Experiments may dramatically underestimate how plants will respond to climate change in the future. That's the conclusion of an analysis of 50 plant studies on four continents, published this week in an advance online issue of the journal Nature, which found that shifts in the timing of flowering and leafing in plants due to global warming appear to be much greater than estimated by warming experiments. "This suggests that predicted ecosystem changes -- including continuing advances in the start of spring across much of the globe -- may be far greater than current estimates based on data from experiments," said Elizabeth Wolkovich, an ecologist at the University of British Columbia who led an interdisciplinary（各学科间的） team of scientists that conducted the study while she was a postdoctoral fellow at the University of California, San Diego.

"These findings have extensive consequences for predictions of species diversity, ecosystem services and global models of future change," said Elsa Cleland, an assistant professor of biology at UC San Diego and senior author of the study, which involved 22 institutions in Canada, Sweden, Switzerland, the U.K. and the U.S. "Long-term records appear to be converging on a consistent average response to climate change, but future plant and ecosystem responses to warming may be much higher than previously estimated from experimental data."

Predicting plant responses to climate change has important consequences for human water supply, pollination of crops and the overall health of ecosystems. Shifts in the timing of annual plant events -- which biologists call "phenology" -- are some of the most consistent and visible responses to climate change.

Long-term historical records show that many plant species have shifted their leafing and flowering earlier, in step with warming temperatures over recent decades. Because historical records are not available in most locations and climate change may produce temperatures higher than previously recorded, however, ecologists often rely on experiments that warm small field plots to estimate plant responses to temperature and project future conditions.

With support from the National Center for Ecological Analysis and Synthesis, a research center funded by the National Science Foundation, the State of California and the University of California, Santa Barbara, the scientists created new global databases of plant phenology（物候学） to compare the sensitivity of plants to temperature -- that is, how much plants shift their timing of leafing and flowering with warming. These were calculated from experiments and then compared to long-term monitoring records.