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41.
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Understanding local perceptions of degradation and attitudes to fire management are critical for gaining support for restoration work and improving livelihoods. Deforestation and annual burning are causing significant land degradation problems in the area around Bandawe, northern Malawi. We mapped evidence of soil erosion and remaining areas of woodland. Gully erosion was common and primarily associated with heavily utilised footpaths. Areas between gullies showed signs of significant soil movement. Remnant patches of native woodland existed but were small, degraded and isolated. We interviewed local households to understand local awareness and impacts of land‐degradation, its perceived cause and preferred methods for restoration. All households were aware of the presence of gullies and reported associated problems of flood damage. Most households believed erosion was a result of deforestation. Burning practices were seen to have exacerbated erosion problems. Changing fire management practice was not seen as realistic as it risked reducing the productivity of grasses and fires were perceived to be too difficult to control. Tree planting was the community's preferred approach to tackling erosion. Their focus was on planting exotic fruit and timber trees around houses and they often requested that such work be done by volunteers. Such attitudes may have been influenced by recent extension work and a desire to secure ownership of utilisable resource. Ecologists in the miombo zone should focus on improving fire management practices and involving communities in creating diverse secondary woodlands that provide a range of goods and services. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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In domestic wastewater, bacterial physiology controls cell production (growth, replication) and cell maintenance, determining how energy is allocated between these two processes. The aim here was to develop a method to quantify these cellular processes so that the bacterial physiological state could be manipulated to lower this source of pollution. We simultaneously used the incorporation of radiolabelled thymidine into DNA (a measure of new cell synthesis) and leucine into protein in wastewater to quantitatively distinguish bacterial growth from maintenance processes. We found that DNA and protein syntheses were coupled in wastewater after substrate enrichment (with glucose or acetate)??balanced growth. Once the substrate was depleted, the two processes became uncoupled??unbalanced growth. In this physiological state, the bacteria were synthesising protein, but fewer bacteria were replicating. More energy was allocated to cell maintenance than replication. A mean Leu/TdR ratio of 7.4 was determined for wastewater and was similar to natural aquatic ecosystems. As the bacterial growth rate decreased, the Leu/TdR ratios increased. We show how the simultaneous measurement of [3H]Leu and [3H]TdR quantitatively distinguishes balanced from unbalanced growth. Low [3H]Leu/[3H]TdR ratios indicated bacteria were physiologically stressed, an ideal state for biological wastewater treatment processes (WWTP) as the bacteria divert more energy to maintenance activities instead of growth. Leu/TdR ratios of 70 have been recorded in natural aquatic ecosystems which suggests WWTP have potential to be manipulated to achieve much higher Leu/TdR ratios than we report here. Changes to plant operation to improve operation efficiency include finding the optimum rate of substrate (pollution supply) or alternating aerobic and anaerobic periods to maximise the Leu/TdR ratio to achieve less biomass production for land disposal and more cost-effective operation that generates less pollution in the effluent. 相似文献
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Aldair JW Pinto Maria M Figueiredo Fabiana L Silva Trycia Martins Marilene SM Michalick Washington L Tafuri Wagner L Tafuri 《Acta veterinaria Scandinavica》2011,53(1):67
Background
The aim of this study was to provide a systematic pathological and parasitological overview of the gastrointestinal tract (GIT), including the stomach, duodenum, jejunum, ileum, caecum and colon, of dogs naturally infected with Leishmania.Methods
Twenty mongrel dogs naturally infected with Leishmania (Leishmania) infantum and obtained from the Control Zoonosis Center of the Municipality of Ribeirão das Neves, Belo Horizonte Metropolitan area, Minas Gerais (MG) state, Brazil, were analyzed. The dogs were divided into two groups: Group 1 comprised nine clinically normal dogs and group 2 comprised 11 clinically affected dogs. After necropsy, one sample was collected from each GIT segment, namely the stomach, duodenum, jejunum, ileum, caecum and colon. Furthermore, paraffin-embedded samples were used for histological and parasitological (immunohistochemistry) evaluation and a morphometrical study were carried out to determine the parasite load (immunolabeled amastigote forms of Leishmania). The Friedman and the Mann Whitney tests were used for statistical analysis. The Friedman test was used to analyze each segment of the GIT within each group of dogs and the Mann Whitney test was used to compare the GIT segments between clinically unaffected and affected dogs.Results
The infected dogs had an increased number of macrophages, plasma cells and lymphocytes, but lesions were generally mild. Parasite distribution in the GIT was evident in all intestinal segments and layers of the intestinal wall (mucosal, muscular and submucosal) irrespective of the clinical status of the dogs. However, the parasite load was statistically higher in the caecum and colon than in other segments of the GIT.Conclusion
The high parasite burden evident throughout the GIT mucosa with only mild pathological alterations led us to consider whether Leishmania gains an advantage from the intestinal immunoregulatory response (immunological tolerance). 相似文献45.
