Analysis

How can Soils Data be Analyzed?

The primary use of the soil quality indicator is to provide baseline information about the status of forest soils so that changes in soil quality can be monitored over time. Spatial and temporal trends in the number and distribution of plots with accelerated erosion, compaction, changes in soil organic matter content, and nutrient or other chemical limitations are evaluated by region or forest type. Results from the trend analyses are then combined with other FIA indicators to evaluate site productivity and forest health.

For example, field variables related to landscape position, soil texture, and ground cover are used in conjunction with other FIA indicator data and outside information to model rates of soil erosion on FIA plots. These estimates can be used to identify regions where certain management practices may be more likely to result in accelerated soil loss. Soil chemical and bulk density data can be combined to develop indices of plant nutrient availability in different systems. These baseline data may provide additional insight into forest health problems identified through other FIA measurements.

A document, " 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", was recently published. This companion to the field guide introduces approaches to the analysis and interpretation of  Soil Quality Indicator data.

Can Related Data Sets Be Used?

In addition to FIA data, information from other sources are used in the analysis of soil quality, including:

• Soil survey data from the National Resource Conservation Service.
• Erosion models developed by the USDA Agricultural Research Service and other federal agencies (e.g., Revised Universal Soil Loss Equation, Water Erosion Prediction Project).
• Climate data from regional weather stations (used in erosion models)

Tables

The first tier of products that result from data analysis are tabular summarizations (core reports). Core tables facilitate the dissemination of analytical results to the public. Since Soil Quality data are currently collected at a scale where regional/state level analysis is most appropriate, state-level summaries may best depict regional differences in estimates of soil parameters.

     View sample core table. (pdf 9K)

The core table above is a fire science-oriented core table. Additional core tables for the wildlife and carbon science are currently in development. All core tables may be manipulated and summarized to suit analyst's specific needs. Core tables form the basis of most advanced summaries, interpretations, maps, and graphs.

Charts and figures

The second tier of analysis are graphical representations of core reports created in such a way as to aid regional and/or State analysts. With core tables in hand, we can graphically depict analytical results and disseminate them to the public. Since Soil Quality data are currently collected at a scale where regional/state-level analysis is most appropriate, state-level summaries may best depict regional differences in estimates of soil properties.

Charts are created from core tables for state reporting. Some tables may also provide a regional context by including soil parameters for surrounding states.

Maps

The third tier of analysis consists of map products. Soil Quality mapping techniques may combine all phases of the FIA inventory, in addition to ancillary data sets, to produce large-scale maps of soil parameters.