Soil as a Living System

Leslie jones Sauer

What most struck the woodland manager of New York City’s Central Park whenhe visited the Adirondacks was a forest floor so soft he could plunge his handinto it. The ground was visibly alive and completely different from the dead,concretized soil of the urban forest in Central Park.

oil wears its problems on the surface.Where trampling or high rates of decom-posrtion prevail, the litter layer and top-soil are entirely absent. Until recently, theannual leaf fall in the woodlands of Central Park

typically did not accumulate or even persistfrom one year to the next. With no litter layer,there was no nursery for the next generation ofthe forest.

Nearly a decade of woodland management isrebuilding the ground layer m Central Park’swoodlands at the north end of the park. The siteis becoming increasingly stabilized as erosionis controlled and bare areas are replanted. Themany small saplings and seedlings that wereplanted or that volunteered after exotics

removal help to hold the ground. During theicebound 1993-1994 winter season, some

remains of autumn’s leaves persisted under theblanket of ice until spring. That was a turningpoint for the woodlands. The following winterwas unusually mild, and by spring 1995 therewas a relatively continuous litter layer.

In time, the organic litter on the forest floorwill create humus, an organic soil homzon.Within it, most of the life of soil occurs. Asorganic matter is continually broken down intohumus, it becomes incorporated into the min-eral layers of the ground surface to build topsoil.Soils are forming all the time, and like vegeta-tion, integrate and express all of the ecosystem’sprocesses. Soil is a reflection of climate, parentmaterial, topography, vegetation, and time. Thelayers of soil tell a more recent history thanthe rocks beneath.The soil’s abiotic, or nonliving, factors are

generally the primary focus of conventional soil

assessment. Much of our thinking in the pastwas oriented toward an "ideal" soil model thatbalanced sand, silt, clay, pore space, moisture,minerals, and organic matter. These standardsdetermined whether a native soil was judgedpoor or good, and where soils did not conform tothe ideal, soil amendments were used to modifytexture, acidity, fertility, or other characteris-tics. Many early mitigation, stabilization, andrestoration projects suffered from this agricul-tural/horticultural approach. Standard soil

specifications, for example, call for routine top-soil stripping, fertilizing, and liming eventhough many disturbed or made soils are alreadyless acid than in their native condition becauseof the repeated addition of lime by means ofconcrete rubble and urban dust. Most regula-tions related to development sites, highways,landfills, and abandoned mines require fromthree to six inches of topsoil spread over newsoil surfaces before revegetating. That topsoilcomes from somewhere, so the restoration ofone site frequently means the destructionof another. We need more research on alterna-tives to topsoil, especially those that reusewaste materials appropriately to amend localsoils and that avoid environmentally costlyproducts such as fertilizers and peat. Evenwhere topsoil has been stockpiled on a sitebefore construction, the living organisms it con-tains die within days.

The Soil Food Web

A food web is the structure of relations amongthe organisms within an ecosystem based onwhat each consumes. Primary producers con-sume water, minerals, carbon dioxide, and a few

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other things to produce organic matter, which isconsumed by most of the rest of the creaturesthat are, in turn, consumed by still others. Someorganisms have very specialized food require-ments while others feed quite omnivorously.Both soil and water are media in which plants

and animals live and grow. And in a very real

way, both are living systems. One of the mostimportant contributions to the history of watermanagement occurred with a shift in perspec-tive that originated with Ruth Patrick andothers. When one views water as a living sys-tem, its quality is measured by the richness ofits biota instead of physical and chemical fac-tors such as flood levels or biological oxygendemand. Its biological components are a defin-ing measure of health that reflect a more

complex array of factors. This same kind ofrevolution is happening in our perceptionof soils.

In 1968 Ruth Patrick wrote about aquaticfood webs:

The various pathways m the food web and thevarious types of interrelationships of species toeach other are two of the most promismgavenues of research.Most food webs are composed of at least four

stages[;] ... the stages tend to be few because somuch energy is lost between stages.... Since thestages of the food web are few, ... diversity isexpressed by many species forming each stage orlevel in the food web.

