Inventory and Evaluation of Selected Old Growth Ponderosa Pine Stands, Cottonwood Resource Area, Idaho
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INVENTORY AND EVALUATION OF SELECTED OLD GROWTH PONDEROSA PINE STANDS, COTTONWOOD RESOURCE AREA, IDAHO by Steven K. Rust Conservation Data Center February, 1998 Idaho Department of Fish and Game Natural Resource Policy Bureau 600 South Walnut, P.O. Box 25 Boise, Idaho 83707 Stephen P. Mealey, Director Cooperative Challenge Cost-Share Project Idaho Department of Fish and Game USDI Bureau of Land Management, Cottonwood Resource Area Abstract Pinus ponderosa is a long-lived, early- to mid-seral species in plant associations within the Abies grandis, Pseudotsuga menziesii, and Pinus ponderosa series. Once abundant and widespread, old growth Pinus ponderosa-dominated forest has declined due to a century of fire exclusion, livestock grazing, and selective harvesting within accessible stands. The loss of seral old growth Pinus ponderosa is a concern for wildlife habitat and maintenance of biological diversity. This report summarizes the inventory of old growth Pinus ponderosa- dominated forest stands located on Bureau of Land Management lands in west central Idaho. A comparison of applicable old growth forest criteria is provided. Old growth forest attributes of stands within the study area typically exceed criteria provided in formal definitions. The ecology and wildlife use of Pinus ponderosa-dominated forest is reviewed in relation to the stands observed within the study area. Additional literary resources, not referred to in the text, are summarized in an annotated and indexed bibliography. Approaches to restoration of old growth stands are identified based on groups of stands with similar growth potential, seral status, and stand structure. The use of non-commercial thinning, followed by pile burning, and prescribed understory burning is identified for many old growth stands within the study area. Old growth sites are prioritized for conservation and restoration activities based of criteria for rarity, richness, representativeness, and viability. Four sites are identified as having the highest priority. TABLE OF CONTENTS Introduction ........................................................... 1 Study Area and Methods ................................................ 1 Results and Discussion ................................................. 2 OLD GROWTH FOREST ECOLOGY.................................... 2 Old growth classification and description .............................. 2 Old growth forest dynamics......................................... 3 Wildlife habitat relations ........................................... 5 Grand fir series .................................................. 6 Douglas-fir series ................................................ 8 Ponderosa pine series ............................................ 13 SITE CONSERVATION AND RESTORATION RECOMMENDATIONS......... 14 Stand maintenance and restoration ................................. 14 Site conservation priorities ........................................ 21 Concluding Summary ................................................. 22 Literature Cited ....................................................... 24 Appendix 1. Tables .................................................... 29 Table 1. Pinus ponderosa-dominated old growth sites...................... 30 Table 2. Summary of plant associations observed......................... 31 Table 3. Summary of old growth criteria................................. 32 Table 4. Summary of the applicability of old growth definitions ............... 34 Table 5. Summary of old growth stand structure observed .................. 35 Table 6. Summary of wildlife use of Pinus ponderosa-dominated old growth .... 36 Table 7. Summary of forested stands ................................... 38 Table 8. Summary of the rarity of plant associations observed ............... 41 Table 9. Summary of conservation priority ranking......................... 42 Appendix 2. Figures 1 - 4 ............................................... 43 Figure 1. Stem structure of Abies grandis/Acer glabrum .................... 44 Figure 2. Comparison of Abies grandis/Spiraea betulifolia stands ............. 45 Figure 3. Stem structure observed in Abies grandis/Calamagrostis rubescens...45 Figure 4. Comparison of Pseudotsuga menziesii/Physocarpus malvaceus stands 46 Appendix 3. Annotated Bibliography ....................................... 47 Literary resources .................................................. 47 Keyword index ..................................................... 80 Appendix 4. Site old growth stand summaries and delineations .................. 