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Forest fuels are the basis of fire occurrences, while ground dead fuels are an important part of forest fuels. Undestanding the pyrolysis characteristics and gas emissions of forest fuels is of great significance to explore the effects of forest fire on atmospheric environment and carbon balance, as well as to prevent and combat forest fire. In this study, the thermogravimetric analysis and gas emission analysis were conducted on leaf litter of six tree species ( Pinus sylvestris var. mongolica , Picea koraiensis , Fraxinus mandshurica , Juglans mandshurica , Quercus mongolica , Betula platyphylla ) in Heilongjiang Province to explore the pyrolysis process and combustibility of forest fuels, to analyze their pyrolysis characteristics, pyrolysis kinetics characteristics, gas emission characteristics. A four-dimensional evaluation of their combustibility was conducted based on pyrolysis parameters. The results showed that the pyrolysis temperature of holocellulose in the leaves of those six tree species ranged in 143.31-180.48 ℃ at the beginning and 345.04-394.38 ℃ at the end, lignin pyrolysis temperature ranged in 345.04-394.38 ℃ at the beginning and 582.85-609.31 ℃ at the end. The pyrolysis of the six kinds of arbor blades during the pyrolysis process affected fuel ash content, quality and temperature of the total pyrolysis. The activation energies of two main pyrolysis stages of leaves of six tree species were 18.88-27.08 kJ·mol -1 and 13.25-27.54 kJ·mol -1 , respectively, and the pre-exponential factors were 3.13-26.28 min -1 and 1.30-22.55 min -1 . The holocellulose activation energy and pre-exponential factor of the pyrolysis stage for P. koraiensis , F. mandshurica , Q. mongolica , and B. platyphylla were greater than that of the lignin pyrolysis stage, while the opposite was true for P. sylvestris var. mongolica and J. mandshurica . The release amounts of CO and CO 2 at the pyrolysis stage of the holocellulose was 535.16-880.11 mg·m -3 and 7004.97-10302.05 mg·m -3 , and that at the pyrolysis stage of lignin was 240.31-1104.67 mg·m -3 and 20425.60-33946.68 mg·m -3 , respectively. The release of CO and CO 2 at the pyrolysis stage of healdellulose was less, but mass loss was greater than that at the pyrolysis stage of lignin. In the four-dimensional combustibility ranking of the six tree species leaves, B. platyphylla was the best ignitable, P. koraiensis was the most combustible, and P. sylvestris var. mongolica was the most sustainable and consumable. The ignitability was significantly positively correlated with pyrolysis kinetics parameters of the holocellulose, while the sustainability was negatively correlated with that of lignin.

Based on the forest resources investigation data and the forest fire inventory in 1953-2011, in combining with our field research in burned areas and our laboratory experiments, this paper estimated the carbonaceous gases carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and nonmethane hydrocarbons (NMHC) emission from the forest fires in Xiao Xing' an Mountains of Heilongjiang Province, Northeast China in 1953-2011. The total carbon emission from the forest fires in the Xiao Xing'an Mountains in 1953-2011 was 1.12 x 10(7) t, and the annual emission was averagely 1.90 x10(5) t, accounting for 1.7% of the annual average total carbon emission from the forest fires in China. The emission of CO2, CO, CH4, and NMHC was 3.39 x 10(7), 1.94 x 10(5), 1.09 x 10(5), and 7.46 x 10(4) t, respectively, and the corresponding annual average emission was 5.74 x 10(5), 3.29 x 10(4), 1.85 x 10(3), and 1.27 x 10(3) t, accounting for 1.4%, 1.2%, 1.7%, and 1.1% of the annual carbonaceous gases emitted from the forest fires in China, respectively. The combustion efficiency and the carbon emission per unit burned area of different forest types decreased in order of coniferous forest > broad-leaved forest > coniferous broadleaved mixed forest. Some rational forest fire management measures were put forward.

Forest fire is the main disturbance factor for forest ecosystem, and an important pathway of the decrease of vegetation- and soil carbon storage. Large amount of carbonaceous gases in forest fire can release into atmosphere, giving remarkable impacts on the atmospheric carbon balance and global climate change. To scientifically and effectively measure the carbonaceous gases emission from forest fire is of importance in understanding the significance of forest fire in the carbon balance and climate change. This paper reviewed the research progress in the measurement model of carbon emission from forest fire, which covered three critical issues, i. e., measurement methods of forest fire-induced total carbon emission and carbonaceous gases emission, affecting factors and measurement parameters of measurement model, and cause analysis of the uncertainty in the measurement of the carbon emissions. Three path selections to improve the quantitative measurement of the carbon emissions were proposed, i. e., using high resolution remote sensing data and improving algorithm and estimation accuracy of burned area in combining with effective fuel measurement model to improve the accuracy of the estimated fuel load, using high resolution remote sensing images combined with indoor controlled environment experiments, field measurements, and field ground surveys to determine the combustion efficiency, and combining indoor controlled environment experiments with field air sampling to determine the emission factors and emission ratio.

