Why are there frequent fires in Liangshan

Experts suggest reducing the planting of flammable tree species and dividing the fire isolation zone

Fighting for 9 days and 9 nights, the fire site in Xiangjiao Township, Muli County, Liangshan Yi Autonomous Prefecture, Sichuan Province, has been effectively sealed.

The reporter learned from the Sichuan Provincial Forest Fire Brigade that as of 11:00 on April 6, after more than 600 fighters had fought nine days and nights, in the forest fire in Xiangjiao Township, Muli County, Liangshan Prefecture, the southern, eastern and western lines of the fire Has achieved no open flame, no smoke, no gas. At present, the smoke point is being further cleaned up.

On April 2, some firefighting teams transferred directly from the Xichang firefield to the Muli firefield. After several days and nights of continuous fighting, some firefighters took only a few hours of rest. On March 30, a forest fire broke out in Jingjiu Township, Xichang City, Liangshan, and 19 fire fighting warriors were killed. A year ago, a forest fire in Liangshan Muli killed 31 firefighters.

Why are there frequent forest fires in Liangshan and it is difficult to fight them? How to reduce the risk of mountain wind mutation to firefighters? In response to these problems, reporters from China Youth Daily and China Youth Daily interviewed relevant experts.

The "crown fire" spreading rapidly in the "flying forest"

"At the end of March, the susceptibility to fire in the southwestern region has a lot to do with the local climate." Liu Futang, member of the Standing Committee of the Forest Fire Prevention Committee of the Chinese Forestry Society, said that Liangshan has two distinct dry and wet climates, and the number of annual sunshine hours ranks first in the country. In March, Liangshan is dry and has little rain, and the vegetation is flammable. From the geographical point of view, the high terrain in Xichang leads to relatively high winds, and the complex terrain causes uncertain wind directions. Factors such as climate and terrain are likely to cause high fire incidence.

Under the blessing of high temperature and strong wind, Xichang's fire control becomes more difficult. Statistics from the Liangshan Prefecture Meteorological Information Center show that from February 21 to March 30 this year, the average temperature in the state was 14.2 ° C, which was 2.0 ° C higher than the same period in history; the average precipitation in the whole state was 12 mm, which was less than the same period in history 44 %, Of which Xichang is 88% less and Muli is 64% less.

Liu Xiaodong, a professor at the School of Ecology and Nature Conservation of Beijing Forestry University, said that from a global perspective, in recent years it has been a "strong activity" year for the El Niño phenomenon, resulting in increased extreme weather, high temperatures and strong winds, and drought and rain in many areas. Once a forest fire occurs, it is easy Out of control, causing serious losses. Therefore, global forest fires are frequent, such as the Amazon rainforest fire, the California fire, and Australia's New Year's fire.

Vegetation is an important basis for forest fires. According to Liu Xiaodong, in order to increase vegetation coverage and protect the ecological environment, "flight seeding" afforestation was implemented in the southern region, that is, planting by plane to create forests. At that time, many conifers were planted in this way in Yunnan and Sichuan. For example, Yunnan pine, these native tree species have strong adaptability, good growth, and rapid forest formation, and have high ecological and economic value. Among them, Liangshan Prefecture is the national key broadcast forest area.

Some eucalyptus trees also appeared near the Xichang fire site. Popular science blogger and plant expert Wang Yuan pointed out that eucalyptus trees are more likely to cause fire than pine trees, and eucalyptus trees are usually planted closer to residential houses and more threatening. Wang Yuan told reporters that eucalyptus contains a lot of volatile oil. The deciduous leaves and plants of eucalyptus are flammable, which can cause the fire to spread quickly. The eucalyptus can recover quickly after the fire.

Liu Xiaodong pointed out that the pine and eucalyptus branches and leaves contain a lot of oil. Once burned, they will decompose and produce a large amount of volatile flammable gas, resulting in violent combustion and it is easy to form a "crown fire". Under the influence of strong winds, the "crown fire" spreads very quickly and generates "flying fire" to form a new fire point, so it is difficult to carry out rapid and effective fire fighting. In the case of a sudden change in wind direction, it constitutes a personal safety for the firefighters. Threat.

Human factors are the main causes of forest and grassland fires. The data shows that from 2010 to 2019, among the forest and grassland fires that have been identified with fire causes, more than 97% are caused by human causes. Among them, the fire for sacrifice, the fire for agriculture, the smoking in the wild, and the reforestation of mountains are ranked in the top 4 Quite a lot of fires in the forest and grasslands were caused.

Liu Futang said that due to historical factors, some local residents have fires such as cooking in the wild, smoking, sweeping near Qingming graves, and production fires such as spring planting and spring planting, burning wasteland and compost, etc., which are likely to cause forest fires. Very few residents neglected the details of fire prevention. When the wind blew, the flames reignited. Failure to extinguish them in time will cause forest fires.

In a forest and grassland fire prevention slogan in Jingjiu Township, it was written: In 2019, Xichang City investigated and prosecuted 97 cases of illegal fire use in the wild, of which 5 were transferred to prosecute, 62 were detained by law and order and 30 were administratively punished.

"The wind is the biggest trouble"

A reporter from China Youth Daily and China Youth Daily learned from the willow stump of Daying Farm in Xichang that 18 professional firefighters from Ningnan County led by a local guide from the willow stump to the fire in the middle of the night on March 30 Advance, but due to the sudden change of wind direction, the fire team's retreat route was cut off by the fire.

