Treesearch

Many pest and beneficial insects overwinter as larvae in a state of diapause, with development resuming in the spring. In these cases, rates of post-diapause development of parasitoids must be synchronised with the vulnerable life stages of their hosts. Phenological asynchrony between introduced parasitoids and their targeted hosts has limited the success of some biological control efforts. Here, we assess the potential synchrony between Collyria catoptron Wahl (Hymenoptera: Ichneumonidae), a parasitoid of the Chinese wheat stem sawfly, Cephus fumipennis Eversmann (Hymenoptera: Cephidae),...

Mountain fens found in western North America have sequestered atmospheric carbon dioxide (CO2) for millennia, provide important habitat for wildlife, and serve as refugia for regionally-rare plant species typically found in boreal regions. It is unclear how Rocky Mountain fens are responding to a changing climate. It is possible that fens found at lower elevations may be particularly susceptible to changes because hydrological cycles that control water tables are likely to vary the most. In this study, we fit models of growing season ecosystem-atmosphere CO2 exchange to field-measured data...

The persistence of ponderosa pine and lodgepole pine forests in the 21st century depends to a large extent on how seedling emergence and establishment are influenced by driving climate and environmental variables, which largely govern forest regeneration. We surveyed the literature, and identified 96 publications that reported data on dependent variables of seedling emergence and/or establishment and one or more independent variables of air temperature, soil temperature, precipitation and moisture availability. Our review suggests that seedling emergence and establishment for both species...

Under climate change, the reduction of frost risk, onset of warm temperatures and depletion of soil moisture are all likely to occur earlier in the year in many temperate regions. The resilience of tree species will depend on their ability to track these changes in climate with shifts in phenology that lead to earlier growth initiation in the spring. Exposure to warm temperatures (‘forcing’) typically triggers growth initiation, but many trees also require exposure to cool temperatures (‘chilling’) while dormant to readily initiate growth in the spring. If warming increases forcing and...

Forest policymakers and managers have long sought ways to evaluate the capability of forest landscapes to jointly produce timber, habitat, and other ecosystem services in response to forest management. Currently, carbon is of particular interest as policies for increasing carbon storage on federal lands are being proposed. However, a challenge in joint production analysis of forest management is adequately representing ecological conditions and processes that influence joint production relationships. We used simulation models of vegetation structure, forest sector carbon, and potential...

Information on the distribution of rare and little known species is critical for managers and biologists challenged with species conservation in an uncertain future. Pacific Martens (Martes caurina) historically resided throughout Oregon and northern California’s coastal forests, but were considered extinct until 1996 when a population in northern California was rediscovered. Only 26 verified contemporary (1989–2012) records were known within Oregon prior to this survey. The coastal subspecies (M. c. humboldtensis) was petitioned for listing under the federal Endangered Species Act in...

The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an important invasive pest of ash (Fraxinus) trees in North America. Two larval parasitoid species, Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) and Spathius agrili Yang (Hymenoptera: Braconidae), and 1 egg parasitoid species, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae), were introduced into the United States in 2007 as part of a classical biological control program. We conducted field studies to assess the flight phenology of introduced and native parasitoids of emerald ash borer in...

The conventional approach to LiDAR-based forest inventory modeling depends on field sample data from fixed-radius plots (FRP). Because FRP sampling is cost intensive, combining variable-radius plot (VRP) sampling and LiDAR data has the potential to improve inventory efficiency. The overarching goal of this study was to evaluate the integration of LiDAR and VRP data. FRP and VRP plots using different basal-area factors (BAF) were co-located in 6 conifer stands near Alberta, Michigan, in the United States. A suite of LiDAR metrics was developed for 24 different resolutions at each plot...

Information needs associated with sustainable forest management are evolving rapidly as the forest sector works to satisfy an increasingly complex set of economic, environmental, and social policy goals. A barrier to the sustainable management of forests and the provision of ecosystem goods and services under these new pressures is a lack of up-to-date and detailed information with regard to the number and characteristics of forest resources. Accurate inventory systems are required that spatially quantify timber and other nontimber goods and services at multiple scales in order to inform...

Fire is a key earth-system and Anthropocene process (Bowman et al. 2009; Smith et al. 2016a). Fire impacts on the global carbon (C) cycle from both anthropogenic and natural sources, with 1350-3400 Tg C emitted from land-use changes, agricultural practices and residential uses, and 2750-4600 Tg C emitted in wildfire events, which exhibit high interannual variability (Westerling et al. 2006; van der Werf et al. 2010; Wotton et al. 2010; Balch et al. 2013; Lannom et al. 2014; Smith et al. 2016a). Biomass burning emissions can be determined from top-down assessments such as the Global Fire...