The Poisson's and Zero Inflated Poisson (ZIP) models that meet the data structure of forest fire occurrence were used to explore the relationships between the forest fire occurrence and climate factors in Daxing' an Mountains in 1980-2005. Compared with the ordinary least squares (OLS) model which often produced poor fitting results (R2 = 0.215), the Poisson's and ZIP models operated better, and had better prediction ability on the forest fire occurrence. The AIC and Vuong tests further indicated that ZIP model produced better fitting results, and thus, had better prediction ability than Poisson model.

By the method of emission factor (EF), this paper estimated the total carbon-containing gas emission from five main tree species in Daxing' an Mountains in forest fires from 1980 to 2005. The results showed that different tree species had different EF. Pinus sylvesstris var. mongolica and Populus davidiana had the maximum and minimum EF of CO2, respectively. Larix gmelinii and Betula platyphylla had the maximun EF of CO and C(x)H(y), while B. platyphylla and L. gmelinii had the minimum EF of CO and C(x)H(y). Based on the carbon storage in different organs and the total biomass of the tree, it was estimated that the total emission of CO2, CO and C(x)H(y) from the five tree in the 25 years was 16.58 Tg, 1.61 Tg and 0.54 Tg, and the contributions of L. gmelinii, P. sylvesstris var. mongolica, B. platyphylla, P. davidiana, and Quercus mongolica were 5.00 Tg, 0.63 Tg and 0.05 Tg, 0.225 Tg, 0.023 Tg and 0.003 Tg, 11.22 Tg, 0.83 Tg and 0.41 Tg, 0.0022 Tg, 0.004 Tg and 0.00034 Tg, and 3.12 Tg, 0.13 Tg and 0.062 Tg, respectively.

The amounts of CO2, CO, CxHy, SO2 and NO released from the combustion of 10 arbor and 9 shrub species in Liangshui Forest Farm of Xiaoxing'an Mountain were determined, with the release amounts and emission factors of these gases calculated. The results showed that the released CO2, the total amount of carbon-containing gases, and the mean value of the total amount of the 5 gases during combustion were larger for arbors than for shrubs, being 1277.04 and 1149.06 mg x g(-1), 1476.27 and 1147.18 mg x g(-1), and 1486.21 and 1459.67 mg x g(-1), respectively, while an opposite pattern of the mean release of CO, NO and SO2 was observed, being 231.58 and 282.93 mg x g(-1), 3.61 and 5.03 mg x g(-1), and 6.32 and 7.46 mg x g(-1) for the arbor and shrub species, respectively. The emission factors of CO2 and CO were also larger for arbors than for shrubs, being 2.8853 and 2.7718, and 0.4558 and 0.2425, respectively.

By using emission factor (EF), this paper estimated the carbon release and the emission of carbon-containing gases from the shrubs, herbages and litters in main forest types in Daxing' an Mountains by forest fires in 1980-1999. The results showed that the EF of shrubs, herbages and litters differed in different forest types, with the maximum and minimum EF of CO2 being 93.08% and 82.56%, respectively in Ledum palustre - Larix gmelinii forest and Pinus sylvestris var. mongolica forest, the maximum EF of CO and C(X)H(Y) being 10.25% and 0.84%, respectively in P. sylvestris var. mongolica forest, and the minimum EF of CO and C(X)H(Y) being 6.55% and 0.30%, respectively in L. palustre - L. gmelinii forest. Combined with the data of biomass and carbon storage of shrubs, herbages and litters in different forests, it was estimated that the total carbon release from shrubs, herbages and litters by forest fires from 1980 to 1999 accounted for 6.56 Tg and 0.33 Tg x a(-1), occupying 11.55%-16.30% of the total annual emissions in China by forest fires, and the emission of CO2, CO and C(x)H(y) was 22.03 Tg, accounting for 85.20%, 14.21% and 0.59% of the total carbon-containing gases emission, respectively.

Based on statistic analysis theory, the occurrence patterns of forest fire in Heilongjiang Province were studied, and the prediction model for forest fire-burnt area was established based on meteorological factors. The results showed that most of forest fires in Larix gmelinii forest region occurred from April to June and in October, and those in broadleaved Korean pine forest region mainly occurred from March to June and in October. By adopting the values of average wind speed, relative humidity and mean temperature, it was predicted that in L. gmelinii forest region, the first three months with greater probability of larger fire occurrence were March, May and June in order, while in broadleaved Korean pine forest region, they were May, March and April. The average precision of the model was 63.3%, suggesting that it could be used to predict the burnt area by forest fires.