Treesearch

Bark beetles (Coleoptera: Curculionidae: Scolytinae) are mortality agents to multiple tree species throughout North America. Understanding spatiotemporal dynamics of these insects can assist management, prediction of outbreaks, and development of "real time" assessments of forest susceptibility incorporating insect population data. Here, dispersal of Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) is estimated over four regions within Colorado and Wyoming from 1994 to 2010. Infestations mapped from aerial insect surveys are utilized as a proxy variable for Douglas-fir beetle (DFB)...

Amid a worldwide increase in tree mortality, mountain pine beetles (Dendroctonus ponderosae Hopkins) have led to the death of billions of trees from Mexico to Alaska since 2000. This is predicted to have important carbon, water and energy balance feedbacks on the Earth system. Counter to current projections, we show that on a decadal scale, tree mortality causes no increase in ecosystem respiration from scales of several square metres up to an 84 km2 valley. Rather, we found comparable declines in both gross primary productivity and respiration suggesting little change in net flux, with a...

Agroforestry systems have been proposed as alternative, environmentally benign systems for agricultural production in temperate North America. Walnut and other hardwoods have been successfully integrated in most agroforestry practices include alley cropping, silvopastural, windbreaks, and riparian buffers. Because of walnuts relatively thin crowns and nut production, it has been the most frequently used woody species. The biophysical research has revealed that the success of complex hardwood-based agroforestry systems will depend on minimizing the negative interactions, especially above...

Nut production from nursery-run black walnuts grown on 225 acres at the Hammons Products Company's Sho-Neff Black Walnut Farm in Stockton, MO, was evaluated from 1995 to 2010 to determine if nut production increased after thinning and fertilization in 2001. The farm consists of 11 upland and 10 bottomland plantings on sites ranging from unsuitable to well suited for growth of walnut. All 21 stands were thinned in 2001, removing about one-third of the trees, and fertilized with 60, 20, and 60 pounds per acre of nitrogen, phosphorus, and potassium, respectively. Nine stands were limed to...

Control of competing vegetation is an important early cultural practice that can improve survival and vigor in hardwood tree plantings. The type of program used depends on landowner objectives, species of weeds present, equipment available, and types of herbicides available. Pre-planting planning can greatly increase effectiveness of an herbicide program for the first several critical years. Basic knowledge of weed species, herbicide modes of action, calibration of equipment, and herbicides available is essential to having an effective program. Although there have been few changes in the...

Biomass burning is a significant contributor to atmospheric carbon emissions but may also provide an avenue in which fire-affected ecosystems can accumulate carbon over time, through the generation of highly resistant fire-altered carbon. Identifying how fuel moisture, and subsequent changes in the fire behavior, relates to the production of fire-altered carbon is important in determining how persistent charred residues are following a fire within specific fuel types. Additionally, understanding how mastication (mechanical forest thinning) and fire convert biomass to black carbon is...

Molecular markers have been used in several walnut species to help reconstruct breeding program pedigrees, to characterize genetic structure in natural Juglans populations, to determine the impact of different timber harvest scenarios on residual levels of genetic diversity, and to quantify the effects of interspecific hybridization on subsequent reproduction success. Pijut et al. (2007) reviewed technological applications of molecular markers used on several temperate hardwood tree species. Modern genomics-based tools are currently being used in several black walnut (J. nigra) studies.

Available soil nitrogen is frequently low in old-field plantings. Underplanting forage legumes and interplanting nitrogen-fixing shrubs can improve growth of hardwood saplings, especially black walnut and pecan. Most of the nitrogen-fixing shrubs and forbs have been introduced, and several are now considered invasive species. Research trials have been established on old-field sites to evaluate the potential benefits of establishing native forbs, grasses, shrubs, and trees with seedlings of black walnut, pecan, chestnut, and five oak species.

After thinning hardwood stands, sprouts often develop on the girdled stems or cut stumps. While sprouts may be left for wildlife, it is usually best to deaden each tree to minimized future competition for soil moisture and nutrients. By applying select herbicides to the stump, sprouting can be eliminated. This study evaluated five herbicides applied as basal bark or cut stem application to black walnut and green ash stumps 90 days after cutting. Trimec®, Crossbow®, Chopper®, Vista®, and Garlon 4® were applied in diesel oil solutions. All herbicides effectively controlled stump sprout when...

A rapid and reliable screening technique is needed for selecting trees with resistance to butternut canker. In a laboratory assay, reagent grade naphthoquinones and crude bark extracts of Juglans species variously inhibited spore germination and growth of Ophiognomonia clavigignenti-juglandacearum, the causal fungus of butternut canker. The in vitro disc assay revealed that the level of inhibition varied by naphthoquinones and by extracts from different species of Juglans and selections of butternut. Ranking the trees by the level of inhibition approximated their level of resistance...