Rocky Mountain Research Station Publications

RMRS Online Publication
RMRS-RP-83: Evaluating indices that measure departure of current landscape composition from historical conditions


Keane, Robert E.; Holsinger, Lisa; Parsons, Russell A. 2011. Evaluating indices that measure departure of current landscape composition from historical conditions. Res. Pap. RMRS-RP-83. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 19 p.

A measure of the degree of departure of a landscape from its range of historical conditions can provide a means for prioritizing and planning areas for restoration treatments. There are few statistics or indices that provide a quantitative context for measuring departure across landscapes. This study evaluated a set of five similarity indices commonly used in vegetation community ecology (Sorenson's Index, Chord Distance, Morisita's Index, Euclidean Distance, and Similarity Ratio) for application in estimating landscape departure (where departure = 1 - similarity). This involved comparing composition (vegetation type by area) of a set of reference landscapes to the compositions of 1,000 simulated historical landscapes. Stochastic simulation modeling was used to create a diverse set of synthetic reference and historical landscapes for departure index evaluation. Five reference landscapes were created to represent various degrees of expected departure from historical conditions. Both reference and historical landscapes were created to contain four important factors that could potentially influence departure calculation: (1) number of classes defining landscape composition, (2) dominance of the classes, (3) variability of area with the classes, and (4) temporal autocorrelation. We found that most evaluated indices are useful but not optimal for calculating departure. The Sorenson's Index appeared to perform the best with consistent and precise behavior across the ranges of the four treatments. The number of classes used to describe vegetation had the strongest influence on index performance; landscape composition defined by few classes had the least accurate, most imprecise, and most highly variable departure estimates. While results from this study show the utility of similarity indices in evaluating departure, it is also evident that a new set of statistics are needed to provide a more comprehensive analysis of departure for future applications.

Keywords: ecosystem management, similarity indices, landscape ecology, historical ecology, historical range and variability, HRV, neutral landscapes


About PDFs: For best results, do not open the PDF in your Web browser. Right-click on the PDF link to download the PDF file directly to your computer. Click here for more PDF help or order a printed copy of this publication.


Download RMRS-RP-83:
http://www.fs.fed.us/rm/pubs/rmrs_rp083.pdf

PDF File Size: 700 K


Title: RMRS-RP-83: Evaluating indices that measure departure of current landscape composition from historical conditions
Electronic Publish Date: February 8, 2011
Expires: Indefinite
Last Update:
February 8, 2011

RMRS Publications | Order a publication | Contact Us