9. Coarse Woody Debris - Other Habitat and Potential Niches

280.  The fasted way to destroy an organism is to destroy its niche – the place where it lives and reproduces (A New Tree Biology Dictionary, Shigo).

281.  Large fallen trees are a finite resource that creates a myriad of changing habitats through time as they decompose and recycle into the forest soil and new, living trees benefit.  (Maser, Tarrant, Trappe and Franklin, 1988,pg45-fig216).  

282.  Often, decay classifications, are based on the external characteristics of a fallen tree and do not adequately convey the internal diversity of niches.  We have found, however, that internal development of niches relates reasonably well to decay class (Maser and Trappe, 1984 pg 5-par5). 

283.  We especially need to know more about the fallen tree – soil interface, probably the single most important habitat and potential niche for the survival of organisms in drastically altered systems (Maser and Trappe, 1984, pg49-par1).    

284.  Recent and current research in Old-growth forest are revealing much about the roles and qualities of fallen trees.  Understanding this information may allow use of fallen trees as sensitive barometers of “habitat health” of a system (Maser and Trappe, 1984, pg48-par1).  

285.  Logs provide essential habitat for a variety of invertebrates and vertebrates. They are used as sites for lookouts, feeding and reproduction, protection and cover, sources and storage of food, and bedding. The high moisture content of logs makes them particularly important as habitat for amphibians (Franklin, Cromack, Kermit, et al. others,  1981).
286.  Fallen trees offer multitudes of both external and internal habitats that change and yet persist through the decades.  One needs an understanding of the synergistic affects of constant small changes within a persistent large structure to appreciate the dynamics of a fallen tree and its function in an ecosystem (Maser and Trappe, 1984, pg 17-par 1).           

287.  Forest floor diversity is partly maintained by windthrown trees that create a pit-and-mound topography as they are uprooted (Maser, Tarrant, Trappe and Franklin, 1988, pg45-fig2.7).   

288.  About 140 years are needed for essential elements to cycle in large, fallen trees and more than 400 years for such trees to become incorporated into the forest floor; they therefore interact with the plants and animals of the forest floor and soil over a long period of forest and stand successional history (Maser, Tarrant, Trappe and Franklin, 1988, pg37-par2).   

289.  During decomposition, logs and other forms of coarse woody debris (defined as wood pieces more than ten centimeters in diameter and more than one meter in length) reduce erosion and affect soil development, store essential elements and water, provide a source of energy and nutrient flow, serve as seedbeds, and provide habitat for decomposers and heterotrophs (Harmon and Hua, 1991).

290.  During decomposition, logs and other forms of coarse woody debris (CWD) reduce erosion, affect soil development, store nutrients and water, are a potentially large source of energy (nutrients) and essential elements, serve as a seed bed for plants, and form an important habitat for fungi and arthropods (Kropp, 1982).

291.  The flow of plant and animal populations, air, water, and essential elements between a fallen tree and its surroundings increases as decomposition continues (Maser and Trappe, 1984, pg 12-par1).

292.  Symplastless trees are structural components of great importance for forest dynamics and forest biodiversity.  The decomposition of trees provides an important link in cycling of nutrients and essential elements in ecosystems.  In addition, many species of plants, fungi, and animals are dependent on symplastless trees for nutrients and essential elements, habitat or substrate and nesting (Kruys and Jonsson, 1999).

293.  Fallen trees that are oriented along the contours of a slope seem to be used more by vertebrates than are trees oriented across contours, especially on steep slopes.  Large, stable trees lying along contours help reduce erosion by forming "a barrier to creeping and raveling soils.  Soil, nutrients and essential elements deposited along the up slope side of fallen trees reduce loss of nutrients and essential elements from the site. Such spots are excellent for the establishment and growth of vegetation, including tree seedlings.  Vegetation becomes established on and helps stabilize this "new soil", and as invertebrates and small vertebrates begin to burrow into the new soil, they not only nutritionally enrich it with their feces and urine but also constantly mix it by their burrowing activities (Maser and Trappe, 1984 pg 4-par1&2).

294.  As a log decomposes, many organisms such as plant roots, mites, collembolans, amphibians, and small mammals, must await the creations of the inner space before they can enter.  The flow of plant and animal populations, air, water, and nutrients as well as essential elements between fallen tree and its surrounding increases as long as aging process continues (Maser and Trappe, 1984, pg 12-par1).

