Forests, Water, Climate, and Management

SRS scientists contribute to book on forest hydrology

by Sarah Farmer, SRS Science Communications
Dozens of scientists collaborated to write and edit the book, which addresses almost every aspect of forest hydrology.

Dozens of scientists collaborated to write and edit the book, which addresses almost every aspect of forest hydrology.

Across the globe, forests cover about a quarter of all land and are important sources of clean water. A new book, edited by U.S. Forest Service Southern Research Station (SRS) scientist Devendra Amatya, examines the interactions between forests, water, climate, and management. The book, Forest Hydrology: Processes, Management and Assessment, was recently published by the Centre for Agriculture and Biosciences International (CABI).

Scientists have been investigating forest hydrology for decades, but until now, much of the information has been accumulating only in journals, proceedings papers, reports, and a few textbooks. The new book is unique because it represents the state of the science on forest hydrology, the study of how water and forests interact, and watershed management.

Several Forest Service scientists contributed to the book as lead authors, including SRS research hydrologist Ge Sun and SRS project leader Jim Vose. In addition to being the lead editor, Amatya contributed to several chapters both as lead and coauthor. Each chapter was written and edited by world-renowned scientists, managers, engineers, and others with extensive background in forest hydrology and management.

“Forests interact with and protect water and soil in a variety of ways,” says Amatya. For example, when rain falls on a forest canopy, some of it is intercepted by the leaves and branches in the canopy and evaporates back to the atmosphere. Trees also suck water out of the soil with their roots, eventually releasing it to the atmosphere via transpiration. Read Amatya’s chapter on the hydrological processes of reference watersheds in U.S. experimental forests.

The scientists also summarize recent findings about evapotranspiration (plant transpiration plus evaporation) and techniques for measuring it. “Evapotranspiration links climate, hydrology, and ecosystem services such as carbon sequestration – especially in the context of trees’ ability to fix atmospheric carbon dioxide,” says Sun, who was lead author of the chapter. “Evapotranspiration is a large component of the water budget and one key aspect of forest hydrology that is rapidly developing.”

Climate change directly affects forest hydrology. When air temperatures increase, the amount of water lost to the atmosphere will potentially increase, causing a decrease in the amount of water that seeps into the earth, eventually depleting groundwater, and potentially streamflow. Several chapters address the potential impacts of climate-related disturbances such as extreme floods, drought, disease, and fire.

The rate of disturbances has increased to unprecedented levels. “It is not clear if the past alone will serve as an adequate model of the future,” says Vose, who was lead author of the chapter on future challenges. “Hydrological cycles have already been altered and changes will continue as climate change, population growth, water diversion, and numerous other environmental changes continue.”

The Forest Service has a long history of studying forest hydrology and maintains premier research facilities. “The long-term research conducted on Forest Service Experimental Forest watersheds has contributed substantially to our understanding of relationships between forests and streamflow,” says Amatya. Amatya and his coauthors discuss the characteristics of 10 relatively undisturbed watersheds across the country, including those at Coweeta Hydrological Laboratory and the Santee Experimental Forest. Their analyses will be useful for assessing the impacts of forest disturbance and restoration projects, and testing models used elsewhere for ecohydrologic studies.

“The book covers almost all aspects of forest hydrology, in multiple environments – from tundra to the tropics,” says Amatya. “It will be useful for graduate students, professionals, land managers, practitioners, and researchers.”

Visit the CABI website to buy a copy of the book.

For more information, email Devendra Amatya at

 Access the latest publications by SRS scientists.

Tagged with: , , , , ,
Posted in Climate Change, Experimental Forests, Forest Watersheds

The Koen Experimental Forest

The base for upland hardwood field research in Arkansas

View of the Koen from the 1960s. Photo by R.W. Neelands.


Established in 1951 in northern Arkansas, the Henry R. Koen Experimental Forest (Koen) is covered mostly in oak-hickory upland hardwood forest and oak-pine stands.

Named for Henry R. Koen, forest supervisor of the Ozark National Forest during the first half of the 20th century, the experimental forest was set aside to develop scientific principles for forest management. At 720 acres, the Koen is the smallest of the 19 experimental forests managed by Southern Research Station (SRS).

Forest Service facilities include an office, garage, and workshop. The Koen also features a handicapped accessible nature trail established in collaboration with several local civic organizations. Visitors from across the United States and around the world use the trail and picnic area.

