Carbon in Amazon forests: unexpected seasonal fluxes and disturbance-induced losses   总被引：1，自引：0，他引：1  

Saleska SR  Miller SD  Matross DM  Goulden ML  Wofsy SC  da Rocha HR  de Camargo PB  Crill P  Daube BC  de Freitas HC  Hutyra L  Keller M  Kirchhoff V  Menton M  Munger JW  Pyle EH  Rice AH  Silva H 《Science (New York, N.Y.)》2003,302(5650):1554-1557

The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarém, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites.  相似文献   

Evaluation of Metal Loadings and Bioavailability in Air, Water and Soil Along Two Highways of British Columbia, Canada     

Humberto F. Preciado  Loretta Y. Li 《Water, air, and soil pollution》2006,172(1-4):81-108

A comprehensive multi-media monitoring field investigation, which included: atmospheric, storm-water runoff, road sediment and soil samples, was carried out at two highway sites in Vancouver, Canada, focused on Cu, Fe, Pb, Mn, and Zn, due to their prevalence in most highway environments, both locally and worldwide. Metal potential bioavailability was evaluated through sequential extraction in the case of particulates and via exchange with a chelating resin for highway runoff. Road sediment showed in most cases a close resemblance with runoff and atmospheric metal concentrations (Fe > Zn > Mn > Cu > Pb), suggesting that road sediment is a useful indicator of current metal loadings and a key factor influencing the quality of urban watersheds. Metals showed increasing bioavailability with decreasing particle size in all samples. Thus, bioavailability was low in roaddust and roadside soils, intermediate in dustfall, and highest in atmospheric suspended particulates and runoff. Speciation analyses in different environmental media suggested that Zn is a metal of future potential concern. Zinc was second in concentration to Fe in most dust, air and water samples, and exhibited the highest mobility and potential bioavailability.  相似文献   

Substitution of Chaetoceros muelleri by Spirulina platensis meal in diets for Litopenaeus schmitti larvae     

Barbarito J. Jaime-Ceballos  Alfredo Hernndez-Llamas  Tsai Garcia-Galano  Humberto Villarreal 《Aquaculture (Amsterdam, Netherlands)》2006,260(1-4):215-220

The nutritional response of Litopenaeus schmitti larvae to substitution of Chaetoceros muelleri by Spirulina platensis meal (SPM) was evaluated. The substitution levels (S) were 0%, 25%, 50%, 75% and 100%, dry weight basis. Final larval length (FL) ranged from 1.98 to 3.16 mm for the different substitution levels. There was a significant relationship between S and FL, described by the following quadratic equation: FL = 2.853 + 0.01598S − 0.000233S². The substitution level (S) yielding maximum FL was 34.2%. Development index (DI) values ranged from 2.84 to 3.93 and were dependent on substitution level. The corresponding equation was DI = 3.799 + 0.00945S − 0.000189S² (P < 0.01). Maximum DI was obtained at 25.0% substitution. Survival was high (82–87%) and no significant differences were found between treatments. Protein digestibility of either microalgae was high, with 92% for SPM and 94% for C. muelleri, with no significant differences between them. The results in this study indicate that an adequate balance of nutrients in relation to the requirements of the species is critical. To simultaneously improve FL and DI, a 30% substitution of C. muelleri by SPM is suggested. This is equivalent to feeding 0.15 mg larvae^− 1 day^− 1 dry weight basis of a 70% C. muelleri/30% SPM diet, representing 0.078 mg protein larvae^− 1 day^− 1, 0.026 mg lipids larvae^− 1 day^− 1 and 2.732 J larvae^− 1 day^− 1.  相似文献   

In vivo dry matter and protein digestibility of three plant-derived and four animal-derived feedstuffs and diets for juvenile Australian redclaw, Cherax quadricarinatus     

Alfredo Campa  a-Torres  Luis R. Martinez-Cordova  Humberto Villarreal-Colmenares  Roberto Civera-Cerecedo 《Aquaculture (Amsterdam, Netherlands)》2005,250(3-4):748-754