295.  The logs being removed would otherwise serve a key role as erosion control and animal activity (Page-Dumroese, Harvey, Jurgensen and Graham, 1991).

296.  Debris has many functions ranging from soil protection to wildlife and microbial habitat. The management of coarse woody debris is critical for maintaining functioning ecosystems (Graham, Harvey, Jurgensen, Jain, Tonn and Page-Dumroese, 1994).

297.  Preservation of a threatened or endangered species involves preservation of its habitat and the diversity that habitat entails. When such becomes a goal of forest management, managers need information not only on owls or small mammals, but also on the mycorrhizal fungi that form the base of the food web.  Removal of ectomycorrhizal tree hosts removes the energy source of ectomycorrhizal fungi, which will not fruit without their host plants (Amaranthus, Trappe and Bednar, 1994).

298.  Large, fallen trees in various stages of decay contribute much-needed diversity to terrestrial and aquatic habitats in western forests. When most biological activity in soil is limited by low moisture availability in summer, the fallen tree-soil interface offers a relatively cool, moist habitat for animals and a substrate for microbial and root activity. Intensified utilization and management can deprive future forests of large, fallen trees. The impact of this loss on habitat diversity and on long-term forest productivity must be determined because management need sound  information on which to base resource management decisions (Maser and Trappe, 1984, Abstract-par2).  

299.  Every living conifer is composed of tissues that perform specific functions.  When a tree dies, the various tissues provide distinguishable substrates that provide different niches (Maser and Trappe, 1984 pg10-par-3).    

300.  As fallen trees progress from decay class I to class II, the scavengers are replaced by competitors with the enzyme systems needed to decompose the more complex compounds in wood. The fungi involved in this activity are often mutually antagonistic, so that a given part of the tree may be occupied by only one fungus that excludes others by physical or chemical means (Maser and Trappe, 1984, pg 27-par4).   (We call this altered area a niche)

301.  As the fallen tree progresses through decay Classes II and III of decomposition, slippage of the bark, and eventually decayed sapwood, removes a favorable environment and the organisms within it from the top and sides of the tree; that material, however, does not disappear.  Most of it accumulates loosely alongside the log to provide a new habitat favorable to many of the same organisms as before, plus larger animals, such as slugs, snails, salamanders, and small mammals (Maser and Trappe, 1984, pg 29-par 3). 

302.  It is in the class IV stage that the fallen tree presents the most diversified habitat and hence supports the greatest array of inhabitants. The decayed heartwood (of heartwood forming trees) is relatively stable, so plants that become established on it have time to grow substantial root systems (Maser and Trappe, 1984, pg 17-par 3).  
303.  As a fallen tree decomposes, it creates a gradually changing myriad of internal and external habitats.  Plant and animal communities within a fallen tree are very different from those outside, but both progress through a series of orderly changes. As a fallen tree decomposes, its internal structure becomes simpler, whereas the structure of the plant community surrounding the fallen tree becomes more complex (Maser and Trappe, 1984, pg 36-par7).    

304.  External succession is related to the changes that take place in the plant community surrounding a fallen tree. A fallen tree is a connector between the successional stages of a community;  it provides continuity of habitat from the previous forest through subsequent successional stages. A large fallen trees therefore provides a physical link – an essential element savings account – through time and across successional stages.  Because of its persistence, a fallen tree provides a long- term, stable structure on which some animal (both invertebrate and vertebrate) populations appear to depend on for survival (Maser and Trappe, 1984, pg 38-par 1).   

305.  Machine entry on an area, which contains trees, reduces diversity because heavy equipment fragments and scatters class IV and V so called rotten wood.  (Sorry to mention equipment) Habitat diversity declines to a fraction of what had been available, probably fewer kinds of organisms can thrive.  Further, because woody substrates serve as long-term soil organic material and essential element reservoirs, increasingly intensive timber management, coupled with shorter rotations, could significantly alter the role of decaying wood in the essential element cycling processes (Maser and Trappe, 1984, pg 48-par 1).   

306.  A fallen tree interacts with its environment through internal surface areas. A newly fallen tree is not yet a habitat for plants or most animals. But once organisms gain entrance to the interior they consume and break down wood cells and fibers. Larger organisms – mites, collembolans, spiders, millipedes, centipedes, amphibians, and small mammals must await the creation of internal spaces before they can enter.  The flow of plant and animal populations, air, water, and essential elements between a fallen tree and its surroundings increases as decomposition continues (Maser, Tarrant, Trappe and Franklin, 1988, 42-par2).   

