United States Department of Soils as an Indicator Agriculture Forest of Forest Health: Service North Central A Guide to the Collection, Research Station Analysis, and Interpretation of General Technical Report NC-258 Soil Indicator Data in the Forest Inventory and Analysis Program Katherine P. O’Neill, Michael C. Amacher, and Charles H. Perry Photographs courtesy of USDA Agricultural Research Service and USDA Natural Resources Conservation Service. Abstract The Montreal Process was formed in 1994 to develop an internationally agreed upon set of criteria and indicators for the conservation and sustainable management of temperate and boreal forests. In response to this effort, the Forest Inventory and Analysis (FIA) and Forest Health Monitoring (FHM) programs of the USDA Forest Service have implemented a national soil monitoring program to address specific questions related to: (1) the current and future status of soil resources and (2) the contribu- tion of forest soils to the global carbon cycle. As the first and only nationally consistent effort to moni- tor forest soil quality in the United States, this program provides critical baseline information on the current status of the soil resource and the potential effects of natural and human disturbance on forest health and productivity. This report provides documentation on the types of data collected as part of the FIA soil indicator, the field and laboratory methods employed, and the rationale behind these data collection procedures. Particular emphasis is placed upon describing generalized approaches for analyzing and interpreting soil indicator variables and discussing the strengths and limitations of individual soil variables. The analytical techniques detailed in this report are not intended to be exhaustive. Details of specific ana- lytical approaches will be provided in a series of subsequent publications. Rather, the purpose of this report is to provide guidance to analysts and researchers on ways to incorporate soil indicator data into reports and research studies. O’Neill, Katherine P.; Amacher, Michael C.; Perry, Charles H. 2005. Soils as an indicator of forest health: a guide to the collection, analysis, and interpretation of soil indicator data in the Forest Inventory and Analysis program. Gen. Tech. Rep. NC-258. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Research Station. 53 p. Documents the types of data collected as part of the Forest Inventory and Analysis soil indicator, the field and laboratory methods used, and the rationale behind these data collection procedures. Guides analysts and researchers on incorporating soil indicator data into reports and research studies. KEY WORDS: Forest inventory, FIA, soils, forest health monitoring, sampling, estimation, analysis, reporting. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national Published by: origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic North Central Research Station information, political beliefs, reprisal, or because all or part of an Forest Service U.S. Department of Agriculture individual’s income is derived from any public assistance program. 1992 Folwell Avenue (Not all prohibited bases apply to all programs.) Persons with St. Paul, MN 55108 disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should 2005 contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). Web site: www.ncrs.fs.fed.us To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, SW, Washington, DC 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. Acknowledgments The soil indicator program began in the early 1990s and has benefited from the efforts and direction of numerous investigators since then. The original pilot studies were led by Mike Papp and Rick Van Remortel at the U.S. Environmental Protection Agency. Berman Hudson (USDA Natural Resources Conservation Service) continued the development of Forest Health Monitoring soil protocols from 1994 to 1996. Craig Palmer (University of Nevada-Las Vegas) served as the Forest Health Monitoring lead for this indicator from 1995 until 2000 and was responsible for developing and implementing many of the protocols described in this document. Before 2000, laboratory analysis of soil samples was directed by Russ Dresbach and R. David Hammer at the University of Missouri Soil Characterization Lab. In 2001, three laboratories were added to the program: (1) the North Central Forestry Sciences Laboratory in Grand Rapids, Minnesota, previously managed by Don Nagel and William Pettit; (2) the Rocky Mountain Forestry Sciences Laboratory in Logan, Utah, directed by Mike Amacher; and (3) the International Institute of Tropical Forestry directed by Mary Jeanne Sanchez. In addition, of vital importance to the soil monitoring program are the State forest health coordinators, regional trainers, field crews, quality assurance staff, and laboratory technicians who collect, verify, and analyze the soil data. Without their efforts and commitment to data quality, the soil monitoring program would not be possible. Table of Contents Page 1. INTRODUCTION . .1 1.1 Indicators of Conservation and Sustainable Management . .1 1.2 History of the Soil Indicator Program . .2 2. SAMPLING DESIGN . .5 3. COMPACTION . .9 3.1 Rationale . .9 3.2 Variables Used to Assess Compaction . .9 3.2.1 Percent compacted area . .9 3.2.2 Type of compaction . .10 3.2.3 Bulk density (see also section 5.3.3) . .10 3.3 Analysis and Interpretation . .11 3.4 Examples of Analyses . .11 3.5 Limitations to Data . .14 4. EROSION . .15 4.1 Rationale . .15 4.2 Variables Used to Assess Soil Erosion . .15 4.2.1 Percent bare soil . .15 4.2.2 Soil texture . .16 4.2.3 Slope angle . .16 4.2.4 Vegetation structure . .16 4.2.5 Forest floor thickness . .16 4.3 Models Used to Assess Erosion . .17 4.3.1 Universal Soil Loss Equation . .17 4.3.2 Water Erosion Prediction Project . .18 4.4 Analysis and Interpretation . .18 4.5 Examples of Analyses . .18 4.6 Data and Model Limitations . .21 4.6.1 USLE . .21 4.6.2 WEPP . .22 5. SOIL PHYSICAL AND CHEMICAL PROPERTIES . .23 5.1 Rationale . .23 5.2 Methods . .24 5.2.1 Forest floor . .24 5.2.2 Upper 20 cm of soils . .24 5.2.3 Organic soils . .24 5.3 Variables Used to Assess Soil Physical Properties . .24 5.3.1 Forest floor thickness . .24 5.3.2 Moisture content . .25 5.3.3 Bulk density (see also section 3.2.3) . .25 5.3.4 Coarse fragment content . .25 5.3.5 Depth to restrictive horizon . .26 5.4 Variables Used to Assess Chemical Properties . .26 5.4.1 Soil acidity (pH) . .27 5.4.2 Exchangeable cations . .28 5.4.2.1 Exchangeable potassium . .29 5.4.2.2 Exchangeable calcium . .29 5.4.2.3 Exchangeable magnesium . .29 5.4.2.4 Exchangeable sodium . .29 5.4.2.5 Exchangeable aluminum . .29 5.4.2.6 Effective cation exchange capacity . .30 Table of Contents continued Page 5.4.3 Extractable phosphorus . .30 5.4.4 Total nitrogen . .30 5.4.5 Total, organic, and inorganic carbon . .30 5.4.6 C:N ratio . .31 5.4.7 Extractable sulfur . ..