The forest litter plays a key role in the occurrence and development of forest fires. Forest litter is one of the main components of forest fuels. The study of the structure, stock volume, and features of forest litter is extremely important for understanding the fire risks in the pine forests of Polissya zone, Ukraine, where a considerable amount of litter is accumulated (from 117 to 862 metric centners per hectare). In the pine stands of the northern and southern parts of the Rivne Polissya, along with the determined reserves, moisture and density (volumetric weight) of the litter were studied. It was found that when the age of pine plantations increases, the volume and the density of the litter also increase. Increasing stock of litter also increases the duration and maximum temperature of combustion. Increasing the density, on the contrary, slows down the burning rate or makes it impossible. It is established that the density of the litter grows deep into the profile with an increase in the proportion of non-structural mortmass. Thus, when the structure of the litter becomes less porous, air access decreases and the time of combustion also increases.
The decay of thermal emission of rough surface layers of different carbon materials under the pulsed laser excitation is analyzed both theoretically and experimentally. For pulsed laser heating of rough surfaces, computer simulations revealed that laser-induced thermal radiation is mainly emitted by peaks of the surface relief, and the emission decay time depends on the relation between the laser penetration depth and the temperature diffusion length. It is also concluded that the presence of surface roughness can significantly increase the emission decay time. In the experiments, carbon materials with different thermal characteristics were used; however, all of the investigated samples demonstrated close values of the emission decay time. This fact shows that the material's characteristics on the peaks of surface relief are similar for different carbon materials at high temperature.
Forest fires are a powerful environmental factor that breaks the balance between the individual components of forest ecosystems. Thermal radiation is one type of the heat distribution during surface fires in forests. The objects of the study were forest soils, the monoliths of which were radiated with heat in specially created laboratory equipment. The facility allows detecting heat flux distribution in soils under laboratory conditions. The peculiarities of the processes for the typical soils for pine and oak stands were revealed. The highest temperature was observed on the surface of the soil. As the depth increased the temperature dropped. The most noticeable decrease was observed in a surface layer from 0 to 4 cm. The difference between the temperatures on the surface and at a depth of 10 cm could be 240–300°С for sandy soils and 260–400°С for gray forest soils. The temperature of deep soil layers increased even after stopping the heat radiation. The heating of dry sandy soils deep in to the profile occurs more strongly than in the moist sample. The sandy soil was found to warm deeper and more intensively as compared to loamy soils.
Унаслідок низових пожеж відбуваються зміни фізико-хімічних і біологічних властивостей ґрунтів. Досліджено пірогенні зміни властивостей ґрунтів у чистих соснових лісах, що ростуть у різних природних зонах України. У соснових насадженнях після низових пожеж у результаті як часткового, так і повного згорання підстилки утворюється попіл, що в подальшому впливає на хімізм верхнього шару ґрунту. Подібні особливості відзначали в різних природних зонах України. Надходження попелу в ґрунт призводило до зростання рН верхнього гумусового горизонту. Оскільки таке явище є одноразовим, то в подальшому після дощів значення рН водного витягу знижувалося до природнього рівня. Причиною пірогенних змін є високий уміст у попелі лужних металів. Інтенсивність змін реакції та вмісту лужних катіонів залежить від рівня згорання підстилки. Найбільш відчутними є зміни у разі повного згорання підстилки. Зазначені зміни мають поверхневий характер, тобто переважно притаманні лише верхньому шару ґрунту. На більшій глибині реакція не відрізняється від контролю.
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