Occurrence of Conifer Seedlings 

 and Their Microenvironments on 

 Disturbed Sites in Central Idaho 



Kathleen Geier-Hayes 



INTRODUCTION 



Successful forest management requires prompt tree re- 

 generation following timber harvesting. With the increase 

 in planting costs, many forest managers have turned to 

 natural regeneration to restock stands (Gashwiler 1970). 

 Natural regeneration of stands to adequate stocking levels 

 is often slow (Fiedler and others 1985; Minore and 

 Dubrasich 1981), and many studies have investigated the 

 seedbed requirements for various conifer species. Few 

 studies, however, have characterized the seedling micro- 

 environment in terms of both seedbed and seedbed cover. 



Seed germination and establishment depends on critical 

 environmental conditions. A microenvironment that pro- 

 vides a seed with the requirements for germination and 

 establishment was defined by Harper (1977) as a "safe 

 site." The absence of a particular species from an area 

 may be due either to insufficient seed dispersed to the site 

 or to a lack of safe sites. Silviculturists use several 

 methods to manipulate the amount of available conifer 

 seed, but little is known about the required safe sites for 

 that seed. Once identified, site preparations after timber 

 harvesting can be manipulated to provide as many safe 

 sites as possible for a desired conifer species. This study 

 was undertaken to define safe sites for coniferous trees in 

 west central Idaho. 



METHODS 



The study was conducted in the Douglas-fir (Pseudotsuga 

 menziesii var. glauca) and grand fir (Abies grandis) forests 

 on the Boise and Payette National Forests in west-central 

 Idaho. In the Douglas-fir forests, Douglas-fir is the domi- 

 nant species often growing with ponderosa pine (Pinus 

 ponderosa) (Steele and others 1981). Grand fir is the domi- 

 nant conifer in grand fir forests, often growing with pon- 

 derosa pine, lodgepole pine (Pinus contorta), Douglas-fir, 

 Engelmann spruce (Picea engelmannii), and western larch 

 (Larix occidentalis). Within these forests, three habitat 

 types based on potential climax vegetation were sampled: 

 Douglas-fir/white spirea (Pseudotsuga menziesii/ 'Spiraea 

 betulifolia) habitat type (h.t.), grand fir/mountain maple 

 (Abies grandis/Acer glabrum) h.t., and grand fir/blue 

 huckleberry (Abies grandis/Vaccinium globulare) h.t. 

 (Steele and others 1981). The Douglas-fir habitat types are 

 normally drier and warmer than the grand fir habitat 

 types. The grand fir/mountain maple h.t. occurs in envi- 

 ronments in the grand fir zone that are warmer than the 

 grand fir/blue huckleberry h.t. environment. 



Sample sites were located in the study area "subjec- 

 tively but without preconceived bias" as described by 

 Mueller-Dombois and Ellenberg (1974). Areas identified as 

 Douglas-fir/white spirea, grand fir/mountain maple, and 

 grand fir/blue huckleberry h.t. were reconnoitered to iden- 

 tify stands with some type of disturbance. Sample points 

 were selected to represent the range of silvicultural 

 methods and site preparation combinations available. 

 The sample points were in representative portions of the 

 stands in areas with uniform treatments. The silvicultural 

 methods sampled included clearcuts, shelterwood cuts, 

 seed-tree cuts, and group selection cuts. Site preparations 

 included none (no slash disposal and little harvesting im- 

 pact), broadcast burning, and two types of scarification- 

 light scarification (from slash disposal or harvesting ac- 

 tivities) and heavy scarification (contour terracing). Only 

 sites with 5-year-old or older disturbances were included. 

 At each sampling point, five 108-ft 2 (10-m 2 ) circular plots 

 were located with one at the center (designated CENTER) 

 and four peripheral (designated LEFT, RIGHT, UP, 

 DOWN) 22.5 ft (6.9 m) from the middle of plot CENTER. 

 Plots UP and DOWN were perpendicular to the contour 

 upslope and downslope of CENTER respectively. Plots 

 RIGHT and LEFT were on the contour to the right and 

 left of CENTER. In using this sampling method, I 

 assumed that safe sites were randomly dispersed within 

 the uniform site treatment. All plots will be referred to as 

 seedling plots. I treated each seedling plot as a separate 

 plot for summarization. 



For each seedling plot, I recorded the percentage of the 

 plot covered by various soil surface conditions (seedbeds) 

 and percentage coverages of vegetation and debris. Infor- 

 mation on all conifer seedlings present included species, 

 seedbed, and species of or kind of overhanging (influential) 

 vegetation or debris. Seedbed categories were litter- 

 covered mineral soil, bare mineral soil, moss mats, residual 

 duff, and rotten wood. Rocks and stumps were also re- 

 corded as seedbeds. 



Seedlings 3 years old or older, but younger than the 

 disturbance, were recorded. Seedlings were clipped and 

 aged in the laboratory, or when possible, were aged on 

 site by counting bud scars or nodes. Each individual seed- 

 ling or cluster of seedlings (cache) was recorded as an oc- 

 currence. For each sample site I recorded aspect, slope, 

 and elevation. The dates (year) of timber harvesting and 

 site disturbance were estimated from management 

 records, plantation signs, tree growth release indications 

 from increment borings, and cross sections of machine 

 scars that occurred during timber harvesting. All sampling 



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