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1.
Blair Robertson Trent McDonald Chris Price Jennifer Brown 《Environmental and Ecological Statistics》2018,25(3):305-323
A new spatially balanced sampling design for environmental surveys is introduced, called Halton iterative partitioning (HIP). The design draws sample locations that are well spread over the study area. Spatially balanced designs are known to be efficient when surveying natural resources because nearby locations tend to be similar. The HIP design uses structural properties of the Halton sequence to partition a resource into nested boxes. Sample locations are then drawn from specific boxes in the partition to ensure spatial diversity. The method is conceptually simple and computationally efficient, draws spatially balanced samples in two or more dimensions and uses standard design-based estimators. Furthermore, HIP samples have an implicit ordering that can be used to define spatially balanced over-samples. This feature is particularly useful when sampling natural resources because we can dynamically add spatially balanced units from the over-sample to the sample as non-target or inaccessible units are discovered. We use several populations to show that HIP sampling draws spatially balanced samples and gives precise estimates of population totals. 相似文献
2.
River damming provides a dominant human impact on river environments worldwide, and while local impacts of reservoir flooding
are immediate, subsequent ecological impacts downstream can be extensive. In this article, we assess seven research strategies
for analyzing the impacts of dams and river flow regulation on riparian ecosystems. These include spatial comparisons of (1)
upstream versus downstream reaches, (2) progressive downstream patterns, or (3) the dammed river versus an adjacent free-flowing
or differently regulated river(s). Temporal comparisons consider (4) pre- versus post-dam, or (5) sequential post-dam conditions.
However, spatial comparisons are complicated by the fact that dams are not randomly located, and temporal comparisons are
commonly limited by sparse historic information. As a result, comparative approaches are often correlative and vulnerable
to confounding factors. To complement these analyses, (6) flow or sediment modifications can be implemented to test causal
associations. Finally, (7) process-based modeling represents a predictive approach incorporating hydrogeomorphic processes
and their biological consequences. In a case study of Hells Canyon, the upstream versus downstream comparison is confounded
by a dramatic geomorphic transition. Comparison of the multiple reaches below the dams should be useful, and the comparison
of Snake River with the adjacent free-flowing Salmon River may provide the strongest spatial comparison. A pre- versus post-dam
comparison would provide the most direct study approach, but pre-dam information is limited to historic reports and archival
photographs. We conclude that multiple study approaches are essential to provide confident interpretations of ecological impacts
downstream from dams, and propose a comprehensive study for Hells Canyon that integrates multiple research strategies. 相似文献
3.
4.
A comprehensive review of climate adaptation in the United States: more than before, but less than needed 总被引:2,自引:0,他引:2
Rosina Bierbaum Joel B. Smith Arthur Lee Maria Blair Lynne Carter F. Stuart Chapin III Paul Fleming Susan Ruffo Missy Stults Shannon McNeeley Emily Wasley Laura Verduzco 《Mitigation and Adaptation Strategies for Global Change》2013,18(3):361-406
We reviewed existing and planned adaptation activities of federal, tribal, state, and local governments and the private sector in the United States (U.S.) to understand what types of adaptation activities are underway across different sectors and scales throughout the country. Primary sources of review included material officially submitted for consideration in the upcoming 2013 U.S. National Climate Assessment and supplemental peer-reviewed and grey literature. Although substantial adaptation planning is occurring in various sectors, levels of government, and the private sector, few measures have been implemented and even fewer have been evaluated. Most adaptation actions to date appear to be incremental changes, not the transformational changes that may be needed in certain cases to adapt to significant changes in climate. While there appear to be no one-size-fits-all adaptations, there are similarities in approaches across scales and sectors, including mainstreaming climate considerations into existing policies and plans, and pursuing no- and low-regrets strategies. Despite the positive momentum in recent years, barriers to implementation still impede action in all sectors and across scales. The most significant barriers include lack of funding, policy and institutional constraints, and difficulty in anticipating climate change given the current state of information on change. However, the practice of adaptation can advance through learning by doing, stakeholder engagements (including “listening sessions”), and sharing of best practices. Efforts to advance adaptation across the U.S. and globally will necessitate the reduction or elimination of barriers, the enhancement of information and best practice sharing mechanisms, and the creation of comprehensive adaptation evaluation metrics. 相似文献
5.
