Treesearch

Field trials to quantify the long-term effect of silvicultural treatments in southern upland hardwood forests began on USDA Forest Service Experimental Forests and Ranges nearly 100 years ago. Many of those outdoor laboratories and the research sites they contain are still being examined by Forest Service scientists and their cooperators. The original field experiments began with a well-documented manipulation of stand density, structure, and composition so that scientists could monitor changes in forest characteristics for many decades. Although the original focus of the early studies was...

Quantifying the spatial and temporal dynamics of stream metabolism across stream networks is key to understanding carbon cycling and stream food web ecology. To better understand intra-annual temporal patterns of gross primary production (GPP) and ecosystem respiration (ER) and their variability across space, we continuously measured dissolved oxygen and modeled stream metabolism for an entire year at ten sites across a temperate river network in Washington State, USA. We expected GPP and ER to increase with stream size and peak during summer and autumn months due to warmer temperatures...

Hardwood forest management practices may wound trees and initiate defects that reduce wood quality and value. Damage to the lower bole of residual stems during harvest operations has been heavily researched. Wounding from prescribed fire has been the subject of more recent studies. Injuries caused by harvesting and prescribed fire activities to tree roots and crowns are in shorter supply. Also, the relationship of wounding to wood value is less well-documented. The effects of wounding on wood value is an interaction among wound position, frequency, severity, and the constitutive and...

Cities are increasingly focused on expanding tree canopy cover as a means to improve the urban environment by, for example, reducing heat island effects, promoting better air quality, and protecting local habitat. The majority of efforts to expand canopy cover focus on planting street trees or on planting native tree species and removing nonnatives in natural areas through reforestation. Yet many urban canopy assessments conducted at the city-scale reveal co-dominance by nonnative trees, fueling debates about the value of urban forests and native-specific management targets. In contrast,...

Widespread changes in arctic and boreal Normalized Difference Vegetation Index (NDVI) values captured by satellite platforms indicate that northern ecosystems are experiencing rapid ecological change in response to climate warming. Increasing temperatures and altered hydrology are driving shifts in ecosystem biophysical properties that, observed by satellites, manifest as long‐term changes in regional NDVI. In an effort to examine the underlying ecological drivers of these changes, we used field‐scale remote sensing of NDVI to track peatland vegetation in experiments that manipulated...

Species at risk of extinction are not uniformly distributed in space. Concentrations of threatened species may occur where threatening processes are intense, in refuges from those processes, or in areas of high species diversity. However, there have been few attempts to identify the processes that explain the distribution of at-risk species. Here, we identified the relative importance of biological traits, environmental factors, and anthropogenic stressors in driving the spatial patterns of both total and at-risk species richness of North American mammals and birds. Environmental factors...

Dry mixed-conifer forests are widespread in the interior Pacific Northwest, but their historical fire regimes are poorly characterized, in particular the relative mix of low- and high-severity fire. We reconstructed a multi-century history of fire from tree rings in dry mixed-conifer forests in central Oregon. These forests are dominated by ponderosa pine (Pinus ponderosa Lawson & C. Lawson), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and grand fir (Abies grandis (Douglas ex D. Don) Lindl.). Across four, 30-plot grids of ~800 ha covering a mosaic of dry mixed-conifer forest types,...

The invasive emerald ash borer (EAB, Agrilus planipennis Fairmaire) causes widespread ash tree mortality in North America, and the CO2 efflux (respiration, F) from coarse dead wood (CDW) following the EAB infestation is unknown. We examined seasonal variations in CO2 fluxes from various types of CDW (cut ash stumps, downed logs, and standing girdled dead stems) and the surfaces of soil and live stemin a black ash wetland in which EAB infestation was simulated. Responses of FCDW to seasonal changes in temperature were less sensitive than that of live stems. However, FCDW from the stump and...

Identifying what determines fish mercury (Hg) bioaccumulation remains a key scientific challenge.While there has been substantial research on spatial variation in fish Hg bioaccumulation, the factors that influence temporal fluctuations in fish Hg have received less attention to date. In this study,webuilt upon a growing body of research investigating young-of-the-year (YOY) yellowperch Hg bioaccumulation and investigated annual fluctuations in YOY yellow perch Hg in six lakes in northeastern Minnesota over eight years. After accounting for spatial variation between the study lakes, we...

Biological soil crusts (BSCs) exist commonly on soil surfaces in many arid and semiarid areas, and disturbed soil surfaces in more mesic environments. BSCs perform many essential ecological functions. Substantial resources have been invested trying to restore or replace BSCs that have been damaged by anthropogenic disturbances, with various levels of success. The nexus of sciences related to BSC establishment and restoration, and to aerobiology suggests that crusts are established and reestablished naturally via commonly occurring ecological processes. Formation of BSCs can be accelerated...