THE SITE, STAND, AND TREE 

 CHARACTERISTICS ASSOCIATED 

 WITH THE RELEASE RESPONSE OF 

 WESTERN REDCEDAR 

 Literature Review 



Growth of shade-tolerant tree species increases in 

 response to the removal of overhead and surrounding 

 competition. Overstory removal has been found effec- 

 tive in increasing growth rates of shade-tolerant 

 coniferous understory species (Leaphart and Foiles 

 1972; Koenigs 1969; Ferguson and Adams 1979; Seidel 

 1977). Likewise, understories of tolerant deciduous 

 trees can be released successfully (Johnson 1975; 

 Carvell 1967; Sander and others 1976). Growth re- 

 sponse after overstory removal is often delayed one or 

 more years as the understory becomes acclimated to its 

 new environment (Herring 1977; Herring and Ethridge 

 1976). Shade-tolerant species are also capable of in- 

 creased growth rates after intermediate stand treat- 

 ments such as cleanings and thinnings (Deitschman 

 and Pfister 1973; Berry 1968). 



Tree characteristics such as diameter, height, crown 

 condition, rooting habit, and age are related to the 

 growth performance of a tree after release. Larger 

 diameter tolerant trees usually show better growth 

 response after release than smaller diameter trees 

 (Leaphart and Foiles 1972; Herring and Ethridge 1976; 

 Johnson 1975). Shade-tolerant trees with extensive 

 symmetrical root systems and little root mortality 

 respond well to release (Leaphart and Grismer 1974; 

 Eis 1974). The response of tolerant species to release is 

 related to tree age in some species such as grand fir 

 (Abies grandis [Dougl.] Lindl.) (Ferguson and Adams 

 1979); however, age is not associated with the response 

 of other species such as subalpine fir (Abies lasiocarpa 

 [Hook.] Nutt) (Herring 1977, Crossley 1976). 



Site characteristics are important in governing the 

 amount of growth that occurs after a tolerant species is 

 released. Most tolerant coniferous species respond best 

 to release from competition on cool, moist sites 

 (Ferguson and Adams 1979; Herring 1977; Herring and 

 Ethridge 1976), as do many deciduous trees (Johnson 

 1975). 



Release cuttings can increase the chance of disease in 

 the residual trees. When the overstory was removed 

 and the residual western redcedar stand thinned in a 

 northern Idaho site, 69 percent of the trees were in- 

 fected by root rotting organisms, while in the untreated 

 stand only 36 percent of the trees were infected 

 (Koenigs 1969). Similarly, Berry (1968) reported high 

 mortality caused by root diseases in thinned stands of 

 white spruce (Picea glauca [Moench] Voss). Release 

 cuttings in stands of western hemlock can increase root 

 diseases by damaging residual trees thus providing 

 entry points for disease causing organisms, and also by 

 creating stumps that can be colonized by root patho- 

 gens (Wallis and Morrison 1975). 



The leaves of shade-tolerant species are adapted to 

 low light conditions and must change or be replaced 

 when exposed to increased light. Shade-tolerant beech 



(Fagus grandifolia Ehrh.) leaves are efficient in dim 

 light with leaf stomata opening rapidly in response to 

 low light levels (Woods and Turner 1971). This allows 

 the species to take advantage of short periods of light 

 for photosynthesis even though the photosynthetic rate 

 may be very low (Loach 1967). In addition, tolerant 

 species have low respiration rates that help them sur- 

 vive in shaded conditions (Loach 1967). Trees with 

 leaves adapted to shaded environments often die or 

 develop parch blight when suddenly exposed to open 

 light conditions (Boyce 1961). The death or damage of 

 trees released from competition can be related to the 

 inability of the foliage to adapt or change to the new 

 light conditions. Depending upon the amount of expo- 

 sure, many shade leaves on a tree will drop when a 

 release cutting occurs, as others adapt to the new light 

 conditions (Tucker and Emmingham 1977). Leaves de- 

 veloping on released shade-grown trees usually have 

 two rows of palisade mesophyll cells compared to one 

 row on the shade-grown leaves (Aussenac 1973). 

 Shade-grown leaves that do not drop will often increase 

 in thickness and in weight-to-length ratios, thus becom- 

 ing more adapted to their new environment (Tucker 

 and Emmingham 1977). 



Methods 



DATA COLLECTION 



A survey approach was used to study the response of 

 western redcedar diameter growth at breast height 

 (d.b.h.), to various kinds of release from competition, 

 including thinning, weeding, cleaning, and overstory 

 removal. To assure that a response could be measured, 

 stands chosen for sampling had a minimum of 10 years 

 of tree growth since the release treatment. Each stand 

 selected was uniform in slope, aspect, soil type, and 

 stand history. Fifteen stands meeting the selection 

 criteria were located on various ownerships in eastern 

 Washington, northern Idaho, and western Montana 

 during the summer of 1979. No western redcedar 

 stands examined in the central portion of the study 

 area satisfied the stand selection requirements (fig. 1). 



Selected stands were described as follows: geographic 

 location, habitat type (Daubenmire and Daubenmire 

 1968), elevation above sea level, slope, slope configura- 

 tion, aspect, and year of release treatment. The habitat 

 types represented by the stands in the study include: 

 Thuja plicata/Pachistima myrsinites (THPL/PAMY), 

 Thuja plicata/Athyrium filix-foemina (THPL/ATFI). 

 Tsuga heterophylla/Pachistima myrsinites (TSHE/ 

 PAMY), and Abies lasiocarpa/Pachistima myrsinites 

 (ABLE/PAMY). 



Within each of the 15 stands, two 5-point clusters 

 were established for sampling the trees and lesser 

 vegetation. Each point was the center of a 1/300-acre 

 (0.00133-ha) fixed-radius plot for measurements of trees 

 up to 5 inches (12.7 cm) d.b.h. and a variable-radius 

 plot for measurements of trees 5 inches (12.7 cm) d.b.h. 

 and larger. A basal area factor was used that resulted in 

 selection of four to six trees in the variable radius plot. 

 For each tree the following were recorded: species, 

 crown class, d.b.h., height, crown ratio (live crown as 



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