Treesearch

Doughts occur regularly in most U.S. forests, but their frequency and intensity vary widely between, as well as within, forest ecosystems (Hanson and Weltzin 2000). In the Western United States, forests commonly experience annual seasonal droughts. In the Eastern United States, forests tend to exhibit one of two prevailing drought patterns: random (i.e., occurring at any time of year), occasional droughts, as typically seen in the Appalachian Mountains and the Northeast; or frequent late-summer droughts, as typically seen in the southeastern Coastal Plain and the eastern edge of the Great...

Tree mortality is a natural process in all forest ecosystems. However, extremely high mortality 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.

The 2013–2027 National Insect and Disease Forest Risk Assessment represents a nationwide strategic assessment of the hazard of tree mortality due to insects and diseases displayed as a series of maps, the National Insect and Disease Risk Maps (NIDRM) (Krist and others 2014) (­gs. 6.1, 6.2, and 6.3). Risk, or more appropriately termed, hazard, is de­ned in the assessment as the expectation that, without remediation, at least 25 percent of standing live basal area >1 inch in diameter will die over a 15-year time frame (2013–27) due to insects and diseases.

Forest health issues are on the rise in the United States, resulting from introduction of alien pests and diseases, coupled with abiotic stresses related to climate change. Increasingly, forest scientists are finding genetic/genomic resources valuable in addressing forest health issues. For a set of ten ecologically and economically important native hardwood tree species representing a broad phylogenetic spectrum, we used low coverage whole genome sequencing from multiplex Illumina paired ends to economically profile their genomic content. For six species, the genome content was further...

Many global change drivers chronically alter resource availability in terrestrial ecosystems. Such resource alterations are known to affect aboveground net primary production (ANPP) in the short term; however, it is unknown if patterns of response change through time. We examined the magnitude, direction, and pattern of ANPP responses to a wide range of global change drivers by compiling 73 datasets from long-term (>5 years) experiments that varied by ecosystem type, length of manipulation, and the type of manipulation. Chronic resource alterations resulted in a significant change in ANPP...

USDA conservation programs and practices seek to address societal resource concerns that arise from intensive agricultural production. These concerns include degradation of water quality and soils, and loss of valued ecological services provided by natural ecosystems

Among the wide array of terrestrial habitats, forest andwooded lands are the richest fromboth biological and genetic points of view because of their inherent structural and compositional complexity and diversity. Although species composition is an important biodiversity feature, forest structuremay be evenmore relevant for biodiversity assessments because a diversified structure is likely to have more niches, which in turn, host more species and contribute to a more efficient use of available resources. Structure plays a major role as a diversity indicator formanagement purposes where maps...

This chapter describes past interaction of human populations with habitats on mainland Yap and the dynamics of the agroecosystem that developed. Recent changes in this system on mainland Yap are described, followed by a description of the nature and threats to agriculture in the Outer Islands. The chapter concludes by asking “Where to now?” and considers a past agricultural intensification relevant to meeting future challenges.

The complex topography of the Inland Northwestern United States (58.4 million ha) interacts with soils and a highly variable climate to provide a mosaic of dry and moist mixed conifer forest settings. Approximately 20% of the area is covered by dry forests dominated by Pinus ponderosa, Pseudotsuga menziesii and contains a diversity of lower vegetation ranging from a grass savannah on the less-productive sites to shrub and forb dominated vegetation on the more-productive sites. An estimated 18% of the area is covered by moist mixed conifer forests with some places growing up to 10 different...