Logging residues and vegetation provide shade, which 

 reduces temperature extremes, thus increasing survival 

 (Edgren and Stein 1974). 



This paper reports postharvest temperatures at the soil 

 surface (surface-air interface), in the air (to 4.5 ft), and in 

 the soil (to 16 inches) following several levels of overstory 

 removal and for four surface conditions resulting from 

 several residue treatments. Temperatures are compared 

 with adjacent uncut stands and with expected responses 

 based on heat fluxes and thermal properties of the sur- 

 faces. Consistency of treatment response is examined by 

 looking at results from three stands in different habitat 

 types. Measured temperatures represent the period imme- 

 diately following treatment to 8 years later. The potential 

 for seedling mortality, based on high and low temperature 

 data, is compared with actual seedHng survival data. 



STUDY AREAS AND METHODS 



We had two study sites in the Flathead Range of Mon- 

 tana and one in the Gros Ventre Mountains of Wyoming. 

 These sites represent a range of climatic conditions that 

 occur in the Northern Rocky Mountains. May through 

 September precipitation ranges from 25 to 45 percent of 

 the annual amount and varies considerably with topog- 

 raphy. Average temperatures also vary considerably 

 throughout the region. Ordination of these three sites 

 along moisture and temperature gradients (fig. 1) is based 

 on growing season May through September precipitation 

 totals and July temperatures. Climax forest series (Pfister 

 and others 1977) are Douglas-fir {Pseudotsuga menziesii 

 var. glauca [Beissn.] Franco) and subalpine fir (Abies 

 lasiocarpa [Hook.] Nutt.). 



COLD 70 I- 



WARM 85 



40 - 



4S - 



25 35 40 25 35 40 



DRY WET DRY WET 



PRECIPITATION, IN 



Figure 1— Ordination of study areas— Corann (C), 

 Lubrecht (L), and Union Pass (U) — along a 

 moisture (annual) and temperature gradient 

 based on July average maximum temperature (A) 

 and July average minimum temperature (B). 



Treatments 



Treatments on the study sites included: (1) a silvicultural 

 prescription requiring overstory removal that varied from 

 none through thinnings, selection cuts, and shelterwoods 

 to clearcutting; and (2) a postharvest residue treatment 

 varying from none to treatments of complete removal, 

 piling, chipping, and burning. Surface conditions of litter, 



burned, mineral soil, and chips resulting from residue 

 treatments were evaluated (fig. 2). This study is superim- 

 posed on a larger study. A description of specific 

 treatments used for each study area follows. 



Lubrecht Experimental Forest— This site is about 

 35 miles northeast of Missoula, MT, at an elevation of 

 4,000 ft. The terrain is gently rolling (slopes to 5 per- 

 cent), with west to northwest aspects. Climatic data, taken 

 at the forest headquarters since 1956 (Montana Forest and 

 Conservation Experiment Station 1983), indicate an aver- 

 age annual precipitation of 18 inches. Maximum July air 

 temperatures average 81.6 °F, and minimum July air 

 temperatures average 42.5 °F. 



Tree cover prior to treatment was a mixed size and age 

 class Douglas-fir forest. Western larch and ponderosa pine 

 (Pinus ponderosa Laws.) were significant components of 

 the stand. This area has a long history of selective logging 

 where merchantable trees were periodically removed from 

 the stands. Habitat type (Pfister and others 1977) is Pseu- 

 dotsuga menziesii/Vaccinium caespitosum (PSMEA^'ACA). 



Logging was done in 1977 with ground skidding equip- 

 ment. The following overstory treatments were compared 

 to the uncut stand: 



1. Clearcut. All merchantable trees were removed on a 

 15-acre clearcut and the rest of the material was felled, 

 leaving 29 tons per acre of residue. 



2. Understory removal. Treatment removed about 

 40 percent of the merchantable volume by cutting the 

 smaller diameter material and leaving the better saw- 

 timber and large pole stems as an overstory. About 18 

 tons per acre of residue was left on the surface. The 

 residual overstory transmitted about 50 percent of full 

 sunlight. 



3. Shelterwood. About half of the merchantable volume 

 was removed, leaving an overstory of small sawtimber and 

 pole stems. Dense clumps of saplings and poles were selec- 

 tively thinned. The residual overstory transmitted about 

 60 percent of full sunlight. This was a common treatment 

 in this tj-^pe of stand in 1977. 



4. Uncut. An adjacent uncut area was used as the 

 control. 



Residue reduction treatments on the study units in- 

 cluded the following: 



1. To simulate close utilization, all residues down to 1 

 inch in diameter were removed. The small material was 

 bunched by hand prior to skidding. The surface was quite 

 uniform looking after treatment (fig. 2B). Except for skid 

 trails, the understory vegetation was essentially undis- 

 turbed. The surface condition used for temperature mea- 

 surement was a litter surface, made up of small twigs, leaf 

 and needle litter, and duff. About 10 percent of the sur- 

 face was exposed mineral soil. 



2. A pile-and-burn treatment in the shelterwood over- 

 story treatment left most of the surface (except under the 

 piles) in the litter and mineral soil surface conditions with 

 an appearance like the close utilization treatment. The 

 litter and mineral soil surface conditions were used for 

 temperature measurement. 



3. Broadcast burning in the clearcut resulted in a 64 

 percent reduction of slash (Steele 1980) creating a com- 

 pletely blackened area with some mineral soil exposed 



2 