Through 1979, research at the Koen focused on upland hardwood forests. Researchers conducted numerous studies from the early 1940s to the late 1970s on the effect of stand structure on white oak stands, forest inventory sampling design, improvement harvesting, and small woodland management. Two long-term datasets resulted from research at the Koen: a study of red cedar that began in the 1940s and ran through the early 1960s, and a watershed study that ended in the late 1970s.

Today, the Koen serves as the fieldwork base for SRS upland hardwood research across Arkansas. SRS research forest ecologist Marty Spetich manages the Koen, where he leads an integrated research program of 17 studies on upland hardwood forest dynamics and both short- and long-term studies at three scales: individual tree, stand, and region. These studies encompass forest species restoration, quantitative silviculture, development of forest management methods, forest ecology, disturbance ecology, landscape ecology, climate change, forest biomass, and diversity of Arkansas upland hardwood forests.

For more information, email Marty Spetich at

Access the latest publications by SRS scientists.

Tagged with: ,
Posted in Experimental Forests, National Forests, Upland Hardwoods

Dry Tropical Forests in the Caribbean and Latin America under Threat

Inventory of woody plants reveals loss of plant diversity

by Zoё Hoyle, SRS Science Communications
Inside the dry tropical forest of the Mona Island Natural Reserve, Puerto Rico. Photo by Humfredo Marcano-Vega, U.S. Forest Service.

Inside the dry tropical forest of the Mona Island Natural Reserve, Puerto Rico. Photo by Humfredo Marcano-Vega, U.S. Forest Service.

The climate and fertile soils of the dry tropical forests of Latin America and the Caribbean have been important to humans as areas to grow crops since pre-Columbian times. Because of this and more recent use for intensive cultivation and cattle grazing, many of these forests have been cleared, with less than 10 percent of original dry tropical forest remaining in many countries.

Even though they support a wide diversity of species found nowhere else in the world, few dry tropical forests are currently protected, according to a study recently published in Science by scientists in the Latin America and Caribbean Seasonally Dry Tropical Floristic Network (DryFlor). U.S. Forest Service Humfredo Marcano-Vega, research biologist based in San Juan, Puerto Rico, contributed to the article.

“We define tropical dry forest as having a closed canopy, distinguishing it from more open, grass-rich savannas,” says Marcano-Vega, who works for the Forest Service Southern Research Station Forest Inventory and Analysis unit. “These seasonally dry forests grow on fertile soil where the rainfall is less than 70 inches a year, with a period of 3 to 6 months of less than 4 inches per month during which most vegetation shows deciduousness — leaf drop — as a special adaptation to water scarcity.”

Using data from 1602 inventories that cover 6958 woody species that occur in dry tropical forests from Mexico and the Caribbean to Argentina and Paraquay, the researchers evaluated the patterns of plant diversity in remaining areas of dry forest, highlighting those areas with the highest diversity and endemism (species confined to a unique location). They also looked at floristic turnover, the rate at which woody species are replaced by new ones across the geographic range of neotropical dry forests.

They found that the variation in woody species composition among inventories defined 12 dry floristic groups and that the remaining dry forests in Latin America and the Caribbean are fairly different from one another — 23 to 73 percent of the species found in each forest are distinct to it – and that there was a high level of floristic turnover across the region. This indicates that remaining dry tropical forests in all of the 12 floristic groups in the region should be protected to prevent the loss of major species diversity.

The DryFlor scientists found the current levels of protection for these forests “woefully inadequate.”

An example is the Andean dry forests, some in small patches, whose species compositions are distinct from one another and from the dry tropical forests of the rest of the region. Some of the distinct floristic groups within these forests currently have no formal protection at all and are under pressure from high local populations who clear them for agriculture and fuelwood.

“It is our hope that our data set for Latin American and Caribbean dry forests and the results shown here can become the basis for future conservation decisions that take into account continent-level floristic patterns and thereby conserve the maximum diversity of these threatened forests,” the authors write in conclusion. “Interdisciplinary viewpoints that recognize the needs of local communities and the effects of management decisions on people are also fundamental for the success of dry forest protection proposals within the region,” adds Marcano-Vega.

Read the full text of the article.

For more information, email Humfredo Marcano-Vega at

Access the latest publications by SRS scientists.


Tagged with: , , , , , ,
Posted in Forest Inventory & Analysis
Subscribe to our newsletter!