Effects of Historic Livestock Grazing on Vegetation at Chaco Culture National Historic Park, New Mexico

Abstract:   Livestock grazing is the most ubiquitous land use in western North America, yet it rarely has been studied in a controlled manner because of the lack of large areas free of grazing. We compared the ecological effects of three grazing treatments—long-term protection, short-term protection, and currently grazed—at Chaco Culture National Historic Park in northern New Mexico. Chaco has a long history of human habitation and is now one of the largest grazing exclosures in the American West. We studied the effects of livestock grazing on the cover of plants, soil crusts, and plant species richness at six sites with different potential natural vegetation. Species richness was higher under long-term protection than under current grazing at all six sites. Trends in shrub and grass response varied significantly across the six sites. Shrub cover increased with long-term protection at four upland sites, and grass cover increased with protection at four sites. The response of Chaco vegetation to release from grazing varied significantly according to each site's ecological potential, determined in part by edaphic and topographic characteristics. These nuances in vegetation response represent natural ecological variation and contrast with the notions of widespread shrub "invasion" often inferred in the past.     

Effects of ultraviolet radiation on skin structure and ultrastructure in Caspian Sea Salmon,Salmo trutta caspius,during alevin stage

Ozone reduction enhances the amount of ultraviolet (UV) radiation reaching the aquatic ecosystems, which can induce adverse effects on fish. In order to study the UV radiation effects on skin structure and ultrastructure, the alevins of Salmo trutta caspius were exposed to two different doses of UV radiation (low doses of: 60 µW cm^?2 UVC; 100 µW cm^?2 UVB; and 40 µW cm^?2 UVA and high doses of: 90 µW cm^?2 UVC; 130 µW cm^?2 UVB; and 50 µW cm^?2 UVA) for 15 min once a day in dark condition. Alevins with no exposure to either solar light or UV exposure served as the control group. No mortality was observed in the control group, whereas all of the alevins died in the 9th day in both UV exposure groups. Light microscopic and scanning electron microscopic studies showed significant reduction in the epidermis thickness, number of skin mucous cells, and percentage of mucus secreting cells in both UV exposure groups. Sunburn cells, lifting epidermis from basal membrane, and disappearance of pavement cell microridges were also observed. Our results showed that UV radiation caused intensive skin cell lesions in the Caspian salmon alevins. Since the skin cells of trout alevins possesses essential roles in respiration, osmoregulation, excretion and defense, the observed damages to the skin could be attributed to their sudden mortality in the UV exposure.     

Organochlorine residues in the avifauna of Tamil Nadu (Southeast coast of India)

Pollution due to persistent pesticides is not a regional but a global problem. Organochlorine pesticides are persistent chemicals, stored and accumulated in the tissues of a wide variety of invertebrates and vertebrates including marine species. In the present study the organochlorine residues HCHs, DDTs and PCBs were measured in different trophic groups of birds (scavengers, inland piscivores, coastal piscivores, insectivores, granivores and omnivores) collected from Tamil Nadu Coast, India. The residue accumulation as a function of sex did not depict distinct variation. However, females had lower residue levels than males in terms of their mean weight and feeding habits. A continuous monitoring programme is recommended to establish the studied organisms as indicator species.     

Effects of daily nickel intake on the bio-accumulation,body weight and length in tilapia (Oreochromis niloticus)

Nickel pollution is a serious environmental problem, and its effects may provoke alterations in the ecosystem and in organism of animals and humans. Dermatitis, eczema, and asthma are some illnesses caused by Ni²⁺ poisoning. In this work, fish fed either Ni²⁺-enriched pellets or commercial pellets were studied. The amount of Ni²⁺ in fish were measurements by adsorptive stripping voltammetry (AdSV) with dimethylglyoxime as a complexing agent. The analysis of Ni²⁺ in fish by AdSV established that its accumulation occurs principally in viscera (670.86 ± 5.82 µg g^?1), in the head (697.12 ± 2.77 µg g^?1) and in the muscle (405.82 ± 3.26 µg g^?1), both after 12 months of experiments. Ni²⁺ adsorbs preferentially in organs such as the stomach, the intestine, and the kidneys and acts in the central nervous system as well. Tilapia growth and mass were significantly affected by Ni²⁺ poisoning. From statistical analysis, observed that the results for lengths, weights and metal concentration were different for each sampling at significance level of p < 0.05. The Ni²⁺ concentration in tilapia was enough to cause the death of tilapias; however, it did not occur because the presence of Zn²⁺ might act as protective agent of heavy metals.     

