Alwyn H. Gentry Forest Transect Dataset
Over 22 years, Alwyn H. Gentry collected data from 226 sites on six continents. Gentry and his collaborators collected all plants with stem diameters equal to or exceeding 2.5 cm diameter at breast height (dbh) along ten 2 x 50 m transects, totaling 0.1 hectare at each site.
Ecological Level: Community
Biome: Temperate & tropical forests
Location: Temperate North America; Mexico, Central America, West Indies; South America; Europe; Africa; Tropical Asia and Australasia - coordinates available
Spatial Scale of data: 0.1 hectare
Dataset Location: http://www.mobot.org/mobot/research/gentry/welcome.shtml
Data collection summary: All plants with stem diameters equal to or exceeding 2.5 cm diameter at breast height (dbh) were surveyed and measured along ten 2 x 50 m transects. Further information is contained in the Monograph in Systematic Botany from the Missouri Botanical Garden entitled "Global Patterns of Plant Diversity: Alwyn H. Gentry's Forest Transect Data Set" authored by Oliver Phillips and James S. Miller.
Data Collected: Species abundances and diameters at breast height (dbh).
Data Structure: The dataset consists of 4 tables (when accessed through EcoData Retriever, those tables are called 'counts', 'sites', 'species', and 'stems'). NOTE: The 'site_code' field in the counts and stems tables links to the 'abbreviation' field in the sites table. Maintainers of the Gentry dataset should consider cleaning up these names so that the same name is used in all tables.
Additional considerations: Given the incredible diversity at many of the sites and the state of taxonomy, many of the individuals are identified to morphospecies only. Cross-site taxonomic comparisons are unreliable. In addition, there is no information linking individual stems to a particular tree, which means that size data is only available for each stem at breast height, not for each individual.
Acquiring & Using Data: The Missouri Botanical Garden is committed to making Al Gentry's transect data available to all researchers but does make several requests to help us track usage and insure that Gentry's work is properly acknowledged. In order to track how often the data is used and where requests are coming from, it is required that an access form be filled out each time that the Web files are consulted.
Researchers who make use of the data in publications are requested to acknowledge Alwyn H. Gentry, the Missouri Botanical Garden, and collectors who assisted Gentry or contributed data for specific sites. It is also requested that a reprint of any publication making use of the Gentry Forest Transect Data be sent to:Bruce E. Ponman Missouri Botanical Garden P.O. Box 299 St. Louis, MO 63166-0299 U.S.A.
Submitted by dmcglinn on Tue, 2017-05-23 18:48 Permalink
I noticed that using the
I noticed that using the version of Gentry that the retriever downloads that the counts table has a total of 74237 individuals but the stems table has a total of 82131 individuals with a DBH greater than zero. My guess for why these are different is that if a single individual tree branched below breast height then that tree would have had more than one dbh recorded for it thus adding more records to the stems table than the counts table.
One other issue I would like to point out is that one of the sites has count data in a different format then all the other sites (each stem is on its own row) - see discussion here: https://github.com/weecology/retriever/issues/217
Submitted by Ethan White on Thu, 2017-06-08 12:07 Permalink
Dan - yes, you're right about
Dan - yes, you're right about the difference that's the distinction. This would definitely be useful information to add to the description here. Likewise I think adding a note to the main document about the differently formatted dataset would be a nice contribution as well.