Accuracy of methods for field assessment of rill and ephemeral gully erosion   总被引：1，自引：0，他引：1  

J. Casalí  J. LoizuM.A. Campo  L.M. De SantistebanJ. Álvarez-Mozos 《CATENA》2006

To properly assess soil erosion in agricultural areas, it is necessary to determine precisely the volume of ephemeral gullies and rills in the field by using direct measurement procedures. However, little information is available on the accuracy of the different methods used. The main purpose of this paper is to provide information for a suitable assessment of rill and ephemeral gully erosion with such direct measurement methods. To achieve this objective: a) the measurement errors associated to three methods used for field assessment of channel cross sectional areas are explored; b) the influence of the number of cross sections used per unit channel length on the assessment accuracy, is analysed and; c) the effect of the channel size and shape on measurement errors is examined. The three methods considered to determine the cross sectional areas were: the micro-topographic profile meter (1); the detailed measurement of section characteristic lengths with a tape (2); and the measurement of cross section width and depth with a tape (3). Five reaches of different ephemeral gully types 14.0 or 30.0 m long and a set of six 20.4 to 29.4 m long rill reaches were selected. On each gully reach, the cross sectional areas were measured using the three above mentioned methods, with a separation (s) between cross sections of 1 m. For rills, the cross sectional areas were measured with methods 1 and 3, with s = 2 m. Then, the corresponding total erosion volumes were computed. The volume calculated with method 1 with s = 1 m for gullies and s = 2 m for rills was taken as the reference method. For each channel, and for each one of the possible combinations of s and measurement method (m), the relative measurement error and the absolute value of the relative measurement error (E_sm^r and |E_sm^r|), defined with respect to the reference one, was calculated. |E_sm^r| much higher than 10% were obtained very easily, even for small s values and for apparently quasi prismatic channels. Channel size and shape had a great influence on measurement errors. In fact, the selection of the more suitable method for a certain gully shape and size seemed to be much more important than s, at least when s < 10 m. Method 1 always provided the most precise measurements, and its results were the less dependent on s. However, s must be < 5 m to guarantee an error smaller than 10%. Method 2 is not recommended, because it is difficult, time consuming and can lead to large errors. Method 3 seems to be enough for small, wide and shallow gullies, and for small rills, but only if s is shorter than 5 m. Results obtained after the analysis of rill measurement errors were similar to those of gullies. The analysis of E_sm^r and |E_sm^r| when calculating channel volumes using a unique representative cross section highlighted the importance of correctly selecting the adequate cross section. Due to the high error values that this method can entail, it is not considered as advisable whenever accurate erosion measurements are pursued.  相似文献   

Earth-Based Observations of the Galileo Probe Entry Site     

G Orton  JL Ortiz  K Baines  G Bjoraker  U Carsenty  F Colas  A Dayal  D Deming  P Drossart  E Frappa  J Friedson  J Goguen  W Golisch  D Griep  C Hernandez  W Hoffmann  D Jennings  C Kaminski  J Kuhn  P Laques  S Limaye  H Lin  J Lecacheux  T Martin  G McCabe  T Momary  D Parker  R Puetter  M Ressler  G Reyes  P Sada  J Spencer  J Spitale  S Stewart  J Varsik  J Warell  W Wild  P Yanamandra-Fisher  G Fazio  J Hora  L Deutsch 《Science (New York, N.Y.)》1996,272(5263):839-840

Earth-based observations of Jupiter indicate that the Galileo probe probably entered Jupiter's atmosphere just inside a region that has less cloud cover and drier conditions than more than 99 percent of the rest of the planet. The visual appearance of the clouds at the site was generally dark at longer wavelengths. The tropospheric and stratospheric temperature fields have a strong longitudinal wave structure that is expected to manifest itself in the vertical temperature profile.  相似文献   

Cancer epigenetics and methylation     

Esteller M  Fraga MF  Paz MF  Campo E  Colomer D  Novo FJ  Calasanz MJ  Galm O  Guo M  Benitez J  Herman JG 《Science (New York, N.Y.)》2002,297(5588):1807-8; discussion 1807-8

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GC-MS determination of isoflavonoids in seven red Cuban propolis samples     

Campo Fernández M  Cuesta-Rubio O  Rosado Perez A  Montes De Oca Porto R  Márquez Hernández I  Piccinelli AL  Rastrelli L 《Journal of agricultural and food chemistry》2008,56(21):9927-9932

In the present study, the phenolic composition analysis of seven red varieties of propolis, collected in different regions of Cuba, was evaluated by gas chromatography/mass spectrometry (GC-MS). Seventeen compounds were identified in all samples by the interpretation of their mass spectra. This appears to be the first report on the GC-MS analysis of isoflavonoids in the propolis. The results confirmed the presence of the main isoflavonoids isolated previously and suggested the general structure for the other five isoflavonoids. Vestitol, 7-O-methylvestitol, and medicarpin were present in high amounts in all propolis samples analyzed. This result indicates that propolis samples rich in isoflavonoids are not exclusively found in Pinar del Rio province and proves that GC-MS technique is a useful and alternative tool for the chemical analysis of tropical red propolis.  相似文献   

Connecting Small Farmers in the Caribbean to Knowledge,Networks, and Institutions Through ICTs     

Kenia-Rosa Kinda Campo  Anton Robinson  Wayne Ganpat 《Journal Of Agricultural & Food Information》2017,18(2):81-95

Information and communication technologies (ICTs) have been shown to be useful in agricultural knowledge systems to improve communication linkages among research, extension services, and farmers. The end result would be new information and technologies being made available to those who need it the most in larger numbers and in a timelier manner. While the role of ICTs in stimulating technological, organizational, institutional, and policy innovations in developing countries has been recognized, in many Caribbean States where ICTs are becoming readily available, the development and use of ICT in agricultural research and innovation systems remain underexploited, despite the fact that the agricultural sector in these developing nations accounts for a significant amount of the total employed labor force. This article traces key developments in ICT use in the agricultural sector in the Caribbean region, while highlighting the challenges as well as the potential of this technology. Several initiatives in the region are described and suggestions made for the development of innovative, appropriate, and efficient information and communication systems.  相似文献