| A unit of Lasting Forests
evolving since March 30, 1999 |
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A Total Forest Management Plan
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Litter is all of the leaves, twigs, bark, and reproductive parts of plants and dead plants no longer attached to live plants or roots. Usually only counted as the small parts, herein it includes the limbs and dead and down wood of the forest and field.
| Stand Number | Depth of Litter (inches) |
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| 33 12 06 22 69 |
3.5 5.2 2 3 4.1 |
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| Maximum = 5.2 Minimum = 2 |
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| *Litter depth is difficult to measure and variable. The standard used herein is to compress the litter (including the present leaf litter) in a representative place with the boot, then to use a large knife to cut a cross-sectional view, then measure (in inches, to the nearest one-fourth inch, recorded in tenths) the thickness or depth of the litter layer from the boot edge to a place where there is more than about 50% mineral, sand, or bed rock . | ||
We concentrate within this unit on one volume of the forest, one layer. Often called a soil layer or horizon, it is the largely organic layer with many different stages undergoing varying rates of change from biological, mechanical, gravitational, and chemical forces.
Our concerns, as those of many others, are for the effects of global warming and major changes on the forests and the effects of increased removals and utilization of trees for forest products for among other things, bioenergy production and pulp and chip mill supply (e.g., whole-tree harvesting). The time differs for each alpha unit, and it will change with global warming and climate change, but in general in the Eastern US, the functional service time of a tree in the forest is 80% while alive, 20% while dead.
The processes in the tree leading to decomposition of the forest floor are as follows:
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Decomposition is largely a successional process to which a variety of organisms contribute. These workers include the actinomycetes, other fungi, protozoa, nematodes, bacteria, earthworms, and crustacea. In the dryer soils the millipedes, woodlice, and lumbricid worms work slowly; in the more moist forest soils, they dominate. In the dry leached soils, the nematodes, enchytraeid worms, mites and springtails perform the work of the larger decomposing creatures. Solving many problems of taxonomy as well as the dynamics of these groups and their relations is challenging and often intractable.
Available nutrients in the surface layers of Earth are readily taken up into plant materials. These plant materials - from mosses to magnolias - produce (primary production) about 3-10 g/sq.m/day (30-40 metric tons per ha) and eventually die. (By comparison, cultivated areas may produce 50-80 metric tons per acre.) The rates at which nutrients are again made available to plants in the terrestrial ecosystem are governed by the rates (1) of leaching (5-25%; Thomas 1970), and (2) of those at which those elements are released from litter by decomposition. (Site quality within the Alpha unit must be addressed in terms of this phenomenon of leaching, now that precipitation estimates are available within a GIS (Klopfer 1998) and fog drip can be estimated.) First year losses in leaf weight are about 35 to 55% (Thomas 1970) (as well as the same percentages for calcium) depending on tree species.
The flow of energy through a system as a result of the decomposers is about 5000 kcal/m2/year.
Leaf bags were 25 x 25 cm and 2mm mesh (Thomas 1970) (others used 10cm x 7 cm. with mesh sizes varying from 7mm to 0.003mm (for microorganism effects) ) 0.5 was used for most organism; 1.0 was used to exclude earthworms. Nylon window screen was used in one study (edges sewn with carpet thread)
Invasive species earthworms in northern forests now cause accelerated litter decomposition (2004).
We need to pay attention to litter buildup but, to date, the only consequences have been nitrogen deficiencies, fully expected with high organic buildups due to the protein build-up by the decomposers. Small additions of nitrogen can have major effects. Burning, while it may reduce the litter layer in areas where decomposition rates are notably low, releases the nitrogen, further depleting the site of this valuable nutrient. Reductions in fungus-eating Collembola and spiders and other predators have been suggested to reduce nitrogen mineralization (Bengtsson et al. 1997).
Conifer forests may lock up nutrients within the litter layer and thus slow their own growth or demonstrate nutrient deficiencies (in one sense, site degradation).
Nutrients that are present in plant parts, after litter decomposition or leaching, can reenter the soil, and when in solution enter not only plants but water courses.
Decomposition rates generally occurs in the order of: stream>pond>forest floor. They seem to be well described by a summation exponential process (Means et al. 1981)
Litter decomposition rate reductions, hypothesized to be reduced by heavy metals at roadsides (Post and Beeby 1996) or malathion (Giles 1970) have not been observed. However moderate contamination by Pb, Zn, Cu, Ni, and Cd has been shown to reduce soil microbial activity.
In some areas the roots may be in the litter, and thus the decomposition may be more related to root functions that to soil and litter chemical properties. Some fungi that produce mushrooms also infect roots of trees and form a mutually beneficial association called mycorrhizae. The presence of these important "root-hairs" in the lower litter layer produce interesting analytical challenges. Are they litter, living parts of the otherwise dead layer?
