Treesearch

Conservation biologists often face the trade-off that increasing connectivity in fragmented landscapes to reduce extinction risk of native species can foster invasion by non-native species that enter via the corridors created, which can then increase extinction risk. This dilemma is acute for stream fishes, especially native salmonids, because their populations are frequently relegated to fragments of headwater habitat threatened by invasion from downstream by 3 cosmopolitan non-native salmonids. Managers often block these upstream invasions with movement barriers, but isolation of native...

Aquatic habitat monitoring is being conducted by numerous organizations in many parts of the Pacific Northwest to document physical and biological conditions of stream reaches as part of legal- and policy-mandated environmental assessments. Remote sensing using discrete-return, near-infrared, airborne LiDAR (Light Detection and Ranging) and high-resolution digital imagery may provide an alternative basis for measuring physical stream attributes that are traditionally recorded by field crews in these monitoring efforts. Here, we compare physical channel characteristics determined from...

It has been hypothesized that velocity reversals provide a mechanism for maintaining pool-riffle morphology in gravel-bed rivers-an important habitat for salmonids, which are at risk in many places worldwide and that are the focus of extensive environmental legislation in Europe and North America. However, the occurrence of velocity reversals has been controversial for over 3 decades. We present a simple one-dimensional criterion that unifies and explains previous disparate findings regarding the occurrence of velocity reversals. Results show that reversal depends critically on the ratio...

The minimum variance multivariate composite estimator is a relatively simple sequential estimator for complex sampling designs (Czaplewski 2009). Such designs combine a probability sample of expensive field data with multiple censuses and/or samples of relatively inexpensive multi-sensor, multi-resolution remotely sensed data. Unfortunately, the multivariate composite estimator is vulnerable to numerical errors, which can cause infeasible or unreliable estimates (Grewal and Andrews 2001:Chapter 6). Numerical errors can exceed random estimation errors, which is especially dangerous if...

River systems have been altered worldwide by dams and diversions, resulting in a broad array of environmental impacts. The use of a process-based, hierarchical framework for assessing environmental impacts of dams is explored here in terms of a case study of the Kootenai River, western North America. The goal of the case study is to isolate and quantify the relative effects of multiple dams and other river management activities within the study area and to informpotential restoration strategies. In our analysis, first-order impacts describe broad changes in hydrology (determined from local...

Long-term, landscape patterns in inorganic nitrogen (N) availability and N stocks following infrequent, stand-replacing fire are unknown but are important for interpreting the effect of disturbances on ecosystem function. Here, we present results from a replicated chronosequence study in the Greater Yellowstone Ecosystem (Wyoming, USA) directed at measuring inorganic N availability (ionexchange resin bags) and ecosystem N pools among 77 lodgepole pine stands that varied in age and density.

Basin physiography and fluvial processes structure the availability of salmonid spawning habitat in river networks. However, methods that allow us to explicitly link hydrologic and geomorphic processes to spatial patterns of spawning at scales relevant to management are limited. Here we present a method that can be used to link the abundance of spawning salmonids to fluvial processes at the mesoscale. We show that the frequency of spawning activity at individual morphological units (riffles, pools, runs) is quantitatively related to a number of fluvial parameters. Of these, bankfull excess...

Successive reaches of the Rio Grande have maintained equivalent channel widths of 50 and 250 m, respectively, over long periods of time. It is hypothesized that alluvial channels adjust bed slope to match the long-term changes in channel width. Analytical relationships show that wider river reaches develop steeper slopes. A modeling approach using daily water and sediment discharges simulates the transient evolution of bed elevation changes. The analytical and numerical models are in very good agreement with the longitudinal profile measurements of the Bosque del Apache reach of the Rio...

We captured >2000 Crawford's gray shrews (Notiosorex crawfordi) in a riparian forest mainly consisting of cottonwoods (Populus deltoides) along the Rio Grande in central New Mexico. Little has been published about abundance and habitat of Crawford's gray shrew throughout its distributional range. During 7 summers, we captured shrews in pitfall traps at 13 study sites in Bernalillo, Valencia, and Socorro counties. Capture rates of shrews were greatest in August and September, and we did not detect a response of shrews to restoration treatments that removed nonnative plants from riparian...

This study examines calculating total sediment discharge based on the Modified Einstein Procedure (MEP). A new procedure based on the Series Expansion of the Modified Einstein Procedure (SEMEP) has been developed. This procedure contains four main modifications to MEP. First, SEMEP solves the Einstein integrals quickly and accurately based on a series expansion. Next, instead of dividing the suspended sediment and bed material samples into particle size classes, the total sediment discharge calculation is based on a median grain size in suspension (d50ss). Thirdly, for depth-integrated...