ag number 3473, one point nine feet,” calls the colleagues John G. “Geoff” Tracey and Leonard “Len” measurer from his contorted position kneeling J. Webb (from Australia’s Commonwealth Scientific and on the rainforest floor. After scanning the data Industrial Research Organisation, or CSIRO), he laid sheet on her clipboard for the tag number, the out what is now known as the Connell Plots Rainforest recorder answers, “Another one that’s barely Network. “grown! It was one point six feet in 1965.” The recorder Connell [see photograph on this page] wanted to better T writes the new measurement next to the original record understand the processes that maintain species diversity on the data sheet, and nonchalantly flicks away the leech in natural communities. Do ecological mechanisms pre- that has inched up her leg. vent common species from monopolizing all available Our field team repeated a similar version of that call- resources? Do rare species sometimes have an advantage and-response for almost 20,000 plants last year, during over the common ones, so that the balance among spe- the fiftieth-anniversary census of one of the world’s lon- cies shifts over time? gest-running rainforest dynamics projects. We worked Connell, Tracey, and Webb chose the roughly four-acre at two plots in Australia: one just south of Brisbane, in tropical site at Davies Creek because it had never been Lamington National Park, and the other at Davies Creek logged; instead, the Queensland Forestry Department set National Park, southwest of Cairns. Both plots were set it aside in 1951 as a reference site against which the effects up—and the first large trees were tagged—in 1963 by of silvicultural treatments at other rainforest sites nearby Joseph H. Connell, now Professor Emeritus at the Uni- could be compared. Logging was still widespread in north versity of California, Santa Barbara (UCSB). About Queensland at the time, and Connell remembers hear- ten members of our team spent two weeks at each plot, ing the buzz of chainsaws when he first visited the site. extending Connell’s legacy to five decades of research. The grounds for choosing the other site, the subtropical With each new round of field observations we better un- location near O’Reilly’s Rainforest Retreat (an inholding, derstand these forests’ diversity and dynamics. or privately owned enclave, within Lamington National Park), might have been he way Connell tells a bit more prosaic: ap- T it, once UCSB gave parently Mrs. O’Reilly’s him tenure he was keen roast lamb at lunch con- to spread his wings and vinced Connell this was explore. Australia was an ideal site for long- irresistible as a research term research. destination in the early Both the Davies 1960s—biologically a bit Creek and O’Reilly’s exotic, English-speak- plots have been closely ing, and unlike several monitored ever since. tropical countries at the Every few years, teams time, politically stable. of hardy field workers K. HARMS Connell’s initial research brave the stinging trees, had been in marine eco- ticks, leeches, and biting systems, and he spent a flies to record the fates year in Australia in 1962 of thousands of tagged setting up permanent plants. The value of these Under the Lunch monitoring quadrats GREEN P. long-term demographic (small sampling areas) Ecologist Joseph H. Connell (above) presciently established long-term for- data sets—records of on Heron Island, deter- est plots of Australian rainforest in 1963, in Lamington National Park south birth, growth and mor- mined to study the pro- of Brisbane and in Davies Creek National Park southwest of Cairns, to study tality—increases with FIFTY YEARS OF RAINFOREST rainforest dynamics. Fifty years later scientists enjoy their noontime break Tree cesses that maintain the at Davies Creek under the Lunch Tree (far left), a northern brush mahogany, age. When those data diverse community of as they work to track the forests’ changes. are collected at multiple DYNAMICS IN QUEENSLAND, AUSTRALIA corals that occurs there. time points (“censuses”), It wasn’t long, however, before the parallels with rain- they reveal the temporal patterns of population change. BY KYLE E. HARMS & PETER T. GREEN forests became obvious: like corals, rainforest plant com- Accordingly, a collection of demographic data sets for the munities contain a high diversity of sessile organisms, so various species that inhabit a natural community provide the fates of individuals can be tracked over time. Con- valuable insights into the patterns of change for the whole nell returned to Australia in 1963, and with the help of community. We’ve accumulated a lot of information over 32 NATURAL H I S TO RY March 2014 March 2014 NATURAL H I S TO RY 33 repeated censuses in five decades of research: for the plots combined, our databases