Impact of Prosopis (mesquite) invasion and clearing on vegetation species composition and diversity in semi-arid Nama-Karoo rangeland,South Africa     

Thabisisani Ndhlovu  Suzanne J Milton  Karen J Esler 《African Journal of Range and Forage Science》2016,33(2):101-110

The Nama-Karoo biome occupies 28% of South Africa’s land area. Alien leguminous trees of the genus Prosopis have invaded large tracts of Nama-Karoo rangeland. We evaluated the impact of Prosopis invasion and clearing on vegetation species composition and diversity (alien and indigenous species richness and cover) in Nama-Karoo rangeland on two sheep farms in the Beaufort West district of the Western Cape province of South Africa. Our results suggest that Prosopis invasion and clearing can significantly change Nama-Karoo rangeland species composition. Invasion and clearing appear to have no effect on alien species richness. Invasion, however, increases alien species cover, while clearing restores it to pre-invasion levels. In contrast, invasion reduces indigenous species richness while clearing restores it to pre-invasion levels. Invasion appears to have no effect on indigenous species cover. This lack of effect appears to be the serendipitous result of a site-specific trade-off between a decline in cover of grasses that are negatively affected by Prosopis invasion and a concomitant increase in the cover of positively affected grasses. Clearing increases indigenous species cover to above pre-invasion levels. The higher than usual indigenous species cover after clearing could be a transient legacy of Prosopis soil nutrient enrichment.  相似文献   

Vegetation dynamics after experimental fire disturbance in the arid Succulent Karoo,South Africa     

Helga van der Merwe  Sebataolo Rahlao  Liesel Hein  Suzanne J Milton 《African Journal of Range and Forage Science》2016,33(2):131-135

Disturbance by fire in the Succulent Karoo is rare but fire events could increase as a result of an increase in grassiness (alien and indigenous species). This study assessed the effects of fire eight years after an experimentally induced burn in Succulent Karoo vegetation. Post-fire monitoring was conducted using the line intercept method and species counts per plot (1 m²) for each of three fire disturbance treatments: control/unburnt, high and low fuel load. Vegetation cover and abundance were compared across treatments and growth forms. Vegetation cover and abundance on fire-disturbed plots had not returned to pre-fire levels after eight years. Resprouters exhibited a rapid recovery and early dominance on burnt plots. Succulent seedlings established slower, but after eight years occurred at higher densities on the burnt than control plots. Recovery after disturbance of density and cover of long-lived, woody non-resprouter non-succulents was slow relative to resprouting non-succulents and reseeding succulents. This study of vegetation change following fire disturbance in an arid system highlights the slow return of canopy cover, immediate regrowth of only two resprouter species and slower re-establishment by seed of non-resprouter species. In addition, fire disturbance led to the numerical dominance of succulents within the first decade after the fire.  相似文献   

Polymorphisms within the prolactin and growth hormone/insulin-like growth factor-1 functional pathways associated with fertility traits in Holstein cows raised in a hot-humid climate     

Leyva-Corona  Jose C.  Reyna-Granados  Javier R.  Zamorano-Algandar  Ricardo  Sanchez-Castro  Miguel A.  Thomas  Milton G.  Enns  R. Mark  Speidel  Scott E.  Medrano  Juan F.  Rincon  Gonzalo  Luna-Nevarez  Pablo 《Tropical animal health and production》2018,50(8):1913-1920

Tropical Animal Health and Production - Prolactin (PRL), growth hormone (GH), and insulin-like growth factor-1 (IGF-1) are in hormone-response pathways involved in energy metabolism during...  相似文献   

Environmental Mercury Rising     

Ainza  Carlos  Trevors  Jack  Saier  Milton 《Water, air, and soil pollution》2008,205(1):47-48

Water, Air, & Soil Pollution -  相似文献   

Solventless Microextraction Techniques for Determination of Trihalomethanes by Gas Chromatography in Drinking Water     

Milton Moreano Rosero  Mauricio Aguirre  Davinson Pezo  Gonzalo Taborda  Carmen Dussán  Cristina Nerin 《Water, air, and soil pollution》2012,223(2):667-678

Three different solventless sample preparation techniques based on microextraction, membrane extraction, and headspace extraction have been developed and optimized for determination of trihalomethanes in drinking water by gas chromatography electron capture detector and mass spectrometry detection. The techniques employed were headspace (HS) solid-phase microextraction, hollow fiber liquid-phase microextraction (HFLPME) and HS extraction. All techniques used were optimized with different experimental designs in order to select the most relevant variables which significantly affect the different processes. The different analytical figures of merit such as limit of detection (LOD), limit of quantification, reproducibility, accuracy, and linear dynamic range were obtained. The new HFLPME method applied used a hollow fiber membrane of polypropylene and the optimized variables were extraction time, extraction temperature, and salting-out effect. The software MODDE 6.0 was used and its design was one central composite on face with a total of 17 runs. The best conditions for the HFLPME were 20 min, 40°C, and 10% NaCl, respectively. The LODs ranged from 0.018 μg·L⁻¹ (for CHClBr₂) to 0.049 μg·L⁻¹ (for CHBr₃), being this technique the most sensitive one among those studied. Finally, after having optimized the sample preparation techniques and chromatographic conditions, several water samples were taken in two different water treatment plants in Spain (Zaragoza) and Colombia (Viterbo, Caldas). The results obtained are shown and discussed.  相似文献   

Bioinformatic Analyses of Bacterial Mercury Ion (Hg2+) Transporters     

Timothy Mok  Jonathan S. Chen  Maksim A. Shlykov  Milton H. Saier Jr 《Water, air, and soil pollution》2012,223(7):4443-4457

