5. Coarse woody debris - Plant Bio-Diversity / Threatened and Endangered Species

142.  Much is repeated from (#4.  Coarse Woody Debris – Reduction of Browsing of Sensitive Plants).

143.  What makes a healthy tree or plant? The availability in the proper proportions of the right "STEW" - Space, Temperature, Elements and Water. And the energy of the sun will be used optimally making a tree into the most efficient system on earth. Everything is recycled. 

144.  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).

145.  With respect to fallen trees. Furrows in the bark on the upper side fill with leaf duff and provide sites for several years for seeds to germinate.  Where the bark is intact, seedlings generally die during summer drought.  If a seedlings roots find a crack or hole in the bark and grow into the decomposed layer between bark and wood, however, it may find enough moisture to survive the summer (Maser and Trappe, 1984 pg 25-par 3).

146.  Besides nitrogen, other essential elements such as Calcium, Magnesium, Potassium, and Phosphorus and other essential elements play key roles in soil, plant and tree health as well as the health of the other associated living organisms (Page-Dumroese, Harvey, Jurgensen and Graham, 1991).

147.  We know some, at least,  plants are likely, obligate CWD user such as Red Hackberry (Vaccinium parvifolium) (Voller and Harrison, 1998). 

148.  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).   

149.  Decomposition of fallen trees releases essential elements for microbial and plant growth (Maser, Tarrant, Trappe and Franklin, 1988, pg37-par1).   

150.  Woody duff, regardless of type or size, takes considerably longer to decompose than needle and leaf duff do.  Needles, leaves, and small twigs decompose faster than larger woody material and essential elements are thereby recycled faster in the forest floor. 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). 
151.  Certainly our knowledge of biological processes and their interactions within forest is incomplete, and we know too little about the cumulative effect of a wide range of stresses on the ecosystem.  But integrative research at the ecosystem level shows clearly that the many processes operating within forest inter-connect in important ways.  Further, diversity of microscopic and macroscopic plant and animal species is a key factor in maintaining these processes (Maser, Tarrant, Trappe and Franklin, 1988, pg1-par2). 

152.  ...dying and symplastless wood provides one of the two or three greatest resources for animal species in a natural forest. ..if fallen timber and slightly decayed trees are removed the whole system is gravely impoverished of perhaps more than a fifth of its fauna (Maser and Trappe, 1984, pg1-par1).  ( The USFS calls removal (killing) - “reforestation”).

153.  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).           

154.  Symplastless trees, especially with soil contact act as a storehouse  for moisture providing moisture for plants and animals during dry times such as summer, so called, drought (Page-Dumroese, Harvey, Jurgensen and Graham, 1991).

155.  During decomposition, logs and other forms of coarse woody debris (CWD) reduce erosion, affect soil development, store essential elements, 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).

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

157.  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 essential element in ecosystems (Kruys and  Jonsson,  1999).  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).

158.  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).

159.  Plant-nutrient –essential element.  The succession of plants on fallen trees is mediated by changes in essential element availability and physical properties over time.  Three broad phases can be defined: initial, optimal, final. Early invaders prepare the tree for later colonization by altering its physical and chemical properties during the initial phase.  The  altered tree provides the best substrate for a wide array of organisms during the optimal phase. Ultimately, the depletion of essential elements and physical deterioration of the wood during the optimal phase diminish its value for many organisms, so fewer species inhabit the final phase (Maser and Trappe, 1984, pg 25-par 5). 

160.  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).  

161.  The interactions of fallen trees with soil are directly affected by steepness of slope and ruggedness of terrain; a fallen tree on flat ground, for example, is much more likely to contact the soil over its entire length than is one oriented either across or along contours on steep or rough terrain. The proportion of a tree in contact with the soil affects the water-holding capacity of the wood (Graham 1925). In our studies of fallen trees in old-growth Douglas-fir forests, the moisture retention through the summer drought was best in the side of trees in contact with the soil. The moisture-holding capacity of the wood affects in turn its internal processes and therefore the succession of plants and animals. In addition, the orientation of a fallen tree to aspect and compass direction and the amount and duration of sunlight it receives, drastically affect its internal processes and biotic community (Maser and Trappe, 1984 pg 4-par3). 

162.  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). 

163.  Fallen trees interact with essential element cycling processes in a forest through such mechanisms as duff  fall (freshly fallen or slightly decomposed plant material from the canopy),  throughfall (rain or dew that picks up elements as it falls through the canopy), nitrogen fixation, and essential element uptake by plants associated with the fallen trees (Maser and Trappe, 1984, pg19-par2).   

164.  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).    

165.  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 tree 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).

166.  Certainly our knowledge of biological processes and their interactions within forest is incomplete, and we know too little about the cumulative effect of a wide range of stresses on the ecosystem. But integrative research at the ecosystem level shows clearly that the many processes operating within forest inter-connect in important ways. Further, diversity of microscopic and macroscopic plant and animal species is a key factor in maintaining these processes (Maser, Tarrant, Trappe and Franklin, 1988, pg1-par2). 

