Treesearch

The development and use of critical loads of air pollutant deposition in the U.S. is gaining momentum, and recent research efforts in the U.S. have produced valuable data for calculating critical loads. Critical loads are used to quantify the levels of air pollutants that are expected to impact forest health, soil fertility, aquatic biota condition, and other ecosystem responses. In addition, model refinements for improving critical loads estimates, and maps for illustrating critical loads for acidification and nitrogen saturation and eutrophication resulting from excess nutrient nitrogen,...

Nonnative plant invasions are a management concern, particularly in riparian forests, but little is known about mechanisms through which they influence vertebrate communities. In the American Southwest, native trees such as cottonwood (Populus spp.) are thought to provide better habitat for breeding birds than nonnative plants, which are more tolerant of human-altered conditions. To evaluate effects of riparian forest composition on riparian-nesting birds, we examined nest plant use along two rivers in New Mexico that differed in abundance of nonnative vegetation. Of the nests we observed,...

The Pacific Northwest (PNW) of the conterminous United States is characterized by large variations in climate and topography, and provides an ideal geographic domain for studying interactions between regional climate and vegetation dynamics. We examined vegetation carbon (C) and water dynamics along PNW climate and topographic gradients using a process-based biogeochemical model, BIOME-BGC, the algorithms of which form bases for a fully-prognostic treatment of carbon and nitrogen cycles in Land Community Model (CLM). Simulation experiments were used to (1) analyze spatial and temporal...

We develop and test a new analytic approach, termed "sib-split", to detect fish passage through road crossings. This new approach is based on the genetic analysis of full-siblings on opposite sides of potential barriers. We used simulations and data from two empirical case studies involving brook trout (Salvelinus fontinalis) movement with respect to barriers that varied in strength of effect on fish passage. Simulations revealed that both sib-split and the population assignment-based method (STRUCTURE) were highly accurate (mean accuracy > 99%) under easy-to-detect conditions (moderate to...

Variable-retention harvesting (VRH) is an approach for sustaining complex structure in managed forests. A criticism of VRH is that ecological benefits may come at a cost of reduced growth of regeneration, due to competition with residual trees. However, the spatial pattern of retention, i.e., dispersed or aggregated, in VRH systems can be manipulated to minimize suppression of regeneration, and resource limitation to regeneration might be mitigated by reduction of woody shrubs. Continued growth of the residual cohort will compensate for growth reduction of regeneration, although this may...

This paper addresses an important set of issues currently facing the forests of western North America - the intersection of 20th Century land use legacies and the emerging impacts of climate change on drought, forest stress, wildfire, and ecosystem change. The presented information comes from a variety of sources in the scientific literature, with a focus on the Southwest United States, particularly including observations from my home landscape of the Jemez Mountains in northern New Mexico. Historic fire suppression and two regionally wet climate periods fostered widespread buildups of...

Trees’ resistance to fire-induced mortality increases with bark thickness, which varies widely among species and generally increases with stem diameter. Because dry forests are more fire-prone than wetter forests, bark may be thicker in these forests. However, where disturbances such as hurricanes suppress stem diameter, trees may not obtain fire-resistant bark thickness. In two hurricane-prone Caribbean dry-forest types in Puerto Rico—deciduous forest and scrub forest—we measured bark thickness on 472 stems of 25 species to test whether tree species obtain bark thicknesses that confer...

Greenhouse gas inventories for the forestry sector rely on large area eslimates of tree biomass. These estimates are calculated by predicting volumes of individual trees, multiplying by a biomass conversion factor; adding individual tree biomass estimates at the plot level, and then averaging over plots to obtain the large area estimates. However, the uncertainty in the model prediction is generally ignored with the result that the precision of the large area estimates is over-estimated. The study objetive was to estimate the effects of model-related uncertainties on large area volumes...

Forest cover maps were produced for the Gabonese Agency for Space Studies and Observations (AGEOS) for 1990, 2000 and 2010 for an area of approximately 102,000 km2 corresponding to 38% of the total area of Gabon and representative of the range of human pressure on forest resources. The maps were constructed using a combination of a semi-automated classification procedure and manual enhancements to ensure the greatest possible accuracy. A two-stage area frame sampling approach was adopted to collect reference data for assessing the accuracy of the forest cover maps and to estimate proportion...

OECD economies, in aggregate, have been sluggish; unemployment remains high in several countries, and minimal gross domestic product gains are forecast for the Euro area through 2016. Recession, sovereign debt problems and lethargic economies continue to constrain Europe’s housing construction market; no improvement is expected before 2015 or 2016; Germany’s positive housing market is an exception. Housing completions in the Russian Federation achieved record levels in 2013, with a total of 912,100 new dwellings built, an increase of 10.3% over 2012 and the largest number of new dwellings...