PINEMAP scientists work toward sustainably managing southern pine plantations
February 15, 2015
Virginia Tech is one of 11 southeastern land-grant universities that conduct research, education, and outreach as part of the Pine Integrated Network: Education, Mitigation, and Adaptation Project (PINEMAP), which is funded by the U.S. Department of Agriculture. The following projects are being carried out by forest resources scientists in the college to achieve PINEMAP’s goal to manage southern forests for increased carbon sequestration, resilience, and sustainability in the face of climate change.
New models enhance satellite images, coordinate databases to manage forests for climate change
Forests are the Earth’s lungs — inhaling carbon dioxide and exhaling oxygen. Efficient forest management and healthy forests are more important than ever to counter climate change resulting from excess carbon dioxide. Virginia Tech scientists are improving the ability to use remote sensing to see important changes in forests and creating models to improve planning and management.
Orbiting the Earth every 16 days, Landsat satellites provide photos that can be used to monitor forest health; however, there have been challenges. The most obvious is clouds, explained Randolph Wynne, professor of forest remote sensing.
Another challenge is the difficulty of identifying minor changes, such as from thinning, said Evan Brooks, a 2013 Ph.D. graduate in forestry from Virginia Tech. Writing for an article in the journal IEEE Transactions on Geoscience and Remote Sensing, he said, “While small changes may appear negligible on a pixel basis, on a cumulative basis, they can be the most important feature of change across a scene.”
“Some 15 to 20 percent of forests in the Southeast U.S. are owned by corporations, who have detailed records of what is happening in their stands,” said Wynne. “But many private landowners don’t keep such careful records, so forest capacity and condition is uncertain.”
Using images from a single Landsat scene from 2005 to 2011, treating each pixel independently, Brooks developed a model that compared satellite images to fill in for cloudy days and enhance detail, correctly detecting shifts in type and quality of land cover across 85 percent of a collection of areas checked against aerial photographs. He tested the method against known regions of thinning, such as the detailed records from corporate forests, and he and colleagues showed that the model was capable of detecting not only subtle thinning, but also regions of regrowth.
“Evan used a chunk of time to develop the approach, but it is now applicable to the whole history of satellite images and into the future,” said Valerie Thomas, assistant professor of forest remote sensing.
“The most useful feature of the method is that it easily incorporates new images as they arrive,” Brooks, Wynne, and Thomas reported to PINEMAP.
“In both applications — seeing past clouds and seeing changes in real time — we are trying to get ready for an unknown set of climate effects,” Wynne said.
Accurately predicting loblolly pine growth and yield under different future climate scenarios also requires models of pine stands that incorporate management practices, climate, geography, and biophysical variables as predictors. “In the past, we had assumed that the influences of climate would average out over 20 to 30 years,” said Harold Burkhart, university distinguished professor. “Now we are saying climate will not necessarily average out, and we wish to make predictions for alternate future climate scenarios.”
Charles Sabatia, a postdoctoral research associate in forest resources and environmental conservation, and Burkhart reported to PINEMAP on several modeling approaches.
Using daily climate data from 1980 to 2011, the forest scientists are comparing approaches to modeling the effect of 24 biophysical variables, such as temperature and moisture.
The college has developed models of forest growth as a function of the kinds of seed stock and silviculture, or management practices used. Burkhart and his colleagues are putting the forest growth, climate, and soils databases together for the first time. “We have databases of climates, soils, and plots all over the region and can layer the data and interpolate values,” said Burkhart.
“Extracting a climate signal out of historical data in a useful way to project future productivity is extraordinarily difficult because genetic improvement and management practices, as well as environmental influences, are all simultaneously varying. The aim is to develop useful predictions for planning rather than just describe the data,” said Burkhart. “We can now make some credible predictions, although with fairly wide error bands.”
The researchers have developed an overall model of pine plantations that reflects varied genetic stock, silviculture, soils, and climatic variables that can be applied with or without biophysical variables. “That is, you can use just management inputs to predict productivity, if you do not want to include soil and climate,” Burkhart said.
He explained that, for some purposes, forest managers may prefer to use the average values reflected in the tree growth data of the past, because predictions of climate for short periods of time, even a normal rotation for forest crops, are not reliable. “Biophysical variables, including soils data and climate, are integrated into a single value called ‘site index’ that is a required input to all of these models. Hence, biophysical variables are indirectly included in a single variable.”
However, adding specific values for soils and climate is necessary to predict growth under alternate scenarios of future climate influences.
“We can anticipate what to expect in terms of product yield and carbon sequestration,” said Wynne. “We also want to be able to advise property owners regarding management to make their stands less sensitive to climate, in particular water availability. Drought, rather than temperature, is what has the biggest impact on forests. Stressed forests are susceptible to disease and insect damage.”
New technique improves measurement of forest carbon sequestration
Forests scientists want to quantify carbon sequestration — the removal of carbon dioxide from the air — and understand how this process changes due to factors like drought and forest management. To measure how much carbon loblolly pine plantations store in soil and trees, the scientists model the carbon captured by plants during photosynthesis and produced by both plants and microbes during respiration.
A challenge has been separating the carbon dioxide removed from the soil by microbes compared with that removed by roots. Master’s student Brett Heim; Brian Strahm, assistant professor of forest soils and ecology; and John Seiler, Alumni Distinguished Professor, have developed and tested a procedure that makes it possible to determine this across the southeastern United States. They drive four-inch wide collars a little over a foot into the ground, which severs the roots from their source of carbohydrates for respiration. Once root respiration drops to zero, what is left is microbial respiration.