Simulated Limnological Effects of the Shasta Lake Temperature Control Device

We estimated the effects of a temperature control device (TCD) on a suite of thermodynamic and limnological attributes for a large storage reservoir, Shasta Lake, in northern California. Shasta Dam was constructed in 1945 with a fixed-elevation penstock. The TCD was installed in 1997 to improve downstream temperatures for endangered salmonids by releasing epilimnetic waters in the winter/spring and hypolimnetic waters in the summer/fall. We calibrated a two-dimensional hydrodynamic reservoir water quality model, CE-QUAL-W2, and applied a structured design-of-experiment simulation procedure to predict the principal limnological effects of the TCD under a variety of environmental scenarios. Calibration goodness-of-fit ranged from good to poor depending on the constituent simulated, with an R ² of 0.9 for water temperature but 0.3 for phytoplankton. Although the chemical and thermal characteristics of the discharge changed markedly, the reservoir's characteristics remained relatively unchanged. Simulations showed the TCD causing an earlier onset and shorter duration of summer stratification, but no dramatic affect on Shasta's nutrient composition. Peak in-reservoir phytoplankton production may begin earlier and be stronger in the fall with the TCD, while outfall phytoplankton concentrations may be much greater in the spring. Many model predictions differed from our a priori expectations that had been shaped by an intensive, but limited-duration, data collection effort. Hydrologic and meteorological variables, most notably reservoir carryover storage at the beginning of the calendar year, influenced model predictions much more strongly than the TCD. Model results indicate that greater control over reservoir limnology and release quality may be gained by carefully managing reservoir volume through the year than with the TCD alone. RID=" ID=" Author to whom correspondence should be addressed. e-mail: John_Bartholow&commat;USGS.gov     

Area-Based Refinement for Selection of Reserve Sites with the Benefit-Function Approach

Abstract:  Optimization of resource use is necessary for efficient conservation planning. Many reserve-selection algorithms aim to identify representative but inexpensive networks, which may lead to selecting small sites due to their lower costs and collectively higher species richness. Nevertheless, larger sites would be preferable regarding species' long-term persistence. An area-based refinement can be used to overcome this problem. We used a reserve-planning framework in which continuous benefit functions valued representation (numbers of populations), and differential species weights were based on a species' local rarity and threatened status. We introduced a refinement based on the species-area relationship that provides relatively higher values for larger sites. We applied the proposed method to rich fen vegetation in southern Finland. The species-area refinement resulted in a network of significantly larger sites with minor trade-offs with representation (numbers of populations). Giving endangered species higher weights ensured that the trade-off occurred mostly between site size and representation of low-priority species. We recommend using a species-area refinement for practical, maximum-coverage conservation planning.     

Adsorption of methylene blue from aqueous solution by chemically treated water hyacinth

Water hyacinth (WH), an aquatic plant macrophyte, was investigated for its ability to perform as a suitable adsorbent for methylene blue (MB) from aqueous solution. The non-living biomass of WH was subjected to several chemical treatments, namely, washing with hot water, washing with hot dilute HCl, soaking in NaOH, soaking in HNO₃, and sulfonation. The system variables studied also include pH and MB concentration. The Langmuir isotherm was found to represent the measured adsorption data well except for WH soaked in NaOH, which was found to be better represented by the Freundlich isotherm. Values of the dimensionless separation factor, K _R, indicated that the adsorption systems in this study are all favorable. Values of the first layer of adsorption were calculated by the non-linear multilayer adsorption model, and the specific surface area values were found to be high and comparable to commercially activated carbons.