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
How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Earth Sciences
23.05.2017 | Life Sciences
23.05.2017 | Physics and Astronomy