Currently, there are five known types of mercury transporters in bacteria: MerC, MerE, MerF, MerH, and MerT. Their general function is to mediate mercuric ion uptake into the cell in preparation for reduction to Hg°. They are present in several bacterial phyla and comprise five distinct families. We have utilized standard statistical bioinformatic tools and the superfamily principle to show that they are related by common descent. After using programs such as Global Alignment Program and SSearch to establish homology, we aligned and analyzed their amino acid sequences to find a single well conserved motif. Although these proteins exhibit 2, 3, or 4 transmembrane helical segments (TMSs), TMSs 1 and 2 are common to all superfamily members. An ancestral sequence was determined, and reliable phylogenetic trees were constructed. The results support the conclusion of homology, establishing that these proteins belong to a single superfamily. This important discovery allows extrapolation of information about structure, function, and mechanism from one protein to all superfamily members to degrees inversely proportional to their phylogenetic distances.  相似文献   

Neotropical small mammals’ diversity in the early cycle of commercial Eucalyptus plantations     

Luís M. Rosalino  Paula S. Martin  Carla Gheler-Costa  Paula C. Lopes  Luciano M. Verdade 《Agroforestry Systems》2014,88(3):427-436

Studies carried out in Brazil revealed that Eucalyptus plantations shelter numerous species of small-size non-flying mammals. However, their distribution pattern inside the Eucalyptus plantations remains unknown. This study aimed at the identification of possible influence of distances from the remaining native revegetation areas and riparian systems, on spatial distribution and abundance of small-size mammals in Eucalyptus plantations. This study was carried at Eucalyptus stands recently planted (0–3 years) at the municipality of Angatuba, Sao Paulo state, Brazil between August 2007 and July 2009. The survey was carried out using pitfall traps at 14 sampling units inside Eucalyptus plantations 60–1130 m away from the borders. With a sampling effort of 2,449 bucket night, the experiment captured 680 individuals belonging to 12 species of small-size mammals (rodents and marsupials). The colonization process of Eucalyptus plantations was apparently initiated by generalist species from open Cerrado. In the present study, we did not find any clear correlation between specific richness and abundance of individuals and the distance from native revegetation areas or closer riparian systems. The study suggests that Eucalyptus plantations are permeable matrices to, at least, more generalist species present in the silvicultural landscapes (i.e. composed by an Eucalyptus plantation as the matrix and native vegetation patches). However, further studies must prioritize analyzing the influence of agricultural/sivilcultural practices (e.g., plantation structure and harvest frequency) on habitat quality and carrying capacity of agricultural/silvicultural landscape matrices, as well as implementing long-term monitoring programs to assess the impact of complete production cycles (some years) and along cycles of Eucalyptus plantations (some decades), on rodents population’s diversity and dynamics patterns.  相似文献   

Environmental Mercury Rising     

Carlos Ainza  Jack Trevors  Milton Saier 《Water, air, and soil pollution》2010,205(1):47-48

  相似文献   

Soil fungal isolates produce different organic acid patterns involved in phosphate salts solubilization     

Jose Martin Scervino  Milton Prieto Mesa  Ivana Della Mónica  Marina Recchi  Nubia Sarmiento Moreno  Alicia Godeas 《Biology and Fertility of Soils》2010,46(7):755-763

Phosphorus availability is a major limiting factor for yield of most crop species. The objective of this study was to compare the solubilization of three sources of phosphorus (P) by different fungal isolates and to determine the possible mechanisms involved in the process. Talaromyces flavus (S73), T. flavus var flavus (TM), Talaromyces helicus (L7b) and T. helicus (N24), Penicillium janthinellum (PJ), and Penicillium purpurogenum (POP), fungal strains isolated from the rhizosphere of crops, are known to be biocontrol agents against pathogenic fungi. The P solubilization efficiency of these fungal strains in liquid media supplemented either with tricalcium phosphate (Ca₃(PO₄)₂; PC), aluminum phosphate (AlPO₄; AP), or phosphorite (PP) depended on the source of P and the fungal species. The type and concentration of organic acids produced by each species varied according to the source of available P. In the medium supplemented with PC, the highest proportion was that of gluconic acid, whereas in the media supplemented with the other P sources, the highest proportion was that of citric and valeric acids. This suggests that the release of these organic compounds in the rhizosphere by these microorganisms may be important in the solubilization of various inorganic P compounds. Results also support the hypothesis that the simultaneous production of different organic acids by fungi may enhance their potential for solubilizing insoluble phosphate.  相似文献   

Effects of season and agro-ecological zone on the microbial quality of raw milk along the various levels of the value chain in Uganda     

Patrice Grimaud  Mohamed Sserunjogi  Milton Wesuta  Nelly Grillet  Moses Kato  Bernard Faye 《Tropical animal health and production》2009,41(6):883-890

Dairy production in Uganda is pasture-based and traditional Ankole cattle make up 80% of the cattle herd, reared in both pastoral and agro-pastoral ecological zones. Regardless of the zone, milk quality is lowest in production basin during the dry season when ambient temperatures are highest and water is scarce. Poor hygiene and quality management contributed to the deterioration of raw milk quality during its storage and delivery to the final consumer, and concealed the seasonal effect when milk reached urban consumption areas. Poor milk quality is a challenge for the Ugandan Dairy Development Authorities who wish to make the milk value chain safe. This study provides baseline information for the implementation of an HACCP-based system to ensure the hygienic quality of milk from the farm to the market place.  相似文献