Brad Muise Dong-Chul Seo E. Earl Blair Trent Applegate 《Environmental monitoring and assessment》2010,163(1-4):95-104
A pilot study was conducted to estimate fungal spore penetration for wall service outlets subjected to a constant air pressure. During the laboratory experiment, a wall chamber was fabricated, and telephone, electrical, and cable service outlets were installed. Penicillium chrysogenum spores were aerosolized into the chamber that was held under pressure. Spores that penetrated the outlets were funneled into an impinger for microscopic enumeration. Thirty trials were conducted for each of the five outlets (N?= 150), and the wall chamber was decontaminated between trials. Results of an analysis of variance suggest wall service outlets allow spore penetration. The penetration factor for the telephone outlet was significantly greater than all other outlets (p?< 0.05), and there was no difference in penetration between electrical outlets with and without plugs. Penetration factor differences were attributed to air leakage rates across the outlets. Due to the experimental design and equipment limitations, further research is needed to support these findings. 相似文献
6.
7.
Thomas A. O'Neil Robert J. Steidl W. Daniel Edge Blair Csuti 《Conservation biology》1995,9(6):1482-1491
Determining which vegetation types organisms perceive similarly and classifying these types into groups that function as similar habitats are necessary steps toward expanding the focus of conservation strategies from single species to ecosystems. Therefore, the methods used to determine these habitat classifications are crucial to the successful design and implementation of these conservation strategies. Typically, this process has been accomplished through best professional judgement. We used quantitative techniques to group vegetation types into habitats based on the occurrence of breeding wildlife species ( n = 420) in Oregon. After calculating faunal similarities among all regional vegetation types ( n = 130), we used cluster analysis to group vegetation types into wildlife habitats. We classified the original 130 vegetation types into 30 wildlife habitat types that we believe function similarly. We tested this classification to assess whether vegetation types could be correctly classified into habitat types based on wildlife species composition. Discriminant analysis correctly classified 95% of the vegetation types into their wildlife habitat types, strengthening our confidence in this approach. This approach for classifying habitat types allows consistent development of conservation strategies at coarse resolutions and aids in identifying vegetation types where additional biodiversity surveys are needed. Finally, this approach can be refined continuously as the precision of vegetation mapping and our understanding of organism-habitat associations improve. 相似文献
8.
9.
Laela S. Sayigh Peter L. Tyack Randall S. Wells Michael D. Scott A. Blair Irvine 《Behavioral ecology and sociobiology》1995,36(3):171-177
Signature whistles of 42 free-ranging bottle-nose dophin calves were compared to those of their mothers. Humans judged their similarity by inspection of spectrograms. There was a sex difference in the tendency of calves to produce whistles similar to or different from those of their mothers; most female calves produced whistles that were different from those of their mothers, whereas male calves were more likely to produce whistles that were similar to those of their mothers. Because matrilineally related females associate together and use signature whistles to establish and/or maintain contact with their calves, there may be a selective pressure for females to produce whistles that are distinct from those of their mothers. There may be fewer constraints governing whistle development in males, with the result that some males produce whistles similar to those of their mothers and others do not. 相似文献
10.
Atrazine induction of a family 4 cytochrome P450 gene in Chironomus tentans (Diptera: Chironomidae) 总被引:1,自引:0,他引:1
Cytochrome P450-dependent microsomal monooxygenase (P450) activity was measured in control and atrazine-exposed third instar midge larvae, Chironomus tentans. Significantly elevated O-demethylase activity was observed in gut homogenates taken from midges exposed to atrazine concentrations from 1 to 10 ppm for 90 h. No significant induction was observed at atrazine concentrations below 1 ppm. A region of a cytochrome P450 family 4 gene was amplified and sequenced from C. tentans larvae. Alignments of inferred amino acid sequences with other insect CYP4 gene homologues indicate a high degree of similarity. Northern blot analysis employing the CYP4 gene fragment as a probe showed an over-expression in C. tentans exposed to atrazine. The results support the previously identified inducibility of cytochrome P450-dependent activity and provide insight into the potential consequences of atrazine exposure to aquatic organisms. 相似文献