Enhancing the access and use of forest resources data in Minnesota.
Minnesota's Bearing Tree Database
The Public Land Survey (PLS) began in 1847 in Minnesota and established the Public Land Survey System (PLSS) network of townships, ranges, and sections. As part of the PLS, surveyors were instructed to record specific information for all bearing trees located during the course of the survey. These bearing trees were notched, blazed, and scribed in a standard way to facilitate the relocation of the survey corner should the wooden corner post or corner stone be lost or moved. The surveyor was required to note for each bearing tree the following information: 1) its type (~ species), 2) its diameter, 3) its distance to the corner, and 4) its azimuth or "bearing" from the corner. Bearing trees were required at both the standard corners of the rectangular survey grid and at points on the survey lines where the surveyors were forced to meander around impassable areas such as lakes.
The Minnesota Department of Natural Resources - Natural Heritage Information System (NHIS) Bearing Tree Database contains computerized records only of the bearing trees at standard section and quarter-section survey corners. Meander corners, which mark the point of departure from section lines in order to traverse around impassable objects, are not included in the database. Codes for the type of vegetation at each standard survey corner are included as stated in the line notes or, alternatively, as inferred from the line summary notes. Except for a very few records from cleanup and resurveys, the NHIS database contains the oldest survey records available for the standard section and quarter-section corners.
These survey records and notes from the PLS in the United States can provide ecologists with valuable information about trees and vegetation. These historical data predate widespread European settlement and are therefore especially valuable in areas where the vegetation has been greatly altered during the past century. However, it is important to emphasize that the purpose of the PLS was not to sample the vegetation, but was a means of raising revenue for the government through the sale of public lands to private individuals of companies. This point is often neglected in the ecological application of PLS notes. Much of the concern about ecological interpretation of bearing tree data has to do with surveyor bias in selecting bearing trees. The original instructions for selecting bearing trees were very general and basically addressed the method of marking trees and the required number of trees to be marked. The PLS bearing tree data is at best a biased ecological sampling. Bias doesn't necessarily render data completely useless, but it requires study and discussion of its affects on ecological interpretation. The great value of the PLS data it its spatial comprehensiveness, and many of the concerns about applying PLS data to ecological problems can be alleviated by selecting large study area.
Almendinger, J.C. 1997. Minnesota's Bearing Tree Database. Biological Report No. 56. Minnesota Department of Natural Resources, St. Paul, MN. 23 p.
Almendinger, J.C. 1985. The late-Holocene development of jack pine forests on outwash plains, north-central Minnesota. Ph.D. Dissertation. University of Minnesota, Minneapolis, Minnesota.
Grimm, E.C. 1981. An ecological and paleoecological study of the Big Woods region of Minnesota. Ph.D. Dissertation. University of Minnesota, Minneapolis, Minnesota.
Marschner Map of Presettlement Vegetation in Minnesota - 18 classes of presettlement vegetation as mapped by Francis J. Marschner in 1930. Marschner based his map on General Land Office Survey records from the 19th and early 20th century. An interpretation of the PLS bearing tree data.
Original Land Survey Bearing Trees - A point database of bearing trees used as references or landmarks during the original Minnesota Public Land Survey (PLS). A variety of information is stored about bearing trees that aid in their use as indicators of vegetation conditions present at the time of the survey. This database is described in greater detail in the publication: 'Minnesota's Bearing Tree Database', by John Almendinger, Biological Report No. 56, Minnesota Department of Natural Resources, 1997.
PLS Corners with Presettlement Vegetation Information - A point database storing information on vegetation type information and general location of bearing trees used in conjunction with the original Public Land Survey (PLS). This database contains the actual location of section corners, rather than the location of the bearing trees themselves. The data are derived from land surveyor notes, which include descriptions of vegetation and landscape characteristics along survey transects. This database is described in greater detail in the publication: 'Minnesota's Bearing Tree Database', by John Almendinger, Biological Report No. 56, Minnesota Department of Natural Resources, 1997.