Combustion Characteristics Of Residues In Larix Gmelinii Plantation Slash

Forest fire is a double-edged sword.Appropriate fire can increase soil fertility and is conducive to the germination and growth of forest plants.Forest fires with high burning intensity can lead to a complete change in the physical and chemical properties of the soil,which will have a beneficial impact on the renewal and transformation of forests and hinder the replacement of forests.Studying soil temperature and soil properties during fires is important for us to understand nature and prevent forest fires.The fire simulation experiment of the cutting-blank of Larix olgensis plantation was established,and the temperature data of each test point at 500s,1000s and 1500s during the fire were obtained by thermocouple temperature measurement.The data were displayed in the form of images to show the soil temperature field at each level during the fire.The results indicated that when the wind speed was less than or equal to 2 m s-1 or greater than or equal to 10 m s-1,combustibles cannot be fully burned.In the case of full combustion of combustibles,the soil temperature of each layer was the highest when the wind speed was 6 m s-1,and the depth of the soil layer was up to 12 cm or more.The maximum temperature of the soil of 3 cm layer can reach above 300?.Compared with the soil at the non-cut stump,the soil at the stump had a higher maximum temperature during the fire,and the soil temperature was higher near the stump.When the wind speed was 6 m s-1,the temperature range of 3 cm layer soil closet to the stump and farthest to the stump was from 315? to 198?.With the deepening of soil level,the change of soil temperature sharply decreased.The soil temperature of the 15 cm layer was almost unchanged during the fire test.The temperature of the 12 cm layer was increased only when the wind speed was 6m/s,and the temperature of the 3 cm layer was the highest.When the wind speed is 6 m/s,The influence of the temperature of soil was the greatest after fire,and soil at stump had the severest damage.The high temperature and high heat released by forest fires directly affect the soil,causing the soil to change its structural properties when subjected to a certain high temperature.In this paper,the thermocouple temperature measurement system is used to obtain the highest temperature experienced by the soil during the fire process,and the histogram method is used to show the changes of soil properties after the fire,and the changes in the structural properties of the soil when subjected to different temperatures are intuitively and profoundly understood.Happening.It is concluded that when the soil temperature reaches 304?,the soil bulk density increases significantly,the soil structure becomes more compact,the organic matter in the soil is almost completely lost,the total nitrogen content is lost by nearly half,the total phosphorus and total potassium content are significantly reduced,and effective nutrition The content of elements increased significantly.When the soil temperature was 151?,the soil bulk density increased significantly,the soil structure was tight,the soil organic matter and total nitrogen content were more serious,the soil total phosphorus content was almost unchanged,and the total potassium content began to decrease slightly.The content of effective nutrient elements increased slightly;when the soil temperature was 64?,the soil bulk density increased slightly,and its original structure had little effect.The organic matter and total nitrogen content in the soil began to decrease slightly,total phosphorus,total potassium and soil nutrients.There was no change in the content;when the soil temperature was lower than 31?,the soil structure and properties did not change.Temperature has a significant effect on soil properties,but differences in the duration of fire can also affect soil properties.In this paper,three types of combustion beds were used to control the combustion duration of 16 min,30 min,and 48 min.The results showed that the longer the duration of the fire,the greater the soil bulk density and the tighter the structure,which also worsened the loss of soil organic matter.The contents of total nitrogen,total phosphorus and total potassium in the soil decreased to different extents,while the available nitrogen,available phosphorus and available potassium increased.The longer the duration of the fire,the greater the variation,and the deeper the affected soil depth.At 48 min,the soil total nitrogen content changed to 12 cm in depth,the total phosphorus content in the affected soil layer was 6 cm,and the total potassium,available nitrogen,available phosphorus,and available potassium content were affected by soil layer of 9 cm;At 16 min,the total nitrogen,total potassium,available nitrogen and available phosphorus were affected by soil layer of 6 cm,and the total phosphorus and available potassium content were affected by soil layer of 3 cm.