Atmospheric Turbulence Observations in the Vicinity of Surface Fires in Forested Environments

Ambient and fire-induced atmospheric turbulence in the vicinity of wildland fires can affect the behavior of those fires and the dispersion of smoke. The presence of forest overstory vegetation can further complicate the evolution of local turbulence regimes and their interaction with spreading fires and smoke plumes. Previous observational studies of wildland fire events in forested environments have shown that turbulence energy and anisotropy in the vicinity of spreading line fires exhibit temporal and spatial variability influenced by the presence of overstory vegetation. This study builds on those previous observational studies to further examine turbulence regimes during two wildland fires in forested environments, with an emphasis on the effects of forest canopies on turbulence energy budgets, the skewness in turbulent velocity distributions, and stability–anisotropy variations before, during, and after fire-front-passage periods. Analyses indicate that turbulence anisotropy tends to persist throughout the vertical extent of overstory vegetation layers even during highly buoyant fire-front-passage periods, with horizontal velocity perturbations dominating over vertical velocity perturbations. The analyses also suggest that the periods before and after fire-front passage in forested environments can be very different with respect to how diffusion and shear production concurrently affect the evolution of turbulence energy within the canopy layer. In addition, horizontal and vertical velocity distribution analyses carried out in this study suggest that spreading line fires can have a substantial effect on the skewness of daytime velocity distributions typically observed inside forest vegetation layers.

The effect of slow-release fertilizers on the soil environment of spread windrows in the Krušné Hory Mts.

The current revitalization of forest ecosystems in the Krušné Hory Mts. is carried out through: (i) spreading line windrows, (ii) chemical amelioration. The aim of this research consisted in: (i) assessing basic pedochemical characteristics of spread windrows, (ii) testing the effect of slow-release fertilizers from the Silvamix^® series and dolomitic limestone on the root ball zone soil five years after application. The results of this study suggest that spread windrows are a suitable environment for forest species: with the only risk being extremely low P concentrations. Our results further show an increase in the amount of soil macrobioelements in the case of Silvamix^® R and Silvamix^® Forte, namely P over 125 and 85%; Mg²⁺ over 84 and 108%; base saturation (BS) over 44 and 40.7%, respectively, compared with a control. Having applied dolomitic limestone, an increase of BS (by 88%), Mg²⁺ (by 250%) and Ca²⁺ (by 37%) was observed; there was a reduction in the level of mobile Al³⁺ (by 25%) compared with the control. Stromfolixyl^® application did not affect the chemistry of the soil environment.

SPREADING RATE OF CREEPING-ROOTED ALFALFA

Creeping-rooted alfalfa plants were studied for rate of spreading when planted in a grid spacing of 1.8 m. One year after planting, only three out of 15 lines displayed 100% creep in all five replicates on the basis of shoot formation. In the second year, all clones of all 15 plant lines had developed above-ground shoots. The range of spread varied from an average of 101 cm for the least spreading line to 176 cm for the strongest spreading line. By the third year they had expanded an additional 27% on the average. The stand density decreased as distance from the center of the plant increased. There were definite differences among creeping-rooted plant lines in rate of spreading ability. In three years most plants had spread horizontally to within each other’s peripheries.