98 v vi Introduction Pinus ponderosa is a long-lived, early- to mid-seral species in plant associations within the Abies grandis, Pseudotsuga menziesii, and Pinus ponderosa series (Steele et al. 1981; Cooper et al. 1991). In pre- settlement times, frequent, low-intensity fires in Pinus ponderosa-dominated forest maintained relatively open, old growth forest stands (Evans 1991 as cited by Agee 1996; Arno et al. 1995; Crane and Fischer 1986; and many others). Fire played an important ecological role in this vegetation by controlling the density of understory tree regeneration and favoring the growth of relatively few, large, dominant, fire tolerant trees; reducing tree susceptibility to disease; and favoring the growth and diversity of understory herbaceous species (Barrett 1988; Crane and Fischer 1986; Agee 1996). The National Biological Service has identified seral old growth Pinus ponderosa forest as one of the most threatened ecosystems in the United States, with an estimated decline of 70 - 84 % (Noss et al. 1995). Once abundant and widespread (Losensky 1992), old growth Pinus ponderosa-dominated forest has declined due to a century of fire exclusion, livestock grazing, and selective harvesting within accessible stands (Steele et al. 1986; Hamilton 1993; Covington and Moore 1994; Sloan 1994; Agee 1996). The loss of seral old growth Pinus ponderosa is a concern for wildlife habitat and maintenance of biological diversity (Everett et al. 1994; Morgan 1994; Arno et al. 1995; Groves et al, 1997). Given this high level of decline, human activities that influence the distribution, abundance, and quality of old growth Pinus ponderosa- dominated forest must be critically evaluated. Principal old growth forest attributes are the density of large diameter, old trees; the presence of tree decadence; and the presence and size of snags and coarse woody debris. Though these ecological attributes describe the life breath critical to species habitats, they also serve an important administrative function in ongoing debates regarding the management of forested lands. Old growth forest definitions that have potential baring in Idaho are provided by Green et al. (1992), Hamilton (1993), Hopkins et al. (1992a and b), and Williams et al. (1992). Questions that provide the impetus for this study include: What are stand structural conditions of remnant stands of Pinus ponderosa-dominated old growth forest in west central Idaho? Where are the greatest opportunities for the conservation and restoration of Pinus ponderosa-dominated old growth forest? How do old growth definitions - derived from the north, south, and west - apply to stands in west central Idaho? The objectives of the study are: (1) inventory and prioritize sites on Bureau of Land Management lands within west central Idaho for the conservation and restoration of old growth Pinus ponderosa-dominated forest; (2) develop preliminary management guidelines to enhance and protect the biological values of selected stands; and (3) as needed, contribute to the resolution of old growth forest definitions. Study Area and Methods The study area includes Bureau of Land Management lands on the Cottonwood Resource Area, Upper Columbia-Salmon Clearwater Districts, in west central Idaho. Sites with high potential for the conservation or restoration of old growth Pinus ponderosa-dominated forest were identified using aerial photography and existing survey and reconnaissance data. Vegetation stands at each site were delineated based on stand environmental features (topography and elevation) and apparent structure and composition (using aerial photography interpretation). In order to optimize the balance between the geographic scope of the study and the need to acquire quantitative information, the intensity of field reconnaissance efforts were stratified within stand delineations. Quantitative and qualitative data was taken to characterize current stand conditions. Qualitative data consists of descriptive field narratives regarding composition, structure, and function. This data is linked to and supported by quantitative data. Intensive quantitative sampling occurred to best represent site conditions, but was limited to selected reference stands within each site. Both data types are geo- referenced. Page 1 Within selected reference stands nested 0.10 and 0.25 acre fixed area plots were used to sample stand composition and structure and measure environmental parameters. Plots were placed within forest patches that are homogeneous in structure and composition. Habitat type (and phase), tree canopy cover, basic environmental parameters (slope aspect, gradient, and horizon; elevation; and micro- and macro-topography), and fuel class were determined on a standard 0.1 acre circular ecology plot. The density and size distribution of live, standing dead, and dead and down trees were sampled on nested 0.10 and 0.25 acre fixed area plots. Trees with diameter at breast height (dbh) > 5 but <