Forestry Inventory and Analysis data provides comprehensive look at forestry in Michigan

The U.S. Forest Service collects and publishes data every five years on the status of forest land and forestry activities in each state.

Every five years, the U.S. Forest Service publishes a report summarizing the data collected through the Forest Inventory and Analysis (FIA) Program. The FIA data provide a snapshot of metrics surrounding the forests of today, and extensive analysis of the data help to identify trends as well as project how the forests will look in 10-20 years from now. Using statistical analysis to project into the future provides a foundation from which to evaluate the sustainability of current forest management policies. This gives citizens and lawmakers the opportunity to work to revise policies to ensure that future generations will enjoy America’s forests just as we do today. FIA data have been collected since 1930 under the direction of the USDA Forest Service, Research and Development Organization. This information has been and continues to be a valuable asset to researchers, foresters and forested landowners throughout the United States. Forestry and Natural Resource Educators of the Michigan State University Extension also find this data helpful in preparing forest related presentations and educational publications. 

What is measured? 

The first step in collecting data for the FIA program is to measure the expanse and fragmentation of forests across the landscape. Originally done with hardcopy aerial photographs, the now digital survey uses satellite imagery to first classify land as either forest or non-forest and calculate data related to fragmentation, urbanization and distance to core forest areas. 

The second step in the process is to actually visit the forest to count and measure the trees as well as collect a variety of other data such as tree growth, removals and mortality. Foresters make visits to sample plots, which are located on federal, state and private land across the landscape. Data are collected at each plot, with one plot occurring every 6,000 acres. To accomplish this, about 20 percent of the sites are visited annually. A sub-set of non-forested plots are also visited to record land use change at the location. 

Forest health indicators are measured at a subset of the aforementioned plots. Indicators include a full vegetation inventory, tree and crown condition, soil data, lichen diversity, coarse woody debris and ozone damage. Fact sheets explaining how each variable is a measure of forest health are available online

In addition to providing data about the condition of forests, the FIA dataset also includes a summary of Timber Products Output in each state. This provides an estimate of industrial and non-industrial uses of roundwood, or logs, which provides a snapshot of the viability of the forest industry.  

Focusing on private lands, FIA data includes the results of the National Woodland Owners Survey, which is implemented to increase the understanding of forested woodlot owners, their intentions and activities, as well as how they obtain information about forest management. This inclusion provides the critical link between forests and society. 

Obtaining the data 

Forest Inventory and Analysis data are available on the internet. This data is useful in helping to identify market trends which help to determine changes in tree species value. 

The last five year report was published for the 2009 inventory; an up-to-date report will be available in early 2016 for the 2014 inventory. Current and past reports are available in tabular, spatial (map) and written formats. In fact, the 2014 FIA data have been available since early 2015 and may be accessed through the EVALIDator tool. There are a variety of tools available that allow the user to query the data and create custom summaries. Tutorials are also available to help better utilize each of the tools.

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