Soil Physicochemical Changes Following Buffelgrass Establishment in Mexico     

Fernando Ibarra-Flores  Jerry R. Cox  Martha Martin-Rivera  Todd A. Crowl  Brien E. Norton  Roger E. Banner 《Arid Land Research and Management》2013,27(1):39-52

Clearing brush from rangeland and seeding it to buffelgrass (Cenchrus ciliaris L.) is a popular range improvement practice in Mexico, but no data are available on the effects of these practices on soil properties. Twenty-nine study sites were randomly selected across 3 major climatic regions in Mexico: 13 in the northwest, 11 in the northeast, and 5 in the southeast. Soils under buffelgrass stands more than 10 years old and on adjacent virgin rangelands were sampled at 0-10, 10-20, and 20-30 cm depths to quantify sand, silt, clay, organic C, total N, pH, EC, CEC, available P, and exchangeable Ca2+, Mg2+, Na+, and K+.Because soil variables were not significantly (P 0.05) different among depths, only data from the surface horizon received further analysis. Soils in the northwest had higher (P 0.05) sand content and were particularly low in total N (0.08%), Ca2+, and K+, while soils of wetter and warmer southeast Mexico were significantly (P 0.05) higher than the other two regions in measures of soil fertility such as organic C (10 times higher), total N, and CEC (both at least 3 times higher). Long-term buffelgrass establishment had the most effect on soils in the southeast and no significant effect (P0.1) on soils of northeast Mexico. Soil organic C and total N both declined (P 0.025) by about 40% under buffelgrass pastures in the southeast; excgangeable Ca2+ decreased (P=0.027) by 21% in the same region, and Mg2+ declined (P=0.03) by 36% under buffelgrass in the northwest. Soil P did not respond to buffelgrass establishment. The findings of this study suggest that high forage yields following conversion of rangeland to buffelgrass pasture will be less sustainable in subtropical regions with high rainfall (mean of 1070 mm in this study) than in the semiarid zone with inherently poorer soils.  相似文献   

Antibacterial activity of plant extracts obtained with alternative organics solvents against food-borne pathogen bacteria     

Martha MendezRaúl Rodríguez  Judith RuizDiana Morales-Adame  Francisco CastilloFrancisco D. Hernández-Castillo  Cristóbal N. Aguilar 《Industrial Crops and Products》2012,37(1):445-450

The objectives of this study were: the chemical characterization of extracts from seven plants (Larrea tridentata, Flourensia cernua, Lippia graveolens, Agave lechuguilla, Yucca filifera, Opuntia ficus-indica, and Carya illinoensis) which are acclimated to the Mexican semi-desert. The extracts were obtained using Soxhlet method by water, ethanol and an infusion method using alternative organic solvents (lanolin and cocoa butter), in addition it was evaluated the antibacterial activity of semi-desert plant extracts against Enterobacter aerogenes, Escherichia coli, Salmonella typhi and Staphylococcus aureus. Chemical characterization of plant extracts showed that they are rich in secondary metabolites; cocoa butter was the non-conventional solvent which it was possible to obtain the highest content of total tannins. It was not possible to identify saponins in those extracts where non conventional solvents were used. While in extract where non conventional solvents were used, it was only possible to detect the presence of terpenes in creosote bush and prickly pear extracts. S. aureus was the bacterial strain that showed the highest growth inhibition as consequence of the plant extracts. The use of semi-desert plant extracts obtained using organic solvents are a good alternative for food-borne pathogen bacteria control because all the bacterial growth decreased with the tested extracts.  相似文献   

Incorporation of dietary nitrogen from fish meal and pea meal (Pisum sativum) in muscle tissue of Pacific white shrimp (Litopenaeus vannamei) fed low protein compound diets     

Luis Martínez‐Rocha  Julián Gamboa‐Delgado  Martha Nieto‐López  Denis Ricque‐Marie  Lucía Elizabeth Cruz‐Suárez 《Aquaculture Research》2013,44(6):847-859

