Treesearch

The Pacific Northwest of North America experiences relatively mild winters and dry summers. For the tall coniferous trees that grow in this region, we predicted that loss in the hydraulic conductivity of uppermost branches would be avoided because of difficulty reversing accumulated emboli in xylem that is always under negative pressure. To test this hypothesis, we measured native percent loss in hydraulic conductivity (PLC; the decrease of in situ hydraulic conductivity relative to the maximum) monthly throughout 2009 in branches at the tops (-50 m) of four species in an old growth forest...

Densely vegetated environments have hindered collection of basic population parameters on forest-dwelling ungulates. Our objective was to develop a mark-recapture technique that used DNA from fecal pellets to overcome constraints associated with estimating abundance of ungulates in landscapes where direct observation is difficult. We tested our technique on Sitka black-tailed deer (Odocoileus hemionus sitkensis) in the temperate coastal rainforest of Southeast Alaska. During 2006-2008, we sampled fecal pellets of deer along trail transects in 3 intensively logged watersheds on Prince of...

Research on the impact of clearcut logging and partial harvesting practices on northern flying squirrels (Glaucomys sabrinus) has shown inconsistent and contrary results, limiting the use of this species as a management indicator species. Much of this variability in study results is due to the labor intensive nature of studying flying squirrels, resulting in small sampling sizes (average = 5.2 sites, n = 14) and high variation (CV = 0.59) across studies. We conducted a meta-analysis of relevant studies from North America to determine how forestry practices affect flying squirrel abundance....

Adequate water transport is necessary to prevent stomatal closure and allow for photosynthesis. Dysfunction in the water transport pathway can result in stomatal closure, and can be deleterious to overall plant health and survival. Although much is known about small branch hydraulics, little is known about the coordination of leaf and stem hydraulic function. Additionally, the daily variations in leaf hydraulic conductance, stomatal conductance and water potential have only been measured for a few species. The objective of the current study was to characterize stem and leaf vulnerability...

Discerning the intricacies of mating systems in butterflies can be difficult, particularly when multiple mating strategies are employed and are cryptic and not exclusive. We observed the behavior and habitat use of 113 male Taylor's checkerspot butterflies (Euphydryas editha taylori). We confirmed that two distinct mating strategies were exhibited; patrolling and perching. These strategies varied temporally in relation to the protandrous mating system employed. Among perching males, we recorded high site fidelity and aggressive defense of small (

Agricultural and urban development alters nitrogen and other biogeochemical cycles in rivers worldwide. Because such biogeochemical processes cannot be measured empirically across whole river networks, simulation models are critical tools for understanding river-network biogeochemistry. However, limitations inherent in current models restrict our ability to simulate biogeochemical dynamics among diverse river networks. We illustrate these limitations using a river-network model to scale up in situ measures of nitrogen cycling in eight catchments spanning various geophysical and land-use...

Desert truffles, hypogeous Pezizales (Ascomycota), are difficult to identify due to evolutionary convergence of morphological characters among taxa that share a similar habitat and mode of spore dispersal. In this paper we document the presence of Picoa lefebvrei (Pat.) Maire (=Phaeangium lefebvrei) in Iran and use phylogenetic analysis of the ITS and 28s rDNA to show that this species belongs to the Geopora-Tricharina clade of the Pyronemataceae (Pezizales, Ascomycota). Picoa lefebvrei was originally placed in the genus Phaeangium because of notable spore ornamentation not present in...

Nitrous oxide (N20) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N20 via microbial denitrification that converts N to N20 and dinitrogen (N2). The fraction of denitrified N that escapes as N20 rather than N20 (i.e., the N2 yield) is an important determinant of how much N20 is produced by river networks, but little is known about the N20 yield in flowing waters. Here, we present the results of whole-stream 15N-tracer additions conducted in 72...

Question: How do pre-fire conditions (community composition and environmental characteristics) and climate-driven disturbance characteristics (fire severity) affect post-fire community composition in black spruce stands? Location: Northern boreal forest, interior Alaska. Methods: We compared plant community composition and environmental stand characteristics in 14 black spruce stands before and after multiple, naturally occurring wildfires. We used a combination of vegetation table sorting, univariate and multivariate statistics to determine the impact of fire severity and site moisture on...

The Asian black truffle Tuber indicum is morphologically and phylogenetically similar to the European black truffle Tuber melanosporum. T. indicum is considered a threat to T. melanosporum trufficulture due to its presumed competitiveness and broad host compatibility. Recently, in independent events, T. indicum was found fruiting in a forest in Oregon, USA, and was detected as ectomycorrhizas within a truffle orchard established with trees believed to have been inoculated with T. melanosporum. We used haplotype networking to assess intraspecific ITS rDNA diversity among Asian and North...