are discussed relative to their effects on seedling growth 

 and root development. 



Tests for significant treatment effects on surface tem- 

 perature were made using one-way analysis of variance to 

 determine if treatments were different for maximum and 

 minimum temperatures (by month). Also, tests of treat- 

 ment differences in air and soil temperatures were evalu- 

 ated using one-way analysis of variance. Analyses were 

 run only for data from May through October. Duncan's 

 multiple range test was used to test for individual treat- 

 ment differences. If variances were not homogeneous, we 

 used approximate i-tests. All tests were done at the 0.05 

 significance level. Differences in the overstory removal 

 treatments were compared using temperatures measured 

 on the litter surface condition of each treatment. Differ- 

 ences between the surface conditions were compared using 

 a common overstory removal treatment (usually the clear- 

 cut). Mineral soil and litter surface conditions at Lubrecht, 

 however, were compared in the shelterwood treatment. 



OVERSTORY REMOVAL AND 

 TEMPERATURE 



Surface, air, and soil temperature data accumulated 

 from treated units were analyzed first to evaluate the 

 effects of level of overstory removal on temperature. To 

 compare overstory treatments on a common basis, data 

 from the litter surface condition were used. 



Surface Temperature 



Lubrecht— The amount of overstory removal signifi- 

 cantly influenced maximum surface temperatures, mean 

 monthly maximum surface temperatures being significant- 

 ly warmer where all or most of the canopy was removed 

 (table 3). From May through October of the first 3 years 

 after harvesting, temperatures on the clearcut surface 

 were significantly warmer than those on the shelterwood 



surface 40 percent of the months, were equal for 40 per- 

 cent of the months, and were significantly lower for the 

 other months. Over the 3 years, surface temperatures on 

 the clearcut and shelterwood treatments were significantly 

 warmer for 80 percent of the months than were surface 

 temperatures on the understory removal or uncut treat- 

 ments. Surface temperatures on the understory removal 

 for some months were up to 11 °F warmer than on the 

 uncut, but for 60 percent of the months differences were 

 not significant. 



Maximum surface temperatures were observed as high 

 as 165 °F and often exceeded 133 °F (fig. 3) for the clear- 

 cut and shelterwood treatments. Temperatures of 122 °F 



200 



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Figure 3 — Maximum daily ground surface 

 temperatures in July 1980 at Lubrecfit for tfie 

 clearcut (cc), shelterwood (sw). understory 

 removal (ur), and uncut treatments. Surface con- 

 dition is litter. The horizontal line through the 

 graph is 133 °F, a seedling survival threshold. 



Table 3— Average maximum surface temperatures (°F) by month for 1978, 1979, and 1980 for 

 the overstory treatments at the Lubrecht study site. Data from the litter surface were 

 used for all treatments. Values for a month (months are not compared) having different 

 letters are significantly different at the 0.05 level. 



Overstory 



treatment 



May 



June 



July 



Aug. 



Sept. 



Oct. 







1978 











Uncut 



61a 



90a 



102a 



95a 



75a 



75b 



Understory removal 



72b 



100b 



106a 



86a 



77a 



61a 



Shelterwood 



72b 



106b 



126b 



117b 



93b 



79b 



Clearcut 



93c 



126c 



138c 



118b 



97b 



93c 







1979 











Uncut 



66a 



75a 







93a 



68a 



Understory removal 



77b 



86a 







91a 



70a 



Shelterwood 



82b 



100b 







126c 



84b 



Clearcut 



104c 



126c 







113b 



81b 







1980 











Uncut 





86a 



104a 



99a 



70a 



61a 



Understory removal 





88a 



95a 



102a 



81b 



64a 



Shelterwood 





93ab 



115b 



127c 



100c 



79b 



Clearcut 





97b 



115b 



118b 



82b 



70ab 