This strategy of many species at each trophiclevel has developed a food web of manypathways which seems to give stability to thesystem ... [W]e see there are many food webswithin systematic groups as well as between

groups. It should also be pomted out that thesize and the rate of reproduction vary consider-ably in each of the major systematic groups.These types of variability in food chain, size oforgamsms, and reproductive rates help to ensurethe maintenance of the various systematicgroups, and in turn preserve the trophic stages ofthe food web of the whole community.’

Soil ecosystems are strikingly similar. Likeaquatic systems, they have a great deal of redun-dancy. Very simple systems with simple foodwebs can be drastically altered by the appear-ance or disappearance of one or a few species. Inmore complex systems there may be multiple

ways in which energy flows through the foodweb. Thus the more complex systems are said tohave redundancy and are not so dramaticallychanged when a few species change. Many soilcomponents even lie dormant until favorableconditions occur. The full soil structure is notrequired for most basic soil functions.

Rather than focusing simply on the nonlivingaspects of soil, restoration should enhance itsliving components, primarily bacteria, fungi,and microfauna. Most of the work of forminghumus is done by plant roots and by animal lifein the soil, which depend on a permeable soilcrust, stratified soil layers, and appropriateamounts of organic matter. There are up tothree thousand arthropods per cubic inch of pro-ductive soil. A litter layer of leaves one-and-one-half inches thick and a yard square mightcontain five thousand miles of fungal filaments.

Plants are the primary producers of organicmatter in the forest soil system. Ants and otherinvertebrates initiate the breakdown of ground-layer litter. Soil microorganisms includingfungi, bacteria, protozoa, and actinomycetescontinue this process of converting organicmatter into soil minerals that in turn becomeavailable as nutrients to plants. In food-webnomenclature, these organisms are "consum-ers." Primary consumers (herbivores) feed

directly on the "producers," which are theplants; secondary and tertiary consumers arepredators and parasites, which feed upon eachother as well as upon herbivores. Food webs alsocontain other decomposers and detritivores thatfeed on litter, such as mites, woodlice, andearthworms. Woodlands typically support morediverse assemblages of soil organisms thangrasslands. If soil orgamsms are included in thespecies count, temperate rainforests are richerin biodiversity than tropical rainforests.The soil food web performs the primary func-

tion of the soil, which is to cycle energy andnutrients, including mtrogen, sulfur, and phos-phorus. Native soil systems are very efficientand succeed in recycling, for example, upwardsof eight percent of the nitrogen in the system.The cycling of nitrogen is intimately associatedwith the cycling of carbon, which is tied uplargely in organic matter. Nitrogen, in part,determines the rate at which carbon is broken

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Ancient forests are filled with dead wood. Downed trees can be important assetsfor re-creatmg mixed-age, mixed-species forests.

down. Bacteria and fungi take up the nitrogen asthey decompose soil organic matter, and somefix atmospheric nitrogen. This nitrogen too isreleased into the soil to be agam available to

plants. Nitrogen’s slow release from an organicto an inorganic form, which is available toplants, is called "mineralization." "

The microbial community performs threemajor functions: as discussed above, conversionof organic mtrogen to a plant-available formsuch as ammonia; nitrification when ammoniais converted to nitrates; and demtrificationwhen nitrogen is recycled into the atmosphereas a gas. The soil microbial community alsocontributes to soil stability, another vital func-tion. Fungal hyphae kmt bits of organic mattertogether to create a denser, stronger litter layerand upper soil homzon.Not all soil food webs are the same. Fungi

appear to dominate in forest soils, bacteria inagriculture soils. Thus, soil communities

change over time as the landscape succeeds toforest. The nature of the vegetation determinesthe nature of the fuel/food available for soilorganisms. Grasslands litter, a relatively easilydecomposed herbaceous material, does not typi-cally contribute all of the soil’s organic matter.The extensive root systems of grasslands arealso a major source of the soil’s organic matter.The roots of grasses exude carbon directly into

