Local observation station is longtime contributor to national network

By Wiley Wood

The three spindly lilac bushes growing near the cooperative weather station on Windrow Road don’t look like much, but they are an unusually well-documented trio of plants. Not the common lilac, which is more lushly flowered, they are a clone, Syringa chinensis “Red Rothomagensis,” planted in 1965 at the behest of scientists from Cornell and the University of Vermont, as part of a network of similar plantings across the Northeast. And every spring since 1968, with a single three-year lapse in the early 1970s, the phases of their spring growth have been recorded, following a well-defined protocol, and transmitted up the chain to researchers with a use for phenology, a branch of science that studies the environmentally influenced timing of cyclic events in the lives of animals and plants, e.g. the emergence of insects, the release of pollen, nest building.

When Ted Childs, the late founder of Great Mountain Forest, agreed to plant the lilac clones in the mid-1960s and started submitting his handwritten observations (a thick file marked “Lilac Phenology Records” in the GMF offices preserves the entire 50-year sequence), the project was funded by the U.S. Department of Agriculture. The idea was to use data from indicator species in combination with weather records to help farmers predict the growth stages of crops and the timing of pest infestations.

By the late 1970s, researchers had discovered a close correlation between certain key phenophases (as growth stages are called) of McIntosh apple and the cloned lilac: the full bloom of McIntosh arrived just before the first flowers of Syringa chinensis, absenting differences in temperature and elevation. By observing the date of the lilac’s first leaf, an accurate prediction could be made of when McIntosh would flower, thus helping orchardists in Vermont, for instance, where three quarters of the apple crop was McIntosh, plan for renting bees or setting up frost-protection equipment during full bloom.

A similar study, although it used different indicator plants, focused on critical phases in the life cycle of the European corn borer, a destructive pest. The first bloom of nannyberry was found to coincide with the first flight of the corn borer’s brood moth, and other plant phenophases were discovered that coincided with other critical points in the insect’s life cycle. All, unlike the insect’s behavior, could be easily observed by a farmer or his agricultural extension agent, providing a practical way to schedule a chemical control program.

Russell Russ examines a lilac bud.

But by the time Ted Childs turned over the phenological observations to his GMF forester, Darrell Russ, in the late 1980s, the program had lost its USDA funding and been shunted to different universities and even shut down altogether for two years (though Darrell Russ continued to record the lilac data). It was a young climatologist in the Department of Geography at San Francisco State University, Mark Schwartz, who revived the network of lilac observers in the Northeast, asking the longtime observers to continue their data collection while he drummed up funding, citing its importance to his climate research.

Schwartz, who eventually moved to the University of Wisconsin, was soon working with NASA on using satellites to chart the “green wave” as spring advanced across the continent, correlating satellite images with direct observational data from the lilac network. He started attending international phenology conferences in Europe and in 1998 organized a symposium of scientists from around the world to discuss phenology’s possible contributions to models of global climate change.

The weedy lilac specimens on Windrow Road do not by themselves offer any grand conclusions. Their evidence is necessarily local. Yet a graph plotting the day on which the first leaf appeared across the years does show a gradual drift to an earlier date from 1968 to 2018. The results might have been more dramatic if a bank of evergreens shading the lilacs from the afternoon sun had not grown to a towering height in the interval.

Russell Russ, a forester at GMF who has, since 2003, been logging the meteorological and phenological data his father recorded before him (and who writes the Norfolk Weather column for this publication), believes that Norfolk’s weather started to get a little warmer in 1998. The lilac leaf buds broke particularly early that year. “And then 2012 was a crazy warm year,” says Russ. “We’re in a warming period. Obviously the plants and animals are reacting to it.”

Russ is acutely aware of the temperature-sensitivity of lilac. Small anomalies in the weather pattern can alter the leaf-out day substantially. “Three nice warm days and they’ll pop in a hurry,” says Russ. “Or else the leaf buds can be very close to breaking,” says Russ, “but five days of cold will really set them back.”

Despite the frailty of the Norfolk dataset, it becomes more robust as part of the far-flung lilac stations that Schwartz has called “the first spatially extensive phenological observation networks in the US.” Those observations, conducted across the country by cooperative weather observers like Ted Childs, directly contributed to Schwartz’s efforts to calibrate satellite data with locally recorded observations and to quantify “the abrupt advance in the timing of spring onset” that began, Schwartz says, in the mid-1980s.

When, in the early 2000s, Schwartz began his efforts to revitalize and broaden the lilac networks into a national framework and to extend observations to other native and non-native plants, the existing lilac observation stations formed the nucleus of what was to become the USA National Phenology Network, “a consortium of individuals and organizations that collect, use and share phenological data.”

One issue that now occupies environmental scientists is how interlinked species are reacting to the warming trend. If the earlier arrival of spring affected all species across an ecosystem uniformly, everything would be simple. But when a species that takes its cue primarily from temperature depends on a species that takes its cue primarily from day length, there can be a disconnect. Concern is mounting, for instance, that migratory birds in the northeast are not keeping pace with the earlier date of green-up. Some might arrive at a nesting site, for instance, to find the insect hatch they depend on already past. Species distribution will clearly be affected by climate change in complex ways.

Today, Russell Russ’s lilac data is logged in directly to the USA-NPN website (www.usanpn.org) and folded into the observations collected by many others, some of them citizen scientists. Observations are being made on hundreds of other plant and animal species now, as well as on cloned lilac. “The success of monitoring programs,” Schwartz writes, “will depend on recruiting, retaining, and managing members of the public to routinely collect phenological observations according to standardized protocols.”

This year’s first first leaf on the Norfolk lilacs, the date when “the widest part of the newly emerging leaf has grown beyond the ends of its opening winter bud scales,” was recorded by Russ on April 24, the earliest date since the mid-1980s—in the hot year of 2012 it happened more than a month earlier. And the date of first flower, when “at least 50 percent of the flower clusters have at least one open flower,” occurred on May 21, delayed several days by unseasonable cold.