307.  Habitats, both external and internal, are influenced by tree size. An uninterrupted supply of new, immature wood in young forests decomposes and recycles essential elements and energy rapidly. Habitats provided by the death of the symplast of young trees are short-lived and rapidly changing.  (E.g., specifically speaking, heartwood-forming trees lack chemical alterations required for production on heartwood).  In contrast, the less frequent, more irregular mortality of the symplast of large trees in old forests is analogous to slow-release fertilization. The lasting quality of large fallen trees creates stable habitats in which large woody debris accumulates. Scattered accumulations of large woody debris are associated with openings in the forest canopy. Large fallen trees in such an area often contact each other physically, creating external habitats of intense biological activity (Maser, Tarrant, Trappe and Franklin, 1988, pg44-par2).   

308.  Decaying, fallen trees contribute to long-term accumulation of soil organic matter, partly because the carbon constituents of well-decayed wood are 80-90 percent residual lignin and humus. Decaying wood in the soil and establishment of conifer seedlings and mycorrhizal fungi on dry sites are positively correlated. Fallen trees also create and maintain diversity in forest communities. Soil properties of pits and mounds differ from those of surrounding soil; such chemical and topographic diversity in turn affects forest regeneration processes.  All this, especially large fallen trees that reside on the forest floor for long periods, adds to spatial, chemical, and biotic diversity of forest soils, and to the processes that maintain long-term forest productivity (Maser, Tarrant, Trappe and Franklin, 1988, pg44-par3).

309.  Maser et al. (1979) reported that 178 vertebrates use logs in the Blue Mountains 14 amphibians and reptiles, 115 birds, and 49 mammals; they tabulated use by log decay classes for each species. Logs are considered important in early successional stages as well as in old- growth forests. The persistence of large logs has special importance in providing wildlife with habitat continuity over long periods and through major disturbances (Franklin, Cromack, Kermit, et al. others,  1981).

310.  So called rotten wood is also critical as substrate for ectomycorrhizal formation. In one forest which contained coniferous trees, over 95 percent of all active mycorrhizae were in organic matter of which 21 percent were in decayed wood.  In another study in the northern Rocky Mountains, decayed wood in soil was important.  In moist, mesic, and arid habitat types (Harvey et al. 1979); it was the most frequent substrate for active ectomycorrhizae on the dry site, probably because of high moisture levels in the wood. Mycorrhizal fungi can colonize logs, presumably using them as sources of water, essential elements and nutrients.  (Franklin, Cromack, Kermit, et al. others, 1981).

311.  Coarse woody debris plays numerous key roles in providing habitat for organisms in ecosystems (Voller and Harrison, 1998).   

312.  Many invertebrates use or require particular species, and different communities of invertebrates occupy and use different decay stages  (Harmon al. 1986; Samuelsson et al. 1994) (Voller and Harrison, 1998). 

313.  The manner, which a fallen tree comes to rest on the forest floor greatly, influences subsequent diversity of both external and internal plant and animal habitats.  The decomposing fallen tree provides a changing spectrum of habitats over many decades’ even centuries.  It provides diversity within a given successional stage and forms a physical-chemical link through the many successional stages of a forest (Maser, Tarrant, Trappe and Franklin, 1988, pg41-par4).  

314.  Checklist of plants and animals – There are few checklists of either plants or animals that inhabit fallen Douglas fir in Pacific Northwest.  [Let alone in other areas with other species in the USA such as hickory – (Termed as profiles or unique features of trees)].   No checklist of the microorganisms in fallen trees of western old-growth forest is available [I know of none in the east.]; the subject has hardly been studied.  (Higher fungi have been cataloged for many kinds of so-called rotten wood in Europe.)  Lawton listed the mosses that occur on so called rotten wood or stumps in the Pacific Northwest.  Deyrup (1975, 1976) has done a thorough job with insects and has identified about 300 species associated with fallen Douglas fir.  The only published checklist for vertebrates that use fallen trees is for northeastern Oregon (Maser and others 1979 not listed in references here).   (Maser and Trappe, 1984, page 18-par 2)   

315.  Conclusion: Logging does not increase habitat.  System health and habitat interconnect.  What purpose and need is there, that the capacity and ability, of CWD, to function as habitat, go unobserved, in the “Burn and Clearcut Project”?

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