Different species of salamanders use different forest structures, some under bark, some under logs. Retention of coarse woody debris meets most needs.
The forest floor is said to have humus. This is a complex mixture of well decomposed organic substances which is found within the dark "rich" looking complex of particles of sand, silt, clay, leaf particles, and larger bark, stem, and leaf particles. The forest floor layer, when well developed, has a distinctive odor. It is typically black or brown and a collective association of the gelatinous, resistant products of decomposition, both those of the original plant material and those synthesized by the decomposers. It is composed of "humic substances", complex large organic molecules. They are phenols produced by bacteria and later transformed into humic polymers (Povoledo and Golterman 1975). Humus improves soil structure, drainage, aeration, water holding properties, cation exchange capacities, and is a source of energy for microorganisms.
Humus slowly releases nutrients useful to plants. It acts to hold water on the land, retaining it where it can be used by plant roots (and the network of fungus fibers that act as root hairs). It also acts as an anti-freeze, changing the nature of moisture in the winter season.
Edwards reported that total litterfall in a tulip poplar forest, not including large branches, was 330 grams/m2. Leaves were 83.3 percent of this, reproductive parts 13.1 percent, and twigs 3.6 percent.
Litter production in temperate deciduous forests normally falls within 2.3 to 4 metric tons/ha/year (Thomas 1970).
Total worldwide annual production of litter in metric tons/ha/year can be estimated from a graph of Bray and Gorham(1964) relating litter to North or South latitude (in degrees). The approximate relationship is:
litter = 11.5 - (0.164 x degrees)
For the approximate central latitude of your forest, the estimated litter is 2.1
Based on a model describing litter as a function of land slope, the following table results:
| Stand Number | Humus (inches) |
| 126 33 22 |
2.3 1.7 2.1 |
Evolution of CO2 from the floor was 3800 grams per sq. meter per year and varied with microclimatic conditions and microbial activity. Anderson (1973) showed many factors affecting the rate estimates and concluded such studies have limited future use. One estimate suggests 10-20 % of the net production in the temperate forest region is directly used by animal communities and the other 80-90% of energy flows through microbial pathways.
The extent of decomposition can determine the suitability of a site for seed germination. Seeds are adapted for soil conditions likely to be found in areas where they are most likely to gain sunlight and moisture for survival (Molofsky and Augspurger 1992). Wilde (1946) commented that the reaction of the soil influences not only the distribution of trees but the distribution of woody and herbaceous plants which may compete with natural tree reproduction.
Means et al. (1985) classed old logs of known ages as 1 to 5 (1 = essentially undecayed to 5 = soft and incorporated) and then used a summation exponential model, summing single exponential models fitted to lignin, cellulose, and the hot acid detergent soluble fraction. That model was the same as a single exponential model. Lignin decayed more slowly than cellulose of the detergent fraction.
Marked changes in soil characteristics, dynamics, and metabolism can be caused by logging (Wilde 1958, Goodall 1970).
Burning leaf and other litter can be considered as very rapid decomposition. Grigal and McColl (1977) reported that "fire modifies nutrient cycling in forests by releasing nutrients from the burned vegetation and forest floor and making them susceptible to rapid movement into soil and resprouting vegetation." In their study, the progression in mobility was was K>Mg>Ca>P>N which differed from reported oak litter which was K>P>N=Mg>Ca.
A C:N ratio higher than 17:1 suggests there will be competition for any N that is present. As soil dries, N is lost from litter as ammonia. As trampling occurs (livestock or recreationists) the loss is reduced, but changed to loss in soluble nitrates and nitric form.
Thomas (1970) observed that calcium was about 1.5% of the dry weight of tree leaves (maple, oaks, tulip poplars). Comparable ash values were about 6%.
In their study there was no difference in the rate of decomposition (measured in litter bags) before and after a forest fire. They said the lack of difference implied a rapid recovery of soil organisms following the fire. Andersen and MacMahon (1985) found more plant species survived on mounds of pocket gophers than on the ash of Mt. St. Helens, further confirming the role of animals in mixing materials in the litter layer.
Leaf litter decomposition is well known; little is known of the rate of bark decomposition.
There seems to be a need for permanent sampling points to establish change over time in these highly variable systems.
Neckles and Neill (1994) formulated a general qualitative model of the rate of decomposition in inundated soils: low decay rates in dry litter because of moisture limitations, low decay rates in inundated soil because of oxygen limitation and high decay rates in flooded but aerobic litter on the soil surface. It seems that a general model of litter decomposition for upland forest soil can be created with upper layers resisting decay, lower layers being moist and having rapid decay, so that collectively a fixed thickness of litter results, differing among years in the factors of litter falling, the moisture levels, and temperatures.
In analyzing mulch, consider cost per linear (or square) foot and the cost of time to install it and the duration of the desired effects.
