Provide Abundant Clean Water
The availability of clean water is intimately linked to healthy forests. However, there are a host of factors impacting the health and sustainability of forests. Working to sustain forests ranging from tropical wetlands to northern forests requires understanding the process by which forests function to produce clean water, and the specific impacts of natural and human caused disturbances on tree growth. This month, we feature a scientist, research, a product and a partnership that demonstrate the role of forests in providing clean water as well as many other benefits.
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Some careers are sparked by growing up steeped in natural resources; John Campbell’s career was inspired by disturbance of natural resources. Now a research ecologist studying forest disturbance, Campbell grew up in suburban New Jersey, where the only remnant of nature in his neighborhood was a stream that was later paved in a flood reduction effort. “It was a shock,” Campbell said. “It struck me forcefully as a child.”
Campbell works at the Northern Research Station’s Hubbard Brook Experimental Forest on the White Mountain National Forest in New Hampshire, where he explores how forest disturbances ranging from ice storms and drought to timber harvesting and air pollution ultimately affect the quality and quantity of stream water. What happens to forests in winter has been the focus of much of his research. “It is an important time of year,” Campbell said. “What happens during those months ripples out through the other three seasons.” Campbell began his career with the U.S. Forest Service as a volunteer in Durham, New Hampshire. He worked for the Forest Service’s Forest Inventory and Analysis Program before leaving the agency for other opportunities, but returned for a position as an information manager for the Hubbard Brook Experimental Forest. He became a research ecologist in 2001. Twenty-three years into his career, forests continue to intrigue Campbell. “They are always surprising me,” he said. “Just when you think you have figured out a change in the forest that you can expect to diminish growth, you find it thriving. That leads to whole new avenues of research.”
The Hubbard Brook Ice Storm Experiment is a case in point. Scientists from the Forest Service, Syracuse University, the Cary Institute of Ecosystem Studies, Cornell University, University of Vermont, and the Hubbard Brook Research Foundation created an experimental ice storm with the objective of improving understanding of short- and long-term effects of ice on northern forests. The hypothesis was that the effects of simulated ice storms ranging from light to extreme icing would result in nitrogen leaching into streams because damaged trees would not take up as much nitrogen from the soil. “The forest has surprised me,” Campbell said. “Preliminary data are not indicating nitrogen spikes in response to this disturbance.”
Working in a forest has not dimmed Campbell’s appreciation for nature. “Whenever I take my kids hiking, I am thinking about the science behind what we’re seeing but it doesn’t obscure the beauty,” he said. “It still gives me a thrill to be outside with the forest.”
Growth-climate relationships across topographic gradients in the northern Great Lakes
Red pine and quaking aspen are both dominant and iconic species in forests in the upper Great Lakes region in North America, but climate change has the potential to impact the health and range of these forests. In the article “Growth-climate relationships across topographic gradients in the northern Great Lakes” published in the journal Ecohydrology, researchers used a natural gradient to explore how temperature and moisture, key climate change variables, combine to impact tree growth.
The scientists, led by Salli Dymond, now a faculty member at the University of Minnesota, Duluth, conducted their study on the Marcell Experimental Forest in northcentral Minnesota. The site provided a topographical gradient over which moisture availability varies depending on location on the slope. In addition, the close balance between soil water availability and potential water loss from trees (evapotranspiration) on the site offered excellent conditions for testing study hypotheses.
Scientists assessed annual tree growth along the topographic gradient by measuring tree ring width from samples obtained using an increment borer. Soil moisture measurements were used to determine amount of water available to the trees. Strong relationships between tree growth and climate (represented by temperature and soil moisture) were found for both tree species. The topographic location of the tree was a significant factor in growth of quaking aspen, with ridge trees more susceptible to declines in soil moisture and trees on the sideslopes and toeslopes responding more to changes in temperature. Generally, in areas with lower moisture levels and higher temperatures there was less tree growth.
