Climate change linked to major plant life shifts


Following up on the previous post about global warming impacts on fauna in the American West, two studies on impacts on flora, both on the land and under the sea.

First, from the U.S. Department of Energy’s Office of Science:

Image courtesy of Denise Krebs (Flickr) via a Creative Commons License. A mixed-grass community prairie in Iowa.

Image courtesy of Denise Krebs (Flickr) via a Creative Commons License. A mixed-grass community prairie in Iowa.

The Science

Climate controls vegetation distribution across Earth, with some vegetation types being more vulnerable to climate change and others more resistant. Because resistance and resilience can influence ecosystem stability and determine how communities and ecosystems respond to climate change, evaluating the potential for resistance in future prairies and other ecosystems is important. Led by researchers from Wyoming, a team found that elevated carbon dioxide levels suppress the dominant plant species in a northern U.S. Great Plains mixed-grass prairie, creating a less diverse community.

The Impact

The economic value of many grasslands depends largely on plant community composition and the relative abundance of key forage species. Findings from this research have implications for managing native grasslands in the face of changing climate and its accompanying precipitation variations.

Summary

A large field experiment conducted in a northern U.S. Great Plains mixed-grass prairie was led by a research team from the University of Wyoming. The scientists tested the effects of elevated carbon dioxide, warming, and summer irrigation on plant community structure and productivity. This study sought to understand changes to stability in the community’s composition and to biomass production. Investigators found that (1) the independent effects of carbon dioxide and warming depend on interannual variation in precipitation and (2) the effects of elevated carbon dioxide are not limited to water saving because they differ from those of irrigation. Also shown was that production in this prairie ecosystem is not only relatively resistant to interannual variation in precipitation, but also rendered more stable under elevated carbon dioxide conditions. This increase in production stability resulted from altered community dominance patterns; that is, community evenness increases as dominant species decrease in biomass under elevated carbon dioxide.

And the impacts on ocean plant life from the University of New South Wales:

 Bleached seaweed. Image: Alexandra Campbell


Bleached seaweed. Image: Alexandra Campbell

A variety of normally harmless bacteria can cause bleaching disease in seaweeds when the seaweeds become stressed by high water temperatures, UNSW researchers have discovered.

Seaweeds are the “trees” of the ocean, providing vital habitat, food and shelter for many species of fish and other coastal marine organism, such as crayfish and abalone.

Read the rest, after the jump. . .

“A lot of attention has been paid to coral bleaching, but seaweeds are also affected by temperature-related diseases,” says study senior author UNSW’s Dr Suhelen Egan.

“In most cases, the infectious agents that cause the diseases are unknown. Improving our understanding these disease processes is not only important for maintaining a healthy marine environment; it also has economic significance, given that seaweeds are increasingly being cultivated as sources of food and feed-stock for biofuels.”

The study, by Dr Egan’s team at the UNSW Centre of Marine Bio-Innovation, is published in the journal Environmental Microbiology.

The researchers collected samples of healthy and diseased red alga, Delisea pulchra, from about 8 metres under the water at different locations on the Sydney coastline. The diseased seaweeds had undergone natural bleaching, in which areas of pigment are lost.

“Bleaching reduces the ability of the seaweed to photosynthesise and harvest energy from the sun, and to reproduce. It also makes them more susceptible to grazing by fish and other herbivores in the ocean,” says Dr Egan.

The researchers isolated microbes that were in greater abundance on the diseased seaweeds and cultured them. They then tested the ability of these microbes to cause bleaching disease in seaweeds in the laboratory.

“We were surprised to identify three very different kinds of bacteria which are usually present in low numbers on seaweeds, but which we now know can all cause the same bleaching disease,” says Dr Egan.

“We also found that the usual balance of microbes was disturbed on the diseased seaweeds, with a lower diversity of microbes present than normal.

“We believe these kinds of opportunistic pathogens are more common in marine environment than had been realised before. They seize the chance to cause disease when the host is stressed, in the same way that normally harmless, common bacteria can cause disease in people who have weakened immune systems.”

The three newly identified pathogens that cause the bleaching disease are members of the AlteromonasAquimarina and Agarivorans genera.

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