Compositional and structural differences in two laurel forest stands (windward and leeward) on Tenerife, Canary Islands     

José Ramón Arévalo  Guacimara González-Delgado  Beatriz Mora  José María Fernández-Palacios 《Journal of Forest Research》2012,17(2):184-192

The laurel forest of Anaga is the most emblematic community of the Canarian Archipelago. Restoration programs are being developed to increase laurel forest area on the island of Tenerife. Structural and spatial characteristics determine many aspects of the community, including regeneration patterns, disturbance level, stand history. In spite of the importance of this information for restoration, few quantitative studies have been conducted on laurel forest dynamics. We analyzed two stands of the Anaga laurel forest of different aspect. The main difference between the two sites was the wind exposure, one leeward and the other windward. Regeneration, spatial distribution of regeneration, tree species composition, asexual regeneration and environmental parameters were analyzed in three 50 × 50 m plots at each site. Both sites differ in important aspects such as species richness, species composition, asexual regeneration and dead tree composition, while they are not different in basal area, density, density of regeneration and density of dead trees. Both sites have had similar management in the last century. Asexual regeneration is able to maintain the present species composition, while sexual regeneration is able to offer future changes in the canopy composition. Regeneration strategies and the effect of some environmental characteristics should be considered in restoration programs.  相似文献   

Influence of tree size, reduced competition, and climate on the growth response of Pinus nigra Arn. salzmannii after fire     

Teresa Valor  Míriam Piqué  Bernat C. López  José Ramón González-Olabarria 《Annals of Forest Science》2013,70(5):503-513

Context

After wildfire, surviving trees are of major ecological importance as they can help in the post-fire regeneration process. Although these trees may be damaged, they may also benefit from reduced fuel hazard and competition. However, little is known about the long-term growth response of surviving trees.

Aims

This study aims to explain short- to long-term variations in the postfire growth of surviving black pines in an area burnt in 1994, focusing on levels of fire severity and tree sizes.

Methods

Relative basal area increments were used to detect time-course variations in postfire radial tree growth depending on fire severity. Linear mixed-effects models were used to describe the factors affecting postfire ring growth.

Results

In the short term, fire caused stronger reduction in growth in small trees with increasing bole char height. However, as time since fire increased, a positive effect of fire on growth due to reduced competition counteracted the short-term fire impacts. Indeed, small surviving trees demonstrated a surge in growth 15 years after the fire.

Conclusion

It was concluded that reduced competition might offset the short-term negative effects of fire in surviving black pines.  相似文献   

Genotype by climate interaction in the genetic evaluation for growing traits of Braunvieh cattle in Mexico     

Luis A. Saavedra-Jiménez  Rodolfo Ramírez-Valverde  Rafael Núñez-Domínguez  José G. García-Muñiz  Nicolas Lopez-Villalobos  Agustín Ruíz-Flores 《Tropical animal health and production》2013,45(7):1489-1494

The objective of this study was to determine the magnitude of genotype by climate interaction (GCI) in the national genetic evaluation for weaning (WW) and yearling (YW) weights of Mexican Braunvieh cattle. The numbers of performance records and animals in the pedigree were 12,364 and 25,173 for WW, and 7,991 and 18,072 for YW, respectively. Performance records were clustered based on climatological variables into: dry tropic (DT), wet tropic (WT), and temperate (TE) climates. Animal models were used to estimate genetic parameters and predict breeding values in each of the climates. Bivariate analyses were carried out for pairwise combinations of climates on each trait, considering the same trait in different climates as a different trait. Criteria to evaluate GCI were genetic correlations (r _g), correlations between predicted breeding values (r _BV), and frequencies of coincidence (FC) in the ranking of the top 25 sires. Results of comparisons between pairs of climates were variable, depending on specific cases. For WW, the r _g, r _BV, and FC ranged from ?0.36 to 0.84, ?0.60 to 0.97, and 0.16 to 0.92, respectively; whereas for YW, they fluctuated between 0.23 and 0.99, 0.33 and 1.00, and 0.60 and 1.00, respectively. For both traits, the results suggest absence of GCI between DT and TE; however, GCI was detected in the other pairs of climates, where WT was involved. To maximize genetic progress, the joint genetic evaluation should be performed only for animals with performance data in DT and TE, whereas a separated evaluation is suggested for animals with performance records generated under WT conditions.  相似文献   