Burke JM Whitley NC Pollard DA Miller JE Terrill TH Moulton KE Mosjidis JA 《Veterinary parasitology》2011,181(2-4):345-349
The objective of three experiments was to determine the impact of supplementing sericea lespedeza (Lespedeza cuneata; SL) in three concentrations in a loose or pelleted diet on gastrointestinal nematodes (GIN) in small ruminants. Experiments on lambs were conducted at the USDA, Agricultural Research Service in Booneville, AR (Exp. 1) and at Louisiana State University in Baton Rouge, LA (Exp. 2); an experiment on goat kids occurred at University of Maryland-Eastern Shore (Exp. 3). Exp. 1 used crossbred hair sheep lambs naturally infected with GIN that were randomly allocated to diets containing 0, 25, 50, and 75% SL diets (n=11 or 12/diet). Exp. 2 consisted of Haemonchus contortus-inoculated crossbred wool breed lambs that were blocked by gender and FEC and randomly assigned to 0, 25, 50, or 75% SL diet (n=8/diet). Fecal egg counts (FEC) and blood packed cell volume (PCV) were not influenced by SL supplementation in Exp. 1 and 2. Exp. 3 consisted of naturally GIN infected Boer crossbred goat kids in individual pens. Kids were blocked by FEC and randomly allotted to treatments of 0, 20, 40, or 60% SL with 9-13 goats/diet. The more SL fed, the greater the reduction in FEC (P<0.001). There was an increase in PCV in SL fed goats (P<0.001). Larval speciation at the end of the experiment indicated that feces from control animals produced 43% H. contortus larva while 20, 40 and 60% SL resulted in 39%, 35% and 31% H. contortus larvae, respectively. Feeding dried SL may be less effective in lambs than kids, though concurrent studies must be conducted to confirm this. 相似文献
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Investigations were conducted on several small neighbouring beef cattle and sheep farms that were found to be contaminated with polychlorinated biphenyls (PCBs). The residues detected contained about 62% w/w chlorine and soil concentrations ranged from 0.35 to 1.9 mg/kg. Beef cattle and sheep grazing the contaminated land had PCB concentrations in their fat of 0.3 to 1.7 mg/kg and 0.19 to 0.45 mg/kg, respectively. The concentration of PCBs in the caudal fat of cattle was 0.3 to 2 times the concentration of PCBs in the land they were grazing and was positively related to stocking rates. PCBs were present in milk fat from cattle at about the same concentration as in caudal fat, and lactation appeared to contribute to decontamination. Wool grease from sheep contained about 1 to 2 times the concentration of PCBs in subcutaneous fat. Calves of contaminated cows also became contaminated. The half-life for decontamination of PCBs in a group of 8 young female beef cattle was calculated at 13 months. PCBs were detected in pasture samples at concentrations ranging from less than 0.01 mg/kg to 0.12 mg/kg. However, PCBs were not detected in any sample of hay cut from these paddocks. In 4 sheep fed a sole ration of this hay, traces of PCBs were detected in their fat following 89 days of feeding. Grazing livestock for meat production on land contaminated with PCBs is not recommended because livestock readily acquire residues, and PCBs persist in soil and livestock for long periods. Grazing sheep for wool production on land contaminated with PCBs may be an option. 相似文献
50.
David J. Lieske Megan MacIntosh Lee Millet Soren Bondrup-Nielsen J. Bruce Pollard Glen Parsons Nic R. McLellan G. Randy Milton Frances MacKinnon Kevin Connor Lauren K. Banks 《Landscape Ecology》2018,33(1):35-57