Stable isotope analyses were applied to explore the relative dietary nitrogen contributions from fish meal and pea meal (Pisum sativum) to muscle tissue of Pacific white shrimp postlarvae (141 ± 31 mg) fed low protein diets having different proportions of both ingredients as the sole dietary protein sources. A negative control diet was formulated to contain 100% pea meal and six more isoproteic diets to have decreasing levels of pea meal‐derived nitrogen: 95%, 85%, 70%, 55%, 40% and 0% of the initial level. Growth rates were negatively correlated to dietary pea protein inclusion due to progressive essential amino acid deficiencies (sulphur amino acids, threonine, lysine, histidine). The nitrogen turnover rate significantly increased in muscle tissue of shrimps fed diets having high levels of pea meal; however, contrary to observations from a previous study using soy protein, the relative contributions of dietary nitrogen from pea meal to shrimp muscle tissue were equal or higher than expected contributions established by the dietary formulations. Results highlight the effectiveness of stable isotope analysis in assessing the nutritional contributions of alternative ingredients for aquaculture feeds and the potential suitability of pea as a source of protein (provided the diets are nutritionally balanced).  相似文献   

Local and systemic gene expression of sesquiterpene phytoalexin biosynthetic enzymes in plant leaves     

Luis David Maldonado-Bonilla  Martha Betancourt-Jiménez  Edmundo Lozoya-Gloria 《European journal of plant pathology / European Foundation for Plant Pathology》2008,121(4):439-449

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Effects of Mexican dwarf mistletoe (Arceuthobium vaginatum subsp. vaginatum) on the growth of Pinus cooperi in Durango,Mexico—A case study     

Martha Gonzlez‐Elizondo  Mnica Yazmín Flores‐Villegas  Rebeca lvarez‐Zagoya  M. Socorro Gonzlez‐Elizondo  Marco A. Mrquez‐Linares  Sergio Quionez‐Barraza  Brian E. Howell  Robert L. Mathiasen 《Forest Pathology》2019,49(1)

Mexican dwarf mistletoe (Arceuthobium vaginatum subsp. vaginatum, Viscaceae) is the most widespread and damaging parasitic plant in Mexico. It parasitizes 10 species of pines (Pinus spp., Pinaceae) as principal hosts, including Pinus cooperi, one of the economically most important pines in the state of Durango. As a case study, we used stem analysis to estimate the effects of Mexican dwarf mistletoe on volume and height growth of dwarf mistletoe‐infected P. cooperi in western Durango (Ejido El Brillante, Municipality Pueblo Nuevo). This case study sampled a total of 48 trees, 12 in each of four infection classes estimated using the 6‐class dwarf mistletoe rating system (DMR): uninfected (DMR 0), lightly infected (DMR 1–2), moderately infected (DMR 3–4) and severely infected (DMR 5–6). Significant reductions in both volume and height growth were found for moderately and severely infected trees when compared to uninfected trees. On average, reductions in volume growth and height growth were as high as 50% and 17%, respectively. The largest growth reductions were for moderately infected trees, but large growth reductions also occurred for severely infected trees. Because of the reduced growth associated with moderate to severe infection, Mexican dwarf mistletoe‐infested pine forests in Durango, where timber production is a high priority, should be managed using harvesting practices that reduce dwarf mistletoe infection, and thereby, increase forest productivity.  相似文献   

Succession and management of tropical dry forests in the Americas: Review and new perspectives     

Mauricio Quesada  G. Arturo Sanchez-Azofeifa  Mariana Alvarez-Añorve  Kathryn E. Stoner  Luis Avila-Cabadilla  Julio Calvo-Alvarado  Alicia Castillo  Mario M. Espírito-Santo  Marcilio Fagundes  Geraldo W. Fernandes  John Gamon  Martha Lopezaraiza-Mikel  Deborah Lawrence  Leonor Patricia Cerdeira Morellato  Jennifer S. Powers  Frederico de S. Neves  Victor Rosas-Guerrero  Roberto Sayago  Gumersindo Sanchez-Montoya 《Forest Ecology and Management》2009

