Treesearch

Apical control is the suppression of growth in lower branches by a higher dominant branch or leader shoot. We investigated possible mechanisms involved in this developmental response in three widely diverse species (Japanese morning glory, Ipomoea nil, hybrid poplar, Populus trichocarpa, x P. deltoides, and Douglas-fir, Pseudotsuga menziesii). The following two hypotheses were tested: (1) the mineral nutrient-deprivation hypothesis, which is that the continued growth of the lower branches is repressed by the diversion of nutrients to the upper dominating branch or shoot, and (2) the...

Many low-elevation dry forests of the Western United States contain more small trees and fewer large trees, more down woody debris, and less diverse and vigorous understory plant communities compared to conditions under historical fire regimes. These altered structural conditions may contribute to increased probability of unnaturally severe wildfires, susceptibility to uncharacteristic insect outbreaks, and drought-related mortality. Broad-scale fuel reduction and restoration treatments are proposed to promote stand development on trajectories toward more sustainable structures. Little...

Interspecific gene flow via hybridization may play a major role in evolution by creating reticulate rather than hierarchical lineages in plant species. Occasional diploid pine hybrids indicate the potential for introgression, but reticulation is hard to detect because ancestral polymorphism is still shared across many groups of pine species. Nucleotide sequences for 53 accessions from 17 species in subsection Ponderosae (Pinus) provide evidence for reticulate evolution. Two discordant patterns among independent low copy nuclear gene trees and a chloroplast haplotype are better explained by...

We investigated the response of hyporheic exchange flow (HEF) to wood removal in a small, low-gradient, gravel bed stream in southeast Alaska using a series of groundwater models built to simulate REF for the initial conditions immediately after wood removal and 1 month, 2 years, 4 years, and 16 years following wood removal. The models were based on topographic surveys of the stream channel and surrounding floodplain, and surveyed water surface elevations (WSEs) were used to assign stream boundary conditions. Using the groundwater flow model, MODFLOW, and the particle tracking model,...

Research into postharvest management of forests often focuses on balancing the need for increased biomass yield against factors that may directly impact the productivity of the subsequent stand (e.g. nutrient and water availability, soil microclimate, etc.), Postharvest organic matter management, however, also exerts a strong influence over the translocation of carbon (C) into and through the soil profile and may provide a mechanism to increase soil C content, The effects of contrasting postharvest organic matter retention treatments (bole-only removal, BO; whole-tree removal, WT) on soil...

Production of high-quality water is a vitally important ecosystem service in the largely semiarid interior Columbia River basin (ICRB). Communities, tribal governments, and various agencies are concerned about maintenance of this water supply for domestic, agricultural, industrial, recreational, and ecosystem uses. Water quantity and quality are widely recognized as important components of habitat for depleted salmonid populations in the ICRB where a large, multiagency effort is underway to restore salmon, trout, and char listed as threatened or endangered under the federal Endangered...

There are opportunities for forest owners and ranchers to participate in emerging carbon markets and contribute to climate change mitigation through carbon oriented forest and range management activities. These activities often promote sutainable forestry and ranching and broader conservation goals while having the potential to provide a new income stream for landowners. We describe current carbon market opportunities for landowners, discuss common steps they must typically undergo to take advantage of these opportunities, and address related questions. We also provide a synthesis of the...

Live tree biomass estimates are essential for carbon accounting, bioenergy feasibility studies, and other analyses. Several models are currently used for estimating tree biomass. Each of these incorporates different calculation methods that may significantly impact the estimates of total aboveground tree biomass, merchantable biomass, and carbon pools. Consequently, carbon markets, bioenergy projects, and similar efforts may be affected. In addition to differences in allometric equations, the various methods are most suitable for particular geographic scales of analysis. We examine three...

Broad discretion is granted at all levels throughout federal land management agencies regarding compliance with the National Environmental Policy Act (NEPA). We explored the diversity of procedures employed in NEPA processes across four agencies, the USDA Forest Service, The USDI National Park Service and Bureau of Land Management, and the U.S. Army Corps of Engineers, through document review and interviews with chief NEPA compliance officers, interdisciplinary team leaders, team members, and decisionmakers within the agencies with regard to how NEPA is perceived and implemented. This...

The continued conversion and development of forest land pose a serious threat to the ecosystem services derived from forested landscapes. We argue that developing an understanding of the full range of consequences from forest conversion requires understanding the effects of such conversion on both components of ecosystem services: products and processes. However, there are unavoidable challenges involved in quantifying the threats from forest conversion and their related costs to human well-being. First, most attempts to quantify the costs of forest conversion on ecosystem services will...