Spatial and temporal distribution of forest fire frequency and forest area burnt in Jilin Province, Northeast China

Forest fires caused by natural forces or human activities are one of the major natural risks in Northeast China.The incidence and spatial distribution of these fires vary over time and across the forested areas in Jilin Province,Northeast China.In this study,the incidence and distribution of 6519 forest fires from 1969 to 2013 in the province were investigated.The results indicated that the spatiotemporal distribution of the burnt forest area and the fire frequency varied significantly by month,year,and region.Fire occurrence displayed notable temporal patterns in the years after forest fire prevention measures were strictly implemented by the provincial government.Generally,forest fires in Jilin occurred in months when stubble and straw were burned and human activities were intense during traditional Chinese festivals.Baishan city,Jilin city,and Yanbian were defined as fire-prone regions for their high fire frequency.Yanbian had the highest frequency,and the fires tended to be large with the highest burned area per fire.Yanbian should thus be listed as the key target area by the fire management agency in Jilin Province for better fire prevention.

The impact of climate change on fire risk in Daxing'anling,China

Daxing’anling is a key region for forest fire prevention in China. Assessing changes in fire risk in the future under multiple climatic scenarios will contribute to our understanding of the influences of climate change for the region and provide a reference for applying adaptive measures for fire management. This study analyzed the changes in fire weather indices and the fire season under four climate scenarios (RCP2.6, RCP4.5, RCP6.0, RCP8.5) for 2021-2050 using data from five global climate models together with observation data. The results showed that the analog data could project the average state of the climate for a given period but were not effective for simulating extreme weather conditions. Compared with the baseline period (1971-2000), the period 2021-2050 was predicted to have an increase in average temperature of 2.02-2.65 °C and in annual precipitation 25.4-40.3 mm, while the fire weather index (FWI) was predicted to increase by 6.2-11.2% and seasonal severity rating (SSR) by 5.5-17.2%. The DMC (Duff moisture code), ISI (initial spread index), BUI (build-up index), FWI and SSR were predicted to increase significantly under scenarios RCP4.5, RCP6.0, and RCP8.5. Furthermore, days with high or higher fire danger rating were predicted to be prolonged by 3-6 days, with the change in the southern region being greater under scenarios RCP4.5, RCP6.0, and RCP8.5.

Supercritical extracts of forest fuels in Great Xing＇an Mountains

Extracts are important components of fuels. Fatty-extracts with high heating value （HV） are hypothe- sized by researchers as positively related to the HV of fuels. The Soxhlet extractor is typically used to extract fatty-extracts but it has shortcomings, including long processing time （8-10 h） and the requirement for large amounts of organic solvent. Supercritical extraction is an alternate and useful technique for extraction of natural products. However, published studies rarely discuss the relationship between extracts and HV. In this study, we assessed the supercritical extracts （SUE） of forest fuels in the Great Xing＇an Mountains. Our results indicated that the optimum conditions for extraction of SuEs were 40-60 mesh, 40-50 MPa, 45℃, 80 min and a CO2 flow rate of 1.5-2.0 dm3/min. The Soxhlet extracts contents and the SuE contents were all related to HV. However, R2 of the coniferous samples （0.8499） and needle samples （0.9722） demonstrated that the correlation between HV and the SuE content was closer. We conclude that supercritical fatty-extracts provide a useful index of the HV of fuels, especially coniferous fuels. SuE data can be used in fire management, for example to estimate the rate of fire spread or fire intensity.

Spotting ignition of larch(Larix gmelinii)fuel bed by different firebrands

Spot fire increase the difficulty of fire-fighting and threaten public safety,and therefore it is important to study ignition probabilities of fuel bed by different firebrands,in order to understand ignition mechanisms and analyze the formation of spot fires.This will provide an important basis for further study to improve the fire-fighting efficiency and reduce casualties.In this study,the ignition probabilities of larch(Larix gmelinii)fuel beds with different moisture levels and packing ratios by diffreent firebrands,including cones and twigs of different sizes,was investigated.Ignition experiments were conducted at different wind speeds generated by fans.The results show that,regardless of moisture content and packing ratio,ignition probability is zero when there is no wind.Both moisture content and wind speed significantly infuence ignition probability,while packing ratio has almost no effect.The maximum moisture content at which firebrand ignition occurred was 50%,and ignition probability increased with wind speed and decreased with moisture content.Cones have the highest ignition probability,followed by large twigs and by small twigs.Ignition probability is also affected by firebrand shapes and sizes that determine their potential heat and contact area to the fuel bed.Two empirical models were established to link ignition probability with fuel properties and wind speed.This study will help clarify the mechanism of spot ignition and reduce corresponding losses.