Land system analysis of Guadalupe Mountains National Park, Texas

Attempts to divide the surface of the earth into areas or units which are internally homogeneous and distinct from adjacent areas, have been undertaken throughout recorded history. Such efforts are generally founded upon the recognition that if we are to use our lands in the best possible ways, it is necessary to develop some form of order or structure within the range of natural variety which surrounds us.

In managing for preservation and recreation or, indeed, any other kind of land management, the data which are used for analysis must meet two basic criteria. Initially the data must include those natural elements whose interactions are predominant in the area of interest. Not all data can be derived from one source, but aerial photography can provide much of it, and other elements or their effects can be inferred, e.g., climate and the presence or absence of water. The data must be detailed enough to provide adequate information for small or unique areas which will require intensive management. Concomitantly, the data should be able to provide information from which meaningful generalizations can be drawn. As a result, the data must be suitable for analysis.

The second basic requirement concerns the organization of the data. Natural elements do not occur in isolation; rather, they form associations whose effects are often more than the sum of the parts. Consequently, data organization should take this into account.

The land system concept accommodates the need for detailed information from which broader generalizations can be drawn as required and, at the same time, organizes the collection and analysis of data in such a way that the interrelationships are recognized and preserved.

LandsQccpe units were delineated on black and white vertical aerial photography at an average scale of 1:32,500. They were then described in terms of slope, vegetation and geologic characteristics. This ground truth data was used to test the boundaries delineated on the aerial photographs, to discover whether or not any of the landscape units were similar, and to determine if the landscape units were more homogeneous than a comparable series of randomly configured units.

The concept of homogeneity is particularly important to management because it is this which can be used to guide the development of various practices. Homogeneity was found to involve the physical and biological composition of sites as well as the number of sites. In regard to the latter, it was noted that the sites exhibited repetitiveness and that the frequency of repetition was particularly associated with the dominant distinct units, those which made up 50 percent or more of a given landscape unit.

This research effort has clearly shown that landscape units can be effectively delineated in a region of extreme diversity and complexity. The boundaries of the delineated units were examined and shown to be real in terms of slope, vegetative and geologic variables. The units were shown to be unique and to be internally homogeneous when compared to randomly configured units of similar size. In addition, it was found that each landscape unit was dominated by limited associations of slope, vegetation and geology. The recognition of dominant distinct units holds particular value for the application of the land system concept to rugged or remote areas. Provided that the landscape units are delineated with care, the necessity for complete ground truth is obviated; hence, only sampling would be required to obtain the necessary data for reliable extrapolation. Areas of particular or critical concern can also be readily identified and sampled more intensively as the situation demands.