Global changes alter the timing of plant growth, scientists say

Sep 04, 2006

Any gardener knows--different plant species mature at different times. Scientists studying plant communities in natural habitats call this phenomenon "complementarity." It allows many species to co-exist because it reduces overlap in the time period when species compete for limited resources. Now, in a study posted online the week of Sept. 4 in the Proceedings of the National Academy of Sciences, ecologists working at Stanford's Jasper Ridge Biological Preserve report evidence that climate change may alter this delicate balance.

"In the natural world, species have evolved to be finely attuned to the seasons--timing is everything," said lead author Elsa Cleland, who performed this research as part of her doctoral dissertation at Stanford and is now a postdoctoral fellow at the National Center for Ecological Analysis and Synthesis in Santa Barbara, Calif. "If climate change alters the timing of plant activity, then it could have a domino effect, impacting the feeding, breeding or migration patterns of the animals that rely on particular plant species."

Cleland's co-authors include Nona R. Chiariello, research coordinator of the Jasper Ridge Biological Preserve; Scott Loarie, who assisted with this research while a Stanford undergraduate; Christopher B. Field, director of the Carnegie Institution's Department of Global Ecology (located on the Stanford campus) and faculty director of Jasper Ridge Biological Preserve, and Harold A. Mooney, the Paul S. Achilles Professor of Environmental Biology at Stanford.

The findings are part of the ongoing Jasper Ridge Global Change Experiment, launched in 1998 and designed to demonstrate how a typical California grassland ecosystem may respond to future global environmental changes. Researchers from Stanford and the Carnegie Institution's Department of Global Ecology conducted the experiment in about two fenced-off acres of the 1,189-acre Jasper Ridge Biological Preserve. The experiment was designed to simulate environmental conditions within the range that climate experts predict may exist 100 years from now--a doubling of atmospheric carbon dioxide; a temperature rise of 2 degrees Fahrenheit; a 50 percent increase in precipitation; and increased nitrogen deposition--as a likely byproduct of fossil-fuel burning.

Scientists applied each of the four experimental treatments--elevated carbon dioxide, warming, increased precipitation and nitrogen deposition--to intact grassland plots both singly and in all possible combinations. The experiment included control plots that did not receive any treatments. Each of 16 possible scenarios was replicated eight times to allow the researchers to tease apart the separate influences of factors and test the statistical significance of their results. Data reported in this study were obtained from 1999 through 2003.

"Under today's conditions, grasses flower early in the growing season and wildflowers flower later, but when we increased the concentration of carbon dioxide to simulate future conditions, the two groups flowered at the same time," Cleland said.

Early spring

In recent decades, scientists have observed accelerated springtime developmental activity in many plant and animal species and have assumed it was a response to global warming. In the experiment, researchers found that warming accelerated springtime flowering of all species. But they were surprised to find differing responses to elevated carbon dioxide and nitrogen deposition: Wildflowers responded to these changes by flowering earlier, while the grasses flowered later. This caused the two groups to overlap in their seasonality, where under current conditions they flower at separate times.

Consequences could be significant, points out co-author Loarie: "If plant species overlap more in the future because their timing is altered by global changes, it could lead to decreases in local plant diversity and negatively impact animals that depend on those plants."

Satellite images in recent years have revealed that some regions of the globe are "greening" earlier in the spring--another signal that the Earth is responding to overall warming. The results of this study also showed that plant growth--as evidenced by peak "greenness"--occurred earlier in the growing season when the grassland was exposed to warming, simulating future conditions.

But plant growth was delayed by elevated carbon dioxide, consistent with the fact that grasses--which make up the majority of plants in this system--were flowering later. "Unless the growing season is extended, slower plant growth under elevated carbon dioxide could reduce the overall productivity of the ecosystem," said Cleland.

Said Mooney, a founder of the Jasper Ridge Global Change Experiment: "This research shows that warming is just one aspect of global change and highlights the surprising ways in which natural communities may respond to changing environmental conditions."

Source: Stanford University

Explore further: Rio's Olympic golf course in legal bunker

add to favorites email to friend print save as pdf

Related Stories

Tropical fish a threat to Mediterranean Sea ecosystems

12 hours ago

The tropical rabbitfish which have devastated algal forests in the eastern Mediterranean Sea pose a major threat to the entire Mediterranean basin if their distribution continues to expand as the climate ...

Global change: Trees continue to grow at a faster rate

Sep 17, 2014

Trees have been growing significantly faster since the 1960s. The typical development phases of trees and stands have barely changed, but they have accelerated—by as much as 70 percent. This was the outcome ...

Scientists discover tropical tree microbiome in Panama

Sep 15, 2014

Human skin and gut microbes influence processes from digestion to disease resistance. Despite the fact that tropical forests are the most biodiverse terrestrial ecosystems on the planet, more is known about ...

Recommended for you

Rio's Olympic golf course in legal bunker

2 hours ago

The return of golf to the Olympics after what will be 112 years by the time Rio hosts South America's first Games in 2016 comes amid accusations environmental laws were got round to build the facility in ...

Unforeseen dioxin formation in waste incineration

13 hours ago

Dioxins forms faster, at lower temperatures and under other conditions than previously thought. This may affect how we in the future construct sampling equipment, flue gas filtering systems for waste incineration ...

User comments : 0