A surprising finding was that the roots accounted for about 20 percent of respiration — it had been assumed that microbes and roots were about equal. This changes the understanding of the carbon balance of these forests and how they might respond to climate and land use.
The research was first developed at the PINEMAP research site in the Appomattox-Buckingham State Forest in Virginia. The technique is now being used by other scientists at other loblolly pine plantation sites to determine net ecosystem productivity across the range of the species.
Enhanced fertilizers, tree genotypes keep forests healthy
In addition to carbon sequestration, PINEMAP goals are pine plantations that are more efficient at nutrient uptake and that adapt across a range of climate conditions.
Virginia Tech forest scientists tracked nitrogen uptake in trees to determine the best times for application and whether enhanced efficiency fertilizers reduce the carbon dioxide and ammonia emissions of the traditional urea-based fertilizer. Doctoral student Jay Raymond; Tom Fox, professor of forest soils and silviculture; and Assistant Professor Brian Strahm compared four types of treatment and no treatment at 18 sites across the range of loblolly pine plantations in the southern U.S. over the course of two years.
Using fertilizers enriched with a stable isotope so it could be tracked, they tested basic urea, a polymer-coated urea, and two variations of urea combined with time-release chemicals that inhibit ammonia and carbon dioxide release (NBPT+urea and phosphate+NBPT+urea). Fertilizers were applied during the winter, which is the common practice, and during the summer.
Sampling of foliage, fine branches, coarse branches, stems, and roots was conducted every six weeks. Also sampled were trees and shrubs that compete with the loblolly pines, forest litter, the forest floor, and mineral soil.
Preliminary results from one site indicate that enriched nitrogenis being incorporated into the above-ground tree biomass through the entire growing season, with the largest levels in the foliage. For three of the four treatments, winter plots had a larger portion of nitrogen from fertilization. Urea enhanced with time-release chemistry (NBPT+urea) performed the best of all the treatments in winter and summer.
Genotyping will help identify forest breeding stock that can adapt to climate change
Forest scientists would like to know why some trees adapt well across a range of climate conditions. “Determining how genetic variation shapes climatic adaptation will help guide pine breeding programs to mitigate the impact of climate change,” said Jason Holliday, assistant professor of forest genetics and biotechnology.
He and researchers at Texas A&M and North Carolina State compared two methods for detecting genetic variation. One method requires custom synthesis of DNA to retrieve specific gene regions. This approach is more expensive but yields more information. The other method uses DNA-cutting enzymes to sequence a random but repeatable subset of the genome, which is less expensive and lends itself to high throughput analysis of the large number of trees in breeding programs.
The researchers conclude that PINEMAP will find both useful. “The PINEMAP project includes several different genetics experiments based on different populations, and both the restriction-enzyme-based and hybrid-capture sequencing methods are likely to find application in achieving the project objectives.”
Undergraduates engage secondary school students on climate change and forest ecosystem issues
A final step in preparing for climate change is education. A novel undergraduate fellowship program provides students with hands-on research experiences that demonstrate the impact of climate change and the importance of forest resources. Then, like dropping a pebble in a pond, the new scientists share their knowledge with hundreds of secondary school students.
Undergraduates are selected from across the country, and each is mentored for 12 weeks by a graduate student at a PINEMAP-affiliated university.
Will Kennerley of Burke, Virginia, worked with Brett Heim of Sheboygan, Wisconsin, a Master of Science candidate in forest resources and environmental conservation at Virginia Tech. “I did everything from tree-coring to stream-monitoring,” said Kennerley, who was a sophomore wildlife science major at Virginia Tech.
It is also a learning experience for the graduate students. “I learned to articulate a task, giving clear and specific description of background and goals,” said Wen Lin, a doctoral student in forestry and environmental resources at North Carolina State University.
The undergrads then return to their home university to fulfill the second phase of the project — outreach. The transition is made possible by a distance-education Effective Communication Skills course. The three-credit course is team-taught by Virginia Tech faculty members.
The course has two major components. First, the course teaches interpersonal, written, oral, and nonverbal communication skills. The undergrads communicate their scientific research by writing an abstract of their work and creating a poster and PowerPoint presentations.
Second, the students must learn to communicate their research to an audience not steeped in the technical language of their discipline. Their communication skills are used to develop presentations that relate their personal research interests and climate-change and forest-resource issues to middle and high school students. And the presentations must target standards of learning (SOL) from their states’ educational guidelines.
For example, Bethany Gregory, of Bastian, Virginia, a senior in wildlife science at Virginia Tech, gave a presentation titled, “Where’s the Water?” to 15 different groups of biology, agriculture, and ecology students.
Each presentation relayed PINEMAP’s goals to manage southern forests for increased resilience and sustainability under changing climates. All presentations touched on practices that students could use to help mitigate climate change or natural resource degradation.
“The Effective Communication Skills course proved to be a useful tool for teaching undergraduates skills related to science communication and education while also engaging students in educating secondary school students about climate change and forest ecosystems,” John B. Kidd, PINEMAP undergraduate fellowship program coordinator at Virginia Tech. Professor John Seiler added, “The course also laid the foundation for fellows to pursue graduate studies and future careers in natural resource disciplines.”
In the first two years of the undergraduate research fellowship program, 17 undergraduates delivered 161 presentations to 3,689 public school students from 39 different schools.
Importance of Southern Pine Forests
- The 34 million acres of southern U.S. pine forests produce more timber than any other country in the world.
- These forests sequester 12 billion metric tons of carbon each year — 36 percent of the carbon sequestered annually by all forests in the contiguous 48 states.