TABLE 111-4 - PATCH SIZE AND SHAPE BY AGE CLASS 



CURRENT 

 AGE 



0-39 years 



STILLWATER STATE FOREST 



MEAN PATCH 

 SIZE 



35 



MEAN PATCH 

 SHAPE 



1.3 



BEAVER LAKE PROJECT AREA 



MEAN PATCH 

 SIZE 



20 



MEAN PATCH 

 SHAPE 



1.3 



40-99 years 



155 



1.6 



33 



1.4 



100-149 years 



93 



1.5 



71 



1.6 



150+ years 



279 



1.8 



384 



1.7 



Total mean for all 

 age classes 



118 



1.5 



86 



1.5 



area prior to 1900. Mean patch shape by cover 

 type on Stillwater State Forest and the Beaver 

 Lake Project area are very similar, with the 

 Beaver Lake patches being slightly more 

 regular. 



Table III-4 shows that the mean patch size by 

 age class on Stillwater State Forest is very 

 similar to the size class by cover type. While 

 the Beaver Lake mean patch size by age class 

 is considerably smaller at, approximately, 86 

 acres, the mean patch shape by age class of 

 both analysis areas is almost identical to the 

 patch shape by cover type. Patch shapes, in 

 general, are considered to be less complex than 

 historic conditions because of stand distur- 

 bance from timber harvesting and other 

 human development based on ownership 

 rather than topography. However, this is not 

 always the case, and it depends on the map- 

 ping techniques used and analysis-area size 

 being discussed. , 



OLD-GROWTH 

 REPRESENTATION 



BACKGROUND, ANALYSIS 

 METHODS, AND AREA 



BACKGROUND 



The SFLMP states that DNRC would seek to 

 maintain or restore old-growth forests in 

 amounts of at least half the average proportion 

 that would be expected to occur with natural 

 processes on similar sites (MT DNRC 1996). 

 Old growth must be retained not only in the 



amounts committed to, but also in appropriate 

 proportions and sites across the landscape. 

 Old growth is defined as stands that are older 

 than 150 years (140 years for lodgepole pine) 

 and that exhibit a range of structural attributes 

 associated with old age. 



ANALYSIS METHODS 



DNRC approaches the issue of old-growth 

 retention from the perspective that the charac- 

 teristics of old stands that make them func- 

 tionally different than other stands should be 

 defined and managed for. 



Although no estimates of historic amounts of 

 old growth are available, there are estimates of 

 historic age-class distributions and accompa- 

 nying estimates of proportions of old stands. 

 This information is available from a forest ' 

 inventory conducted in the 1930s across 

 western Montana. Losensky (1997) summa- 

 rized the 1930s' inventory showing propor- 

 tional age-class distributions by climatic 

 section. The proportion of old stands within a 

 given analysis area, compared to the climatic 

 section proportion from the 1930s', inventory, 

 is DNRC's numeric criterion for assessing 

 compliance with our commitment to retaining 

 a minimum of 50% of old-growth amounts 

 that would be expected to occur with natural 

 processes on similar sites. DNRC will assess 

 the structural attributes associated with old 

 age that characterize the variety of forest 

 conditions that would have naturally occurred 

 on the landscape. Stands should be assessed 

 as they come up for treatment on a project-by- 

 project basis, keeping some with high old- 

 growth qualities, while possibly harvesting 



m-6 



Stillwater State Forest • Beaver Lake Timber Sale Project 



