Sustainability of the Southern Forest

The ecological and economic sustainability of southern forests is being questioned because there are many competing uses for these forests and because there are large regional shifts in forest land use. To adequately understand the state of our forests and their use with respect to sustainability, several significant changes have been made in programs of the U.S. Department of Agriculture Forest Service’s Forest Inventory and Analysis (FIA) and Forest Health Monitoring Research Work Units. These changes are enabling these units to better assess the status of and sustainability of our forests. The FIA Program has replaced the 70-year-old periodic forest survey sampling design with a continuous annual sampling program. The new sampling design provides for continuous monitoring and reporting, with the emphasis on current status and trends in forest resources and many of the criteria and indicators of sustainable forest management as identified by the Montreal Process. The program is a collaborative partnership among the Southern State forestry agencies and the U.S. Department of Agriculture Forest Service, Southern Research Station. The process used to develop the new annual forest inventory program has provided the opportunity to build stronger partnerships with State forestry agencies, universities, nongovernmental organizations, and the forest industry. These new and renewed partnerships are of considerable value in defining, interpreting, and reporting on criteria and indicators related to sustainable forestry. Recent collaborative research has produced methods for estimating forest area and area change from satellite imagery, initiatives on how to quantify and report nontimber forest products, and potential uses of remote sensing instruments for on-plot measurements; e.g., global positioning system units, lasers, and camera systems. INTRODUCTION The ecological and economic sustainability of our Nation’s forests is being questioned. The definition of forest sustainability is not fixed. As knowledge of forest processes and uses expands, conceptions and components of sustainability will change. At a minimum, sustainability must include both ecological and human dimensions: underlying ecological integrity of soil, water, atmosphere, biological diversity and productivity must relate to human needs for food, water, health, shelter, fuel, and culture. The U.S. Department of Agriculture Forest Service (Forest Service), Forest Inventory and Analysis (FIA) and Forest Health Monitoring (FHM) Programs have been expanding their roles to include analyses of biological diversity and productivity as influenced by soil, water, and atmospheric composition. For example, in the past decade these two programs have been modified to provide the monitoring data and analyses required for the investigation of environmental concerns about air pollutant impacts and effects of climate change on forests. Concern over perceived and real trends in forest resource conditions has led to numerous requests for improvement in the quantity, quality, and timeliness of information about forests and enhanced access to this information. To address these concerns, FIA and FHM contribute data and analyses to a variety of national and global assessments. The FIA and FHM data address at least 38 of the 67 criteria and indicators of sustainability for reporting under the Montreal Process. FIA and FHM data are essential to those who produce reports required by the Resources Planning Act (RPA) and are increasingly employed to support regional resource assessments used as a basis for forest planning. In response to these needs, FIA and FHM have implemented an annual forest inventory and monitoring program nationwide. 1 Mathematical Statistician and Project Leader, U.S. Department of Agriculture Forest Service, Southern Research Station, Research Triangle Park, NC 27709; Research Forester and Research Forest Products Technologist, U.S. Department of Agriculture Forest Service, Southern Research Station, Blacksburg, VA 24060, respectively. So ut he rn F or es t Sc ie nc e: Pa st , P re se nt , a nd F ut ur e Fo re st H ea lt h 180 THE FIA MISSION The FIA Program has been in continuous operation since 1930. It is the only consistent, credible program that provides forest data for all public and private land within the United States. The program reports on the current status of and trends in forest area, in species composition, in tree size, volume, growth and mortality, and in harvest removals. The FIA and FHM Programs provide additional information on attributes considered to be indicators of forest health. The FIA Program also collects and reports information on wood production and utilization rates by various products, and on forest land ownership. The FIA Program provides the most objective and scientifically defensible information available about the extent of forests, change in forest area, change in tree species composition, and rates of tree regeneration, growth, mortality, and harvesting. This information is used to help formulate State and Federal policy decisions, including international reporting; serve as a starting point for more intensive studies on key ecosystem processes; formulate business plans that are economically and ecologically sustainable; and inform the public about the health and sustainability of the Nation’s forests. Historically, the FIA Program has reinventoried each State’s forests at intervals of about 10 years. Prior to the annual inventory, FIA had established that (1) forest land remains the predominant land use in the South, (2) the forest land base in the South has been stable for several decades, (3) the pine component of the South’s forest is moving steadily toward more planted and fewer natural stands, (4) fears of a southern pine growth decline related to air pollutants have abated, and (5) growth rates on forest industry lands have continued to increase over the last four decades. The annual inventory program enables FIA to identify changes in trends much more quickly than the previous decadal scale design allowed. FOREST HEALTH MONITORING MISSION The purpose of FHM is to make statements about the status of and trends in the health of forest ecosystems in the United States. The FHM Program was established in 1991 to address environmental concerns about how natural factors such as insects, disease, and extreme weather events, and anthropogenic stresses such as air pollutants, climate change, population growth, and nonnative species affect forests. The National Acid Precipitation Assessment Program (NAPAP) Forest Response Program of the mid-1980s was in many ways a precursor of the FHM Program. During the mid-1980s there was increased concern that many forests in the United States were exposed to acidic deposition and other pollutants and that these regionally distributed pollutants might be damaging forests (Barnard and others 1990). Suspected declines in either the productivity or health of southern pines, red spruce, and sugar maple have been attributed to causes of this kind. Many of the policy and