the soil as sugar, amino

acids, and other forms tofeed soil fungal associatesand activate bacteria andother microbes.As the landscape matures,

the litter becomes more dif-ficult to break down. Whileherbaceous litter is prima-rily cellulose, the litter ofthe forest becomes increas-ingly higher in lignin, thewoody component of plants.Tree leaves have more ligninthan grasses, and the leavesof late successional species,like beech (Fagus grandi-folia) and oak (Quercusspp.), typically have morelignin than ash (Fraxinus

spp.), tulip poplar (Liriodendron tulipfera), andother early successional species. In woodlandsan important shift occurs as leaf fall and otherlitter become the most important sources oforganic matter, rather than the direct contribu-tion of carbon by the roots, as m the grasslands.There are also larger volumes of wood on theground in the form of fallen twigs and limbs,which directly foster fungi because bacteria areunable to decompose lignin. The mycorrhizalfilaments from tree roots reach up into the oldwood to extract the valuable nutrients. Insectssuch as beetles and ants are also able to breakdown wood. Wood in contact with the soil and

standing dead trunks, "snags," create manyopportunities for various wood and soil inverte-brates of the forest.The soil communities contmue to change

along with the vegetation communities. Overtime, the cycling becomes less rapid. In a

humus-rich forest soil, the organic matter thatremains the longest is the rather stable organiccompounds that degrade much more slowly. Bythen the humus is important more as a site forimportant chemical processes and for the physi-cal qualities it gives the soil than as a stockpileof nutrients. The humus, for instance, increasesthe water-holding capacity of the soil.Another important role of dead wood is to

serve as a water reservoir for the forest in times

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of drought. Dead wood, especially larger logsapproaching a foot or more in diameter, soaksup water like a sponge and retains it for longperiods. Old logs or stumps make great nurserysites by carrying vulnerable seedlings throughdry spells. Salamander populations also dependon large logs for needed moisture, which is, inpart, why they are absent so long after clearcutsand timbering, although they may number oneor two per square yard in old-growth forests.Logs increase local stormwater retention as wellby inhibiting overland flow and by absorbingwater in place.

Fungi in general foster acid soil conditions,whereas bacteria can increase alkalinity. Thebacteria and their predators in grasslands helpmaintain the soil’s pH and the form in whichmtrogen is made available, as well as nutrientcycling rates that work to the advantage ofgrasses. Where fungi are more abundant, as innatural forests, the mtrogen is converted toammonium, which is strongly retained in thesoil system. In bacteria-dominated systems, thebacteria convert nitrogen to nitrate instead ofammonium. Nitrate leaches more easily fromsoils than ammonium; however, the growingpatterns of grasses tolerate this condition. Butwhen woodland soils become bacteria domi-nated, rapid leachmg may leave most native old-

~--

Logs laid on the ground disappear qmckly. Usmg them as seedbeds for plantmgavoids soil disturbance while enhancmg survival.

growth species poorly nourished while invasiveexotics and some early successional natives areflush with nutrients. Some species are moresensitive than others to soil nutrition. Conifersdo not grow in bacteria-dominated soils whereasagricultural crops cannot be grown in fungi-dominated soils. Indeed, in woodlands, a highratio of bacteria to total biomass is an indicatorof disturbance.2 These factors, which seem todepend on soil organisms, play a greater role insuccession than previously recognized.3