Termites help convert dead wood to mineral soil, shange wood surface area to attacks by microbes, and serve as food for other animals. They may be controlled by "termiticides." Sunterranean termites are found in every state of the US except Alaska. Predominant subterranean termites causing 95% of damage are Reticulitermes, Coptotermes formosanus Shiraki and Heterotermes. Most subterranean termite damage occurs to buildings in formerly forested areas. Termites simply begin feeding on new sources of wood (e.g., a house) conveniently available and the usual food source (dead wood and stumps are not available). Prevention of termite damage involves proper design, construction, pre-treatment with effective termiticide, and regular inspections.(From Mauldin 1982)
References
See environmental science methods, select topics in ecology, theoretical ecology, soil science, litterfall, fungus insect relations (Quentin Wheeler 1981), mycorrhizae, humus chemistry (Stevenson 1982), lignin biodegradation (Crawford, Wiley), straw decay, mulch effects
Andersen, D.C. and J.A. MacMahon. 1985. Plant succession following the Mount St. Helens volcanic eruption: facilitation by a burrowing rodent, Thomomys talpoides. Amer Midland Nat. 114(1): 62-69
Anderson, J.M. 1973. Carbon dioxide evolution from two temperate, deciduous woodland soils. J. Appl. Ecol 10(2):361-378.
Anderson, J.M. and A. MacFayden 1976. The role of terrestrial and aquatic organisms in decomposition processes (British ecol. soc. symposium series) 476 pp.
Adams, S.N. 1974. Some relations between forest litter and growth of Sitka spruce on poorly drained soils, J. Appl. Ecol 11(2):761-765.
Bengtsson, J, T. Persson, and H. Lundkvist. 1997. Longterm effects of logging residue and removal on macroarthropods and enchytraeids. J. Appl ecol. 34:1014-1022
Bray, J.R. and E. Gorham. 1964 Adv. Ecol. Res. 2:101-157.
Lead: N.T. Edwards, G.J. Dodson MR71-64 Oakridge Natl Lab, Oakridge, TN 37830
Dickinson, C.H. and G.J.H. Pugh. 1974 Biology of plant litter decomposition, 2 vol, Academic Press, London vol.1, 241 pp, vol 2. 775 pp.
Goodall,D.W. 1970. Studying the effects of environmental factors on ecosystems p. 19-28 in D.E. Reichle ed. Ecological studies !, Analyses of temperate forest ecosystems Springer-Verlag, New York
Mauldin, J.K. 1982. The economic importance of termites in North America, in The Biology of Social Insects,
Means, J. E., K Cromack, and P>C> McMillian. 1981. Fitting decomposition models to Douglas fir Pseudotsuga menziesii log density data in a 450-year-old forest. Bull. Ecol. Soc Amer 62(2): 104 (Abstract)
Means, J. E., K Cromack, and P>C> McMillian. 1985. Comparison of decomposition models using wood density of Douglas fir logs. Canadian J. Forest Research 15: 1092-1098
Odum, E.P. and A.A. de la Cruz. 1963. Detritus as a major component of ecosystems. Bioscience 13(3):39-40 Morse, J.C. editor, 1984. Proceedings of the Fourth International Symposium on Trichoptera (Clemson, July 1983) Series Entomoligca, Vol 30, Junk, The Hague (distributor Kluwer, Boston, Hingham, Mass 486pp
Molofsky, J. and C.K. Augspurger, 1992. The effect of leaf litter on early seedling establishment in a tropical forest. Ecology 73(1):68-77.
Neckles, H.A. and C. Neill. 1994. Hydrologic control of litter decomposition in seasonally flooded prairie marshes. Hydrobiologica 286:155-165.
Pololedo, D. and H.L. Golterman eds 1975. Humic substances - their structure and function in the biosphere,)Proc. of a meeting) Pudoc, Wageningen 368 pp.
Post, R.D. and A.N. Beeby. 1996. Activity of the microbial decomposer community in metal contaminated roadside soils, J. Appl. Ecol 33:703-709
Thomas, W.A. 1970. Weight and calcium losses from decomposing tree leaves on land and in water. J. Appl. Ecol 7(1):237-241.
Wheeler, W.M. 1910. Ants: their structure, development and behavior 663 p.
Wilde, S.A. 1946. Forest soils and forest growth, Chronica Botanica Co., Waltham, Mass 241pp
Wilde, S.A. 1958. Forest soils: their properties and relation to silviculture. The Ronald Press, NY, NY 537pp.
A discussion list on "Dead Wood Ecology and Management" has been established to meet a communication need identified at the "Dead Wood Ecology and Management in Western Forests" symposium held in Reno Nevada in November 1999. The discussion list is open to all who wish an outlet for discussing dead wood ecology and management issues.
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Last revision June 30, 2004.
