Using Soil Survey Information to Protect Spotted Owl Habitat

Yakima County


The northern spotted owl is one of many federally protected species found within the boundaries of the Yakama Reservation. In an effort to identify areas which will be able to support and sustain the spotted owls and other species , the Yakama Nation (YN) is implementing a variety of land management practices designed to balance both natural resources and cultural objectives.  The YN is currently exploring the use of Geographic Information Systems (GIS) combined with spotted owl data and a detailed National Cooperative Soil Survey database provided by the Natural Resources Conservation Service (NRCS). The GIS and soil survey information is proving highly valuable in indicating where wildlife habitat of dense forests might be most attainable.


Yakama Nation; Department of Interior (DOI) - Bureau of Indian Affairs (BIA) - Soils Department; USDA-NRCS MLRA Soil Survey; U.S. Fish & Wildlife


Recently on the Yakama Reservation there has been a need to identify the potential habitat of many federally protected species, most notably the spotted owl. Protecting significant wildlife and plants has always been important to the YN, therefore, they are always considered by resource managers in addition to the immediate resource challenge at hand.

Renewed interest in the spotted owl came about in an effort to better balance its habitat requirements with the other myriad of forest management factors necessary to create a healthy forest. In particular, the forests on the reservation are considered overgrown by forest managers and as a consequence, are showing signs of stress. Stress makes the forest more susceptible to disease and insects. Typically in a Pre-European setting it is believed that forest fires would have naturally reduced the density of trees within this area. To mimic this natural selection process, the forest managers of the YN wish to reduce the density of trees in selective areas to more sustainable levels by thinning. The spotted owl though is known to prefer to nest in dense tree stands.

In an effort to balance these two resource challenges, the YN and BIA are undertaking a study to determine what areas of the forest spotted owls prefer. Armed with this information they hope to be able to adapt their management accordingly in areas with a high potential of supporting spotted owls. Otherwise forest management will have to defer to maintaining tree stand density of those areas that are ideal for the spotted owl, regardless of the other forest management factors involved.


USDA-NRCS National Cooperative Soil Survey Database


Not surprisingly, one of the first tools that proved successful in identifying the occurrence of the spotted owl on the reservation was their soil survey information. This is because soil properties have a strong relationship with the type of vegetative communities that an area can support. To identify the factors involved in supporting spotted owl habitat, a number of known spotted owl nest sites and telemetry location sites were overlain with a series of spatial layers within a GIS system. From this visual display, descriptive statistics, and their own intuition, the YN scientists involved were able to infer a number of soil and land surface properties that were capable of discriminating between areas of high and low occurrence of spotted owl. The most straight forward relationships were found to be a combination of soil temperature and moisture classes. That alone captured 90 percent of the known owl nest sites and telemetry locations. What the owls seem to shy away from the most are areas of extreme of cold and wet or warm and dry. The relationship between the owl sites and environmental factors though are “far from simple” says Dr. Steve Wangemann, the resident BIA soil scientist. Upon further investigation, Dr. Wangemann and Mike Tari, a YN GIS Analyst, also discovered a combination of other soil properties that were useful in discriminating owl sites. These included soil properties that are associated with productive forest site conditions, such as very deep soils with high amounts of water storage or compensating amounts of precipitation. The results of this analysis are even challenging preconceptions of the scientists involved. For instance, in an intermediary soil climate zone that maintains a more continuous supply of soil moisture throughout the year, the occurrence of owls are much less frequent. This is puzzling because this soil climate promotes denser tree stands, which the owls should supposable prefer. Again this just proves how complicated the relationships of species to their environment can be. After all, it may be that there are areas which could support spotted owls, but are missing other critical factors.


Scientists working for the YN have used an innovative approach to link combinations of soil and land surface properties to the capability of a site to support spotted owl habitat.  They can now manage the forest while giving due consideration to the occurrence of spotted owls. By using GIS analysis techniques, accurate spatial data, National Cooperative Soil Survey Data, and extensive research on the local spotted owl population, the scientists working for the YN are closer to balancing natural resources, cultural, and economic values.


Kelley Paup-Lefferts, NRCS Soil Scientist, 509-829-3003 ext. 112

NRCS, 2-2008
 

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