Forest Inventory and Analysis, previously known as Forest Survey, is one of the oldest research and development programs in the USDA Forest Service. Statistically-based inventory efforts that started in Scandinavian countries in the 1920s raised interest in developing a similar program in the U.S. The U.S. Congress established the research branch of the U.S. Forest Service in 1928, shortly after Dr. Yrjö Ilvessalo, leader of the first Finnish national forest inventory, met with President Calvin Coolidge. Congress charged the Forest Service to find “facts as may be necessary in the determination of ways and means to balance the timber budget of the United States”. As a result, Forest Survey maintained a timber focus for much its history. As society’s interest in forests changed over time, so did information needs. Conflicts over resource allocation and use could not be resolved without up-to-date knowledge of forest status and trends. In response to society’s needs, the Forest Inventory and Analysis program has evolved from Forest Survey to address diverse topics such as forest health, carbon storage, wildlife habitat, air pollution, and invasive plants, while continuing its mandate to monitor the Nation’s timber supply. The Forest Inventory and Analysis program collects data on all land ownerships on an annual basis. The data are used to develop reports on a regular basis; reports and raw data are available to the public at no cost. The data are also used by scientists in a growing number of applications. A short history of the Forest Survey is presented with several examples of current research based on Forest Inventory and Analysis data.
The Forest Inventory and Analysis (FIA) program, previously known as Forest Survey, is one of the oldest research and development programs in the USDA Forest Service. The program is considered the nation’s "forest census", because it includes all forest types and land ownerships in the United States. The forests are diverse both in terms of their type - ranging from boreal spruce forests in Alaska to subtropical hardwoods in Florida - and their use - including intensively managed, industry-owned forests in the Pacific Northwest and unmanaged public wilderness in the Rocky Mountains (
Prior to the 20th century, North American forest resources were treated primarily in an extractive manner with little regard to regeneration or sustained yield. Forests were essentially mined as the wave of European settlement proceeded from east to west. In the late 19th century, as concerns about the diminishing forest resource increased and scientific forestry began to establish a foothold, interest in assessing the status and trends of the resource began to emerge. Early inventories - for example, Hough’s
In 1929, Forest Survey planning began in Oregon and by 1932 the inventory of the western Cascades was complete. In the same year, inventories were started in Idaho, the Great Lakes States, and some southern states. During World War II there was a temporary halt to the survey. The last 3 states - Arizona, New Mexico, and Nevada - were completed in 1962, marking the end of the first inventory cycle in the coterminous 48 states. In the 1960s and 1970s, funding for the program increased; almost all states were visited again, and some twice during the period. The average re-visitation cycle between the first and second inventory was then 13-15 years. In the 1980s the Survey was active in all states except Utah and Ohio. Nationally, the re-visitation interval averaged about 12 years, but some of the southeastern states were re-inventoried as frequently as 5 or 6-year intervals (
In the late 1980s and early 1990s the program adopted a fixed periodic inventory system, with a 10-year cycle in most western states and a 5-year cycle in most southern and eastern states. However, some states, for a variety of reasons, were not re-inventoried on schedule and some states were not revisited for 15-20 years. By the early 1990s, some users of FIA data recognized that aging periodic inventories - even those done at 5-year intervals - did not meet their needs. Rapid changes, such as hurricanes and insect outbreaks, prematurely outdated periodic inventory data. As a result, the U.S. Congress included language in the 1998 Farm Bill requiring the FIA program to convert to a continuous annual inventory system and produce state-level results on a regular schedule.
Today, the FIA program operates 4 regional programs (
FIA inventories are conducted using a double sampling design, with plots arranged on a systematic grid. It is sometimes referred to as a 3-phase design, although this is not a precise description of the statistical design. The third “phase”, described below, actually consists of additional variables that are measured on a subset of plots. The term “phase” is commonly used to refer to plot type and will also be used here. Phase 1 (P1) plots are based on remotely sensed data and are used for stratification. In the past, Phase 1 consisted of airphoto points located on a 1-kilometer grid, but the availability of satellite imagery now allows for continuous (wall-to-wall) stratification. Phase 1 points are used to determine expansion factors for strata (
Phase 2 (P2) plots, also known as standard FIA plots, are located at 5-kilometer intervals, equal to an intensity of approximately 1 field plot per 2388 hectares. The P2 plot design consists of 4 subplots of 0.017 ha each, with centers 36.6 m apart (
Phase 3 (P3) plots, also known as Forest Health Monitoring plots, are a subset of P2 plots, with 1 field plot per approximately 38 850 ha (16x the area represented by a P2 plot). On P3 plots, several “health indicators” are measured woody material, soils, lichens, crown conditions, and ozone as well as all P2 variables. P3 plots were remeasured on a 5-year cycle, but recently have been synchronized to the local P2 cycle.
