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61.
Large wood in central Appalachian headwater streams: controls on and potential changes to wood loads from infestation of hemlock woolly adelgid
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Large wood (LW) is an important component of forested headwater streams. The character of LW loads reflects a balance between adjacent valley processes that deliver LW to the channel (herein recruitment processes) and stream channel processes that either retain or transport LW through the reach (herein retention processes). In the central Appalachian Mountains, USA, LW characteristics in headwater streams located in eastern hemlocks (Tsuga candensis) forests are expected to change because of infestation of hemlock woolly adelgid (Adelges tsugae, HWA), an exotic, invasive insect. We examined LW characteristics in 24 headwater streams ranging from un‐infested to severe infestation, as determined by hemlock canopy health. The objectives of this work were to: (i) quantify wood loads; (ii) assess the relative importance of valley recruitment and in‐stream retention mechanisms in controlling reach‐scale wood loads; and (iii) assess if there was a detectable influence of HWA on LW loads. We hypothesized that LW loads would be similar to other forested streams in eastern USA and dominated by recruitment processes. In addition, higher LW loads would correspond with advanced HWA infestation. Mean wood frequency was 38 pieces/100 m ± 17 (standard deviation); mean wood volume was 3.69 m3/100 m ± 2.76. In general, LW load characteristics were influenced by both recruitment and retention parameters; jam (accumulations ≥ 3 pieces) characteristics were dominated by retention parameters. Results suggest that adjacent stand basal area influences LW loads and once LW is recruited to the channel, streams lack sufficient hydraulic driving forces, despite having lower resistance structures, to transport LW out of the reach. Sites in moderate decline had higher proportions of short (1–2 m and 1–4 m) and very long (>10 m) LW with higher frequency of jams that were low in volume. We present a hypothesized conceptual model of expected changes to LW loads associated with HWA infestation and hemlock mortality. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Vanessa M. Adams Katie Moon Jorge G. Álvarez-Romero Örjan Bodin Michaela Spencer Deborah Blackman 《社会与自然资源》2018,31(7):755-772
Effective natural resource management (NRM) often depends on collaboration through formal and informal relationships. Social network analysis (SNA) provides a framework for studying social relationships; however, a deeper understanding of the nature of these relationships is often missing. By integrating multiple analytical methods (including SNA, evidence ratings, and perception matrices), we were able to investigate the nature of relationships in NRM social networks across five service types (e.g., technical advice, on-ground support) in our case study region, Daly catchment Australia. Only one service type was rated as highly associated with free choice in establishing relationships: technical advice/knowledge. Beneficial characteristics of NRM organizations, such as collaborative and transparent, were associated with the presence of freely chosen relationships between organizations. Our results suggest a need to improve our understanding of organizational roles and characteristics, in particular for use in applied NRM contexts, such as network weaving or disseminating information. 相似文献
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Seth S. Haines Jay E. Diffendorfer Laurie Balistrieri Byron Berger Troy Cook Don DeAngelis Holly Doremus Donald L. Gautier Tanya Gallegos Margot Gerritsen Elisabeth Graffy Sarah Hawkins Kathleen M. Johnson Jordan Macknick Peter McMahon Tim Modde Brenda Pierce John H. Schuenemeyer Darius Semmens Benjamin Simon Jason Taylor Katie Walton-Day 《Natural Resources Research》2014,23(1):3-17
Natural resource planning at all scales demands methods for assessing the impacts of resource development and use, and in particular it requires standardized methods that yield robust and unbiased results. Building from existing probabilistic methods for assessing the volumes of energy and mineral resources, we provide an algorithm for consistent, reproducible, quantitative assessment of resource development impacts. The approach combines probabilistic input data with Monte Carlo statistical methods to determine probabilistic outputs that convey the uncertainties inherent in the data. For example, one can utilize our algorithm to combine data from a natural gas resource assessment with maps of sage grouse leks and piñon-juniper woodlands in the same area to estimate possible future habitat impacts due to possible future gas development. As another example: one could combine geochemical data and maps of lynx habitat with data from a mineral deposit assessment in the same area to determine possible future mining impacts on water resources and lynx habitat. The approach can be applied to a broad range of positive and negative resource development impacts, such as water quantity or quality, economic benefits, or air quality, limited only by the availability of necessary input data and quantified relationships among geologic resources, development alternatives, and impacts. The framework enables quantitative evaluation of the trade-offs inherent in resource management decision-making, including cumulative impacts, to address societal concerns and policy aspects of resource development. 相似文献
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Jenni E. Sherriff Keith N. Wilkinson Poppy Harding Hayley Hawkins Rhys G. O. Timms Daniel S. Adler Emily J. Beverly Simon P. E. Blockley Boris Gasparyan Christina J. Manning Darren Mark Samvel Nahapetyan Katie J. Preece 《第四纪科学杂志》2022,37(1):6-27
The significance of the southern Caucasus in understanding Pleistocene hominin expansions is well established. However, the palaeoenvironments in which Palaeolithic occupation of the region took place are presently poorly defined. The Hrazdan river valley, Armenian Highlands, contains a rich Palaeolithic record alongside Middle Pleistocene volcanic, fluvial and lacustrine strata, and thus offer exciting potential for palaeoenvironmental reconstruction. We present the first results of sedimentological, geochemical, tephrostratigraphical and biological (diatoms) study of the sequence of Bird Farm 1, located in the central part of the valley. These data show six phases of landscape development during the interval 440–200 ka. The sequence represents the first quantitative Pleistocene diatom record from the Armenian Highlands and the southern Caucasus, and indicates the persistence of a deep, stratified lacustrine system, with evidence for changing lake productivity that is tentatively linked to climate. Furthermore, major element chemical characterization of visible and crypto-tephra horizons in the sequence enables the first stages of the development of a regional tephrostratigraphy. Together, the evidence from Bird Farm 1 demonstrates the importance of lacustrine archives in the region for palaeoenvironmental reconstruction and highlights the potential for linkages between archives on both a local and regional scale. 相似文献