State-and-Transition Models for Heterogeneous Landscapes: A Strategy for Development and Application     

Brandon T. Bestelmeyer  Arlene J. Tugel  George L. Peacock  Daniel G. Robinett  Pat L. Shaver  Joel R. Brown  Jeffrey E. Herrick  Homer Sanchez  Kris M. Havstad 《Strength and Conditioning Journal》2009,62(1):1-15

Interpretation of assessment and monitoring data requires information about how reference conditions and ecological resilience vary in space and time. Reference conditions used as benchmarks are often specified via potential-based land classifications (e.g., ecological sites) that describe the plant communities potentially observed in an area based on soil and climate. State-and-transition models (STMs) coupled to ecological sites specify indicators of ecological resilience and thresholds. Although general concepts surrounding STMs and ecological sites have received increasing attention, strategies to apply and quantify these concepts have not. In this paper, we outline concepts and a practical approach to potential-based land classification and STM development. Quantification emphasizes inventory techniques readily available to natural resource professionals that reveal processes interacting across spatial scales. We recommend a sequence of eight steps for the co-development of ecological sites and STMs, including 1) creation of initial concepts based on literature and workshops; 2) extensive, low-intensity traverses to refine initial concepts and to plan inventory; 3) development of a spatial hierarchy for sampling based on climate, geomorphology, and soils; 4) stratified medium-intensity inventory of plant communities and soils across a broad extent and with large sample sizes; 5) storage of plant and soil data in a single database; 6) model-building and analysis of inventory data to test initial concepts; 7) support and/or refinement of concepts; and 8) high-intensity characterization and monitoring of states. We offer a simple example of how data assembled via our sequence are used to refine ecological site classes and STMs. The linkage of inventory to expert knowledge and site-based mechanistic experiments and monitoring provides a powerful means for specifying management hypotheses and, ultimately, promoting resilience in grassland, shrubland, savanna, and forest ecosystems.  相似文献   

Grazing Intensity on Vegetation Dynamics of a Typical Steppe in Northeast Inner Mongolia     

Yan Liang  Guodong Han  He Zhou  Mengli Zhao  Hennie A. Snyman  Dan Shan  Kris M. Havstad 《Strength and Conditioning Journal》2009,62(4):328-336

Vegetation features radiating from residential areas in response to livestock grazing were quantified for an arid steppe rangeland in the Keshiketeng Banner, Chifeng Prefecture, in northeastern Inner Mongolia in 2004 and 2006. The aim of this study was to estimate grazing impacts on the vegetation dynamics of these historical grazed ecosystems. Grazing intensities were classified as reference area (RA), light (LG), moderate (MG), and heavy (HG) according to the vegetation utilization across the study area. Rangelands were studied along a grazing gradient, where characteristics of plant communities, heights of dominant species, aboveground vertical structures, and belowground biomass were investigated. Along this grazing gradient, vegetation changed from the original dominant plant species Leymus chinensis (Trin.) Tzvel. to a semi-subshrub species Artemisia frigida Willd. when moving from the reference area (RA) to the region around the settlement. Canopy coverage, aboveground productivity, and the number of perennial species declined as one moved toward the residential area. Heights of five dominant species, except for Stipa grandis P. Smirn., declined with increased grazing intensity. Aboveground vertical structure in the RA treatment showed more resilience than the other treatments. There was no difference in root biomass in the top 1 m of soil (P > 0.05) between the RA treatment and the area immediately around settlement (HG treatment). Generally, we found that the intensity of grazing disturbance did not exceed the tolerance of the rangeland ecosystem within LG treatment. However, vegetative conditions in HG treatment became worse with increased grazing pressure. Rangelands in this arid steppe are under tremendous threat due to excessive forage utilization, which cannot be considered a sustainable practice.  相似文献   

Simultaneous reduction in incidence of Bemisia tabaci (Hemiptera: Aleyrodidae) and Sylepta derogata (Lepidoptera: Pyralidae) using velvetleaf,Abutilon theophrasti as a trap crop     

Lin  Kejian  Lu  Yanhui  Wan  Peng  Yang  Yizhong  Wyckhuys  Kris A. G.  Wu  Kongming 《Journal of pest science》2015,88(1):49-56

Journal of Pest Science - Trap cropping is a useful tool in sustainable pest management. Trap crops usually target a single species or genus of insect pests. In this study, we assessed the...  相似文献   

Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field     

Kris Broos  Lynne M. Macdonald  Michael St. J. Warne  Mary B. Barnes  Mike J. McLaughlin 《Soil biology & biochemistry》2007,39(10):2693-2695

The size of the soil microbial biomass carbon (SMBC) has been proposed as a sensitive indicator for measuring the adverse effects of contaminants on the soil microbial community. In this study of Australian agricultural systems, we demonstrated that field variability of SMBC measured using the fumigation-extraction procedure limited its use as a robust ecotoxicological endpoint. The SMBC varied up to 4-fold across control samples collected from a single field site, due to small-scale spatial heterogeneity in the soil physicochemical environment. Power analysis revealed that large numbers of replicates (3-93) were required to identify 20% or 50% decreases in the size of the SMBC of contaminated soil samples relative to their uncontaminated control samples at the 0.05% level of statistical significance. We question the value of the routine measurement of SMBC as an ecotoxicological endpoint at the field scale, and suggest more robust and predictive microbiological indicators.  相似文献   

The use of reclaimed water in electric power stations and other industrial facilities     

K. Anthony Selby  Paul R. Puckorius  Kris R. Helm 《Water, air, and soil pollution》1996,90(1-2):183-193

There has been much recent progress in the use of reclaimed water (treated municipal sewage plant effluent) for use in the cooling circuits of electric utility plants and other industrial facilities. In the greater Los Angeles area, reclaimed water has been used industrially for over 25 years but some major new projects have been initiated in 1995. By using reclaimed water, electric utility generating stations and other industrial facilities can reduce their need for water from higher quality water sources which can then be conserved for other purposes, such as municipal drinking water. This paper presents an overview of the factors required to successfully use reclaimed water as makeup to recirculating cooling systems. The primary focus is on the possible effects on equipment relative to corrosion, deposition and biological fouling and on the required changes in water treatment. Implementation of the use of this water in some new projects began in May 1995. The paper provides some of the latest available results on the use of this water. The pretreatment process for ammonia removal and chlorination practices is also discussed.  相似文献   

Congenital diffuse hyperplastic goiter associated with perinatal mortality in 11 captive-born bottlenose dolphins (Tursiops truncatus).     

Michael M Garner  Carol Shwetz  Jan C Ramer  James M Rasmussen  Kris Petrini  Daniel F Cowan  James T Raymond  Gregory D Bossart  Gregg A Levine 《Journal of zoo and wildlife medicine》2002,33(4):350-355

Diffuse hyperplastic goiter was diagnosed by histopathology in 11 perinatal bottlenose dolphins (Tursiops truncatus) that died at four separate zoos and aquaria. Thyroid morphology of these animals was compared with the histologically normal thyroids of two stranded wild bottlenose dolphin calves, a neonate and a 2-mo-old calf. Histologic changes included reduced follicular luminal diameter, markedly reduced or absent luminal colloid, hypertrophy of follicular epithelium, and follicular dysplasia. The etiology of the thyroid gland lesion was not identified. Cause of death was not determined for most of these animals, but they were presumed to have died from metabolic derangements associated with the thyroid lesion, drowning, or dystocia.  相似文献   

Comparison of temporospatial and kinetic variables of walking in small and large dogs on a pressure-sensing walkway     

Kim J  Kazmierczak KA  Breur GJ 《American journal of veterinary research》2011,72(9):1171-1177

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Physics. The best materials for tiny, clever sensors     

Van Hoof C  Baert K  Witvrouw A 《Science (New York, N.Y.)》2004,306(5698):986-987

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Effects of gas-supersaturated water on Rana catesbeiana tadpoles     

John Colt  Kris Orwicz  Dale Brooks 《Aquaculture (Amsterdam, Netherlands)》1984,38(2):127-136

Rana catesbeiana tadpoles were exposed to gas supersaturated water which resulted in inflation of the gastrointestinal tract with gas. Affected tadpoles floated on the surface, either with their left sides elevated or on their backs. These clinical signs, similar to those of gas bubble disease, could be reversed by reducing the dissolved gas levels. Based on post-exposure observation for 30 days, a 4-day exposure to a ΔP of 160 to 170 mm Hg had no effect on survival. A 10-day exposure increased mortality and the levels of systemic Aeromonas hydrophila bacteria, the etiology of a serious amphibian disease, “Redleg”. Bacterial levels returned to control levels after a 6-day recovery period.  相似文献   

Albert Eric Mercker honored     

Kris P. Bemis 《American Journal of Potato Research》1955,32(10):394-395

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