Status of selenium and vitamin E on Norwegian organic sheep and dairy cattle farms     

Espen Govasmark  Arvid Steen  Turid Strøm  Sissel Hansen  Bal Ram Singh  Aksel Bernhoft 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(1):40-46

Herbage selenium (Se) concentration is generally low in Norway. It is unknown whether feeding practices on Norwegian organic farms fulfil the dietary needs of Se and vitamin E for sheep and dairy cattle. Therefore we analysed Se in soil and herbage, and Se and vitamin E in animal blood in the indoor feeding season at 14 organic dairy and 14 organic sheep farms. The herbage Se concentration was low. Approximately 50 and 35% of all samples in the first and second cut, respectively, had Se concentrations below the detection limit of 0.01 mg/kg dry matter (DM). The median (10th, 90th percentile) Se concentrations were <0.01 (<0.01, 0.03) and 0.02 (<0.01, 0.06) mg/kg DM in the first and second cuts, respectively. Whole blood Se concentrations were 0.10 (0.04, 0.15) μg/g in dairy cattle and 0.14 (0.03, 0.26) μg/g in sheep. Vitamin E concentrations were 4.2 (2.7, 8.4) mg/l in dairy cattle and 1.3 (0.9, 2.4) mg/l in sheep. None of the soil or plant variables explained the variation in herbage Se concentration, although Se in soil and plant tended to be correlated. Herbage Se concentration was inadequate to meet the dietary Se requirements. Vitamin E requirement was only met in dairy herds. We recommend Se and vitamin E supplementation to ruminants on organic farms.  相似文献   

Development of functional marker for distinguishing Glu-B3b allele of LMW-GS found in Indian common wheat cultivars     

Shikha Sharma  Sewa Ram  Ranjan Gupta  Indu Sharma 《Journal of Cereal Science》2013

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Soil carbon and nitrogen changes after clearing mulga (Acacia aneura) vegetation in Queensland,Australia: Observations,simulations and scenario analysis     

Miko U.F. Kirschbaum  Ben Harms  Nicole J. Mathers  Ram C. Dalal 《Soil biology & biochemistry》2008,40(2):392-405

In the work reported here we examine the changes in soil (organic) carbon and nitrogen that are observed after converting a stand of nitrogen-fixing mulga trees (Acacia aneura) to buffel-grass (Cenchrus ciliaris) pasture that contained no nitrogen-fixing legumes. A range of previously reported field measurements was compared against the output of CenW 3.1, a reformulated version of the CENTURY model.The model successfully reproduced the observed patterns of soil carbon, C:N ratios and nitrogen mineralisation rates under mulga vegetation. This included relatively small changes in carbon concentration down to 1 m, C:N ratios of around 11–13 across all soil depths, substantial nitrogen mineralisation rates to a depth of 90 cm and, after clearing, an on-going decrease in soil organic carbon and nitrogen stocks.Interpretation of experimental observations was made difficult by the addition of a large amount of ‘dead’ organic matter from killed mulga roots after clearance. This material may be excluded through sieving (to 2 mm) in measurements taken shortly after tree removal, but may be included in later-year sampling as the partly decomposed material might be able to pass through sieves. Past work has usually ignored consideration of dead coarse roots. For the site carbon budget, changes in live biomass and surface litter significantly outweighed the small changes in soil organic carbon, and changes in decaying coarse roots were quantitatively more important than changes in other organic carbon pools.Modelled nitrogen mineralisation rates were lower under buffel-grass than those under mulga and showed significant year-to-year variations that were in line with varying rainfall. It showed no consistent trend over the first 20 years after clearing because the effect of decreasing nitrogen stocks was balanced by an increase in organic matter quality with the change from lignin-rich mulga litter to buffel-grass litter with lower lignin concentration. Nitrogen mineralisation rates gradually decreased thereafter as nitrogen stocks continued to decrease but litter quality stabilised.A scenario analysis showed that soil carbon and nitrogen trends could be affected by changing the nitrogen budget through inclusion of legumes or cessation of nutrient removal by grazing animals. Inclusion of legumes was needed to halt the decline in soil nitrogen and to ensure the long-term maintenance, or increase, in nitrogen stocks.  相似文献   

