How Sustainable are Eucalyptus Plantations?

Forest Service scientists develop model to estimate water use in eucalyptus plantations

by Ying Ouyang and Theodor D. Leininger, SRS Center for Bottomland Hardwoods Research
(A) The hydrological processes at the plantation level, and (B) the compartmental model for water movement within the eucalyptus tree used for this study. Models by Ying Ouyang.

Models used in this study: (A) The hydrological processes at the plantation level, and (B) the compartmental model for water movement within the eucalyptus trees. Models by Ying Ouyang.

Eucalypts – woody plants originally found in Australia — have been identified as one of the best feedstocks for bioenergy production due to their fast-growth rate and coppicing ability, but there are concerns about adverse environmental effects, some related to water consumption, and their water use efficiency is still poorly understood.

U.S. Forest Service research scientists from the Southern Research Station Center for Bottomland Hardwoods Research (CBHR) have developed a system dynamic modeling tool to investigate this issue using the STELLA (Structural Thinking and Experiential Learning Laboratory with Animation) software. Results were recently published in the journal Ecological Engineering.

After calibration and validation, the model was used to quantify the hydrological processes and water use in a 40 meter-square eucalyptus plantation. “The model was able to predict eucalyptus water use in a site-specific plantation under normal, wet, and dry soil conditions,” says Ying Ouyang, CBHR research hydrologist and the study’s lead author. “A characteristic monthly variation pattern was predicted for soil evaporation, leaf transpiration, and root uptake, with water use increasing from winter to summer and decreasing from summer to the following winter.”

“For the simulation conditions used in this study, the maximum rate of leaf transpiration was about five times greater than that of soil evaporation, and the cumulative annual water use by the eucalyptus trees in the plantation was 3200 liters per tree,” says Ouyang.

This study suggests that the system dynamic model developed with STELLA is a useful tool to estimate hydrological processes and water use in a eucalyptus plantation or other tree species plantations.

Read the full text of the article online.

For more information, email Ying Ouyang at youyang@fs.fed.us

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Posted in Biomass and Bioenergy, Bottomland Hardwoods, Forest Watersheds

Landscape Ecology Meeting Draws Forest Service Scientists and Record Attendance

by Stephanie Worley Firley, Eastern Threat Center
US-IALE President Janet Franklin (third from left) recognized the efforts of meeting organizers from the Eastern Threat Center (left to right: Bill Hargrove, Kurt Riitters, Danny Lee, Stephanie Worley Firley, and Steve Norman) during the US-IALE awards banquet. Photo by Jeffrey Hepinstall-Cymerman, University of Georgia.

US-IALE President Janet Franklin (third from left) recognized the efforts of meeting organizers from the Eastern Threat Center (left to right: Bill Hargrove, Kurt Riitters, Danny Lee, Stephanie Worley Firley, and Steve Norman) during the US-IALE awards banquet. Photo by Jeffrey Hepinstall-Cymerman, University of Georgia.

After more than a year of planning, local organizers from the U.S. Forest Service Eastern Forest Environmental Threat Assessment Center were thrilled to finally welcome attendees of the annual meeting of the U.S. International Association for Landscape Ecology (US-IALE), held last month in Asheville, North Carolina. It was the 29th annual and the largest ever US-IALE annual meeting, drawing approximately 500 professionals (including about 40 Forest Service scientists) and students from 22 countries and 42 states.

The meeting explored topics of concern to the Forest Service and partners related to a “Landscape Change” theme and offered attendees a place to share, critique, and strengthen ideas for an all-lands approach to research and management. Hundreds of presentations, dozens of posters and live demonstrations, and several training workshops fostered discussion and learning. Six scientific excursions allowed exploration of environmental and social issues associated with landscape change in and around Asheville. A Forest Service Research and Development exhibit featured the faces of landscape science in the agency, along with information about scientists’ wide-ranging projects and interests.

“I think that what makes the annual US-IALE meeting so great is that it is attended by people who believe that the best science comes from the overlaps in scientific subjects — the intersection between multiple disciplines,” says Bill Hargrove, a research ecologist with the Eastern Threat Center and chair of the meeting’s organizing committee. “Because of their common interests, meeting attendees engage in deeper attempts at cross-disciplinary thinking, bridging vocabulary and terminology across subjects. This is one of the unique aspects of the annual US-IALE meeting and why it has been my favorite meeting to attend over the last three decades.”

