Prescribed Fire Effects on Advanced Regeneration in Mixed Hardwood Stands

Abstract Fire treatments were initiated in 1990 to evaluate effects of low-intensity prescribed fires on composition and structure of the advanced regeneration pool under mature mixed-hardwood stands on upland sites in the Piedmont of South Carolina. One spring burn was as effective as three winter burns in reducing midstory density, considered a prerequisite for subsequent development of oak (Quercus spp.) advanced regeneration. Burning increased the number of oak rootstocks, reduced the relative position of competing species, and increased root-to-shoot ratios of oak stems in the regeneration layer. These favorable effects of fire on oak regeneration outweigh the removal of small, poorly formed oak stems from the midstory/understory strata during burning. Prescribed burning in hardwood forests may solve some of the current oak regeneration problems, especially on better upland sites in the South. South. J. Appl. For. 22(3):138-142.</jats:p

Observations on the adherence of Proteus mirabilis onto polymer surfaces.

Aims:  Infection of the catheterized urinary tract with Proteus mirabilis causes blockage of the catheter by crystalline bacterial biofilms. The aim of this work is to identify a surface-coating for catheters that is not vulnerable to colonization by Pr. mirabilis. Methods and Results:  A parallel-plate flow-cell and phase contrast microscopy were used to follow bacterial adhesion onto polymer films. Experiments with a urease-negative mutant of Pr. mirabilis suspended in buffer or urine, identified agarose as a polymer on which biofilm did not form. In tests with wild-type urease-producing cells in urine, no adhesion of cells onto agarose was observed for 3 h but then as the pH rose above 8·2, the surface rapidly became colonized by crystalline biofilm. Conclusions:  In urine at pH below 8·0, Pr. mirabilis does not adhere to agarose-coated surfaces. When the pH rises above 8·2, however, aggregates of crystals and bacteria form in the urine and are deposited on such surfaces. Significance and Impact of the Study:  Strategies to prevent the formation of crystalline biofilms on urinary catheters will need to consider both the properties of the surface-coatings and the requirement to prevent the alkaline conditions that induce crystal formation in urine