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11.
17β-estradiol and testosterone are naturally occurring steroids that co-occur in poultry litter. The effects of litter on sorption of these hormones to soil are not known. Sorption isotherms were developed for C-labeled testosterone and H-labeled estradiol in a Cecil sandy clay loam with and without poultry litter addition. The effect of applying the hormones alone (single-sorbate) or together (multisorbate) was also investigated. C-testosterone sorption in soil increased from 2 to 48 h and remained relatively constant thereafter. H-estradiol sorption in soil was relatively constant from 2 to 24 h and then decreased to 72 h. These differences may reflect transformation of the parent hormones to products with different solid-phase affinity. The maximum sorption coefficient () in soil for C-testosterone (20.2 mL g) was similar to that for H-estradiol (19.6 mL g) in single-sorbate experiments. When hormones were applied together, sorption of both hormones in soil decreased, but the C-testosterone (12.5 mL g) was nearly twice as large as the H-estradiol (7.4 mL g). We propose this resulted from competition between the hormones and their transformation products for sorption sites, with C-testosterone and its expected transformation product (androstenedione) being better competitors than H-estradiol and its expected transformation product (estrone). When poultry litter was mixed with soil, sorption increased for H-estradiol but decreased for C-testosterone. This may have been because poultry litter slowed the transformation of parent hormones. Our results show that poultry litter could have important effects on the mobility of estradiol and testosterone.  相似文献   
12.
Romeis, J. Joshua, C. Rhett Jackson, L. Mark Risse, Andrew N. Sharpley, and David E. Radcliffe, 2011. Hydrologic and Phosphorus Export Behavior of Small Streams in Commercial Poultry‐Pasture Watersheds. Journal of the American Water Resources Association (JAWRA) 1‐19. DOI: 10.1111/j.1752‐1688.2011.00521.x Abstract: Few watershed‐scale studies have evaluated phosphorus export in streamflow from commercial poultry‐pasture operations. Continuous streamflow and mixed‐frequency water quality datasets were collected from nine commercial poultry‐pasture (AG) and three forested (FORS) headwater streams (2.4‐44 ha) in the upper Etowah River basin of Georgia to estimate total P (TP) loads and examine variability of hydrologic response and water quality of storm and nonstorm‐flow regimes. Data collection duration ranged from 18 to 22 months, and approximately 1,600 water quality samples were collected. Significant (p < 0.1) inverse relationships were detected between peak flow response variables and both drainage area and fraction of forest cover. Order‐of‐magnitude differences in TP and dissolved reactive P (DRP) concentration were observed between AG and FORS sites and among AG sites. TP yields of FORS sites ranged from 0.01 to 0.1 kg P/ha. Yields of AG sites ranged from 0.031 to 3.17 kg P/ha (median = 0.354 kg P/ha). With 95% confidence intervals, AG yields ranged from 0.025 to 13.1 kg P/ha. These small‐watershed‐scale yields were similar to field‐scale yields measured in other studies in other regions. TP yields were significantly related to area‐weighted Mehlich‐1 soil test P concentrations (p = 0.0073) and base‐flow water sample P concentrations (p 0.0005). Water quality sampling during base‐flow conditions may be a useful screening tool for P risk‐based management programs.  相似文献   
13.
Abstract:  Studies on riparian buffers have usually focused on the amount of land needed as habitat for the terrestrial life stages of semiaquatic species. Nevertheless, the landscape surrounding wetlands is also important for other key processes, such as dispersal and the dynamics of metapopulations. Multiple elements that influence these processes should therefore be considered in the delineation of buffers. We analyzed landscape elements (forest cover, density of roads, and hydrographic network) in concentric buffers to evaluate the scale at which they influence stream amphibians in 77 distinct landscapes. To evaluate whether our results could be generalized to other contexts, we determined whether they were consistent across the study areas. Amphibians required buffers of 100–400 m of suitable terrestrial habitat, but interspecific differences in the amount of habitat were large. The presence of amphibians was related to roads and the hydrographic network at larger spatial scales (300–1500 m), which suggests that wider buffers are needed with these elements. This pattern probably arose because these elements influence dispersal and metapopulation persistence, processes that occur at large spatial scales. Furthermore, in some cases, analyses performed on different sets of landscapes provided different results, which suggests caution should be used when conservation recommendations are applied to disparate areas. Establishment of riparian buffers should not be focused only on riparian habitat, but should take a landscape perspective because semiaquatic species use multiple elements for different functions. This approach can be complex because different landscape elements require different spatial extents. Nevertheless, a shift of attention toward the management of different elements at multiple spatial scales is necessary for the long-term persistence of populations.  相似文献   
14.
