Amphibian Has Vital Role in Decomposer Chain : Acid Rain Seen as Peril to Salamander
The most abundant land vertebrate, and the forest life of the Northeast that depends on it, could be imperiled by acid rain, ecologists believe.
What is the most common terrestrial backboned animal? The red-backed salamander, according to a report in a recent issue of the journal Ecology.
Two ecologists who study the amphibians found that the cryptic residents of the forest floor do not like or survive well in acid soils.
Richard L. Wyman and Dianne S. Hawksley-Lescault said of the red-backed salamander, known to scientists as Plethodon cinereus, “Its wide range and high density . . . probably make this species the most abundant terrestrial vertebrate in the northeastern United States.”
Estimated at 100 Billion
Wyman, who is director and resident biologist at the E. N. Huyck Preserve and Biological Research Station in Rensselaerville, N.Y., estimated there are 18 billion red-backed salamanders in New York and over 100 billion throughout their North American range. “At least there used to be,” Wyman said in a telephone interview.
The range of the salamander extends from southern Canada to North Carolina, and as far west as Ohio. This overlaps the section of the country which has been hardest hit by “acid deposition,” Wyman said, including acid rain, acid snow, and dry particles of pollution that fall to earth.
Salamanders in forest ecosystems “may be more important than previously believed,” the scientists said. They are a favorite food of blue jays and other birds, snakes, foxes, raccoons and other forest mammals.
Like Lions and Tigers
But more important, salamanders are the “lions and tigers of the decomposer food web,” Wyman said. This web is an essential group of organisms that includes dead plants and animals and the fungi and insects that consume dead things.
“Without those, the forest would quickly suffocate in its own waste,” Wyman said. In addition, he said the decomposers “recycle minerals and nutrients that trees” and other plants need to continue growth and sustain forest life.
Wyman said people are more familiar with the “grazer” food chain that is based on animals such as deer and consumption of living plants. But in fact, the “decomposer” food chain is more important in forests. He said 20% of the total calories consumed in a forest pass through the grazer food chain, whereas 80% pass through decomposers.
Fungi Also Sensitive
Wyman said several key members of the decomposer food chain were especially sensitive to acid conditions. In addition to the salamander, which he believes can even be used as a living indicator of acid conditions, the fungi--which are the first link in the decomposer chain--are very sensitive.
The scientists looked for the salamanders in 1,044 forest floor study plots, each about one square yard, in two wooded sites in Delaware County, N.Y. The salamanders are 4.5 to 6 inches long and narrower than a pencil.
The soil in the study plots varied in acidity, and the pair found that plots with the most acid soil were far less likely to have salamanders than other plots. Young salamanders were never found on the more acid soils.
Field Tests Confirmed
The ecologists confirmed their field observations in the laboratory by giving the salamanders soil preference and acid tolerance tests.
From these studies, the ecologists found that acid conditions--such as those in the most acid plots in the forests they studied--can be acutely and chronically lethal to salamanders, which breathe through their skin and must live in intimate contact with the moist soil. They concluded the evidence supported their belief the acidity of soils could determine whether salamanders would live in a site or not.
The scientists noted that soils may become more acidic due to natural processes, but said, “the increased rate of acidic deposition over the last several decades may accelerate the rate of soil acidification,” to the detriment of the salamander.
They recommended a regional study to measure directly whether soils and salamanders in the Northeast are suffering from the effects of increasing acid precipitation.
