Interest in tracking phenology has grown, with the founding of organizations like the USA National Phenology Network, which uses citizen volunteers to contribute observations to studies. But because historical records are not available in many places and the future may bring ever-higher temperatures, many scientists are also trying to project by doing experiments in which they heat small field plots and measure the responses.
The researchers in the Nature study created new global databases of plant phenology, pitting calculations from experiments versus those from long-term monitoring of natural records. They included data from 50 different studies covering 1,643 species on four continents. Their analysis showed that experiments predicted every degree rise Celsius would advance plants' flowering and leafing from half a day to 1.6 days. But in looking at actual observations in nature, they found advances four times faster for leafingand over eight times faster for flowering. In sum, the natural records showed that phenological events advancing on average, five to six days per degree Celsius. The finding was strikingly consistent across species and datasets. Wolkovich said this suggests that long-term records "are converging on a consistent average response," and that future plant and ecosystem responses to climate change may be much higher than estimated from experimental data alone.
A number of factors could explain the discrepancies, said the researchers. These could include effects of longer-term climate change, including shifts in plants' genes as they adjust to warming, which would not be mirrored by shorter-term experiments. Or, it could be specific aspects of the exper
|Contact: Kim Martineau|
The Earth Institute at Columbia University