A Global Baseline for Spawning Aggregations of Reef Fishes   总被引:1,自引:0,他引:1  
Abstract: Species that periodically and predictably congregate on land or in the sea can be extremely vulnerable to overexploitation. Many coral reef fishes form spawning aggregations that are increasingly the target of fishing. Although serious declines are well known for a few species, the extent of this behavior among fishes and the impacts of aggregation fishing are not appreciated widely. To profile aggregating species globally, establish a baseline for future work, and strengthen the case for protection, we (as members of the Society for the Conservation of Reef Fish Aggregations) developed a global database on the occurrence, history, and management of spawning aggregations. We complemented the database with information from interviews with over 300 fishers in Asia and the western Pacific. Sixty‐seven species, mainly commercial, in 9 families aggregate to spawn in the 29 countries or territories considered in the database. Ninety percent of aggregation records were from reef pass channels, promontories, and outer reef‐slope drop‐offs. Multispecies aggregation sites were common, and spawning seasons of most species typically lasted <3 months. The best‐documented species in the database, the Nassau grouper (Epinephelus striatus), has undergone substantial declines in aggregations throughout its range and is now considered threatened. Our findings have important conservation and management implications for aggregating species given that exploitation pressures on them are increasing, there is little effective management, and 79% of those aggregations sufficiently well documented were reported to be in decline. Nonetheless, a few success stories demonstrate the benefits of aggregation management. A major shift in perspective on spawning aggregations of reef fish, from being seen as opportunities for exploitation to acknowledging them as important life‐history phenomena in need of management, is urgently needed.  相似文献   
15.
16.
Germplasm collection is important to preserve and maximize genetic diversity for germplasm conservation. Tsuga dumosa ( D. Don) Eichler in Engler & Prantl. and T. chinensis var. forrestii (Downie) Silba germplasm was collected from three localities in China: Mt. Yulong, Wenfeng Temple and Mt. Dishiergu, Yunnan Province. Accessions were identified based on morphological characters and RAPD markers. The shapes of the apices and margins of needles were examined, and the length and width of needles, cones and seeds from accessions of mature plants were used to compare the morphological differences and to identify the germplasm. Molecular markers generated by randomly amplified polymorphic DNA (RAPD) were also used to characterize the taxa. Although the clustering based on RAPD markers was inconsistent with the morphological characters of the needles, based on the overall morphological characters and on RAPD markers, the accessions from Mt. Yulong and Wenfeng Temple were identified as T. chinertsis var. forrestii, and those from Mt. Dishiergu identified as T. dumosa. Taxonomic identification of the accessions was made based on morphology and by RAPD markers concurred. The results indicate that the shapes of the apices and margins of needles particularly from young plants could not be used as a possible key to identify T. dumosa and T. chinertsis var. forrestii. Fig 6, Tab 3, Ref24  相似文献   
17.
不同植被对工业污染区盐渍土的改良效果   总被引:1,自引:0,他引:1  
以包头市西郊工业污染区盐渍化弃耕地为对象,研究了不同植被对土壤水盐动态和体积质量的影响。研究表明,造林后使林地内草本植物得到较快恢复,且归还土壤的枯落物比木本植物多,改良盐渍土壤和促进脱盐的作用较好;随植被盖度增加,盐渍土土壤含盐量和体积质量降低,盐渍土性状逐步改善。因此,在实施以耐盐树种造林为先导的工业污染区盐渍土恢复植被工程时,应适当降低造林密度,以利于林地内草本植物的恢复和建立林草复合植被,提高工业污染区盐渍土的生物治理效果。  相似文献   
18.
Abstract: Bumble bees are a group of pollinators that are both ecologically and economically important and declining worldwide. Numerous mechanisms could be behind this decline, and the spread of parasites from commercial colonies into wild populations has been implicated recently in North America. Commercial breeding may lead to declines because commercial colonies may have high parasite loads, which can lead to colonization of native bumble bee populations; commercial rearing may allow higher parasite virulence to evolve; and global movement of commercial colonies may disrupt spatial patterns in local adaptation between hosts and parasites. We assessed parasite virulence, transmission mode, and infectivity. Microparasites and so‐called honey bee viruses may pose the greatest threat to native bumble bee populations because certain risk factors are present; for example, the probability of horizontal transmission of the trypanosome parasite Crithidia bombi is high. The microsporidian parasite Nosema bombi may play a role in declines of bumble bees in the United States. Preliminary indications that C. bombi and the neogregarine Apicystis bombi may not be native in parts of South America. We suggest that the development of molecular screening protocols, thorough sanitation efforts, and cooperation among nongovernmental organizations, governments, and commercial breeders might immediately mitigate these threats.  相似文献   
19.
Preventing groundwater contamination is vastly cheaper than remediation. Recognizing this, attention in water and land management agencies in North America increasingly turn to groundwater protection. Local agencies, such as municipalities and watershed management districts, are vital to successful groundwater protection, but they face daunting challenges. In the United States, senior governments have recognized these challenges and provide considerable support for local agencies. In Ontario, Canada, local agencies are, to a much greater extent, on their own. The aims in this paper are to analyze factors that shape local capacity for groundwater protection, focusing on Ontario, and to recommend avenues for capacity building. Interrelationships among five dimensions of capacity (technical, financial, institutional, social, and political) are explored through an analysis of three smaller Ontario communities: City of Guelph (population 93,400), Town of Orangeville (population 22,188), and Town of Erin (population 11,000). Size clearly influences capacity for groundwater protection. However, other considerations unrelated to size appear to be as important. These other factors include the ability to form horizontal and vertical linkages with external agencies, political leadership and commitment, and citizen involvement. Thus, smaller communities in Ontario (and other jurisdictions with limited senior government support) would do well to focus on these areas at the same time as they develop their technical, financial, and institutional capacity.  相似文献   
20.
This paper examines the changing trends in world tin demand for the period 1962–1985. In the early 1970s tin production peaked, and has since declined. The reasons for the decline are examined in terms of changes in product composition of income (i.e. mix of goods and services), changes in material composition of products, decline in gross domestic investment and the rising price of tin.  相似文献   
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