Volney Spalding's Plant Community Ecology Studies

Tumamoc Hill has the world's oldest permanent plant ecology study plots. The truth is, we are not even 100% sure whether they date from 1905 or 1906! A handwritten letter from Volney Spalding, who established them, dates from 1905. He notifies the laboratory's administration of his new research direction, and recommends that they be studied for a very long time. We have Spalding's field notes from 1906. But his field notes from 1905 are lost, so we cannot be sure if the plots he worked on in 1905 were the same as those he worked on in 1906.

In 1906, there were 19 plots, 18 of them squares, each 10 meters on a side. Today, over a century later, we are still collecting good data from nine of Spalding's plots. The others have been lost to indifference and ignorance, mostly in the 1970s during the construction of West Anklam Road along our northeastern border.

In 2012, with support from the National Science Foundation, the US Geological Survey, and the National Park Service, the old Spalding plots were remapped using such tools as satellite positioning (GPS), their borders digitized precisely, and another census taken.

What did Spalding want to do and why did he want to do it?

One of the hottest topics in ecology during the first decade of the 20th century was ecological succession. Ecologists thought Nature responds to disturbances by gradually re-establishing its norms. Groups of species grow up in the most recently disturbed land only to be replaced by other groups, and then others in a regular parade until a community of species called the climax system takes root and persists in the absence of further disturbance.

It is a big idea, namely, that ecological communities are not merely a ragtag bunch of species going their independent ways, but instead are coordinated wholes that reflect a Balance of Nature.

We'll have more to say about this idea on a different page of the website; it is that important. For now, let's just say that Spalding believed it and wanted to observe it in the Sonoran Desert. So he set out his plots (called quadrats) and then he tagged, measured, identified and photographed every single bush, shrubby tree and thorny cactus in them.

And so began the story of the world's longest investment in the observation of ecological processes and the collection of ecological data.

We are proud and privileged to keep it going.

One of the four ancient iron stakes that mark a corner of Plot IX.

A page from Volney Spalding's letter of 28 July 1905 to Director Daniel T. MacDougal. "...between fifteen and twenty quadrats were located. the species growing within them determined, photographs made and specimens of the species kept for reference and verification." On the next page, Spalding recommends that study of the plots be "continued and extended." Original now in the collection of The Arizona Historical Society.