Design of Optimum Response Surface Experiments for Electro-Coagulation of Distillery Spent Wash     

R. Krishna Prasad  R. Ram Kumar  S. N. Srivastava 《Water, air, and soil pollution》2008,191(1-4):5-13

Electro-coagulation (EC) of a distillery spent wash has been optimized by Box–Behnken design of surface response analysis in terms of color removal. The design was employed to derive a statistical model for the effect of parameters studied on removal of color using iron anodes. The current density (31 mA/cm²), dilution (17.5%) and time of electrolysis (4 hours) had been found to be the optimum conditions for maximum 95% color removal. The actual color removal at optimized conditions was found to be 93.5% which confirms close to the predicted response using response surface methodology.  相似文献   

Genetic Diversity Among Some Promising Indian Local Selections and Hybrids of Cashew Nut Based on Morphometric and Molecular Markers     

Ram C. Jena  Kailash C. Samal  Ajantaa Pal  Basant K. Das 《International Journal of Fruit Science》2016,16(1):69-93

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Natural Fluorescence of Red and White Wheat Kernels     

M. S. Ram  Larry M. Seitz  Floyd E. Dowell 《Cereal Chemistry》2004,81(2):244-248

Red and white wheats must be segregated for marketing purposes because they have different end uses. Identification of wheat color is not straightforward, and currently there is interest in characterizing red and white wheats using spectroscopic methods and chemical tests. The kernels of both red and white wheats exhibit natural fluorescence that can be readily viewed under UV light, although it is not possible to differentiate the fluorescence spectra of red and white wheats by visual inspection only. Fluorescence emission spectra in the wavelength range of 370–670 nm for 91 wheat samples consisting of 48 red (from 30 cultivars) and 43 white (from 18 cultivars) were analyzed by partial least squares (PLS) and neural networks analyses (NNA). Samples included cultivars that were difficult to classify visually as well as wheat harvested after rainfall. Classification accuracies were ≈85% for calibration and ≈72% for the validation samples by both analyses. A plot of β‐coefficient vs. wavelength in PLS analysis indicated that fluorescence of red wheat cultivars was greater than that for white wheat cultivars at 425 (±20) nm wavelength. Fluorescence of white wheat cultivars was greater than that for red cultivars at 587 (±35) nm. Fluorescence emission at ≈450 nm from wheat samples increased in intensity after treatment with NaOH. The increase was greater for red than for white wheat. Wheat harvested after rainfall also exhibited a slight increase in fluorescence.  相似文献   

Lipid Extraction from Wheat Flour Using Supercritical Fluid Extraction     

J. D. Hubbard  J. M. Downing  M. S. Ram  O. K. Chung 《Cereal Chemistry》2004,81(6):693-698

Environmental concerns, the disposal cost of hazardous waste, and the time required for extraction in current methods encouraged us to develop an alternate method for analysis of wheat flour lipids. Supercritical fluid extraction (SFE) with carbon dioxide has provided that medium and the method is fully automatic. Crude fats or nonstarch free lipids (FL) were extracted from 4–5 g of wheat flour by an SFE system. To develop optimum conditions for SFE, various extraction pressures, temperatures, and modifier volumes were tried to provide a method that would produce an amount of lipids comparable to those extracted by the AACC Approved Soxhlet Method and the AOCS Official Butt Method using petroleum ether as solvent. Using several wheat flour samples, the best conditions were 12.0 vol% ethanol (10.8 mol%) at 7,500 psi and 80°C to extract the amount of FL similar to those by the AACC and AOCS methods. Using solid‐phase extraction, lipids were separated into nonpolar lipid (NL), glycolipid (GL), and phospholipid (PL) fractions. The mean value of five flours was 1.15% (flour weight, db) by the SFE method, 1.07% by the Butt method, and 1.01% by the Soxhlet methhod. The SFE‐extracted lipids contained less NL and more GL than either the Butt or Soxhlet methods. All three methods extracted lipids with qualitatively similar components. The overall benefit for SFE over the Soxhlet or Butt methods was to increase the number of samples analyzed in a given time, reduce the cost of analysis, and reduce exposure to toxic chemicals.  相似文献