Migration of creosote components from timbers treated with creosote and processed using Best Management Practices.

While creosote components have very low water solubility, concerns have been raised about potential environmental effects and stimulated research to minimize migration. Best management practices have been developed but there are few data quantifying their effects. The effects of post-treatment steaming on migration of polycyclic aromatic hydrocarbons (PAHs) from horizontally oriented creosote treated southern pine decking subjected to simulated rainfall were examined. Twelve of the 16 PAHs examined were detected in runoff during the rainfall exposure but at concentrations well below those predicted by water solubility. PAH levels declined with increasing rainfall time, although the differences were sometimes slight. Steaming for 1 h had minimal effect on PAH levels in runoff while 3 h of steaming produced more noticeable reductions ranging from ~20 to 80% for naphthalene, acenaphthylene, and acenaphthene. Longer post-treatment steaming times reduced initial losses of creosote components from treated wood.

Role of Leaf Litter in Above-Ground Wood Decay.

The effects of leaf litter on moisture content and fungal decay development in above-ground wood specimens were assessed. Untreated southern pine specimens were exposed with or without leaf litter contact. Two types of leaf litter were evaluated; aged (decomposed) and young (early stages of decomposition). The moisture content of specimens was monitored, and specimens were periodically removed for visual evaluation of decay development. In addition, amplicon-based sequencing analysis of specimens and associated leaf litter was conducted at two time points. Contact with either type of leaf litter resulted in consistently higher moisture contents than those not in contact with leaf litter. Visually, evident decay developed most rapidly in specimens in contact with the aged leaf litter. Analysis of amplicon-based sequencing revealed that leaf litter contributes a significant amount of the available wood decay fungal community with similar communities found in the litter exposed wood and litter itself, but dissimilar community profiles from unexposed wood. Dominant species and guild composition shifted over time, beginning initially with more leaf saprophytes (ascomycetes) and over time shifting to more wood rotting fungi (basidiomycetes). These results highlight the importance of the contributions of leaf litter to fungal colonization and subsequent decay hazard for above-ground wood.

RNAi of AGAMOUS genes in sweetgum alters reproductive organ identity and decreases fruit persistence.

Sweetgums (Liquidambar), members of the family Altingiaceae (Altingiales), have inflorescences and floral organs that are distinctive in structure compared with other angiosperms in which the roles of floral homeotic genes have been studied. To begin to understand the role of AGAMOUS (AG)-a floral homeotic gene that has a major role in stamen and carpel development-in development of the monosexual flowers of sweetgum, we used RNAi to reduce the expression of two members of the AG subfamily. Because AG suppression should induce floral sterility, RNAi might also provide a tool to mitigate the risks of invasiveness-and to reduce the production of its nuisance fruits or allergenic pollen-when sweetgum is used as an exotic shade or forest tree. We tested 33 independent transgenic events and non-transgenic controls during 10 years in the field. The RNAi-AG sweetgum trees maintained normal growth, phenology, and vivid fall coloration during the 10 years of study, but 8 insertion events had highly modified inflorescence and floral morphology. The modified flowers had anthers and carpels that were converted to flat leaf-like structures lacking pollen grains and ovules, respectively. The female inflorescences developed into dry papery structures that failed to produce seeds. These infructescences were smaller than control infructescences, and lost a greater percentage of biomass in a controlled decay assay. RNAi against AG genes was highly effective at impairing fertility and modifying reproductive development without significant vegetative effects in sweetgum and gave phenotypes distinct from, but similar to, that of AG loss of function in other angiosperms.

Culture-based identification to examine spatiotemporal patterns of fungal communities colonizing wood in ground contact.

Timber durability is often assessed using small wood stakes exposed in direct soil contact, and the assessment generally emphasizes effects on wood rather than organisms involved. Understanding fungal colonization patterns can help identify key decay agents under varying conditions and use these patterns to improve wood protection strategies. Fungal colonization of red alder (Alnus rubra), Douglas-fir (Pseudotsuga menziesii) heartwood/sapwood, and western redcedar (Thuja plicata) field stakes was assessed over 2 y in western Oregon. Spatiotemporal fungal community variations were identified via culturing and DNA sequencing, where 814 isolates were identified from 84 stakes. Forty-six ascomycete genera were identified, with Phialophora, Trichoderma, and Epicoccum species occurring most frequently. Twenty-three basidiomycete genera were identified, with Trametes and Phanerochaete being the most common. Douglas-fir and western redcedar stakes contained the highest and lowest diversity levels, respectively, reflecting natural durability differences of these species. Fungal species abundance was higher below ground than in the above ground and groundline zones, likely reflecting more stable moisture regimes, proximity to soil-based fungi, and potential nutrient migration into wood beneath the soil surface. Ascomycetes were proportionally more abundant early in the exposure period, but basidiomycetes were also observed early in the process, and there appeared to be no consistent colonization pattern.