Treesearch

White spruce (Picea glauca (Moench) Voss) is a dominant species in late-successional ecosystems along the Tanana River, interior Alaska, and the most important commercial timber species in these boreal floodplain forests. Whereas white spruce commonly seed in on young terraces in early primary succession, the species does not become a conspicuous component of the vegetation until after 60-80 years. To address what abiotic and/or biotic factors may explain the paucity of spruce in earlier stages of succession, we examined germination and growth of planted white spruce seedlings across an...

Despite the critical roles fungi play in the functioning of ecosystems, especially as symbionts of plants and recyclers of organic matter, their biodiversity is poorly known in high-latitude regions. In this paper, we discuss the molecular diversity of one of the most diverse and abundant groups of ectomycorrhizal fungi: the genus Lactarius Pers. We analysed internal transcribed spacer rDNA sequences from both curated sporocarp collections and soil polymerase chain reaction clone libraries sampled in the arctic tundra and boreal forests of Alaska. Our genetic diversity assessment, based on...

Phylogenetic analysis of the ITS and LSU rDNA of Pachyphloeus species from Europe and North America revealed a new truffle genus. These molecular analyses plus sequences downloaded from a BLAST search in GenBank indicated that Pachyphloeus prieguensis is within the Pezizaceae but well outside of the genus Pachyphloeus. Morphological differences in the peridial and glebal hyphae and spores distinguish this genus from Pachyphloeus. We here propose the monotypic new genus Calongea, with the type species C. prieguensis comb. nov., in honor of Prof. Francisco de Diego Calonge, who has long...

Despite the importance of fungi for restoration, their presence in revegetated sites has received little attention. We compared the diversity and composition of macrofungi (i.e., those that form fleshy mushrooms and truffles) in 12 sites where 3- to 6-year-old native trees and shrubs had been planted (woodland restoration sites), with that in 6 woodland remnants. All sites were within an agricultural landscape near Holbrook in New South Wales. Of 58 fungal genera recorded, 57 percent occurred in woodland restoration sites and 83 percent in nearby patches of remnant woodland. Of the genera...

Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6-km valley segment. For each reach, we estimated net change in discharge, gross hydrologic loss, and gross hydrologic gain from tracer dilution and mass recovery. Four series of tracer tests were performed during relatively...

Climate change in high latitudes can lead to permafrost thaw, which in ice-rich soils can result in ground subsidence, or thermokarst. In interior Alaska, we examined seasonal and annual ecosystem CO2 exchange using static and automatic chamber measurements in three areas of a moist acidic tundra ecosystem undergoing varying degrees of permafrost thaw and thermokarst development. One site had extensive thermokarst features, and historic aerial photography indicated it was present at least 50 years prior to this study. A second site had a moderate number of thermokarst features that were...

Most wilderness areas still lack accurate distribution information on tree species. We met this need with a predictive GIS modeling approach, using freely available digital data and computer programs to efficiently obtain high-quality species distribution maps. Here we present a digital map with the predicted distribution of white spruce (Picea glauca) in Alaska (4 km resolution, accuracy over 90%). Our presented concept represents a role-model for predicting tree species distribution for remote areas world-wide. Although this model intends to be accurate in making predictions rather than...

Observations and measurements were made of physical and ecological changes that have occurred since 1985 at a tundra site near Healy, Alaska. Air temperatures decreased (1985 through 1999) while permafrost warmed and thawed creating thermokarst terrain, probably as a result of increased snow depths. Permafrost, active layer and ground-ice conditions at the Healy site are the result of the interaction of climatic, ecologic and other factors. The slow accumulation of ground ice in an intermediate permafrost layer formed by upward freezing from the permafrost surface leads to long-term...

At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These rapid changes may be a bellwether of changes to come at lower latitudes and have the potential to affect ecosystem services related to natural resources, food production, climate regulation, and cultural integrity. We highlight...

To meet the challenge of maintaining the Holocene state, we propose a framework based on 'planetary boundaries'. These boundaries define the safe operating space for humanity with respect to the Earth system and are associated with the planet's biophysical subsystems or processes. Although Earth's complex systems sometimes respond smoothly to changing pressures, it seems that this will prove to be the exception rather than the rule. Many subsystems of Earth react in a nonlinear, often abrupt, way, and are particularly sensitive around threshold levels of certain key variables. If these...