Understanding tropical forest succession is critical for the development of tropical forest conservation strategies worldwide, given that tropical secondary forests can be considered the forests of the future. Tropical dry forests (TDF) are among the most threatened tropical ecosystems, there are more secondary forests and forest restoration efforts that require a better understanding of successional processes. The main goal of this synthesis for this special issue on the ecology and management of tropical dry forests in the Americas is to present a summarized review of the current knowledge of the ecology and management implications associated to TDF succession. We explore specific issues associated to tropical dry forest succession with emphasis on the use of chronosequences, plant diversity and composition, plant phenology and remote sensing, pollination, and animal–plant interactions; all under the integrating umbrella of ecosystem succession. We also emphasize the need to conduct socio-ecological research to understand changes in land-use history and its effects on succession and forest regeneration of TDF. We close this paper with some thoughts and ideas associated with the strong need for an integrating dimension not considered until today: the role of cyberinfrastructure and eco-informatics as a tool to support sound conservation, management and understanding of TDF in the Americas.  相似文献   

Can the Land Use Master Plan Control Urban Expansion and Protect Farmland in China? A Case Study of Nanjing          下载免费PDF全文

Zinan Shao  Tejo Spit  Zhifeng Jin  Martha Bakker  Qun Wu 《Growth and change》2018,49(3):512-531

Urbanization represents a challenge for plans aimed at controlling urban expansion and protecting farmland, such as the land use master plan (LUMP) instituted by the Chinese national government. This paper studies the effectiveness of such top–down plans under the authoritarian regime through the case study of Nanjing. In contrast to previous studies that compare actual and planned land‐use maps, we compare actual and planned land‐use patterns. We use land‐use change data to examine spatio‐temporal land‐use change between the years 1997 and 2014. The results indicate that the actual amount of urban‐rural built‐up land exceeded planned regulatory amount by 50,185 ha and the total farmland was 70,541 ha less than the target outlined in the LUMP (1997–2010). Based on these results, and the fact that the allowed total urban‐rural built‐up land had already been surpassed in 2014, it is to be expected that the target of farmland protection outlined in the LUMP (2006–2020) will be broken, signaling the ineffectiveness of the plan to control urban expansion and protect farmland. Plan‐led developments (e.g., new towns, development zones) and market forces (e.g., housing market, foreign direct investment) explain these developments. This study indicates that when cities embrace “growth‐led” development and entrepreneurial governance, the ability of plans to control urban expansion and protect farmland is severely limited.  相似文献   

Genomic prediction of the general combining ability of maize lines (Zea mays L.) and the performance of their single crosses          下载免费PDF全文

Marcelina Vélez‐Torres  José Jesús García‐Zavala  Martha Hernández‐Rodríguez  Ricardo Lobato‐Ortiz  José Jesús López‐Reynoso  Ignacio Benítez‐Riquelme  José Apolinar Mejía‐Contreras  Gilberto Esquivel‐Esquivel  Paulino Pérez‐Rodríguez  Xuecai Zhang 《Plant Breeding》2018,137(3):379-387

The objective of this study was to assess the effectiveness of genomic selection (GS) on predicting the general combining ability (GCA) of maize lines and the performance of their single crosses. Eight maize lines developed from the different self‐pollination generations of Chalqueño race, along with their 24 single crosses, were evaluated in the field during the years of 2011, 2012 and 2013. Genomic prediction results using genotyping‐by‐sequencing‐based single nucleotide polymorphisms showed that the GCA classification of the parental lines estimated from the SNP information was consistent with the phenotypic classification of the lines evaluated from the field trial data. The prediction accuracy values estimated from the cross‐validation method ranged from 0.49 to 0.61 in the different prediction models. Yield performance of the unevaluated single crosses was predicted based on their SNP information. The total genetic variance of the yield of the single crosses was most explained by the GCA effects. Compared with phenotyping method, GS is a more effective and efficient approach to predict the GCA of maize lines and their hybrid performance.  相似文献   