Damaged Soil SystemsSoils are far more damaged and damageable thanwe realize, but the problem is often hidden. Thecumulative effects on forest systems and otherenvironments of acid rain, nitrogen deposition,global warming, ozone thinning, unnecessarygrading, and stormwater changes have left alegacy of severely altered soil conditions andtotally modified soil food webs. The conse-quences and remedies are still largely unknown.Many of these changes are so pervasive that

we take them for granted. Take earthworms,many nonnative, which now are abundantthroughout the urban forest system. In fact,they are not part of the historic communityof living creatures in native forests and aretypically associated with more disturbed land-

scapes. Earthworms in gen-eral increase soil fertility byinitiating the breakdown oforganic matter, aerating andmixing the upper soil, andcreating a microenviron-ment that stimulates thebacteria that convert ammo-nium to nitrate. High earth-worm populations alsofoster nitrification by sup-plying the oxygen necessaryto convert ammonium tonitrates. They take a systemalready disturbed by addednitrogen and push it fartherfrom normal by consumingthe litter layer five timesas rapidly as fungi and con-verting excess food intonitrate. The same kind of

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self-reinforcing cycle can beseen when aquatic systemsfill with algae.4 Each shiftin the soil character willin turn ripple throughthe entire system. Unfortu-

nately, in many woodlandsthat look mature because

they have larger trees, thereis a lag in the succession ofthe soil, which may still bedominated by earthwormsand bacteria and impover-ished in terms of types of

fungi, invertebrates, and

other, more efficient pathsfor nutrient cycling.

Building Soil SystemsThe object in restoration is to restore the nutri-ent cycling and energy flow of the historical soilsystem. First, work to protect existing soilresources and then explore techniques to

increase the overall biomass of the soil and tofoster the diversity of native soil flora and fauna.

Recommendations

Identify, protect, and monitor areas of nativesoil that are relatively undisturbed.Most areas contain places where there is less-disturbed soil that can serve as rough models oflocal soil conditions. Studying the more naturalsoils at the same time remediation is beingdocumented in a disturbed landscape will pro-vide a standard for measuring the success ofdifferent approaches. The natural sites alsoserve as propagation sources for locally adaptedmicroorganisms.

Reduce local sources of soil contamination,including added nitrogen.Evaluate local air pollution impacts, especiallythat of automobile exhaust. Removing roadswherever possible is of paramount importance,especially in more natural areas. What is conve-ment, even to the restorer, such as easy access,may be lethal to the most jeopardized species.Educate the community about regional air pol-lution impacts. Many other management prac-tices, such as pesticide use, also affect the realm

A thm mulch of raw leaves enriches the soil and promotes the growth of new wood.

of the soil. The most popular herbicide, forexample, glyphosate, which is often used to con-trol exotics, enhances conditions for bacteriabut makes a poor substrate for the developmentof forest fungi.

Recognize that the user is inseparable fromthe solution.

No treatment of soil will make it impervious tocompaction, erosion, and other such distur-bances. Confine all use in forests and othernatural landscape fragments to designated trailsto minimize degradation from feet, hooves, andwheels. Prohibition alone never is enough.Users will stay on trails to the extent that trailscreate the elements of satisfaction that keepthem there and provide access to desired desti-nations. The gradual building of the litter layerand the absence of bare soil off the trail are hall-marks of success.

Minimize "working the soil. "

Despite a lot of knowledge about the damagedone to living systems by constant perturbation,there is still a tendency to overwork soil.

Beyond the familiar structural damage-such asthat caused by working a heavy soil while it iswet or by the erosion that accompanies any soildisturbance-the soil’s level of microorganismsis also severely affected. For example, plowingand any mechanical disturbance to the soil will

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Tramplmg and stormwater runof prevent reproduction of the next generation offorest in many parks.

Vertical stakes made from cut branches dnven mto compacted ground in a densepattern convey water and moisture downward mto the root zone. They loosen thesurface as they decompose, mthout disturbmg the stability of the surface.

tend to foster the rapid growth of bacteria,which in turn generate exopolysaccharides,which cause the soil to slump in rain. Othersubstances make soil hard to wet, or hydropho-bic. Cultivating soil is almost always deleteri-ous to natural areas and constantly resets the

time clock back to distur-bance rather than allowingmore complex, stable, anddiverse soil systems to

develop.We need to try new tech-

niques, such as planting newseedlings in logs or stumps,to avoid soil disturbancewhile enhancing survival.Another technique is verti-cal staking, wooden twigsdriven vertically into thesoil. Vertical staking servesto aerate and loosen the soilwithout damaging the rootsof existing vegetation, andit avoids the need to com-

pletely turn the soil. In

addition, it favors the devel-opment of fungi msteadof bacteria because it incor-

porates wood into the soil.

