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| Index to Reed Noss' Statement
Late Seral and Old-growth Definitions Potential Effects of PL’s Definitions and Late-Seral Harvest Plans on Biological Diversity |
Reed Noss |
Statement of Reed Noss Regarding the Adequacy of Late Seral and Old Growth Definitions in Pacific Lumber’s HCP/SYP and the Potential Effects of Implementing The Proposed Late Seral Management Guidelines on Species Associated with Older Forests in the Planning Region
I am Reed F. Noss, a conservation biologist, forest wildlife ecologist, and co-director of the Conservation Biology Institute (800 NW Starker Ave., Suite 31C, Corvallis, OR 97330). I have a M.S. in ecology from the University of Tennessee, a Ph.D. in wildlife ecology from the University of Florida, and 18 years experience in the fields of biology and conservation. I have published more than 140 papers and two books on biological topics and am President-Elect of the Society for Conservation Biology, the largest professional organization in the field. I am currently serving as science team leader for Save-the-Redwoods League in their master planning process. In that capacity I am editing a book on redwood forest ecology and conservation, to be published in 1999 by Island Press. My statements here reflect my own professional opinion as a scientist and do not necessarily represent the views of Save-the-Redwoods League.My comments address the definitions of late seral and old-growth forest in the PL HCP/SYP, the proposed methods for retaining late seral habitat through silviculture, and the effects of applying these definitions and harvest regimes on biological diversity. Late seral redwood and Douglas-fir forests are known to contain a number of habitat structures, native plants and animals, and ecological processes that are not found in young forests, or are found in reduced abundance there. Hence, conservation of adequate amounts of late seral forest in a configuration that favors retention of these structures, species, and processes is crucial to the long-term persistence of these features on the landscape.
Late Seral and Old-growth Definitions
As noted by Hunter (1989), “there is no generally accepted or universally applicable definition of old growth.” Similarly, Tuchmann et al. (1996) stated that “specifying exact age ranges for late-successional and old-growth forests is impossible because of variations in climate, soil quality, disturbances, and numerous other factors.” Nevertheless, Hunter (1989) pointed out that the core of a conceptual definition would be “old-growth forests are relatively old and relatively undisturbed by humans.” In the Pacific Northwest, the planning team for the President’s Forest Plan, as a “general rule,” defined late-successional (= late seral) forests as those with trees at least 80 years old and old-growth forests as a “subset of late-successional forests with trees 200 years or older.” The planning team was referring largely to Douglas-fir forests. As I will note below, redwood forests at 80 years are generally considered young-growth.The working definitions of the President’s Northwest Forest Plan are generally consistent with others that have been offered for Douglas-fir and other coniferous forests in the Pacific Northwest and coastal California. Franklin (1982) specified age ranges for several seral stages in these forests: herb and shrub: 30 years, young forest: 30-100 years, mature forest: 100-200 years, old growth: 200-800 years, climax forests: >800 years. In the Oregon Coast Range Hansen et al. (1991) defined age classes as young (40-80 years), mature (80-200 years), and old growth (>200 years). Morrison (1988) recognized three categories of old growth: (1) “classic” old growth-stands meeting all minimum old-growth criteria in which at least 8 trees per acre exceed 300 years in age or 40 inches in diameter. Included in this grouping are stands that may be considered super old growth, with trees exceeding 700 years in age or 72 inches in diameter. (2) “early” old growth-stands meeting all minimum old-growth criteria in which at least 8 trees per acre exceed 200 years in age or 32 inches in diameter. These stands may include some older trees but in insufficient numbers to qualify as classic old growth. (3) “Mature”-stands where more than 20 trees per acre exceed 80 years in age or 21 inches in diameter. Included in this category are stands which fail to meet one or more of the minimum old-growth criteria.
Morrison (1988) also noted that “old-growth stands less than 80 acres in size are not viewed as viable old-growth units because external influences can easily penetrate and because they are vulnerable to disturbances such as windthrow.” Most forest ecologists agree that small patches, especially when isolated, cannot be considered viable forest ecosystems.
Importantly, most definitions of old growth consider more than simply tree age. Among the frequently noted characteristics are deep, multi-layered canopies, abundant shade-tolerant species, numerous large, standing snags and downed logs in various size and decay classes, and abundant tree cavities (Franklin et al. 1981, Franklin 1982, Old-growth Definition Task Group 1986, Morrison 1988, Norse 1990). As I will note below, these structural characteristics are important in determining the biological diversity of redwood forests, as in other forest types. Variation in site class (i.e., suitability of conditions for tree growth) has an influence on the age at which a stand develops old-growth structural characteristics. For Douglas-fir/tanoak forests in California, Beardsley and Warbington (1996) considered old-growth conditions to begin at 180 years on high site classes, 240 years on medium site classes, and 300 years on low site classes.