“The topographical gradient served to emulate impacts of changing climate on red pine and quaking aspen and demonstrates that the two species respond significantly to climate variation,” said Randy Kolka, research soil scientist with the U.S. Forest Service’s Northern Research Station and study co-author. The northern Great Lakes region is anticipated to get warmer with more extreme wet and dry periods as the climate changes. “Ultimately these impacts may lead to loss of vigor of these forests and possibly local extinction affecting both forest productivity and the character that defines the Northwoods,” said Kolka.
New Insights into how Forests Provide Clean, Secure Water Supplies
In the United States, forests are an important source of clean water for millions of people. But even for scientists, that statements begs the question: exactly how do forests produce clean water?
Watershed 3 at the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, where hydrological records date back to 1957, gave Northern Research Station Geologist Scott Bailey and his colleagues an opportunity to create a new approach to answering that question. Using detailed water chemistry data, Bailey and a team of international scientists developed a model of water transport that establishes the important underground pathways that water takes to move through the watersheds and how long it takes water that falls as rain or snow to reach the outlet to Watershed 3.
Long-term data also gave scientists a means of testing the model by setting it to predict historic water flow and variations in water quality. Because they were able to check the model’s predictions against actual data, scientists are confident in the model’s ability to predict current stream characteristics. Bailey said that without the historic data against which scientists could test the model, it would have taken years to establish the model’s accuracy.
“The ability to maintain studies and collect data over decades, not just the life of one project over 3 to 5 years, sets the Forest Service apart in the scientific community,” Bailey said. “Experimental forests throughout the United States have generated long-term data sets that are being used in new and innovative ways to answer questions that make a difference to the health of forests as well as people.”
The model shows that the median time water spends in Watershed 3 varies from about 50 days during wet periods to nearly 200 days during dry periods. At all times, there is a small portion of the water that has been in the watershed for as long as 3 or 4 years. The model predicts the variation of water ages over the long-term record and shows how this variation in water transit times controls the variation in water quality observed in weekly samples collected at the weir, a data set that goes back to 1963.
Besides showing the value of long-term data sets on streamflow rates and chemistry, this research demonstrates the power of collaboration and partnership to answer complicated research questions. This study was possible because of the contributions of several Italian scientists who are global leaders in the mathematics behind water transit time modelling, along with Research Hydrologist Mark Green of the Northern Research Station and Plymouth State University and Research Ecologist John Campbell of the Northern Research Station, who are measuring the isotopic composition of water at Hubbard Brook.
Research, Outreach, and Capacity Building in Tropical Wetlands through SWAMP
Tropical wetlands, such as peatlands and mangrove forests, are highly valued ecosystems that occupy 0.25 percent of the Earth’s land surface but store 3 percent of the terrestrial carbon. In addition to providing food, fiber, fuel, and storm protection for local people and habitat for rare species, they play an important role in climate change adaptation and mitigation. Their global importance spurred the formation of an international partnership, the Sustainable Wetlands Adaptation and Mitigation Program (SWAMP), to help tropical countries with conservation and carbon accounting for these ecosystems.
The U.S. Forest Service International Programs, the Northern Research Station, the Center for International Forestry Research, and many other organizations and institutions comprise the partnership which is supported by the U.S. Agency for International Development. Objectives of the program include advancing the science of measuring, reporting and verifying carbon storage and greenhouse gas emissions, establishing permanent wetland plots, filling knowledge gaps in carbon dynamics and building regional capacity for climate change research and carbon accounting.
Recent products developed through the partnership include the SWAMP Toolbox, which helps people understand the importance of wetlands as carbon reservoirs, and the Global Wetlands Map identifying the locations of tropical wetlands. “Sharing research information with regional policymakers and land managers can help garner support for sustainable management of these wetlands in the face of many competing demands,” said Randy Kolka, research soil scientist with the Northern Research Station and the Forest Service lead for the SWAMP partnership.
The SWAMP partnership is currently working in 27 countries in Latin America, Africa and Southeast Asia and is preparing to expand work in more countries.