FIA data are used by many sectors of society, each of which prefers data or analyses in different formats. The distinction in the title of this paper between science and society the former of which is obviously a subset of the latter is based on both data needs and the extent to which in each group has historically used FIA data. Basic FIA products, such as State or National Forest inventory reports are used by a wide variety of clients for information and planning purposes. FIA also produces special reports on topics such as forest health or timber products output. In addition to hardcopy format, these reports are accessible to the public on the worldwide web at no cost.
If a user needs more data and tables than are presented in FIA reports, he or she can produce customized tables or download raw data using the Forest Inventory Mapmaker web interface (http://www.ncrs2.fs.fed.us/4801/FIADB/index.htm). Data may be summarized at the state and county level, by user-defined latitude-longitude boundaries, or within a circle of user-defined center and radius. Output may be obtained in the form of a standard table set, user-defined tables, maps, or dump files ready for input in the Forest Vegetation Simulator (
In response to user demand in recent years, the FIA program has devoted significant resources to the development of map products and mapping techniques. These products are produced by combining FIA data with a wide variety of GIS data (usually at 250m to 1km resolution), using multivariate analysis methods.
FIA scientists have long used FIA data as a research data set, and have implemented many studies designed to improve inventory and monitoring techniques. In addition, FIA scientists frequently collaborate with scientists at universities and other government agencies on a variety of studies. Over 1425 citations related to the FIA program were published from 1976 to 2001, including over 50 master’s theses and 100 doctoral dissertations (
Recent examples of silvicultural and ecological research in the Interior West include development of density management diagrams (
The ponderosa pine density management diagram (
In the aspen study (
Assessment of drought effects in pinyon-juniper woodlands was possible because implementation of the annual inventory system was coincident with the beginning of the drought in the American Southwest (
A common and important aspect of these studies is that the results were obtained using data available to the public in other words, the results can be produced (or reproduced) by anyone. Although verifiability is an important tenet of scientific inquiry, access to researchers’ data can be difficult at times. However, data collected under the FIA program, which is publicly funded, are available to all. This fact in itself constitutes an important contribution to science and society. That being said, there are also safeguards in place to ensure confidentiality of data collected on private lands and the integrity of permanent plot locations. This (perhaps unique) combination of openness and security contribute to users’ confidence in the integrity of the FIA program.
The discussion above of mortality in pinyon-juniper woodlands alluded to the value of continuous inventory under the annual system. However, recent events in particular, the devastating effects of hurricanes Katrina and Rita on the southeastern U.S. (
Over 2.000.000 ha of forest were affected by Katrina
The value of timber affected is greater than $US 5.000.000.000
If recoverable, damaged wood is sufficient to produce 800.000 single family homes and 20.000.000.000 kilos of paper products
Most of the damage occurred within 95km of the Gulf Coast
Approximately 2/3 of the damage occurred in Mississippi
Detailed FIA assessment has already started, and the inventory will be updated annually as annual panels are completed
It should be noted that continuing assessment of hurricane damage will not require a change in FIA sampling protocol, although grid intensification or other ad-hoc changes may be made to answer specific questions. The annual inventory system, conducted on a routine basis, will permit not only assessment of hurricane damage, but also the effects of salvage, insect outbreaks, and fire in the affected areas, as well as monitoring recovery over time.
The USDA Forest Service Forest Inventory and Analysis program serves a broad segment of society by keeping a comprehensive inventory of the forests of the U.S., and producing data, summaries, and analyses for a variety of audiences. Use of FIA data has been growing steadily over the past 3 decades, but use in scientific applications is still lower than potential. However, the list of research applications is growing as more scientists become familiar with the program. Open access to data, the integrity of the program, and continuing service to society has earned support that is important in a time of tight budgets. Finally, the recent evolution of the FIA program into a continuous annual inventory system ensures that FIA data will only become increasingly valuable with time.
Examples of forest diversity from around the United States. (A) White spruce (
Regional Forest and Inventory and Analysis units and approximate forested area included in each.
FIA plot design (A) and example of mapping several conditions on one plot (B). FWD = fine woody debris and CWD = coarse woody debris. Woody debris diameter ranges are listed with the portion of the transect on which the classes are recorded.
DCA plot of aspen structure and composition in the western United States. Labels are at approximate DCA coordinates for geographic regions (from
Progression of pinyon mortality (% of basal area) 2000-2004, based on FIA annual inventory data from 4 western states (from
Forest damage typical of areas severely affected by hurricanes Katrina and Rita. Dominant species on this site was loblolly pine (