Vegetation in transition: the Southwest's dynamic past century
This article is part of a larger document. View the larger document here.Abstract
Monitoring that follows long-term vegetation changes often requires selection of a temporal baseline. Any such starting point is to some degree artificial, but in some instances there are aids that can be used as guides to baseline selection. Matched photographs duplicating scenes first recorded on film a century or more ago reveal changes that help select the starting point. Interpretation of the observed changes may be strengthened by quantitative measures from permanent long-term study plots established at sites near the photo stations. The gradual infusion of exotic plants and animals into ecosystems may complicate baseline selection. Because these new additions often interact with the native biota, the timing of their appearance on the scene should be recognized, and provides further direction for judging appropriate temporal baselines.