Eastern Threat Center research ecologists Kurt Riitters and Steve Norman, Center Director Danny Lee, and biological science information specialist Stephanie Worley Firley also helped to organize the meeting’s program on behalf of US-IALE.

The Forest Service has a long history of membership and support for US-IALE, though this is only the second time the agency has played a key role in organizing the annual meeting. Three Forest Service scientists have served as US-IALE President, including Riitters, who says, “The US-IALE annual meeting is an ideal opportunity to broaden one’s perspective and make new connections – to deliver on the promise of ecology as an interdisciplinary science.” The next opportunity to get involved comes when university colleagues and the host city of Baltimore welcome attendees to the US-IALE annual meeting in April 2017.

For more information, email Bill Hargrove at whargrove@fs.fed.us.

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Posted in Threats

How Drought Affects Forests and Streams

Understanding the interactions among drought, hydrology, and vegetation

by Zoё Hoyle, SRS Science Communications
Forested watersheds across the U.S. supply drinking water for nearby urban populations. Photo by U.S. Bureau of Land Management.

Forested watersheds across the U.S. supply drinking water for nearby urban populations. Photo by U.S. Bureau of Land Management.

Across the U.S., forested watersheds filter surface water that drains into the rivers that supply drinking water for many of the nation’s cities. Besides providing high quality water for humans needs, forest trees regulate streamflow, mitigate flooding, and help create and maintain the water conditions that support healthy aquatic ecosystems.

Drought affects the ability of forests to continue these important functions. In areas of the U.S. that experience seasonal drought on a regular basis, forest and stream ecosystems are often able to adapt to the hydrologic changes that take place, but severe or long lasting drought can push systems to the breaking point. In the western U.S., for example, more prolonged and frequent droughts have ramped up the spread and intensity of insect attacks that, in some cases, kill nearly all of the canopy trees in forest stands. Loss of forest canopy in turn affects the quality and quantity of water from those forests.

Western forests are not alone in their vulnerability to drought. The warmer temperatures and longer dry spells projected under climate change will probably lead to more extreme drought conditions for forests in all regions of the U.S. Forest vegetation can either mitigate or worsen the effects of drought on the ecosystems supported by forests, depending on the species composition of the forest and how those species make use of water and tolerate stress.

Understanding how drought, hydrologic processes, and vegetation interact in U.S. forests – the ecohydrological context – is the subject of a new article in the journal Forest Ecology and Management by U.S Forest Service scientists and collaborators. The review article is a modified version of a comprehensive synthesis on the effects of drought on U.S. forests and rangelands developed by some of the same authors to provide information for the sustained National Climate Assessment process.

“Understanding how drought impacts ecosystems requires knowledge of how it impacts the ecohydrological processes of individual tree species in relation to species composition and physical factors such as slope and soil,” said Jim Vose, lead author of the article and project leader of the Forest Service Center for Integrated Forest Science and Synthesis. “With this understanding we can start to develop management options that minimize the impacts of drought on water and water quality.”

For the article, the researchers examined how differences in forest species composition and structure impact evapotranspiration – the loss of water vapor through tree leaves – and how this in turn impacts the quantity and quality of water from forest watersheds. Sections include discussions of the forest harvesting research that has provided much of what is known about how changes in forest structure impact streamflow and water quality, as well as what is known about groundwater interactions with drought, and drought impacts on water quality and stream water temperature.

After noting the challenges to predicting the impacts of drought on hydrological processes, the authors review management options for minimizing impacts on water quantity and quality, including the idea of harvesting to increase water yield, which research has shown is not sustainable in the long run. Replanting cut forests with species that consume less water is another possibility, as are limiting streamwater withdrawals and wastewater discharge during periods of low streamflow, or restoring and maintaining riparian buffers to increase shade and reduce sediment loads.

“There’s still so much uncertainty about drought projections, so it is difficult to predict the ecohydrological interactions among trees, water, and ecosystems,” cautioned Vose. “This uncertainty means that there will be a continuing need for monitoring and adaptive forest management.”

Despite these challenges, new technologies coupled with data from established and emerging networks – such as Forest Service Experimental Forests and Rangelands and Forest Inventory and Analysis plots, the Ameriflux network, NEON, LTER sites, and USGS streamflow gauges — offer ways to measure and visualize ecohydrological processes at a range of spatial scales that may lead to new insights into how to respond to the inevitability of drought.

Read the full text of the article.

For more information, email Jim Vose at jvose@fs.fed.us.

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Posted in Climate Change, Forest Watersheds
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