Reevaluate the usefulnessof current methods ofstockpiling topsoil.Harris, Birch, and Shortdescribe the progressiveimpacts of stockpiling,which is a frequently usedmethod to retain a site’s top-soil during construction.5The first phase is an instan-taneous kill of many of the

living creatures in the soilthat occurs with the initialremoval and stockpiling.During the next few monthsthere is a flush of bacterialgrowth as well as fungi butonly in the upper soil on theoutside of the pile, the new"topsoil." During the next

half year or so the soil stratifies in layers. Theprimary distinctions reflect the amount of oxy-gen in the soil because of its depth in the pile orlevel of saturation with water. The developinglayers consist of both near-surface aerobic anddeeper anaerobic zones as well as a shifting tran-

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sition area between them. When the soils are

restripped and replaced elsewhere, there isanother instantaneous kill of most living organ-isms followed by a flush of bacterial growth.

Experiment with alternative strategies thatbetter preserve native soil food webs whenmoving soil is necessary.Experiment with methods that keep soil hori-zons intact, such as moving blocks of soil. Prac-titioners are using and modifying equipmentlike old sod forks and front-end loaders as wellas developing new equipment for this purpose,such as the soil-mat lifter devised by JohnMonro.~

Reevaluate the addition of organic matter toenrich disturbed soils.

The continuous rain of airborne nutrients ontosoils in the form of acid rain and nitrogen depo-sition from air pollution raises serious concernsabout many traditional management practiceswith regard to the use of organic matter as a soiladditive and our almost automatic addition ofnutrients to disturbed soils. Researchers haveshown repeatedly that fertilizer benefits weedspecies. Creating less-hospitable conditions inthe conventional sense can actually enhance theperformance of native species. Using elementalsulfur on test plots, Jean Marie Hartman and herco-workers at Rutgers University lowered thepH and reduced nutrient availability in a mixedmeadow to foster native species over exotics.’Many invasives, both native and exotic, are nitro-philes and do poorly under such conditions.

Reevaluate the use of mulch and soilamendments that are harvested fromlandscape communities other than thosenative to the site.

Because to a great extent soil organisms arewhat they eat, bringing in organic material fromother sources will not necessarily foster thegrowth of the same soil organisms as are in thedesired native community. In an artificial soilsuch as made land or a highly contaminatedsoil, it’s not the addition of organic matter butwhat kind we use that will impact the nature ofplant succession on the site. The more indig-enous the existing landscape, the more impor-

Brush piles improve long-term soil quahty andprovide habitat for soil orgamsms. Omented toreceive some direct sunhght, they also give shelter to ,

small creatures.

tant it is to minimize the use of dissimilarmaterials.

Reevaluate the conventional management ofbrush, dead wood, and leaves.Even where no additional fertilizer is added, itis important to modify our management ofdead wood and vegetative debris to more closelymimic natural conditions. This sounds obvious,but how often is organic matter collectedfrom a site, taken to another location to becomposted, and then used at still another loca-tion when it is "well rotted"? Under morenatural forest conditions, however, the majorcontribution of organic matter is not well-rottedcompost but rather wood, twigs, and leavesthat slowly break down in the place where theyfall. Adding wood and raw, rather than

composted, leaves more closely mimics thenatural scenario.

Develop new ways of observing andmonitoring soil health.