"Wind is the biggest trouble." A Sichuan Forest Fire Brigade Commander who commanded the scene told reporters that under the influence of strong winds and changing wind directions, a smoke point and a Mars may develop into an open fire at any time.

Wind direction and wind force are also important reasons for the resurgence and spread of the Xichang fire site. On the afternoon of April 1st, strong winds of magnitude six or seven appeared in the southern area of ​​the Lushan Fire Field, and the southerly winds prevailed. In the evening, the wind direction suddenly changed to southeast winds, which caused the fire to accelerate.

Mao Dezhong, deputy director of the Sichuan Provincial Emergency Management Department, said in an interview with CCTV News that the Xichang fire field has steep hills, dry air and dry materials, and it is very difficult to rescue. The most troublesome thing is, "Every morning we put a lot of energy into Around two o'clock in the afternoon, the wind is very heavy, and it is very chaotic, and the rescue risk is very high. "

Many experts said that sudden changes in wind direction often occur in fires. Liu Xiaodong pointed out that the fire site will form a microclimate of the fire site. As the fire gets bigger and bigger, the air above the fire site will expand due to heat, and the surrounding cold air will replenish and form convection to form wind. Under the action of the main wind and complex terrain, it is easy to produce sudden changes in wind direction.

"Fire fighting in this environment requires a commander with extensive fire fighting experience." Liu Xiaodong said that they can predict the risk of sudden changes in fire behavior. In foreign countries, before extinguishing the fire, the firefighters usually find or set up a fire safety zone and set up a special fire site observer. Once the wind direction changes suddenly, the firefighters evacuate to the safe area as soon as possible.

Wang Zhenshi, a senior engineer at the Guangdong Forest Fire Prevention Research Center, also said that sudden wind changes are common. After the fire, at different times and at different locations, the wind speed and wind direction will show different characteristics. The wind speed and wind direction of the mountain tops and valleys will change with the change of the fire; from the time period, the wind direction is also different, morning and afternoon , The wind direction will change at night.

Wang Zhenshi emphasized that 12: 00-18: 00 is a high-risk period for fighting forest fires. During this period, the temperature is the highest, the humidity is the lowest, and the fire spreads faster. "In places where there is a large amount of combustible materials and people with limited mobility, we must pay attention to the sudden change of wind direction and the danger of the fire team being surrounded by forest fire."

Severe fire prevention situation in many places across the country to prevent "two hands"

At present, the fire prevention situation is severe in many areas of the country. On April 1, the Emergency Management Department issued a document saying that from April 2nd to 6th, parts of southern Sichuan and northern Yunnan will reach extremely dangerous levels, and the fire prevention situation will be extremely severe. In addition, some areas in northern Beijing, northern and southwestern Hebei, and southeastern Shanxi will maintain a high level of forest fire risk.

Liu Xiaodong pointed out that the current severe situation of forest fire prevention and control in China is mainly caused by three factors. One is the climate factor. At present, there are many places with high temperature and drought, and the fire hazard weather level is high. The second is the forest fuel factor. With the implementation of natural forest protection projects and large-scale afforestation, the forest coverage rate has increased year by year. The load is also increasing; the third is the fire source factor, which shows the characteristics of complex fire source and difficult control. The combined effect of the three has made it more difficult to prevent and control forest fires in China. Coupled with weak infrastructure, lack of professionals, low investment in scientific research, and insufficient scientific and technological support, there is still a long way to go in the process of advancing the modernization of forest fire management systems and management capabilities.

For areas with frequent mountain fires, Wang Yuan suggested reducing the cultivation of flammable tree species, dividing fire isolation zones, planting fire-resistant refractory tree species at intervals, constructing fire extinguishing water points, and not cultivating flammable tree species near residential houses. He also mentioned several forms of establishing fire barriers: one is to cut off all the plants in the barriers; one is to plant fire-resistant evergreen shrubs after the barriers are cut; and another way is to plant evergreen fire-resistant at intervals arbor.

"There is no source of fire." Liu Futang said that controlling fire sources is the key to preventing forest fires. To play a prevention-oriented strategy, the government and people need to work together. Liu Xiaodong also emphasized that in terms of fire source control, it is necessary to stratify responsibilities, take joint management, and prevent and control the masses in order to reduce fires, especially the occurrence of major fires; constantly improve relevant laws and systems, and increase the number of fire accidents The punishment of the person.

In the event of a fire, the expertise of the rescue force is crucial. Liu Xiaodong called on the local professional fire fighting team to play a vital role in the initial fire fighting and is a necessary supplement to the national fire rescue team. The professional and professional construction of the local fire fighting team should be strengthened. It is recommended to set up corresponding occupations To formulate and improve the standards for the construction of professional fire fighting teams, the selection and training of team members, the standard for safe forest fire fighting, and improve the treatment of fire fighting personnel.

Liu Futang said that when fighting, first of all, the personal safety of the firefighters must be protected, an experienced commander should be selected, a safe place should be found, the situation should be judged, and the correct decision should be made. In addition, we continue to strengthen the training of firefighters to improve the team's ability to fight fires.

China Youth Daily · China Youth Daily trainee reporter Zhao Limei Shijia reporter Wang Lin Source: China Youth Daily