This posting will look at three of Greg Asner’s publications from nearly a decade ago. By analyzing the articles and the references cited, I hope to answer two of the questions from the introduction.
Can you see any patterns in their literature use?
Where might they systematically look for information?
Each article will be briefly summarized, clarified, and then references will be analyzed. Please note that I am summarizing the articles to the best of my ability (practicing geologist 1988 -1998); moreover, any technical glitches are mine and mine alone – they should not be attributed to the study subject.
Spectrometry of pasture conditions
Most of the previous “remote sensing studies of the Amazon Basin have focused on land-cover changes.” This study was concerned with the composition of the soil and plant matter. The question proposed – “Are there alternative biophysical remote sensing measurements that could be made in the dry season to indicate time-integrated canopy and biogeochemical processes?” Several study sites were chose; physical samples of the soil were collected and analyzed. Next the canopy structure was analyzed using spectrometry [measurement of wavelengths of light or other electromagnetic radiation]. Specifically, the plant area index was determined and then shortwave reflective data was collected along a transect [a predetermined study area]. Then reflective data collected was used in a photon transport model. [A model is a highly specific piece of computer software that predicts on outcome based on the data given – like the models used to predict weather.] The report concluded that photon transport modeling “provided a physically consistent way to convert the data to canopy structural attributes.” The study also found that the older pastures and those with coarser soil texture (e.g. sandy) had lower levels of carbon and nitrogen; moreover, potassium also decreased with age of the pasture. The authors concluded that their method of using hyperspectral reflectance data and photon transport inverse modeling” showed promise and with the deployment of new space born imagers the results could get even better.
Asner, G. P., Townsend, A. R. & Bustamante, M. M. C. (1999). Spectrometry of pasture condition and biogeochemistry in the Central Amazon Basin. Geophysical Research Letters, 26 (17), 2769-2772. Retrieved February 3, 2009 from Google Scholar.
The references for the above article include eight journals, one technical report and one book on soil analysis. The journals included Remote Sensing of Environment, Geoderma, Oecologia, BioScience, Journal of Quantative Spectroscopy and Radiative Transfer, Agricultural and Forest Meterology, Science, and Annual Review of Ecology Systematics. Not surprisingly given the topic of the article, four different articles from Remote Sensing of Environment were cited.
Measuring Fractional Cover
This study compared five different approaches to measuring ground cover: “(1) digital imagery with Agricultural Digital Camera (ADC), (2) radiation transmittance with an LAI-2000 Plant Canopy Analyzer, (3) radiation transmittance with a Ceptometer quantum line sensor, (4) ecosystem height variation with airborne laser altimetry and (5) destructive sampling with an LI-3000 leaf area meter and photographic analysis.” The area tested was shrubland which exists in hot, dry areas and “cover approximately 9% of the Earth’s vegetated surface.” Monitoring the amount of shrubland is “important for natural resource managers.” There is a discussion of the test site (Jornada Long-Term Ecological Research), the methodology of each sampling method, and comparison between the methods. The destructive sampling was the least effective method as the choice of the representative plant sample was subjective. The results of the study “suggest that ADC is both efficient and accurate for long term or large-scale monitoring of arid ecosystems.”
White, M.A., Asner, G.P., Neman, R.R., Privette, J.L. & Running, S.W. (2000). Measuring fractional cover and leaf area index in arid ecosystems: digital camera, radiation transmittance and laser altimetry methods. Remote Sensing of Environment, 74, 45-57. Retrieved February 3, 2009 from Google Scholar.
The references for the above article include 18 journals, four books, and one operating manual. The journals included Remote Sensing of Environment, Ecology, Climate Change, Agronomy Journal, International Journal of Remote Sensing, and Canadian Journal of Forest Research. Once again Remote Sensing of Environment had the most citations at eight. Book citations included articles from Ecosystems of the World series, Physical Ecology of North American Desert Plants, and Forest Ecosystems: Analysis at Multiple Scales.
New Directions
This article was written with the specialist in mind. By specialist, someone who is either in the field of remote sensing, land use management, or spectral analysis. From the abstract,
multiangle measurement enable retrieval of physical scene characteristics, such as aerosol type, cloud morphology and height, and land cover (e.g., vegetation canopy type), providing improved albedo accuracies as well as compositional, morphological and structural information that facilitates addressing many key climate, environmental, and ecological issues…With the advent of a new generation of global imaging spectroradiometers capable of acquiring simultaneous visible/near-IR multiangle observations, namely, the Along-Track Scanning Radiometer-2, the Polarization and Directionality of the Earth’s Reflectances instrument, and the Multiangle Imaging SpectroRadiometer, both qualitatively new approaches as well as quantitative improvements in accuracy are achievable that exploit the multiangle signals as unique and rich sources of diagnostic information.
If I hadn’t already read the previous two articles, I would have not been able to make it through the abstract and the introduction. The reason this article was chosen is that it was published in the time frame selected and the references cited.
Diner, D.J., Asner,G.P., Davies, R. & et al. (1999). New directions in Earth observing: scientific applications of multiangle remote sensing. Bulletin of the American Meteorological Society, 80 (11), 2209-2228. Retrieved February 3, 2009 from Google Scholar.
This article was the mother-load of references. There were a total of 143 individual references of which 125 were from journals. The remaining references were from algorithm documents, conference/symposium papers, books, reports and a dissertation. Three of the journals had at least fifteen different articles cited: Journal Geophysical Research, IEEE Transactions on GeoScience & Remote Sensing, and Remote Sensing Environment.
Summary and Analysis
Scientists generally prefer to get their information from journals than from books (see Grefsheim & Rankin above). Journals have greater currency over books; moreover, with so many journals now available online one can potentially find information even faster. The number of journals cited was not surprising; however, the type of books cited was interesting. The books all tended to be either encyclopedic in nature or methodology directed. On further reflection, perhaps it is not so surprisingly as with any rapidly advancing field books date quickly. So can we see a pattern in literature use among these three articles? Journals are the primary source of information for the field of remote sensing with Remote Sensing Environment being the most cited individual journal. Books provide background, methodology and supplemental information. Papers from conferences and symposiums are also used and would provide the same currency as journal articles. A systematic search for literature within the field of remote sensing would start with journals of that field. Other fields would include ecology, land management use, physics (spectroanalysis), and geography.
Next posting – What’s happening at the Carnegie Airborne Observatory?
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Your scientist's research is very interesting. My scientist's research focuses a little bit on remote sensing, but tackles it from the mathematical side, calculating the algorithms to make the sensing more uniform and effective. I find he also relies on essential conferences, like IEEE, and journals that are the pioneers and the most respected in the field. As you said, books could be used for quick reference and help with methodology. Although the field is always changing, ecological theories from the past could still be very useful, as research is always building on past findings.
ReplyDeleteAsner's research is really interesting. I also find it interesting that the books used in referencing where for methods and data purposes. I guess with the rate that science changes it is easier to get relevant and up to date information from a journal rather than a book.
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