Treesearch

This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools into (1) near-surface soils where SOC is affected by seasonal freeze-thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not...

Multiple plant stresses can affect the health, esthetic condition, and timber harvest value of conifer forests. To monitor spatial and temporal dynamic forest stress conditions, timely, accurate, and cost-effective information is needed that could be provided by remote sensing. Recently, satellite imagery has become available via the RapidEye satellite constellation to provide spectral information in five broad bands, including the red-edge region (690-730 nm) of the electromagnetic spectrum. We tested the hypothesis that broadband, red-edge satellite information improves early detection...

Productivity of a managed grazing system is dependent upon both the grazing strategy of ungulates and decisions made by humans. Herds of domestic reindeer (Rangifer tarandus tarandus) graze on discrete ranges of the Seward Peninsula, Alaska with variable production rates. We show that the 15N natural abundance of reindeer forages vary significantly and the δ 15N value of collagen deposited in antler bone from spring until ossification was significantly correlated with the δ 15N signature of the diet. Calf weight in June was related to isotopic signatures in antler and soft tissue of adult...

The plant secondary metabolite papyriferic acid (PA) deters browsing by snowshoe hares (Lepus americanus) on the juvenile developmental stage of the Alaska paper birch (Betula neoalaskana). However, the physiological mechanism that reduces browsing remains unknown. We used pharmacological assays and molecular modeling to test the hypothesis that inhibition of succinate dehydrogenase (SOH) is a mode of action (MOA) of toxicity of PA in snowshoe hares. We tested this hypothesis by measuring the effect of PA on the activity of SOH in liver mitochondria isolated from wild hares. In addition,...

Quantification of a relationship between salmon escapement in rivers and riparian tree-ring δ 15N could allow reconstruction of prehistorical salmon abundance. Unfortunately, attempts to quantify this link have met with little success. We examined the feasibility of the approach using natural abundance of δ 15N in riparian tree rings formed before and after extirpation of salmon and 15N tracer studies in a river and riparian soils.

Microsatellite primers were developed for the first time in the species Corallorhiza maculata, a nonphotosynthetic orchid that is becoming a model for studying mycorrhizal specificity. Eight polymorphic microsatellite markers were developed using an enrichment and cloning protocol. The number of alleles for each locus ranged from two to seven. The loci were tested in three populations, and the resulting high FsT values suggested that these loci have utility in illuminating population structure. Cross-amplification was also achieved in the sister species C. mertensiana. These microsatellite...

Insect outbreaks are major ecosystem disturbances, affecting a similar area as forest fires annually across North America. Tree mortality caused by bark beetle outbreaks alters carbon cycling in the first several years following the disturbance by reducing stand-level primary production and by increasing the amount of dead organic matter available for decomposition. The few studies of biogeochemical cycling following outbreaks have shown a range of impacts from small responses of net carbon fluxes in the first several years after a severe outbreak to large forest areas that are sources of...

The carbon (C) storage capacity of northern latitude ecosystems may diminish as warming air temperatures increase permafrost thaw and stimulate decomposition of previously frozen soil organic C. However, warming may also enhance plant growth so that photosynthetic carbon dioxide (C02) uptake may, in part, offset respiratory losses. To determine the effects of air and soil warming on C02 exchange in tundra, we established an ecosystem warming experiment—the Carbon in Permafrost Experimental Heating Research (CiPEHR) project—in the northern foothills of the Alaska Range in Interior Alaska....

Despite widespread use of intensive vegetation control (VC) in forest management, the effects of VC on allocation of biomass and nutrients between young trees and competing vegetation are not well understood. On three Pacific Northwest sites differing in productivity, soil parent material, and understory vegetation community, we evaluated year-5 effects of presence/absence of 5 years of VC on allocation of aboveground biomass and nitrogen (N) between planted Douglas-fir (Pseudotsuga menziesii var. menziesii) and competing vegetation. Equations for predicting bole, branch, foliar, and total...

Relationships between discrete-return light detection and ranging (LiDAR) data and radiata pine leaf area index (LAI), stem volume, above ground carbon, and carbon sequestration were developed using 10 plots with directly measured biomass and leaf area data, and 36 plots with modelled carbon data. The plots included a range of genetic types established on north- and south-facing aspects. Modelled carbon was highly correlated with directly measured crown, stem, and above ground biomass data, with r = 0.92, 0.97, and 0.98, respectively. LiDAR canopy percentile height (P30) and cover, based...