Treesearch

Hillslope threshold response to storm rainfall is poorly understood. Basic questions regarding the type, location, and flow dynamics of lateral, subsurface flow remain unanswered, even at our most intensively studied field sites. Here we apply a forensic approach where we combined irrigation and excavation experiments at the well studied Maimai hillslope to determine the typology and morphology of the primary lateral subsurface flowpaths, and the control of bedrock permeability and topography on these flowpaths. The experiments showed that downslope flow is concentrated at the soil bedrock...

We quantified the downstream transport of invertebrates, organic matter and inorganic sediment from 60 fishless headwater streams in the Wenatchee River Basin located on the eastern slope of the Cascade Range in Washington, U.S.A. Streams were classified into four groups (each n = 15) based on their position within two ecological subregions (wet and dry) and the extent of past timber harvest and road development (logged and unlogged). Time and ecoregion were significant for all response variables as transport varied across sampling periods, and dry ecoregion streams displayed significantly...

Truffles (Tuber) are ectomycorrhizal fungi characterized by hypogeous fruitbodies. Their biodiversity, host associations and geographical distributions are not well documented. ITS rDNA sequences of Tuber are commonly recovered from molecular surveys of fungal communities, but most remain insufficiently identified making it difficult to determine whether these sequences represent conspecific or novel taxa. In this meta-analysis, over 2,000 insufficiently identified Tuber sequences from 76 independent studies were analyzed within a phylogenetic framework. Species ranges, host associates,...

Tuber gibbosum Harkn., described from northern California, originally was thought to be a single, variable species that fruited from autumn through winter to spring. It has become popular as a culinary truffle in northwestern USA, where it is commercially harvested. Morphological studies suggested it might be a complex that includes at least two species. We conducted morphological and phylogenetic studies of the complex to determine how many species it might contain and how they differed morphologically, geographically and seasonally. We also provide the first LSU phylogeny for the genus...

Mechanistic assessment of how transpiration influences subsurface flow is necessary to advance understanding of catchment hydrology. We conducted a 24-day, steady-state irrigation experiment to quantify the relationships among soil moisture, transpiration and hillslope subsurface flow. Our objectives were to: (1) examine the time lag between maximum transpiration and minimum hillslope discharge with regard to soil moisture; (2) quantify the relationship between diel hillslope discharge and daily transpiration; and (3) identify the soil depth from which trees extract water for transpiration....

In this review, we first summarize how hydrologic connectivity has been studied for riverine fish capable of moving long distances, and then identify research opportunities that have clear conservation significance. Migratory species, such as anadromous salmonids, are good model organisms for understanding ecological connectivity in rivers because the spatial scale over which movements occur among freshwater habitats is large enough to be easily observed with available techniques; they are often economically or culturally valuable with habitats that can be easily fragmented by human...

We measured the hyporheic microbial exoenzyme activities in a floodplain river to determine whether dissolved organic matter (DOM) bioavailability varied with overlying riparian vegetation patch structure or position along flowpaths. Particulate organic matter (POM), dissolved organic carbon (DOC), dissolved oxygen (DO), electrical conductivity and temperature were sampled from wells in a riparian terrace on the Queets River, Washington, U.S.A. on 25 March, 15 May, 20 July and 09 October 1999. Dissolved nitrate, ammonium and soluble reactive phosphorus were also collected on 20 July and 09...

An understory of shade-tolerant species often develops in stands in the Douglas-fir region of western Washington and Oregon and can have a disproportionate effect on relative density indices, such as Reineke stand density index and Curtis relative density. The effects of such understories and of other departures from The even-aged condition are illustrated with selected stand data. In general, the summation methods are less influenced by departures from the even-aged condition than are the conventional calculations based on quadratic mean diameter. Recommendations are made for consistent...

It is suggested that diversity destabilizes individual populations within communities; however, generalizations are problematic because effects of diversity can be confounded by variation attributable to community type, life history or successional stage. We examined these complexities using a 40-year record of reassembly in forest herb communities in two clearcut watersheds in the Andrews Long-term Ecological Research Site (Oregon, USA). Population stability was higher among forest than colonizing species and increased with successional stage. Thus, life history and successional stage may...

Forest management for carbon sequestration is a low-cost, low-technology, relatively easy way to help mitigate global climate change that can be adopted now while additional long-term solutions are developed. Carbon-oriented management of forests also offers forest owners an opportunity to obtain a new source of income, and commonly has environmental co-benefits. The USA is developing climate change policy that recognizes forestry as a source of offsets in carbon markets, and the emissions trading programs and standards that have developed to date offer opportunities for afforestation,...