As warm weather arrives sooner in many parts of the nation, forest plants and trees on the banks flourish, shading the stream from sunlight and causing an overall decrease in productivity in the late spring and summer.
A research paper published in this month’s issue of Global Change Biology titled “Unexpected effect of climate change: Stream ecosystem responses to the 2007 spring freeze” describes how a small change in canopy cover can dramatically impact a stream.
“The study implies that the algal productivity pulse in the stream that drives the ecosystem during the spring months could be shortened with climate change if leaf-out continues to occur earlier each year,” said ORNL researcher Patrick Mulholland, author of the paper. “The stream no longer gets that period of peak productivity in spring because the leaves are shading the stream when the sun angle is relatively high.”
For this particular study, an Arctic air mass sent temperatures to below 28 degrees Fahrenheit for several nights in succession, freezing many of the newly emerged leaves and leaving the stream exposed to higher than normal levels of sunlight over the next several months.
This early April freeze resulted in positive effects for a well-studied East Tennessee stream and reiterated the importance of sunlight on the growth of algae, bacteria, snails and other organisms in forest streams.
Compared to typical conditions, the post-freeze conditions set in motion a chain reaction.
“Increased light levels caused a cascade of ecological effects in the stream, beginning with considerably higher growth rates during the late spring and summer months when normally low light levels severely limit stream production,” said Mulholland, a member of the Environmental Sciences Division.
In this case, a freeze caused the Walker Branch stream to prosper, but an ecosystem cannot count on unexpected weather events to maintain productivity.
“The stream ecosystem cannot depend on an Arctic air mass moving in every year, killing the leaves and exposing the stream to sunlight, resulting in increased growth,” Mulholland said. “It’s an unpredictable weather occurrence. On the other hand, we see that early leaf emergence has become predictable and has negative effects on the stream ecosystem during the critical spring period when many stream organisms are dependent on algae for food.”
Although canopy cover in the spring leads to decreased organism growth, in the autumn, bacteria and fungi decompose the leaves and grow from the nutrients, thus stimulating productivity.
This research was funded by the Office of Biological and Environmental Research within the DOE Office of Science. Co-authors of the research paper are John Smith of ORNL, Brian Roberts of Louisiana Universities Marine Consortium and Walter Hill of the University of Illinois.
ORNL is managed by UT-Battelle for the Department of Energy.
Emma Macmillan | Newswise Science News
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
21.03.2018 | Physics and Astronomy
21.03.2018 | Materials Sciences
21.03.2018 | Life Sciences