Effects Of Pinus Sylvestris Linn.Var. Sylvestriformis Plantation Fire On Soil Temperature Field And Physicochemical Properties

Fire is an important driving force to change soil properties and ecosystem.Fire can cause great changes in soil physical and chemical properties.Among them,the maximum temperature that soil can reach during fire and the duration of fire determine the change degree of soil properties,and the state during fire is affected by wind speed.Therefore,wind speed is an important factor affecting soil physical and chemical properties after fire.Studying the changes of soil temperature and properties during fire under different wind speeds and the changes of soil physicochemical properties within two years after fire can provide theoretical basis for artificial restoration or artificial promotion of natural restoration of forests,and is of great significance to our understanding of nature and soil cultivation.The experiment is set up in the stumpage simulation experiment field of Pinus sylvestris Linn.var.Sylvestriformis plantation.The fire experiment is carried out in an environment that ensures absolute safety and no wind all day long.Four common wind speeds are selected in this area,and the wind speed achieved by changing the blower gear is 1.1m/s,3.05m/s,5.2m/s,7.1m/s.Calculate the fire spread speed and fire line intensity according to the time when the fire reaches each benchmark,and then use the thermocouple temperature measurement system to obtain the temperature data of each layer of soil test points at 400 s,800s,and 1200 s during the fire process under each wind speed.Soil temperature field image to get the change of soil temperature during the fire.At the end of the experiment,soil samples are taken from 3cm,6cm,and 9cm layers of soil to measure their physical and chemical properties,and then they are measured again every 2 months,a total of 12 times.The method of bar chart and line stacking chart is used to intuitively depict the immediate and long-term effects of fire on soil physical and chemical properties under different wind speed conditions,and more intuitively show the changes of soil physical and chemical properties.Experimental data show that the soil is most seriously affected by the fire when the wind speed is 5.2m/s,and the soil can reach the highest temperature.When the wind speed is 7.1m/s and 1.1m/s,some combustibles cannot be fully burned.The highest soil temperature in the 3cm layer can reach 347℃,but with the deepening of the soil,the soil temperature drops sharply,and the soil temperature in the 15 cm layer is only affected by the fire when the wind speed is5.2m/s.Compared with non-standing tree soil,standing tree soil is hotter during fire,and the temperature is higher as it is closer to the standing tree.The bulk density of deep soil only increases under low wind speed fire,and the content of each element is less affected by fire,and it can return to normal levels within two years.The loss of organic matter and total nitrogen in soil also occurs at 200℃ and is difficult to recover naturally.A large amount of total phosphorus and total potassium loss occurs at higher temperature,but the soil exposed after fire would lead to continuous loss.The content of available nutrients,such as available phosphorus and available potassium,also increase to varying degrees in the initial stage after the fire.At this time,artificial restoration can make it be effectively utilized.