Unfortunately, standard soil tests are of limitedassistance to the restorationist. For example,nitrogen levels are poorly evaluated when theyare measured only as concentrations at any onetime rather than as total flux over time. Con-ventional tests also ignore the biotic componentaltogether. A number of researchers are workingon new methods. One, Jim Harris of the Univer-sity of East London in England, who has beenmonitoring soil changes associated with restora-

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tion, has developed a set of techniques for mea-suring the size, composition, and activity of asoil’s microbial community. These measure-ments can be used for comparison with a less-disturbed target community to assess the levelof recovery of the soil system. He and otherresearchers have developed methods that, atleast in England, have increased fungal popula-tions with significant beneficial impacts to soildevelopment and nutrient cycling.

Build populations of soil fungi.As noted earlier, heavy nitrogen enrichmentfrom air pollution and increased compaction,erosion, and sedimentation have tended to favorthe growth of bacteria over fungi and inverte-brates. Thoughtful management promoting thedevelopment of fungi through appropriate treat-ment of the soil, soil surface, and litter layer canhelp restore indigenous food webs in forest soils.

Management to Foster Fungi and OtherForest OrganismsBecause only fungi can break down lignin, thewoody component of plant matter, allowingdead wood and woody debris to remain on theground layer is a major component of the effortto rebuild soil fungi. Raw woodchips and smalllimbs on the soil surface provide an ideal matrixfor the rapid development of a dense fungal net-work in the soil that, unlike bacterial decom-posers, also provides surface stabilization. Thewebby, sticky quality of the mycelia of fungiserve to knit the surface particles and litter toreduce erosion and conserve moisture that isvital to the life of forest soil. While a deep layerof woodchips can create a growth-suppressingmulch that later floods the area with nutrients,a very thin layer of woodchips stimulates thedevelopment of more complex soil biota whilelimiting the overall rate of the addition of nutri-ents. Wood’s slow rate of decomposition is alsoimportant where rates of decomposition haveaccelerated dramatically. Because lignin has avery low decomposition rate, it is a more

durable groundcover that promotes the develop-ment of a stable litter layer.

Occasionally it may be necessary to inoculatethe soil or vegetation with mycorrhizal fungi,

although in most cases local sources of inocu-lum are likely to be available from wind andanimal dispersal. Where soils are high in nutri-ents it may be more important to manage nutri-ents and foster fungi than directly inoculate,especially if inoculation is not required to estab-lish plant species. Small amounts of soil fromanalogous sites nearby or woodchips colonizedby local mycorrhizae may be used to inoculatesites where natural processes have not been

effectual, where there is a substrate limitation,such as thin soil over bedrock, or where plant-specific requirements do not occur.Jim Harris recommends using thin blankets

of fresh woodchips from one-half to one inchthick, which create ideal surface conditions forthe development of fungi. Within weeks, a net-work of fungi colonizes the surface so denselythat the woodchip layer can actually be shakenloose from the soil by hand and moved else-where to inoculate an area nearby with localfungi. This method, local harvesting and dis-persal of indigenous fungi, should become animportant part of soil management programsand is preferable to using a mass-produced com-mercial inoculum for restoration purposes.8We can also manage blowdowns better than

by simply removing fallen trees, as is the cur-rent convention. Instead, we can minimize thehazard of a falling tree to area walkers whilemimicking more natural processes of decompo-sition that encourage the growth of fungi andinvertebrates in the soil by partially upendingthe stump. The upended root mass reveals anear-perfect seedbed for native species andmaintains enough of the tree’s still living rootsto maximize the extent to which its nutrientsare passed directly to neighboring trees.Commercially produced mycorrhizae have

been very successful in reforesting drasticallydisturbed lands, such as mine spoils, all over theglobe. Sites in Kentucky, for instance, wheresoils were extremely acid, with pH values aslow as 2.8, have produced pulpwood for harvestin just fifteen years from inoculated seedlings.9When considering such products, however,evaluate their potential impact on native sub-species of mycorrhizae. Like commercial plantpropagation, this approach risks hastening the

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extinction of local varieties. We still need to

develop appropriate procedures and protocolsfor dissemmating fungi and other soil orgamsmsas much as we do for larger plants and animals.Such techniques are well developed in the west-ern states but have only recently been applied inthe East.