Dry matter and protein digestibility of three plant-derived and four animal-derived feedstuffs and diets in which they were included were evaluated for juvenile Australian redclaw. The ingredients evaluated were: soy paste, textured wheat, sorghum meal, two sardine meals (67% and 58% crude protein), squid meal, and red crab meal. A reference diet was formulated and produced in the CIBNOR nutrition laboratory. Seven experimental diets were then made including 15% of each ingredient in the reference diet. The experiment consists of a single-factor, completely randomized design with five replicates per treatment. Digestibility was measured indirectly, using chromic oxide as a marker. Plant-derived ingredients and the corresponding diets had, in general, a higher digestibility than animal ingredients. Soy paste and sorghum meals, and the diets in which they were included, showed an excellent dry matter (over 87%) and protein (approximately 90%) digestibility. Some of the animal ingredients such as sardine meal 67% CP and squid meal had a good dry matter digestibility (over 80%), but were significantly lower than plant-derived ingredients. The lowest dry matter and protein digestibility was recorded for sardine meal 58% CP and red crab meal. It is concluded that juvenile redclaw are omnivorous and able to efficiently consume diets containing plant- and animal-derived ingredients, but they can digest plant-derived ingredients more efficiently.  相似文献   

Nutritive value of squid and hydrolyzed protein supplement in shrimp feed   总被引：4，自引：0，他引：4  

Julio Humberto Crdova-Murueta  Fernando Luis García-Carreo 《Aquaculture (Amsterdam, Netherlands)》2002,210(1-4):371-384

Though some protein sources like squid and protein hydrolysates are assumed as growth enhancers for shrimp, little is known about the biochemical basis of this phenomenon. Low, heat-dried squid (Dosidicus gigas) (SQ) and two commercial protein hydrolysates from fish (FH) and krill (Euphasia sp.) (KH) were assayed in feeding trials with Penaeus vannamei. Feeds were prepared with the tested proteins at 3%, 9%, and 15% of the total crude protein. A total of nine experimental feeds plus a commercial one as control (C32) were tried. Additionally, digestibility in vivo and in vitro was evaluated. Survival was not different among groups. Weight gain of shrimp and total and specific proteolytic activity for trypsin and chymotrypsin were affected by type and quantity of supplemented protein. In vivo and in vitro digestibilities were also influenced by the source and quantity of the protein supplement. Shrimp fed feed with FH at 3% protein supplementation grew more than those fed with higher supplementations. Groups fed SQ had similar results as those fed FH, and gained more weight when fed the lowest SQ quantity. SDS-PAGE showed a large concentration of small peptides in SQ, which may explain results similar to FH. KH enhanced shrimp growth at all supplementations and had a lower degree of hydrolysis (DH) than FH. SQ also demonstrated good growth performance, but better at the lower supplementation, probably because of the presence of small peptides and possibly free amino acids from protein hydrolyzed by endogenous enzymes in the squid mantle. We conclude that hydrolyzed protein is a good supplement for shrimp feeds, but it must meet specific requirements for adequate assimilation.  相似文献   

A Partial Energy Budget for the Australian Crayfish Cherax tenuimanus   总被引：5，自引：0，他引：5  

Humberto  Villarreal 《Journal of the World Aquaculture Society》1991,22(4):252-259

The freshwater crayfish Cherax tenuimanus (marron) has been attracting an increasing degree of attention for aquaculture due to its high growth rate and large harvest size. In this study some important parameters related to the physiological energetics of C. tenuimanus were defined in a series of independent experiments.
Food consumption by marron increased when fed a variety of foods, providing up to 29 joule/g dry wt crayfish per hour. Mean energy content of feces was 7, 941 joule/g dry wt representing up to 17% of ingested food while excreted energy was not important in the overall budget. Metabolic requirements per hour were 5.4 joule/g dry wt. Gross conversion efficiency was up to 58% for the experimental diets. This ability gives the species a marked advantage for commercial culture over other related species with more subdued growth efficiencies.  相似文献   

