INTRODUCTION 



The Circle West Vegetation studies, established to describe existing vegetation 

 and to monitor the long-term productivity and canopy-coverage of selected 

 plant communities in McCone County, Montana, began in 1976 at the request of 

 Dreyer Brothers, Inc. 



The Circle West Vegetation Baseline Study (Prodgers 1978) identified community 

 types for the study area through cluster analysis of 1976 vegetation data. 

 Community types were described botanically and associated sites were charac- 

 terized. Using this information, thirteen exclosures (figure 1) were chosen 

 for long-term monitoring in order to provide a data base for assessment of 

 strip mine reclamation success and possible air pollution effects. Produc- 

 tivity was measured at these exclosures from 1977 to 1981, and canopy-coverage 

 was measured from 1978 to 1981 (Montana Department of Natural Resources and 

 Conservation 1979a, 1979b, 1981.) 



This fourth annual monitoring study is similar to those conducted in previous 

 years. It compares 1981 data with that of the 1977 baseline study and the 

 annual monitoring studies of subsequent years. In addition, new types of data 

 have been added. Because of the dramatic effect of climate on plant community 

 composition and productivity, and in accordance with DNRC's recommendations 

 (DNRC 1981), climatic and soil moisture measurements have been added. Agri- 

 cultural productivity and associated measurements also have been monitored 

 and reported. Finally, at the request of the Department of State Lands, shrub 

 density of the silver sagebrush exclosure (Arca/Agsm/Bogr community) has been 

 measured and included in this report. 



Due to an error in computer programming, productivity confidence intervals 

 reported in the Third Annual Report (DNRC 1981) were miscalculated. Correct 

 confidence limits are presented in this report. 



