Study On The Effects Of Pinus Sylvestris Gall Rust On Its Combustibility

Pinus sylvestris is an important afforestation species in the Northeast,and pine gall rust is one of the most serious diseases of Pinus sylvestris.Pinus sylvestris forests,especially Pinus sylvestris plantation,were infected by Cronartium querccum.The tunors formed contains a large amount of oil.After many years’ growth of mycelium in the gall tumors,the change of wood composition caused great harm to the growth of trees and the health of stands.The diseased trees were more flammable,and the risk of forest fires increased.In this paper,the Pinus sylvestris plantation in Heilongjiang Province was selected as the research object,and the typical diseased forests were selected.Because the pine gall rust mostly occurred on the lateral branches and trunk of Pinus sylvestris,the trunk and lateral branches of diseased Pinus sylvestris,and disease-free Pinus sylvestris were sampled separately.And the oil content of Pinus sylvestris was determined by organic solvent extraction method.The component content of Pinus sylvestris was determined according to national industry standards.The combustion properties of Pinus sylvestris were measured by cone calorimeter.The differences were analyzed by statistical software and the specific results were as follows:1.Pine gall rust has different effects on the moisture content,ash content,organic solvent extract and alkali extract content,holocellulose,acid insoluble lignin and lignin content of Pinus sylvestris.The moisture content of the lateral branches and trunk of diseased Pinus sylvestris was lower than that of disease-free Pinus sylvestris.If burned,the burning speed will increase.The ash content of Pinus sylvestris was the lowest about 0.27%.The more the substances involved in combustion,the higher the calorific value is.The extracts have a significant contribution to the burning of forest combustibles.The higher the content of organic solvent extracts and alkali extracts in the diseased Pinus sylvestris,the greater the decay degree of Pinus sylvestris,increasing the amount of combustibles involved in combustion.That is,it is easy to form fire-burning trees.The content of holocellulose in the trunk and lateral branches of Pinus sylvestris is about 50%,which is lower than that of diseased-free Pinus sylvestris about 81.29%.And the disease-free Pinus sylvestris has good flame retardant effect,while diseased Pinus sylvestris is the main supplier of flammable volatiles when the combustion is heated to high temperature.The content of acid-insoluble lignin and lignin in the lateral and trunk branches of Pinus sylvestris is lower than that of disease-free Pinus sylvestris.Lignin is the main undertaker of flameless combustion,so it is not easy for diseased Pinus sylvestris to keep smoldering state after ignition compared with disease-free Pinus sylvestris.2.The percentage of oil on the side branches and trunk of Pinus sylvestris was 19.00%±0.41 a and 19.33%± 0.62 a respectively.The percentage of oil on the two groups was about 10%higher than that of disease-free Pinus sylvestris.The pine gall rust was significantly improved the oil content of the diseased Pinus sylvestri and promotes its evolution into a flammable forest.At the same time,once a fire occurs,it is easy to cause trunk fire and canopy fire.3.The igniting time of the lateral and trunk branches of the diseased Pinus sylvestris were 9.33 ± 0.58 ab and 8.33 ± 2.52 b respectively,which were nearly one time shorter than that of disease-free Pinus sylvestris.The diseased Pinus sylvestris was more flammable,among which trunk was relatively flammable than lateral branches.The peak heat release rate(HRR)of different parts of Pinus sylvestris showed that the heat release from the trunk of Pinus sylvestris was the largest about 1.7 times and 1.5 times as much as that from the lateral branches of Pinus sylvestris and the disease-free branches of Pinus sylvestris respectively.It reached 178 kW/m2 and the surface heat of combustion and conduction was the largest in unit time.And its pyrolysis rate is the fastest and the largest amount of volatile combustibles are generated.It accelerates the spread of flame.Once a fire occurs,the greater the impact on the fire,the higher the risk.EHC analysis also showed that the main trunk of Pinus sylvestris var.mongolica was the easiest to burn and released the most heat while the side branches of Pinus sylvestris var.mongolica and Pinus sylvestris var.mongolica without disease and Pinus sylvestris var.mongolica were slower to burn.The fire occurrence index(FPI)of different parts of Pinus sylvestris showed that the fire resistance of disease-free Pinus sylvestris was stronger and the fire resistance of diseased Pinus sylvestris was weaker,that is,diseased Pinus sylvestri was the flammable tree.If the fire happened,it would easily lead to the spread of fire,which was related to the higher amount of oil and other combustible materials in diseased Pinus sylvestris.4.The correlation analysis between each component and fire occurrence index showed that water,organic extract and alkali extract were negatively correlated with fire occurrence index,while ash,holocellulose,lignin and acid-insoluble lignin were positively correlated with fire occurrence index.