Yesterday:
Forest Leaves, Autumn 7001, Gleanings from the Stream
By Roy Brubaker (written in 2001 when Roy was a Service Forester)
Roy is presently a District Forester with the Pennsylvania Bureau of Forestry
Before a trip to the Stroud Water Research Center in Chester County (PA), I thought I had the lowdown on the importance of streamside forests. I understood that trees help prevent sediments and excess nutrients from entering streams. I knew that shade from trees helps keep water temperature slow enough for trout and other cold-water critters. However, the visit opened my eyes to the truly fascinating and complex relationship between stream ecology and forest buffers. By sharing the knowledge I gleaned from the field trip, I hope that others will also come to a deeper appreciation for the need to restore and enhance forests along our streams and rivers.
The Stroud Water Research Center is a privately-funded facility located on 900 acres of mixed farm and forestland about 40 miles west of Philadelphia. It provides an excellent living, laboratory for helping us to understand how changes to the landscape affect stream ecology.
Dr. Bernard Sweeney, Stroud's Director, was our host for the day. He explained that while it comprises just a small fraction of the earth's water resources, freshwater is vital for our continued existence. Hence, understanding the systems that maintain the quantity and quality of freshwater is imperative.
Dr. Sweeney stressed that the primary importance of streamside forest buffers is not only to prevent nutrients and toxins from getting into the water, but to foster a diversity of life forms within the steam. Since stream organisms use nutrients and degrade toxins, ensuring a healthy variety of organisms is vital to processing the chemicals and nutrients that do enter the water.
Before my visit to Stroud, it never occurred to me that streams flowing through forested areas tend to be wider and shallower than streams flowing through unforested areas. The reason involves the fact that some grasses can grow well in waterlogged soils. On the other hand, roots from most trees die if immersed in water during the growing season. Thus, forested streams tend to develop wide and shallow channels as tree roots recede from the water's edge and banks naturally erode back to a more natural condition. Streams in open areas tend to become deep and narrow as grasses grow right up to the water's edge.
Since most biological activity takes place on the bottom of small streams, wider streams provide greater "surface area" for biological activity. More habitat area within the stream means more organisms are present to use nutrients and degrade toxins.
Subtle differences in stream form can have important consequences for aquatic organisms. For example, Dr. Sweeney explained that some stoneflies and other insects need partially submerged rocks to complete their lifecycles. These critters use the rocks to crawl to the water's surface when they change from a wingless, immature, aquatic form to a winged adult. Because streams without forest buffers tend to be deep and narrow, partially exposed rocks within the stream channel are often rare, preventing stoneflies from ever taking flight for the reproductive phase of their life cycle.
When habitat conditions eliminate species, entire ecosystems are changed. Because it is very difficult to predict how the elimination of any one species will affect the functioning of the entire ecosystem, our goal should be to protect all native species.
Moreover, I had never considered the fact that plant materials are the basis of the food chain in streams, just like on the land. In small streams, many aquatic animals derive their nutrition from the leaves, twigs, and other plant materials that fall into the water from the surrounding land.
Stroud researchers conducted experiments to see what plant materials native insects prefer. In all cases, the researchers found that insects grow and survive better when fed leaves from native forest plants. The intricate relationship between aquatic and terrestrial ecosystems evolved over thousands of years. So, if you think any type of woody plant will do just fine in our forest buffers, think again!
To preserve the function of our streams, we need to maintain the natural species composition of our streamside forests. (As a note of interest, Stroud scientists couldn't get anything to survive and grow on the leaves of multiflora rose-a nonnative shrub that is very common in our region!)
In addition to plant materials that fall or wash into streams from surrounding forests, aquatic animals eat plants that grow in the water, especially algae. Just as in forests, the amount of available light changes the composition of plants in streams. Not surprisingly, stream insects prefer to graze on the types of algae that grow under the shade of a forest canopy.
In streams that flow through open areas, more light reaches the stream bottom and different types of algae predominate. For instance, the stringy green and blue-green algae that are common in streams flowing through open pasture and agricultural lands are virtually useless to many of our native aquatic insects, because they did not "develop a taste" for the algae, evolutionarily speaking! Thus, our native stream insects may become rarer as stringy green and blue-green algae replace the species of algae adapted to low-light conditions (such as single-celled diatoms).
"Probably, if we'd give them several thousand years, a new suite of organisms would evolve to utilize the stringy green and blue-green algae, but who wants to wait that long for healthy streams, when what we've got in our forested streams works so well already?" Dr. Sweeney pointed out.
Forest buffers-far from being a stop gap, least cost measure to prevent the fouling of our waterways-are rather a fundamental means of rebuilding the native and necessary ecological relationships of our landscape.
I hope these few examples illustrate a concept that became clear to me as I toured the Stroud Water Research Center: we must foster the natural functioning of all of our ecosystems to protect and enhance the health of our environment.
Editor's Note: Mr. Brubaker and other Pennsylvania Bureau of Forestry employees toured the Stroud Water Research Center during a summer' meeting of PA Service Foresters. The Stroud Water Research Center seeks to advance the knowledge of freshwater ecosystems through interdisciplinary research into all aspects of streams, rivers, and their watersheds.
For more information, visit www.stroudcenter.org or contact them at 970 Spencer Road: Avondale, PA 19311. Phone 610-268-2153. This is a shorter version of an article that originally appeared in the Town Creek Ecosystem Management Project Newsletter. Used with permission.
Today:
With the importance of riparian buffers being ever relevant, Pennsylvania’s conservation districts have been installing new acres since 2018 with the help of a sub-grant program through PACD provided by the PA Department of Conservation and Natural Resources. Since 2018, PACD has received several grants from DCNR to continue the program. Since 2018, funding has been allocated to approximately 90 acres of riparian buffer projects.
Currently, there is about $18,000 available in the 2019-2023 grant. Please visit the PACD sub-grant page here for more information.
About $25,000 is available in the 2021-2024 grant. Please visit the PACD sub-grant page here for more information.
Financial and other support for this project is provided by the Pennsylvania Association of Conservation Districts, Inc. through a grant from the Pennsylvania Department of Conservation and Natural Resources, Bureau of Recreation and Conservation.
Tomorrow:
PA’s Buffer Initiative: From DCNR’s website
Pennsylvania has more than 86,000 miles of rivers and streams. Maintaining and restoring buffers is a key strategy for improving water quality and aquatic habitat in Pennsylvania.
The commonwealth has a goal of planting 95,000 acres of riparian forest buffers statewide by 2025 to improve waterways in Pennsylvania and the Chesapeake Bay.
