MISSION STATEMENT 



This study is a working component of the Montana Natural 

 Heritage Program's (MTNHP) grasslands/shrublands ecological 

 classification project (GSCP) and The Nature Conservancy's 

 ecology program in the western United States. The Nature Conser- 

 vancy program provides key information on plant communities to be 

 used for conservation planning, management, research, and moni- 

 toring. Although grasslands and shrublands cover over 75% of the 

 Montana landscape, an exhaustive review of existing information 

 (MTNHP 1990) revealed them to be the least documented vegetation 

 types of the state. Therefore, the GSCP is designed to complete 

 the classification over the full range of ecological conditions 

 and to conduct regional correlations of existing classifications. 

 The information provided by the project will be the basis for 

 programs to model the effects of management, global changes, and 

 other variables on the vegetation types and diversity patterns, 

 and their implications for further management and conservation 

 planning. The project will continue to focus on strong collabor- 

 ative work with the various state and federal agencies (BLM, 

 USFS, BIA, DOD) and other institutions (e.g. Montana universi- 

 ties) in order to contribute to the development of a tightly 

 integrated state-wide classification system. 



ABSTRACT 



Interrelationships betv;een vegetation composition and envi- 

 ronment were studied using 125 vegetation plots sampled in a 12.5 

 million acre (50,000 km^) area of predominantly mixed-grass 

 prairie in northeastern Montana. Using a combination of two-way 

 indicator species analysis, detrended correspondence analysis, 

 and detrended canonical correspondence analysis (DCCA) , 24 

 community types were identified. The patterns in community 

 composition were strongly correlated with soil disturbance and 

 moisture gradients and these relationships are discussed. Keys 

 for each community type sampled (and 54 additional types docu- 

 mented in the literature) are provided. 