Specific to redwood, the tree species of most concern in the PL HCP/SYP, Helms (1994) notes that “most existing stands on alluvial flats are about 800 years old, although redwood may grow vigorously for 2000 years.” Bingham and Sawyer (1991) characterized redwood stands in the Angelo Reserve (central redwood forests section) as young at 40-100 years, mature at 100-200 years, and old-growth at 200-560 years. Helms (1994) agreed that 100-year old stands of redwood are young-growth: “young growth stands at 100 years have yields ranging from 10,600 cubic feet per acre on low-index sites to 51,080 cubic feet per acre on high-index sites.” Although redwood is a relatively fast-growing tree, its long life span and potentially huge final size suggest that true late seral and, especially, old-growth conditions are slow to develop. Old-growth redwood stands are composed of very large, tall trees. The tallest known living redwood is 112.0 meters in height; the tallest historically reported redwood was 115.8 m tall. There are 16 living redwood trees known to be over 110 m tall. Old-growth redwoods have immense diameters; for example, the Fieldbrook Stump in Humboldt County is 9.8 m in diameter at a point 1.5 meters from the ground. Another tree, cut in 1926, was only 6.6 m diameter at the base, but had such a slight taper that by 60 m off the ground it was still 4.6 m in diameter (Sawyer et al. 1999a).
Considering these well-accepted definitions and characterizations of late seral and old-growth forests, the definitions given in the PL HCP/SYP appear to be far outside the range of scientific opinion. The PL HCP/SYP (Vol. I, pages 15-16) defines late seral forest as “made up of stands with overstory trees that on average are larger than generally 24" dbh and may have developed a multi-storied structure. It occurs in stands as young as 40 years old but more typically in stands about 50 to 60 years old and older.” By most definitions of age classes for both Douglas-fir and redwood, forests below 100 years in age would be considered young forest.
The PL HCP/SYP (Vol I, pages 15-16) correctly considers old growth “a late seral type” and in its plan includes only unentered stands in the old-growth category. Nevertheless, old growth is further defined by PL as stands with “multiple canopy layers dominated by trees over 30 inches dbh.” Given the tremendous potential diameter of redwood-as well as Douglas-fir-this dbh threshold seems extremely low.
Potential Effects of PL’s Definitions and Late-Seral Harvest Plans on Biological Diversity
PL’s plans for “late seral selection” (Vol III, Part B, page 10) have, as a goal, the creation and maintenance of “multi-storied, uneven-aged, late-seral forest habitat.” They plan to use selection harvesting to “enhance the growth of a few large trees while creating and maintaining special habitat elements including decadent trees, snags, downed logs, and other woody material.” Given PL’s definition of late-seral forest, however, there is no assurance that true late-seral forests will be created or maintained. Indeed, the table of desired residual basal area by diameter class shows that only 52% of the trees left on site after harvest will exceed 30 inches in diameter and no (0%) trees larger than 48 inches dbh will be retained. This silvicultural system will not maintain true late-seral redwood or Douglas-fir forest, much less old growth.What are the potential consequences of losing large, old trees from PL’s lands? One must begin by recognizing the larger context of the redwood ecosystem. Approximately 96% of the original, old-growth redwood forest has already been destroyed by logging (U.S. Fish and Wildlife 1997). Much of the remaining forest is highly fragmented, i.e., small, remnant stands isolated from other old-growth stands across a second-growth or third-growth landscape. This landscape matrix serves as habitat for early successional and generalist species, but generally not for old-growth species (Diaz and Bell 1997). Some of the second growth is beginning to achieve old-growth characteristics or retain these characteristics as residual features of the former, old-growth stands. In some cases second-growth redwood stands that retain residual old-growth components are suitable habitat for typically late-seral species such as the northern spotted owl, red tree vole, flying squirrel, and fisher (Noon and Murphy 1997, Thornburgh et al. 1999). Nevertheless, species adapted to the unique environment of old-growth forests, such as canopy alectorioid lichens and other nonvascular epiphytes, as well as many invertebrates, cannot persist in young forest patches (Thornburgh et al. 1999).
Species that rely on snags and coarse woody debris, such as many salamanders, also do not occur or persist in young forests, unless considerable woody debris remains from the old growth that formerly occupied the site. The California slender salamander, for example, is significantly more abundant in mature and old-growth redwood forest compared to young forest (Welsh, in Cooperrider et al. 1999). Furthermore, an amazing 320 species of fungi have been found in redwood forests. Most of these species depend on coarse woody debris-i.e., large, downed logs that retain moisture in the dry season. These structures are supplied in abundance and perpetuity only in true late seral forests. Thinning can increase the rate of recovery of old-growth forest conditions in young stands (Menges 1994, cited in Thornburgh et al. 1999), but it is too early to say how long it takes to reestablish a complete old-growth community.