contain records for about 100,000 individual plants in about 300 species. any plots exist throughout the tropics that fol- M low the fates of individual trees. Most of those plots are smaller than the Connell Plots at Davies Creek and O’Reilly’s (one-quarter of an acre and two-and-a-half acres are standard sizes), and a few plots are substantially larger (a few dozen sixty-plus-acre plots exist, including a relatively new one at Robson Creek, about six miles away from the Davies Creek plot). Where- as multiple small plots scattered across a landscape are useful for understanding geographic patterns of distribution, large plots are invaluable for un- derstanding a forest’s internal dynamics (births, deaths, and growth of individual stems). Within this mix, the unique value of the Davies Creek plot is its age and inclusion of the smallest tree size classes right from the beginning. ARMS H For a variety of logistical reasons, more ef- K. fort has been put into the Davies Creek plot than the O’Reilly’s plot. The initial plot cen- sus yielded 550 individual trees larger than four inches in diameter in nearly 160 species. A few species were common, but most species were rare. Some species are only represented on the plot by one or two individuals. For ex- ample, the Lunch Tree—the tree that serves as the team’s assembly point for beginning a day’s work, having lunch, or preparing to walk back to the vehicles—is the only individual of its spe- cies on the plot. This magnificent specimen is a 115-foot-tall northern brush mahogany (Geis- sois biagiana), with large buttresses and sinuous roots that extend several yards in all directions from its base. Not all species were well known to science, and in fact the most common species on the plot, a member of the genus Niemeyera, in the plant family Sapotaceae, remains unde- scribed by taxonomists. In 1965 Connell and his colleagues laid out sev- eral transects across the research plot to facilitate a census of the seedlings and small saplings. This early addition to the project added another fifty species to the plot’s species list, and has proven es- pecially valuable now that nearly five decades of records have accrued for seedling and small-sap- ling dynamics. The forest is sharing its otherwise GREEN P. Strangler fig twining Measurements made of modest growth in the forests (Davies around its freestanding well-kept secrets through patterns revealed by Creek, top; O’Reilly’s, bottom). The measuring tapes held side by host tree in the Davies statistically analyzing the long-term data set. For side (bottom) show the heights of “Tag 3403” (a steelwood tree, K. HARMS Creek plot. example, the data clearly show that recruitment— Sarcopteryx stipata) in 1965 (left) and in 2013 (right). 34 NATURAL H I S TO RY March 2014 March 2014 NATURAL H I S TO RY 35 the production and germination of seeds, and the establish- to ground level at most locations in the forest. Many plants ment of seedlings—is localized and sporadic for most spe- that were one or two feet tall in 1965 are only a few feet cies. At one extreme lies satin sycamore (Ceratopetalum suc- taller now, and age estimates using these growth data in- cirubrum), one of the largest canopy species at Davies Creek. dicate that seven-foot-tall saplings of many species could Individuals of this species have flowered, seeded, and pro- be eighty to one hundred years old. It seems that light is so duced carpets of seedling recruits near the parent trees only limiting that rates of photosynthesis are barely greater than three times in almost a half century, at roughly decadal rates of respiration. The canopy giants of these shade-toler- intervals. Similarly, the dozen or so mature Queensland ant species must be truly ancient. On the other hand, there kauri pines (Agathis atropurpurea)—magnificent, flaky- is a smaller group of light-demanding species whose seeds barked coniferous canopy trees—have produced only are able to reach light gaps created by the death and top- about two dozen new seedlings. The long-term data yield pling of large trees. Over the decades we have tracked the many stories like this, and in an effort to understand this recruitment of seedlings and their transitions into repro- ductively mature adults of the white basswood, or pencil cedar (Polyscias murrayi), in a large gap near the center of the plot. Unlike the “slow and steady” persistence of the shade-tolerating species, these white basswoods have lived com- paratively fast and died comparatively young, having enjoyed several good years of reproduc- tion through the 1990s and early 2000s. The infamous gympie stinger (Dendrocnide moroides) is another fast-growing but short-lived species at Davies Creek, and the very large light gaps it requires to establish have been uncommon on LER the plot.