The use of pasture reflectance characteristics and arbuscular mycorrhizal root colonization to predict pasture characteristics of tallgrass prairie grazed by cattle and bison     

M. Villarreal  R. C. Cochran†  D. E. Johnson‡  E. G. Towne§  G. W. T. Wilson§  D. C. Hartnett§  D. G. Goodin¶ 《Grass and Forage Science》2006,61(1):32-41

An experiment was conducted to evaluate the potential for using arbuscular mycorrhizal fungal (AMF) root colonization and pasture reflectance characteristics as indicators of changes in tallgrass prairie vegetation resulting from differences in grazing history. The experiment was conducted within the context of a separate long‐term experiment in which eight 4·9‐ha pastures were grazed by either bison or cattle for nine consecutive years. Two separate ungrazed pastures were selected for comparison with grazed areas on the basis of similarity in burning regime, vegetation, soil and topographic characteristics. Four 45 m‐long transects were located in the upland sites within each pasture, and four plots were clipped to ground level along each transect. Reflectance readings were taken with a hand‐held radiometer at each sampling location and a soil core was collected within each plot for analysis of AMF root colonization. Reflectance readings at sixteen different wavelengths were used directly as inputs during multiple regression development or were transformed into each of three vegetation indices (normalized difference vegetation index, soil‐adjusted vegetation index and wide‐dynamic‐range vegetation index) and used in simple linear regressions. Ungrazed pastures were characterized by higher (P < 0·01) grass biomass, total biomass and canopy height than grazed pastures, but had a lower proportional abundance of forbs (P < 0·01) and amounts of forb biomass (P = 0·04). Species of herbivore did not significantly influence above‐ground characteristics that were measured. In general, AMF root colonization was relatively small and was not significantly affected by treatment and, accordingly, the variation was insufficient to test its potential as an indicator of grazing effects on vegetation or its potential relationship with pasture reflectance. Multiple regression equations based on individual wavelength reflectance values explained significantly more of the variation in above‐ground vegetation characteristics than did simple regressions using vegetation indices as predictor variables (r² values from 0·36 to 0·46 vs. 0·11 to 0·27) and have the potential to predict above‐ground vegetation characteristics in heterogeneous rangelands.  相似文献   

Assessment of the phenotypic diversity in natural populations of Annona coriacea Mart.: implications for breeding     

de Sousa  Samara Raquel  Costa  Marcones Ferreira  Filho  Carlos Humberto Aires Matos  Vasconcelos  Lúcio Flavo Lopes  de Araújo  Ademir Sérgio Ferreira  Castro  Antonio Alberto Jorge Farias  de Farias  Ruth Raquel Soares  Ferreira-Gomes  Regina Lucia  de Almeida Lopes  Ângela Celis 《Genetic Resources and Crop Evolution》2022,69(3):1121-1135

Genetic Resources and Crop Evolution - Annona coriacea Mart. is a native tree to the savannas of Brazil that produces fruits that have economic, ecological, and dietary potential for use by local...  相似文献   

PRECODEPA,a successful model for a new concept in Regional Cooperation for International Agricultural Development     

John S. Niederhauser  Manuel Villarreal 《American Journal of Potato Research》1986,63(4):237-240

  相似文献   

Soybean drought-stressed plants impair Anticarsia gemmatalis (Lepidoptera: Erebidae) midgut proteolytic activity and survival     

Faustino  Verônica Aparecida  de Almeida Barros  Rafael  da Silva Júnior  Neilier Rodrigues  Barbosa  Samuel Lessa  Vital  Camilo Elber  da Silva  Felipe Lopes  Cabrera  Yaremis Beatriz Meriño  Campos  Wellington Garcia  de Oliveira Ramos  Humberto Josué  de Almeida Oliveira  Maria Goreti 《Phytoparasitica》2021,49(4):491-500

Phytoparasitica - Soybean plants are exposed to multiple stresses during development. Co-occurring stresses can activate common defense pathways on plants, increasing end products concentrations,...  相似文献