One of the species most dependent on old-growth redwoods, which is unlikely to fare well under the silvicultural systems proposed in the PL HCP/SYP, is the marbled murrelet. Experts on this species will have more to say about it than I can, but it is clear that the species is dependent on old growth. Murrelet nests in California are found exclusively on old-growth trees, above 30 m in height on large limbs with high vertical cover (K. Nelson, in Cooperrider et al. 1999). Murrelets have declined by some 90% since European settlement and continue to decline at a rate of about 4-7% annually (Beissinger 1995, Ralph and Miller 1995). The PL plan, because it fails to regenerate true old-growth forests, will likely contribute to this decline.
Another striking feature of old-growth redwood forests that will not be maintained or created through PL’s late-seral selection system is the remarkably complex forest canopy. Large redwood trees (i.e., generally much larger than the trees that will be retained under PL’s system) develop a complex canopy structure. Main trunks often snap and resprout; even branches can sprout new erect stems that are essentially new trunks, each of which develops a complex crown. Highly reiterated crowns resemble forest stands more than individual trees (Sillett, in Sawyer et al. 1999b). A considerable amount of debris collects in these crowns, forming canopy soil. These canopy ecosystems support diverse assemblages of vascular and nonvascular plants, insects, earthworms, mollusks, and amphibians (Sillett, in Sawyer et al. 1999a). The clouded salamander, for example, has been found to nest 40 m high in the canopy soil of old-growth redwoods (Welsh, in Cooperrider et al. 1999). The redwood canopy communities are only beginning to be studied. It is not unlikely that species new to science will be discovered in these and other habitats of late-seral forests. These communities will essentially disappear under PL’s silvicultural systems.
An important consideration for the maintenance of redwood forests is the role of fog. During the summer, when rainfall in the redwood region is extremely low, fog serves as an additional water source. Studies have confirmed that fog can reduce water stress, enhance growth, and perhaps influence the long-term survival of redwoods (Dawson 1996, 1998, Dawson, in Sawyer et al. 1999). Because of the increased surface area of complex canopies, fog is probably “stripped” from the atmosphere and added to the system (through needle drip, increasing soil moisture) more effectively in large patches of old-growth trees with complex canopies, compared to the young forest that would be maintained under PL’s plan.
Finally, type conversions, which can take place rapidly through clearcutting and planting or slowly through the effects of selection logging, are of great concern to ecologists and conservationists because of their often profound effects on the biological diversity of forests locally and regionally. The PL HCP/SYP will result in a declining ratio of redwood to Douglas-fir over time. Veirs and Lennox (1981; cited in Sawyer et al. 1999a) noted that the density ratio of canopy redwood to canopy Douglas-fir in current old growth ranges from 10:1 to 3:1. They also noted that the situation is reversed in current second-growth forests of Redwood National Park, an artifact of aerially seeding Douglas-fir. A linear regression analysis suggested that, left alone, these stands would reach a 1:1 ratio at 100 years of age and a 2:1 ratio of redwood to Douglas-fir after 250-300 years. Thinning of Douglas-fir produced stands at 60 years that had ratios similar to those of old growth.
In contrast, the PL plan would result in a pronounced shift from redwood to Douglas-fir over the life of the plan (12 decades). Whereas redwood accounts for 65% of the harvest in the first decade, it will account for only 26% of the harvest by decade 12. Douglas-fir will increase from 25% to 72% of the harvest over the same period. This type conversion will not bode well for species dependent on old-growth redwoods in the plan area. For example, marbled murrelets in California are known to occur primarily in the coast redwoods; only a few observations-and no nests-have been recorded in Douglas-fir dominated forests (however, nests may occur in Douglas-fir trees in redwood-dominated forests) (Nelson, in Cooperrider et al. 1999).
In summary, the PL HCP/SYP will fail to maintain true late-seral and old-growth forest in the planning area, disguises this failure by defining “late seral” to include what almost all ecologists would consider young forest, and will lead to a general type conversion of redwood to Douglas-fir. Thus, the plan has a high probability of contributing to a loss of the species and ecological functions associated with true late-seral redwood forest in the region.
Literature Cited
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Bingham, B.B.,and J.O. Sawyer. 1991. Distinctive features and definitions of young, mature, and old-growth Douglas-fir/hardwood forests. Pages 363-377 in L. F. Fuggiero, K. B. Aubry, A. B. Carey, M. H. Huff,editors. Wildlife and vegetation in unmanaged Douglas-fir forests. USDA Forest Service, Pacific Northwest Research Station General Technical Report PNW-GRT-285. Portland, OR.
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Veirs and Lennox 1981. Reference not available (sited in Sawyer et al. 1999a).