November and December 2006



Guest Columnist

Forester’s Log: Habitat Typing

By Mary Stuever

It’s PIED/CEMO behind the Jemez Ranger Station. This year the stand is somewhat tricky to key out with the lush response of forbs and grasses from the recent rains. PIPU/CAFO or possibly PIPU/FEAR up by Oscar’s Grave near Alpine — that would explain the sporadic response of the aspen sprouting despite the nine foot tall elk fence. These are just a couple of the observations that were made during two week-long Habitat Typing Workshops held this summer in Arizona and New Mexico.

Habitat typing, also known as identifying plant associations, is an important skill set for natural resource managers working in woodlands or forests. The classification of forests into plant associations gives managers the vocabulary to discuss the finer points of management with better precision. For example, what would be called a ponderosa pine forest by the untrained, can, with the right books and bit of training, be identified as one of forty or so “habitat types” that support “ponderosa pine forests.” Knowing the habitat type allows managers to compare, contrast, and predict the responses of plants to various activities such as burning, thinning, and logging.

The types are named for the most shade tolerant tree the site can support, and an understory plant that best represents the site — ideally an indicator plant thrives in the specific plant association, but does poorly in other places. Frequently though, the dominance of a plant in the understory will nominate it for community name status. Plant associations have names such as “pinyon pine-mountain mahogany”, which when using scientific names for plants would be “Pinus edulis/Cercocarpus
montanus.” Since habitat types were originally developed for government workers, and government workers are famed for creating acronyms, the name is often shortened to unintelligible monikers by using the first two letters of both genus and species for each plant, thus PIED/CEMO.

Knowing the habitat type provides one with specific information not apparent to a casual observer. For example, many people believe consider the ponderosa pine forest on the Mogollon Rim in central Arizona as one of the largest, homogenous stands of ponderosa pine in the world. The habitat typer however sees variation in the forest. A ponderosa pine/screwleaf muhly (PIPO/MUVI) type is wetter than a ponderosa pine/screwleaf muhly-Arizona fescue (PIPO/MUVI-FEAR) stand, which is still moister than a ponderosa pine/ Arizona fescue (PIPO/FEAR) forest. Near the edges of this vast pine stand, ponderosa/blue grama (PIPO/BOGR) is even drier.

Habitat typing was developed in the Pacific Northwest in the 1960’s, and plant associations have been classified in all of the western states. The first comprehensive plant association classification of Southwestern forests was completed in the 1980’s. I attended training on these types and then shared the information I gained in the class with my colleagues. Soon I was teaching courses as a contractor with the Forest Service. In the mid 1990’s I also updated the regional Plant Association guides which resulted in a two volume set of books.

During a period of ten years, I facilitated over 30 week-long trainings involving about 600 resource managers throughout Arizona and New Mexico. And this summer I sponsored two wellattended courses, one in each state.

Near Oscar’s grave, we visited a blue spruce/dryspike sedge (PIPU/ CAFO) site, which alternated with blue spruce/Arizona fescue (PIPU/FEAR), the latter type having a more minor role for aspen trees. The ponderosa pine/black sagebrush (PIPO/ARNO) is similar to the more common forest type where big sagebrush is a dominant shrub, but in this stand near Tres Piedras, the sagebrush is much smaller in stature. One of the largest and most widespread habitat types is ponderosa pine/gambel oak (PIPO/QUGA) which we encountered almost daily on our far ranging field trips.

Each week included five days in the woods, full of spirited discussion and learning, and visits to a plethora of plant communities from the woodlands to the spruce-fir alpine transition. I know I came back to my job excited about forests and I hope the workshop participants will use this knowledge to apply the best activities to promote forest health across the landscape.

The Forester’s Log is a monthly column written by forester Mary Stuever. Mary can be contacted at


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