Streamflow Alteration Impacts Fish Diversity in Local Rivers plus 1 more

[USGS Newsroom <oc_web@xxxxxxxx>]

Title: USGS Newsroom

Streamflow Alteration Impacts Fish Diversity in Local Rivers plus 1 more

---

Streamflow Alteration Impacts Fish Diversity in Local Rivers

Posted: 16 Jan 2014 06:00 AM PST

A new USGS study quantifies change in fish diversity in response to streamflow alteration in the Tennessee River basin.

The USGS study highlights the importance of the timing, magnitude, and variability of low streamflows and the frequency and magnitude of high streamflows as key characteristics critical to assessing how fish communities change in response to streamflow alteration. This study was completed using fish community data collected by the Tennessee Valley Authority, and predictions of streamflow characteristics at more than 600 locations.

The Tennessee River basin is one of the richest areas of aquatic diversity in the country, if not the world.  However, expanding urban development, more than 600 privately held small dams on medium to small streams, and withdrawal of more than 700 million gallons of water each day threaten this diversity.  Understanding the effect of streamflow alteration on aquatic ecology is increasingly important as change in land use and human population are projected. 

One of the examples from the study shows that as maximum October streamflow deviates outside reference conditions by approximately 6 cubic feet per second per square mile, fish diversity may decline by almost nine species in the Blue Ridge ecoregion of eastern Tennessee and western North Carolina.  Results such as this were identified across the Blue Ridge, Ridge and Valley, and Interior Plateau ecoregions for 11 categories of fish and will help resource managers identify when streamflow alteration may result in too much ecological degradation.

“Managing river flows to meet the needs of our growing communities and economies will become increasingly challenging in the future”, said Sally Palmer, director of science for The Nature Conservancy in Tennessee. “Maintaining our rivers to support an abundance of natural wildlife, including our native fish, is an important goal as well. Studies like these give us better information to make management decisions which more effectively balance all the demands placed on our river resources.”

The National Park Service, responsible for the protection and management of Big South Fork National River and Recreation Area and the Obed Wild and Scenic River in Tennessee, has a need to assess potential impacts to the resources they are charged with protecting.  “This research enhances our ability to respond to current development pressures and serves as the foundation to develop a decision support tool to address future water resource issues” said Jeff Hughes, hydrologist with the NPS.

Additional information regarding environmental flows research in the Tennessee River basin can be found online. This work was completed as part of the USGS Cooperative Water Program in collaboration with the Tennessee Wildlife Resources Agency, Tennessee Department of Environment and Conservation, and The Nature Conservancy.

Large Old Trees Grow Fastest, Storing More Carbon

Posted: 15 Jan 2014 09:00 AM PST

THREE RIVERS, Calif, — Trees do not slow in their growth rate as they get older and larger — instead, their growth keeps accelerating, according to a study published today in the journal Nature.

"This finding contradicts the usual assumption that tree growth eventually declines as trees get older and bigger," says Nate Stephenson, the study's lead author and a forest ecologist with the U.S. Geological Survey. "It also means that big, old trees are better at absorbing carbon from the atmosphere than has been commonly assumed."

An international team of researchers compiled growth measurements of 673,046 trees belonging to 403 tree species from tropical, subtropical and temperate regions across six continents, calculating the mass growth rates for each species and then analyzing for trends across the 403 species. The results showed that for most tree species, mass growth rate increases continuously with tree size — in some cases, large trees appear to be adding the carbon mass equivalent of an entire smaller tree each year.

"In human terms, it is as if our growth just keeps accelerating after adolescence, instead of slowing down," explains Stephenson. "By that measure, humans could weigh half a ton by middle age, and well over a ton at retirement."

This continuously increasing growth rate means that on an individual basis, large, old trees are better at absorbing carbon from the atmosphere. Carbon that is absorbed or "sequestered" through natural processes reduces the amount of carbon dioxide in the atmosphere, and can help counter-balance the amount of CO₂ people generate.

However, the researchers are careful to note that the rapid absorption rate of individual trees does not necessarily translate into a net increase in carbon storage for an entire forest.

"Old trees, after all, can die and lose carbon back into the atmosphere as they decompose," says Adrian Das, a USGS coauthor. "But our findings do suggest that while they are alive, large old trees play a disproportionately important role within a forest’s carbon dynamics. It is as if the star players on your favorite sports team were a bunch of 90-year-olds."

The study was a collaboration of 38 researchers from research universities, government agencies and non-governmental organizations from the United States, Panama, Australia, United Kingdom, Germany, Colombia, Argentina, Thailand, Cameroon, Democratic Republic of Congo, France, China, Taiwan, Malaysia, New Zealand and Spain. The study was initiated by Stephenson and Das through the USGS Western Mountain Initiative and the USGS John Wesley Powell Center for Analysis and Synthesis.

Accompanying Information for Press Release 

• TABLE 1: Continent/Sample Size/Species Breakdown
• TABLE 2: List of Institutions Contributing to the Study