Copper,Zinc-Superoxide Dismutase Activity in Exercising Horses Fed Two Forms of Trace Mineral Supplements     

Elizabeth L. Wagner  Gary D. Potter )  Pete G. Gibbs  Elena M. Eller  Brett D. Scott  Martha M. Vogelsang  Rosemary L. Walzem 《Journal of Equine Veterinary Science》2010

Nine mature horses were used to evaluate superoxide dismutase (SOD) response to a low-intensity standard exercise test and the effect of copper (Cu) and zinc (Zn) supplement form on enzyme activity. The modified switchback experiment was conducted over seven 28-day periods. Horses were conditioned to perform an average daily workload of 3.93 kg∗km∗10⁻³ with a digestible energy (DE) demand of approximately 29 Mcal. Following a controlled Cu and Zn repletion-depletion diet sequence, horses were fed a diet intended to be marginally deficient in Cu and Zn with the minerals supplemented in either sulfate or organic chelate forms. Horses were then subjected to a standardized exercise test to enable evaluation of SOD activity during exercise and immediate recovery. In the final analyses, mineral contents of the experimental diets were significantly different (P < .05). The mean mineral concentration of the sulfate diet was 6.28 ppm Cu and 35.99 ppm Zn, while the chelate diet contained 23.62 ppm Cu and 90.67 ppm Zn. Even so, resting SOD activity was not altered by diet (1793.47 ± 323.00 U/g Hb for the sulfate diet, 1355.70 ± 148.32 U/g Hb for the organic-chelate diet), nor did SOD activity change in response to the low-intensity workout. The SOD activity was unchanged by feeding a Cu and Zn supplemented diet to horses fed to be in a mineral-deficient state. These exercise bouts did not appear to have a significant impact on SOD activity. Other types of oxidative stress should be considered when trying to evaluate the antioxidant responsiveness of this enzyme.  相似文献   

Sorghum growth,root responses,and soil‐solution aluminum and manganese on pH‐stratified sandy soil§     

Gregory Miller  Martha Mamo  Rhae Drijber  Charles Wortmann  Roger Renken 《植物养料与土壤学杂志》2009,172(1):108-117

A stratified subsurface layer of acidic soil can develop in minimally disturbed soil such as no‐till receiving injection of N fertilizer (e.g., anhydrous ammonia). The objective of this study was to evaluate the effectiveness of subsurface band treatments in alleviating soluble Al³⁺ and Mn²⁺ toxicities on sorghum growth. Soil columns 40 cm in length were packed with soil (Valentine fine sand mixed mesic Typic Ustipsamment and Thurman loamy sand mixed Mesic Udorhentic Haplustoll) with treatments applied at the 10–18 cm depth to mimic soil pH stratification. The treatments at this depth were: (1) entire layer at soil pH of 3.7; (2) band of soil 6 cm wide at pH of 5.8 with the rest of the soil at pH 3.7; (3) band of soil 6 cm wide at pH of 6.3 with the rest of the soil at pH 3.7; and (4) entire layer at soil pH of 5.8. The soil above and below the 10–18 cm depth was at pH 5.8. Sorghum (Sorghum bicolor L. Moench) was grown in the soil columns under a controlled environment for 6 weeks. High concentration of Al in soil solution was found in soil at soil pH 3.7 which was overcome by either banding to pH 5.8, 6.3, or having the soil layer at pH 5.8. Treatment with pH of 5.8 throughout the soil 10–18 cm depth produced significantly greater top growth, although all other pH or liming strategies performed better than the soil pH 3.7 treatment. The banded treatments at pH 5.8 and 6.3 allowed roots to grow below the 10–18 cm layer of soil, but root growth was still significantly less than in the soil where the entire soil treatment layer was at pH 5.8. The increase in biomass yield with soil pH of 5.8 in the entire treatment layer was higher compared to band treatment at pH 5.8; however, the lime requirement would be 3.4 times more with liming the entire layer compared to banding a portion of the soil to pH 5.8 and would thus be translated into a higher liming cost.  相似文献