Lifu Shu

Emissions of volatile organic compounds from heated needles and twigs of Pinus pumila

A study was conducted to explore the mechanism that emissions of volatile organic compounds (VOC) from heated needles and twigs (200°C, within 15 min) of Pinus pumila affect fire behaviours using the technology of Thermal Desorption — Gas Chromatography — Mass Spectrometry (TD-GC-MS). The results indicated that the main components of VOC from heated needles and twigs are terpenoids. Most of these terpenoids are monoterpenes. Terpenoids account for 72.93% for the needles and 92.40% for the twigs of the total VOC, and their emission ratios are 61.200 μg·g−1 and 217.060 μg·g−1 respectively. Heated twigs can emit more terpenoids than heated needles because twigs had more volatile oils than needles. In actual fires, these large amounts of terpenoid emissions, especially the monoterpene emissions, have strong effects on fire behaviors that are not only in the initial stage but also in the fast propagation stage of fires. These flammable gases are capable of causing violent combustion and creating crown fires. In addition, if these gases accumulate in an uneven geographical area, there will be a possible for eruptive fires and/or fires flashover to occur.

Changes in forest fire danger for south-western China in the 21st century

This paper predicts future changes in fire danger and the fire season in the current century for south-western China under two different climate change scenarios. The fire weather index (FWI) system calculated from daily outputs of a regional climate model with a horizontal resolution of 50 × 50 km was used to assess fire danger. Temperature and precipitation demonstrated a gradually increasing trend for the future. Forest fire statistics for 1987-2011 revealed that the FWI, initial spread index and seasonal severity rating were significantly related to the number of forest fires between 100 and 1000 ha in size. Over three future periods, the FWI component indices will increase greatly. The mean FWI value will increase by 0.83-1.85, 1.83-2.91 and 3.33-3.97 in the periods 2011-2040, 2041-2070 and 2071-2100. The regions with predicted FWI increases are mainly in central and south-eastern China. The fire season (including days with high, very high and extreme fire danger ratings) will be prolonged by 9-13, 18-21 and 28-31 days over these periods. This fire season extension will mainly be due to days with an extreme fire danger rating. Considering predicted future changes in the forest fire danger rating and the fire season, it is suggested that climate change adaptation measures be implemented.

Future impacts of climate change on forest fire danger in northeastern China

Climate warming has a rapid and far-reaching impact on forest fire management in the boreal forests of China. Regional climate model outputs and the Canadian Forest Fire Weather Index (FWI) System were used to analyze changes to fire danger and the fire season for future periods under IPCC Special Report on Emission Scenarios (SRES) A2 and B2, and the data will guide future fire management planning. We used regional climate in China (1961–1990) as our validation data, and the period (1991–2100) was modeled under SRES A2 and B2 through the weather simulated by the regional climate model system (PRECIS). Meteorological data and fire danger were interpolated to 1 km2 by using ANUSPLIN software. The average FWI value for future spring fire seasons under Scenarios A2 and B2 shows an increase over most of the region. Compared with the baseline, FWI averages of spring fire season will increase by −0.40, 0.26 and 1.32 under Scenario A2, and increase by 0.60, 1.54 and 2.56 under Scenario B2 in 2020s, 2050s and 2080s, respectively. FWI averages of autumn fire season also show an increase over most of the region. FWI values increase more for Scenario B2 than for Scenario A2 in the same periods, particularly during the 2050s and 2080s. Average future FWI values will increase under both scenarios for autumn fire season. The potential burned areas are expected to increase by 10% and 18% in spring for 2080s under Scenario A2 and B2, respectively. Fire season will be prolonged by 21 and 26 days under Scenarios A2 and B2 in 2080s respectively.

Spatial fluctuation of forest fires and their regional behaviors

Historical forest fire records from Alaska State (1950–2000), California State (1895-2001), USA and Heilongjiang Province (1980–1999), China were used to calculate the longitude and latitude of the annual burned area’s centroids for these regions. Fluctuation phenomena by year were analyzed using spectrum analysis. The results show that centroids of burned areas in these three regions are in a fluctuating condition that encircles the distribution center. The distribution centers are 151.11°W, 64.96°N in Alaska State, 120.02°W, 37.11°N in California State and 127.07°E, 49.59°N in Heilongjiang Province, respectively. The fluctuation of the burned area’s centroids in Alaska State and California State in longitude has obvious periodicity, and the periodicities are 4.2 years, 6.25 years in Alaska State and 6.24 years, 106 years in California State. The fluctuation of the burned area’s centroids in Heilongjiang Province has a periodicity both in longitude and latitude, and the periodicities are both 3.3 years, 6.67 years. Fluctuation of the burned area’s centroids in Alaska State and California State in latitude does not have periodicity, and big forest fires with low frequencies predominate.