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Using Niche-Based Models to Improve the Sampling of Rare Species 总被引:7,自引:0,他引:7
ANTOINE GUISAN†† OLIVIER BROENNIMANN ROBIN ENGLER MATHIAS VUST NIGEL G. YOCCOZ† ANTHONY LEHMANN§ NIKLAUS E. ZIMMERMANN‡ 《Conservation biology》2006,20(2):501-511
Abstract: Because data on rare species usually are sparse, it is important to have efficient ways to sample additional data. Traditional sampling approaches are of limited value for rare species because a very large proportion of randomly chosen sampling sites are unlikely to shelter the species. For these species, spatial predictions from niche-based distribution models can be used to stratify the sampling and increase sampling efficiency. New data sampled are then used to improve the initial model. Applying this approach repeatedly is an adaptive process that may allow increasing the number of new occurrences found. We illustrate the approach with a case study of a rare and endangered plant species in Switzerland and a simulation experiment. Our field survey confirmed that the method helps in the discovery of new populations of the target species in remote areas where the predicted habitat suitability is high. In our simulations the model-based approach provided a significant improvement (by a factor of 1.8 to 4 times, depending on the measure) over simple random sampling. In terms of cost this approach may save up to 70% of the time spent in the field. 相似文献
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Design and Performance of a Channel Reconstruction Project in a Coastal California Gravel-Bed Stream 总被引:1,自引:0,他引:1
A 0.9 km-reach of Uvas Creek, California, was reconstructed as a sinuous, meandering channel in November 1995. In February 1996, this new channel washed out. We reviewed project documents to determine the basis for the project design and conducted our own historical geomorphological study to understand the processes operating in the catchment and project reach. The project was designed using a popular stream classification system, based on which the designers assumed that a "C4" channel (a meandering gravel-bed channel) would be stable at the site. Our historical geomorphological analysis showed that the reach had been braided historically, typical of streams draining the Franciscan Formation in the California Coast Ranges, with episodic flows and high sand and gravel transport. After the project washed out, Uvas Creek reestablished an irregular, braided sand-and-gravel channel, although the channel here was narrower than it had been historically, probably due to such factors as incision caused by gravel mining. Our study casts doubt on several assumptions common in many stream restoration projects: that channel stability is always an appropriate goal; that channel forms are determined by flows with return periods of about 1.5 years; that a channel classification system is an easy, appropriate basis for channel design; and that a new channel form can be imposed without addressing the processes that determine channel form. 相似文献
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Post-project appraisals (PPAs) can evaluate river restoration schemes in relation to their compliance with design, their short-term
performance attainment, and their longer-term geomorphological compatibility with the catchment hydrology and sediment transport
processes. PPAs provide the basis for communicating the results of one restoration scheme to another, thereby improving future
restoration designs. They also supply essential performance feedback needed for adaptive management, in which management actions
are treated as experiments. PPAs allow river restoration success to be defined both in terms of the scheme attaining its performance
objectives and in providing a significant learning experience. Different levels of investment in PPA, in terms of pre-project
data and follow-up information, bring with them different degrees of understanding and thus different abilities to gauge both
types of success. We present four case studies to illustrate how the commitment to PPA has determined the understanding achieved
in each case. In Moore's Gulch (California, USA), understanding was severely constrained by the lack of pre-project data and
post-implementation monitoring. Pre-project data existed for the Kitswell Brook (Hertfordshire, UK), but the monitoring consisted
only of one site visit and thus the understanding achieved is related primarily to design compliance issues. The monitoring
undertaken for Deep Run (Maryland, USA) and the River Idle (Nottinghamshire, UK) enabled some understanding of the short-term
performance of each scheme. The transferable understanding gained from each case study is used to develop an illustrative
five-fold classification of geomorphological PPAs (full, medium-term, short-term, one-shot, and remains) according to their potential as learning experiences. The learning experience is central to adaptive management but rarely
articulated in the literature. Here, we gauge the potential via superimposition onto a previous schematic representation of
the adaptive management process by Haney and Power (1996). Using PPAs wisely can lead to cutting-edge, complex solutions to
river restoration challenges. 相似文献
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