0.21and0.07t/hm2; B. platyphylla forests,17.48,1.35,0.07and0.04t/hm2; P. sylvestris var. mongolica forests,12.30,1.18,0.13and0.03t/hm2; Q. mongolica forests,40.89,3.37,0.19and0.09t/hm2; coniferous forests,58.43,3.66,0.27and0.14t/hm2; broad-leaved forests,36.36,2.34,0.11and0.08t/hm2; coniferous broad-leaved mixed forests,9.53,0.84,0.05and0.02t/hm2.5) Total forest fire carbon emissions for Heilongjiang Province temperate forest during1953-2012(60years) were estimated to be5.88x107t, or an average of9.80×105t yr-1. Calculated forest fire carbon emissions per unit area for various forest types were:broad-leaved Pinus koraiensis forests,12.50t/hm2; L. gmelinii forests,16.84t/hm2; B. platyphylla forests,20.07t/hm2; B. platyphylla-L. gmelinii forests,12.99t/hm2; P. sylvestris var. mongolica forests,22.25t/hm2; Abies nephrolepis-Picea asperata forests,25.60t/hm2; B. platyphylla-Populus davidiana forests,23.97t/hm2; hardwood forests,12.74t/hm2; Q. mongolica forests, 13.58t/hm2; coniferous forests,29.75t/hm2; broad-leaved forests,26.42t/hm2; coniferous broad-leaved mixed forests,7.05t/hm2. The60-year soil organic carbon emissions from forest fires totaled1.92×107t and the average annual emissions were3.20x105t, accounting for2.83%of the national average annual forest fire carbon emissions.6) Levels of emissions of four major carbonaceous gases from forest fires were estimated for Heilongjiang Province temperate forest. Forest fire carbonaceous gas (CO2, CO, CH4and NMHC) emissions in Heilongjiang Province temperate forest were estimated to be1.89×108t,1.06×107t,6.33×105t and4.43×105t, respectively. Its average annual emissions were3.15×106t,1.77×105t,1.05×104t and7.38×103t, respectively. Emissions of the four major carbonaceous gases (CO2, CO, CH4, and NMHC, listed respectively below) calculated per unit area for each forest type were:broad-leaved Pinus koraiensis forests,39.07,2.64,0.14and0.09t/hm2; L. gmelinii forests,52.87,3.39,0.18and0.13t/hm2; B. platyphylla forests,66.06,3.62,0.24and0.15t/hm2; B. platyphylla-L. gmelinii forests,41.72,2.15,0.13and0.08t/hm2; P. sylvestris var. mongolica forests,7.27,3.99,0.20and0.18t/hm2; A. nephrolepis-P. asperata forests,85.55,3.72,0.25and0.20t/hm2; B. platyphylla-P. davidiana forests,76.56,4.46,0.27and0.20t/hm2; hardwood forests,41.30,2.10,0.15and0.11t/hm2; O. mongolica forests,43.93,2.54,0.15and the0.11t/hm2; coniferous forests,97.72,4.48,0.28and0.23t/hm2; broad-leaved forests,87.80,3.83,0.31and0.20t/hm2; coniferous broad-leaved mixed forests,21.49,1.45,0.06and0.05t/hm2.7) A corresponding forest fire management strategy and optimal path for forest fire management is outlined. During the analysis of carbon emissions from forest fires, we found that the forest fire carbon emissions varied widely for these two study areas; emissions were especially influenced by combustion efficiency and other factors influencing emissions. These factors need to be considered when developing a forest fire management strategy and optimal path for forest fire management.8) Changes in the average annual carbon emissions in Heilongjiang Province have an important impact on the carbon cycle and carbon balance in that area. Fires in the Daxing’anling boreal forest annually produce an average of about6.00%of the national average annual forest fire carbon emissions, and annual soil organic carbon emissions in this area account for about4.22%of the national average annual forest fire carbon emissions. Annual emissions of the four major carbonaceous gases (CO2, CO, CH4and NMHC) accounted for5.22,7.63,10.60and4.12%of the national average annual forest fire emissions of these gases, respectively or for0.76,1.29and2.20%of the national average annual biomass from carbonaceous gas emissions from burning, respectively. Annual emissions from forest fires in Heilongjiang Province temperate forest account for about8.66%of the national average annual forest fire carbon emissions, while annual soil organic carbon emissions in that area account for about2.83%of the national average annual forest fire carbon emissions. Annual emissions of the four main carbonaceous gases (CO2, CO, CH4and NMHC) accounted for7.74,6.52,9.42and6.53%of the national average annual forest fire emissions of carbonaceous gases, respectively, accounting for5.22,7.63,10.60and4.12%of the national average annual biomass from carbonaceous gas emissions from burning, respectively. |
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