Treesearch

The volume and complexity of their vascular systems make the dynamics of tong-distance water transport in large trees difficult to study. We used heat and deuterated water (D20) as tracers to characterize whole-tree water transport and storage properties in individual trees belonging to the coniferous species Pseudotsuga menziesii (Mirb.) Franco and Tsuga heterophylla (Raf.) Sarg. The trees used in this study spanned a broad range of height (13.5-58 m) and diameter (0.14-1.43 m). Sap flow was monitored continuously with heat dissipation probes near the base of the trunk prior to, during...

We analyzed demographic data from northern spotted owls(Strix occidentalis caurina)from 14 study areas in Washington, Oregon, and California for 1985-2003. The 14 study areas made up approximately 12 percent of the range of the subspecies and included federal, tribal, private, and mixed federal and private lands. Our primary objectives were to estimate fecundity, apparent survival, and annual rate of population change, and to determine if there were any temporal trends in these population parameters. The meta-analysis on fecundity indicated substantial annual variability with no increasing...

The air-seeding hypothesis predicts that xylem embolism resistance is linked directly to bordered pit functioning. We tested this prediction in trunks, roots, and branches at different vertical and radial locations in young and old trees of Pseudotsuga menziesii. Dimensions of bordered pits were measured from light and scanning electron micrographs, and physiological data were from published values. Consistent with observations, calculations showed that earlywood tracheids were more resistant to embolism than latewood tracheids, mainly from earlywood having stretchier pit membranes that...

It is assumed that geographic isolation of Dendroctonus Erichson species populations or their plant hosts determines genetic structure. This structure can be analyzed with respect to the biogeographic pattern that describes the species in a region. The Trans-Mexican Volcanic Belt (TMVB) is located between the Neartic and Neotropical regions and is a center of diversification and endemism of trees in the genus Pinus L. Dendroctonus mexicanus Hopkins is polyphagous within Pinus species and has a continuous geographic distribution across the TMVB. We explored whether the population genetic...

The stable oxygen isotope ratio (δ18O) of tree-ring cellulose is jointly determined by the δ18O of xylem water, the δ18O of atmospheric water vapor, the humidity of the atmosphere and perhaps by species-specific differences in leaf structure and function. Atmospheric humidity and the δ18O of water vapor vary seasonally and annually, but if the canopy atmosphere is well mixed, atmospheric characteristics should be uniform among co-occurring trees. In contrast, xylem water δ18O is determined by the δ18O of water being drawn from the soil, which varies with depth. If co-occurring trees draw...

The hydrochemical signatures of forested ecosystems are known to be determined by a time-variant combination of physical-hydrologic, geochemical, and biologic processes. We studied subsurface potassium (K), calcium (Ca), and nitrate (NO3) in an experimental red-pine mesocosm to determine how trees affect the behavior of these nutrients in soil water, both during growth and after a harvest disturbance. Solution chemistry was monitored for 2 years at the end of a 15-year period of tree growth, and then for 3 more years after harvest and removal of aboveground biomass. Concentrations were...

The Starkey Project is a unique program that has combined long-term research with multi-disciplinary, multi-partner involvement. The research was, and still is, designed to answer management questions. Even studies designed as basic research have been conducted in a manner that could identify mechanisms relevant to management. What is particularly noteworthy is that this research approach has resulted in a wide array of information critical to the management of elk, mule deer, cattle, forests, and rangelands. Importantly, results have provided a better understanding of the many interactions...

In a nitrogen (N) saturated forest downwind from Los Angeles, California, the cumulative response to long-term background-N and N-amendment on black oak (Quercus kelloggii) was described in a below-average and average precipitation year. Monthly measurements of leaf and branch growth, gas exchange, and canopy health attributes were conducted. The effects of both pollutant exposure and drought stress were complex due to whole tree and leaf level responses, and shade versus full sun leaf responses. N-amended trees had lower late summer carbon (C) gain and greater foliar chlorosis in the...

Over the past two decades, unprecedented levels of disturbance have occurred in the white spruce forests of Alaska. Spruce bark beetles, fires, and timber harvests have left millions of acres of dead spruce with little spruce regeneration. To assist public and private landowners, Pacific Northwest Research (PNW) Station scientists are testing various approaches to white spruce regeneration. In search of a competitive advantage for spruce seedlings, experimental plots have been designed and replicated on five sites across Alaska. Researchers are testing mechanical and chemical approaches to...

Decisionmakers concerned with Pacific salmon and trout have, out of necessity, relied on limited, site-scale information when planning and evaluating efforts to protect or restore freshwater habitat. To help broaden the context of conservation approaches, scientists in the Coastal Landscape Analysis and Modeling Study (CLAMS) have developed tools that characterize the species-specific potential of streams to provide habitat for these wide-ranging fish.The CLAMS scientists began by creating a computerized regional stream map that is consistent across all ownerships and stores important...