Fire also acts as a stimulus to many wood

fungi and invertebrates and reduces bacteria,which m turn fosters the growth of fungi. In astudy of changes in beetle populations followingfire in boreal coniferous forests in Finland, sci-entists found a sudden appearance of a diverse

group of beetles that feed on wood fungi, whichin turn implies an even more rapid response byfungi.’° These wood-fungi-feeding forest beetlesare fire specialists and represent an importantevolutionary adaptation at an ecosystem levelto recurrent fires of the past; they are a side-benefit of restoring natural patterns of fire tothe forest.Native soil conditions and biotic communi-

ties and processes need to be the models for ourinterventions in restoring native habitats. Theremaining remnants of native soil are, therefore,bioreserves for the richness that once character-ized our soil heritage. The approach should beto restore, rather than replace, soils. Soil madein place is favored over the imported topsoil.Instead of reintroducing missing componentswith inputs from outside the environment,we should instead focus on fostering the resto-ration of remnant and mdigenous communitiesof soil biota, which furthers the general goal of"restoring-in-place" to the extent feasible. Bydoing so, we also minimize the casual dispersalof local subspecies of soil microorganismsand exotic soil orgamsms. In the worst-casescenarios, such as areas where soil is completelydepleted, some materials from outside will beneeded, but even in these situations the soil-building resources inherent to the site should beused to the maximum extent possible.

Endnotes

1 Ruth Patrick, Natural and abnormal communities ofaquatic life in streams. Via 1, Ecology m Design(University of Pennsylvama, Graduate School of FmeArts, 1968), 37.

2 M J. McDonnell, S. T A Pickett, and R. V Pouyat,Application of the ecological gradient to the studyof urban effects. In Humans as Components ofEcosystems, The Ecology of Subtle Effects andPopulated Areas, ed. G. E. Likens and W. J Cronon(New York: Springer-Verlag, 1993), 175-189.

3 E. R. Ingham, Restoration of soil communitystructure and function in agriculture, grassland andforest ecosystems in the Pacific Northwest.

Proceedmgs, Society for Ecological RestorationConference (Seattle, 1995), 31.

4 W. Nixon, As the worm turns. American Forests( 1995~ 101 ~9~: 34-36.

5 J. A. Harns, P. Birch, and K. C. Short, The impact ofstorage of soils during opencast mining on themicrobial community A strategist theoryinterpretation. Restoration Ecology (1993) 1: 88-100.

6 The tool, available for sale in several sizes, wasdeveloped by Monro Ecological Services,Harleysmlle, PA, and is available through BentleyDevelopment Co , P.O. Box 338, Old Route 22,Blairsville, PA 15717, 412/287-0671.

7 J. M. Hartman, J. F. Thorne, and C. E. Bristow,Variation m old field succession Proceedmgs (Design+ Values) of annual meeting, Council for Educators mLandscape Architecture (Charlottesville, VA, 1992),55-62.

8 J. A Harris, et al , op cit

~ C E. Cordell, D. H. Marx, and C Caldwell,Operational application of specific ectomycorrhizalfungi m mmeland reclamation. Unpubhshed paperpresented at annual meeting of the American Societyfor Surface Mining and Reclamation (Durango, CO,May 14-17, 1991 /

’o J. Muono and I Rutanen, The short-term impact offire on the beetle fauna in boreal coniferous forest.Annales Zoologici Fenmci (1994) 31: 109-121.

Leshe Sauer is principal and landscape architect withAndropogon Associates, Ltd , based in Philadelphia,Pennsylvania, and adjunct professor at the University ofPennsylvania This article is adapted from The Once andFuture Forest A Guide to Forest Restoration Strategies,which was developed by Andropogon Associates and isbased on their approach to integrating environmentalprotection and restoration with landscape architectureand design. Their work on Central Park’s North Woodsis only one of many restoration projects The Once andFuture Forest is pubhshed by Island Press (800/828-1302or www.islandpress.org).