167.  The forest's character changes with succession. Net primary productivity is greater in young forests than in old ones. Old forests conserve essential elements, whereas very young forests are susceptible to erosion and essential element loss. Forests of the Coast Range interior valleys produce less wood than do those on more moist sites nearer the ocean. And internally, the old managed forest is more diverse than many young and mid-age forests. Old forests have deeper, multi layered canopies, larger accumulations, of coarse woody debris (any symplastless standing or fallen tree stem at least 4 inches in diameter at breast height (d.b.h.) on snags and at the large end on fallen trees), and more specialized plants and animals than so called young forests have (Maser, Tarrant, Trappe and Franklin, 1988, pg5-par3).   

168.  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).   

169.  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).

170.  Logs also serve as sites for reproduction of tree species, especially western hemlock.  This is clearly an important function in natural stands since these seedlings and saplings supply replacements as openings appear in the overstory canopy. In one old growth stand at mid-elevation in the Cascade Range, over 64 percent of the western hemlock and 4 percent of the Pacific silver fir reproduction was rooted in so called rotten wood.  The phenomenon of nurse logs is widespread in the forest types of the Pacific North- west. Minore (1972) found that seedlings of both Sitka spruce and western hemlock was more numerous and taller on so called rotten logs than on the adjacent forest floor at Cascade Head Experimental Forest (Franklin, Cromack, Kermit, et al. others, 1981). 

171.  Coarse woody debris, functions as seed beds or nurse logs for some trees species and many species of bryophytes, fungi, and lichens, and some flowering plants (Table 7.6) (Samuelsson et al. 1994; D.F. Fraser, pers. comm., 1995; E.C. Lea, pers. comm., 1995) (Voller and Harrison, 1998).   

172,  In the Crowsnest Forest, 40-70% of natural seedlings were rooted in decayed wood in old growth and 24% were rooted in decayed wood in cutblocks (S. Berch, pers. comm., 1995). CWD may be important to the establishment of vascular plants around wet sites such as ponds and bogs (Voller and Harrison, 1998)    (Voller and Harrison, 1998).     

173.  NOTE: Page 203 has a list of some vascular plants closely associated with CWD in BC (Voller and Harrison, 1998).     

174.  We know other species are either associated with CWD or perhaps with the fungi that use CWD as their parasitic intermediate, such as the gnome plant (Hypopitis congestum), candystick (Allotropa virgata), and other ericaceous species. Ryan and Fraser (1993) reported that cryptogam species richness in coastal Douglas-fir forests was strongly influenced by available substrate. In forested sites, the presence  and rock substrates resulted in substantial increases in species richness. The review of Samuelsson et al. (1994) states that distinct Succession of bryophyte and lichen communities occurs as trees die, fall, and decay.  In B.C., known decomposer macrofungi that are dependent on CWD  include 162 species of bracket or shelf fungi/ conks, 364 species of other macrofungi, and some commercially harvested mushrooms, such as oyster mushrooms (S. Berch, pers. comm., 1995). These communities play roles in the germination and growth of other epiphytic and quasi-epiphytic communities. Climatic factors influence epiphytic communities, with lichens dominating drier ecosystems and bryophytes replacing them as conditions become wetter. The longevity of individual pieces  is critical to the persistence of many species with poor dispersal abilities. Dispersal in many species is from one log to the next, so logs close to each other are required. Samuelsson et al. (1994) note that large logs play a more important role than small logs in the ecology of bryophytes and lichens. Large logs last longer, have greater surface area, and have higher, steeper sides that prevent ground-dwelling species from invading. They may also be important in providing a relatively duff-free substrate for the establishment of some species of cryptogams (D.F. Fraser, pers. comm., 1995) (Voller and Harrison, 1998). 

175.  Plant species diversity on river bars is related to the area, sediment, and woody debris of river bars (Malanson and Butler 1990) (Voller and Harrison, 1998). 

176.  In class IV element content of the fallen tree at this stage may exceed the original content because minerals have been added by duff fall from the canopy and by throughfall of rain, have been brought in by animals or have been translocated from underlying soil by fungi or roots.  Nitrogen may be added by similar means and by biological fixation.  These circumstances provide an excellent rooting medium for plants.  A great variety of fungi, both decomposers and symbionts, thrive in the complex of niches within the fallen tree (Maser and Trappe, 1984 pg 26-par 5, pg 27-par 1).

177.  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 – (Termed as profiles or unique features)].   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)  
178.  Conclusion:     What purpose and need is there, that the capacity and ability, of CWD, to enhance the health of threatened and endangered species go unobserved in this “Burn and Clearcut Project”.

Go Back

Dictionary MAIN PAGE
Text & Graphics Copyright © 2013 Keslick & Son Modern Arboriculture

Please report web site problems, comments and words of interest, not found.