research questions asked by NAPAP are similar to those addressed by the current FHM Program. The FHM Program covers all forested lands through a partnership involving the Forest Service, State Foresters, and other State and Federal Agencies and academic groups. The FHM Program uses data from ground plots and ground surveys, aerial surveys, and other biotic and abiotic data sources to address forest health and sustainability issues. There is one key difference between FHM as implemented in the United States and similar monitoring efforts for Western Europe. Efforts in Europe have opted for onsite monitoring of pollutants and weather variables, while efforts in the United States have relied on the monitoring of bioindicator plants and other variables to monitor the effects of natural and anthropogenic stresses. A key example is that of monitoring the potential impact of ozone. It is known that high levels of ozone do not injure plants unless their stomata are open. High ozone and temperatures often occur at the same time, and these episodes often occur when stomata are closed. Thus, FHM has opted to monitor bioindicator species that are sufficiently sensitive to specific pollutants. This allows for assignment of injury to specific causes and for more accurate estimation of the spatial distribution of injury. The FHM Program is implemented through five major activities. (1) Detection monitoring uses nationally standardized ground and aerial surveys to evaluate the status of and change in forest conditions. (2) Evaluation monitoring determines the extent, severity, and causes of undesirable changes in forest health identified through detection monitoring. (3) Research on monitoring techniques creates sampling designs and analytical techniques used to develop bioindicators of forest health, provide early detection of invasive species, and devise methods for monitoring urban and riparian forests. (4) Intensive site monitoring enhances understanding of cause-effect relationships by linking the current 181 status of and trends in surveyed attributes and bioindicators to process-level studies of specific issues such as calcium depletion and carbon cycling. (5) Analysis and reporting produces peer-reviewed publications about analysis and interpretation of sampled populations and reports on forest health at national and regional levels. Since 1999, the FHM ground plot network used for detection monitoring has been integrated with the more intensively sampled forest inventory network maintained by the FIA Program. Currently, FIA has one plot per 6,000 acres, and FHM has one plot per 96,000 acres. Also, FIA has adopted annual survey methods similar to those used in the FHM Program. The merger of the FIA and FHM plot networks and increased coordination of survey methods enable both programs to produce annual estimates of forest area, forest inventory, and bioindicators of forest health. Moreover, the FHM (phase 3) field plots expand the suite of attributes sampled. The FHM attribute list now includes tree crown conditions, cover and diversity of lower vegetation (shrubs, forbs, grasses, and vines), soils, lichen diversity (as an indicator of air quality), indicator plants for ozone presence, and coarse woody debris. This expanded sampling provides data that can be used to estimate forest carbon and forest fire fuel loads. Readers are encouraged to visit http://fia.fs.fed.us/ library.htm#manuals for a thorough explanation of all FHM indicators. The assessment of forest health should be based on definable criteria. The Forest Service’s monitoring programs have adopted the Montreal Process and criteria and indicators for evaluating forest health and conditions to provide information for sustainable forest management. Some of the challenges and concepts that must be considered in integrating and redesigning inventory and monitoring programs are discussed in the following section. DESIGNING AN INVENTORY AND MONITORING SYSTEM In designing an inventory and monitoring system, it is important to recognize that definitions of sustainability change over time and vary according to location and interests. Changes in forest type and condition have accelerated, and the rapid pace of change likely will continue in the South. The combination of real change, introduction of new sampled attributes, and definitional changes over time calls for a resilient and simple sampling frame. This goal C ha pt er 1 7. S us ta in ab ili ty o f th e So ut he rn F or es t is very different from the situation in most inventories, in which the sampling strategy is directly tied to the need to efficiently estimate one or two closely related attributes of interest. Fortunately for the continuity of FIA inventory work, the types of measurement data that were used to estimate forest resources 30 years ago remain equally useful today. Nevertheless, a dominant consideration in planning a long-term monitoring program is the inevitability that a highly efficient sample design, one that optimizes on one or very few resources of interest, will go out of date. Examples in forest inventory work include the use of overly detailed stratification and variable probability of selection based on volume or value per unit area. Design features that involve complex sample structure create potentially serious difficulties, whereas an equal-probability design permits greater adaptability and flexibility. To minimize sample design obsolescence, structure should be employed sparingly and with awareness of its undesirable effects. Variable probability sampling designs and other complex sampling schemes are less amenable to the multiple and changing objectives that long-term monitoring designs must address, and therefore should be avoided (Overton and Stehman 1996). Simplicity is desirable for many reasons. It is not only that sample elements will change over time (as when forest plots become parking lots); it is also that overall objectives change. Another reason for simplicity is the growing recognition that data collected by federally funded monitoring programs should be accessible to the public at large (Cowling 1992). With a relatively simple sample design, it is more likely that valid results and conclusions can be reached by various public users of the databases. The simplicity and resiliency needs of the southern FIA Program have resulted in the use of an equal-probability systematic sample design (Roesch and Reams 1999). The new annualized sample design employs five annual panels, whereby plots measured in year one will be remeasured in year six (fig. 17.1). The southern FIA Program has historically used a completely overlapping single-panel design for periodic inventories and is implementing a similar design in its annual surveys (Reams and Van Deusen 1999). To transition from the single-panel periodic survey measured once every 10 years to an annual survey, FIA subpaneled the periodic plot list into five panels. Panels represent a sample in which the same elements (plots in this case) are measured on So ut he rn F or es t Sc ie nc e: Pa st , P re se nt , a nd F ut ur e Fo re st H ea lt h 182 1 2 3 4 5