Treesearch

Forests cover a vast area of the United States: 303.1 million ha or approximately onethird of the Nation’s land (Smith and others 2004). These forests are of substantial ecological, economic, and social importance. Both their ecological integrity and their continued capacity to provide goods and services are of considerable concern in the face of a long list of threats, including insect and disease infestation, fragmentation, catastrophic fire, invasive species, and the effects of global climate change.

Analyzing patterns of forest pest infestation is necessary for monitoring the health of forested ecosystems because of the impacts that insects and diseases can have on forest structure, composition, biodiversity, and species distributions (Castello and others 1995). In particular, introduced nonnative insects and diseases can extensively damage the diversity, ecology, and economy of affected areas (Brockerhoff and others 2006, Mack and others 2000). Examining pest occurrences from a landscape-scale perspective is useful, given the regional extent of many infestations and the interaction...

Tree mortality is a natural process in all forest ecosystems. However, extremely high mortality also can be an indicator of forest health issues. On a regional scale, high mortality levels may indicate widespread insect or disease problems. High mortality may also occur if a large proportion of the forest in a particular region is made up of older, senescent stands.

Purpose Mercury (Hg) is a naturally occurring element and a pervasive toxic pollutant. This study investigated the dynamic loads of Hg from the Cedar-Ortega Rivers watershed into the Lower St. Johns River (LSJR), Florida, USA, using the better assessment science integrating point and nonpoint sources (BASINS)-hydrologic simulation program - FORTRAN (HSPF) model. Materials and methods The site-specific BASINS-HSPF model was developed for dynamic loads of Hg based on watershed, meteorological, and hydrological conditions. The model was calibrated and validated with existing field data. It...

Renewed interest in short-rotation woody crops for bioenergy and bioproducts has prompted a reevaluation of the Eucalyptus species for the southern United States. One question that arises about the potential effects of introducing a nonnative species is what effect will there be on fire behavior. Our approximate answer based on modeling fire behavior using the Fuel Characteristic Classification System is that surface fire behavior in young stands differs little from surface fires common to pine plantations in the southern Coastal Plain. By the age of 9, the absence of a shrub layer, along...

Catastrophic disturbances often provide “natural laboratories” that allow for greater understanding of ecological processes and response of natural populations. The 1980 eruption of the Mount St. Helens volcano in Washington, USA, provided a unique opportunity to test biotic effects of a large-scale stochastic disturbance, as well as the influence of post-disturbance management. Despite severe alteration of nearly 600 km2 of habitat, coastal tailed frogs (Ascaphus truei) were found within a portion of the blast area five years after eruption. We investigated the genetic source of recoloniza...

Logistic regression models used to predict tree mortality are critical to post-fire management, planning prescribed bums and understanding disturbance ecology. We review literature concerning post-fire mortality prediction using logistic regression models for coniferous tree species in the western USA. We include synthesis and review of: methods to develop, evaluate and interpret logistic regression models; explanatory variables in logistic regression models; factors influencing scope of inference and model limitations; model validation; and management applications. Logistic regression is...

This paper calibrates climate controls over radial growth of floodplain white spruce (Picea glauca (Moench) Voss) and examines whether growth in these populations responds similarly to climate as upland trees in Interior Alaska. Floodplain white spruce trees hold previously unrecognized potential for long-term climate reconstruction because they are the source of driftwood that becomes frozen in coastal deposits, where archeological timbers and beach logs represent well-preserved datable material. We compared ring width chronologies for 135 trees in six stands on the Yukon Flats and Tanana...

A method was developed to estimate carbon consumed during wildland fires in interior Alaska based on medium-spatial scale data (60 m cell size) generated on a daily basis. Carbon consumption estimates were developed for 41 fire events in the large fire year of 2004 and 34 fire events from the small fire years of 2006-2008. Total carbon consumed during the large fire year (2.72 x 106 ha burned) was 64.7 Tg C, and the average carbon consumption during the small fire years (0.09 x 106 ha burned) was 1.3 Tg C. Uncertainties for the annual carbon emissions ranged from 13% to 21%. Carbon...

Mycorrhizal fungi have substantial potential to influence plant distribution, especially in specialized orchids and mycoheterotrophic plants. However, little is known about environmental factors that influence the distribution of mycorrhizal fungi. Previous studies using seed packets have been unable to distinguish whether germination patterns resulted from the distribution of appropriate edaphic conditions or the distribution of host fungi, as these cannot be separated using seed packets alone. We used a combination of organic amendments, seed packets and molecular assessment of soil...