High abundance and role of antifungal bacteria in compost-treated soils in a wildfire area.

Compost has been widely used in order to promote vegetation growth in post-harvested and burned soils. The effects on soil microorganisms were scarcely known, so we performed the microbial analyses in a wildfire area of the Taebaek Mountains, Korea, during field surveys from May to September 2007. Using culture-dependent and -independent methods, we found that compost used in burned soils influenced a greater impact on soil fungi than bacteria. Compost-treated soils contained higher levels of antifungal strains in the genera Bacillus and Burkholderia than non-treated soils. When the antifungal activity of Burkholderia sp. strain O1a_RA002, which had been isolated from a compost-treated soil, was tested for the growth inhibition of bacteria and fungi isolated from burned soils, the membrane-filtered culture supernatant inhibited 19/37 fungal strains including soil fungi, Eupenicillium spp. and Devriesia americana; plant pathogens, Polyschema larviformis and Massaria platani; an animal pathogen, Mortierella verticillata; and an unidentified Ascomycota. However, this organism only inhibited 11/151 bacterial strains tested. These patterns were compatible with the culture-independent DGGE results, suggesting that the compost used in burned soils had a greater impact on soil fungi than bacteria through the promotion of the growth of antifungal bacteria. Our findings indicate that compost used in burned soils is effective in restoring soil conditions to a state closer to those of nearby unburned forest soils at the early stage of secondary succession.

Fine structure and X-ray microanalysis of silicified woods from a Tertiary basin Pohang, Korea by scanning electron microscopy.

Anatomical descriptions are provided on silicified woods from a Tertiary basin Pohang, Korea by scanning electron microscopy and X-ray microanalysis. The silicified woods appeared to retain the original exterior morphology of the once grown trees, and exhibited various colors on the surface. As a component of the axial system in the secondary xylem, pores were oval to globose and measured approximately 200-300 microm in diameter in transverse planes. Seemingly bordered pits were also frequently observed in the tracheary elements. As a component of the axial system in the secondary phloem, sieve elements were found to have many sieve pores that were filled with numerous fine particles. In tangential planes, rays in the vascular cambium were approximately 500 microm long, and usually several cells wide (multiseriate). Meanwhile, several forms of microbial growth such as bacterial chains and hyphal growth of either fungi or actinomycetes were evident in the vessel lumens of unpolished silicified wood pieces. Some fracture surfaces were mainly characterized by the occurrence of polyhedral crystals, probably quartz, in the fissures. By X-ray microanalysis, iron was detected from the brown-colored regions, whereas calcium was also detected together with iron in the black-colored regions. Based on the rare occurrence of tracheids as the axial system in the secondary xylem, the silicified woods in this study can be intrinsically categorized into angiosperm groups in the region.