Long-Term Plant-Monitoring Program Digitized By Arizona Researchers
April 30, 2013

Long-Term Plant-Monitoring Program Digitized By Arizona Researchers

April Flowers for redOrbit.com - Your Universe Online

More than a hundred years of growth data on individual plants has been digitized by a team of researchers at the University of Arizona´s Tumamoc Hill. The team has made this data available for study by people around the globe.

New insights into the behavior of ecosystems can be developed by knowing how plants respond to changing conditions over many decades.

Tumamoc Hill´s permanent research plots represent the world´s longest running study monitoring individual plants, according to Larry Venable, director of research at Tumamoc Hill.

The oldest plots date from 1906, with the birth, growth and death of the individual plants on those plots having been periodically recorded for 106 years. Venable, a UA professor of ecology and evolutionary biology has been studying the plants at Tumamoc Hill since 1982. He says the searchable archive is unique and invaluable.

"You can see the ebb and flow of climate, and you can see the ebb and flow of vegetation," he said.

Susana Rodriquez-Buritica, a postdoctoral research associate in the UA department of ecology and evolutionary biology, notes, "Long-term data sets have a special place in ecology."

Some desert perennials are very long-lived, according to Venable, and the Tumamoc Hill records have allowed researchers to estimate life spans for these species. Additionally, changes in the Sonoran Desert have been revealed by the Tumamoc Hill data, as well as helping to make key advances in the science of ecology.

Such advances include overturning the long-standing idea that plant communities progress through a series of steps to a stable collection of species known as a climax community.

"The desert wasn't progressing toward a climax community," Venable said in a statement. Each species and plot was changing to its own rhythm instead of being in synch.

The research team, which included Helen Raichle and Robert H. Webb of the US Geological Survey (USGS) and Raymond M. Turner, formerly of USGS, published a description of their data in the journal Ecology. The Carnegie Institution for Science (formerly known as the Carnegie Institution of Washington) established the Desert Laboratory at Tumamoc Hill in 1903. Since then, landmark research on the physiology and ecology of desert plants has been conducted, studying how plants cope with living in the desert.

Volney Spalding established the first permanent plots in 1906, which were generally 33 feet by 33 feet. Nine of those original plots exist today. Forrest Shreve established additional plots in the 1910s and 1920s. Two more plots were added in 2010, bringing the current total to 21.

The ecologist recorded the species, area covered, and location of every perennial plant in each plot, even identifying and mapping seedlings. Repeated photographs of the plots, kept in the Desert Laboratory Collection of Repeat Photography at the USGS in Tucson, have been taken since 1906.

The plots have been censused and re-censused by botanists and ecologists over the years. Raymond Turner took over the work when he became a UA botany professor in 1957, continuing even after he left UA to work for the USGS and into retirement. Robert Webb took over the project in 1993, and currently keeps the census going.

It was a huge challenge to sort through data recorded from 1906 to 2012, according to Rodriguez-Buritica. She was able to build on prior work done by Janice Bowers of the USGS, who had begun to archive the records but retired before finishing. The task ended up taking much more than the initial estimate of one year, partially because the records are kept in several places - some at the library or in storage at Tumamoc and some in the UA library's Special Collections.

Another challenging aspect is that the methods of collecting and recording data has changed over time. Long before the age of computers, Spalding recorded his observations in a small notebook. This method of field notebooks and maps created on graph paper continued well into the latter part of the 20th century. Rodriguez-Buritica had to digitize all of those paper records.

Scientists only started pinpointing plant locations and other observations directly onto a map using GPS and GIS technology within the last 20 years.

Rodriguez-Buritica realized she needed to standardize the information so it could be analyzed by other scientists, and her expertise in applied statistics and spatial ecology was perfect for the job. She also computerized the series of maps created over time, allowing new researchers to see all the plant location maps used since 1906.

Creating a standard digital format and making the data easily accessible on the Web has ensured other researchers can build on and expand this unique data set.

According to Venable, Tumamoc Hill is one of the birthplaces of plant ecology.

"In the first half of the 20th century, all the great plant ecologists either worked here or came though here [sic]," he said. "Plant ecologists from the Desert Lab were key in founding the Ecological Society of America [ESA] and its flagship journal, Ecology. It is satisfying to see the project come full circle and be permanently archived 100 years later by the journal that these researchers started."