mycorrhizae and establishment of trees on strip-mined land

MYCORRHIZAE AND ESTABLISHMENT OF TREESON STRIP-MINED LAND1 2

DONALD H. MARX

USDA Forest Service, Southeastern Forest Experiment Station,Forestry Sciences Laboratory, Athens, Georgia 30602

ABSTRACTMARX, DONALD H. Mycorrhizae and

establishment of trees on strip-minedland. Ohio J. Sci. 75(6): 288, 1975.

This paper presents a brief introduc-tion into ecto- and endomycorrhizalassociations of plants and discusses theirpotential value in revegetation, especiallyreforestation, of strip-mined lands. Thesignificance of ecologically adapted ecto-mycorrhizal fungi, such as Pisolithustinctorius, to survival and growth of pinesand other tree species has practical im-portance in these forestation efforts.Data from pilot studies on strip-minedcoal spoils in Ohio, Virginia and Kentuckyshow that pines tailored with Pisolithusectomycorrhizae prior to planting sur-vive and grow significantly better thantrees with other fungal symbionts. Theperformance of grasses and other her-baceous plants used in revegetation ofstrip-mined lands may also be improvedby use of specific endomycorrhizal fungi.Manipulation of mycorrhizal fungi onroots of plants for revegetation purposeshas great potential in the reclamation ofdrastically disturbed lands.

Microorganisms are present in greatnumbers near the feeder roots of plantsand they play vital roles in numerousphysiological processes. These dynamicmicrobial processes involve saprophytism,pathogenicity, and symbiosis. The mostwidespread symbiosis of plants is themycorrhizal association which involvesvarious root-inhabiting fungi and plantfeeder roots. The prevalence of mycor-rhizal associations on plants is so commonunder natural soil conditions that a non-

manuscript received January 10, 1975(#75-5).

2Presented as part of a symposium, BiologicalImplications of Strip Mining, held at BattelleMemorial Institute, Columbus, Ohio, on No-vember 15, 1974.

mycorrhizal plant is the exception ratherthan the rule. Only a few plants, such assedges, crucifers and certain aquatics, donot form mycorrhizae. Other plants,and especially those of major economicimportance to man, such as forest treesand agronomic crops, form abundantmycorrhizae on their roots.

There are three classes of mycorrhizaeon plants. Ectomycorrhizae occur nat-urally on many of the important foresttree species of the world. All members ofthe gymnosperm family Pinaceae, e.g.,pine, spruce, fir, larch, hemlock, etc., aswell as certain angiosperms, e.g., willow,poplar, aspen, walnut, hickory, pecan,oak, beech, eucalypt, and others, are ecto-mycorrhizal. Several of these tree spe-cies can be either ectomycorrhizal orendomycorrhizal, depending on soil con-ditions.

ECTOMYCORRHIZAEEctomycorrhizal infection is initiated

from spores or hyphae (propagules)of the fungal symbionts in the rhizo-sphere of feeder roots. The propaguleis stimulated by root exudates and growsvegetatively over the feeder root surface,forming the fungus mantle. Followingmantle formation, hyphae develop inter-cellularly in root cortex, forming theHartig net which may completely replacethe middle lamellae between the cortexcells. The Hartig net is the main dis-tinguishing feature of ectomycorrhizae.Ectomycorrhizae may appear as simpleunforked roots, bifurcate roots, multi-forked (coralloid) roots, nodular-likeroots, or in other configurations (fig. 1).Color of ectomycorrhizae is apparentlydetermined by the color of the hyphae ofthe fungal symbionts. Ectomycorrhizaemay be brown, black, white, red, yellow,or blends of these colors. Individualhypha, strands of hyphae, or rhizomorphsmay radiate from fungus mantles into the

No. 6 MYCORRHIZAE AND RECLAMATION 289

FIGURE 1. Five morphologically distinct forms of ectomycorrhizae of Pinus taeda, each formed bya different species of ectomycorrhizal fungus.

soil and to the base of fruit bodies of thefungi.

Most fungi which form ectomycor-rhizae with forest trees are Basidio-mycetes that produce mushrooms or puff-balls. Certain Ascomycetes, such astruffles, also are symbiotic. Over 2,100species of ectomycorrhizal fungi havebeen estimated to exist on trees in NorthAmerica. These fungi produce millionsof spores in their fruit bodies that arewidely disseminated by wind and water.Most ectomycorrhizal fungi are depend-ent on their tree hosts for essential car-bohydrates, amino acids, vitamins, etc.,in order to complete their life cycles.Ectomycorrhizal development, therefore,is usually a prerequisite for fruit bodyproduction by these fungi, however, notall fungal species which form mushroomsand puff balls are ectomycorrhizal. Manyof these fungi are saprophytes that playan important role in the decompositionof organic matter and the mineral cyclein forest soils.

Under normal forest soil conditions,many species of fungi are involved in theectomycorrhizal associations of a forest,a single tree species, an individual tree,

or even a small segment of lateral root.As many as three species of fungi havebeen isolated from an individual ecto-mycorrhiza. Just as a single tree speciescan have numerous species of fungi cap-able of forming ectomycorrhizae on itsroots, a single fungus species may enterinto ectomycorrhizal association withnumerous tree species. Some fungi,however, are apparently rather hostspecific, whereas others have broad hostranges and form ectomycorrhizae withnumerous tree genera in diverse families.

ENDOMYCORRHIZAEMost of the economically important

agronomic and forage crops, as well asfruit and nut trees, such as peach, citrus,apple, plum, cherry, almond, etc., nor-mally form endomycorrhizae. Important,forest trees, such as maples, elms, gums,ash, sycamore, cotton wood, alder, anddogwood, and other trees not formingectomycorrhizae normally form endo-mycorrhizae. As mentioned earlier, someof these trees can form both endo- andectomycorrhizae. Endomycorrhizal fungiform a loose network of hyphae on feederroot surfaces, and do not develop the

290 DONALD H. MARX Vol. 75

dense fungus mantle found on ecto-mycorrhizae. Most often these fungiform large, conspicuous, thick-walledspores on the root surfaces, in the rhizo-sphere, and sometimes in feeder root tis-sues. Hyphae of the endomycorrhizalfungi penetrate the cell walls of theepidermis and progress into the corticalcells of the root. These infective hyphaemay develop specialized absorbing ornutrient-exchanging structures (haus-toria) called arbuscules in the cortexcells. Thin-walled, spherical-to-ovatevesicles may also be produced in the cor-tex cells by the fungus. The term "vesi-cular-arbuscular" mycorrhizae has beencoined to denote this type of endomycor-rhizae. As in ectomycorrhizae, endo-mycorrhizal fungus infection does not oc-cur in meristematic or vascular tissues.Unlike ectomycorrhizae, however, endo-mycorrhizal infection does not causemajor morphological changes in roots.Endomycorrhizae may have a yellowishcolor in comparison to noninfected roots.

The fungi which form endomycorrhizaewith trees are mainly Phycomycetes.They do not produce large, above-groundfruit bodies or wind-disseminated sporesas do most ectomycorrhizal fungi, butsome of them produce large zygosporesand chlamydospores on or in roots.Some species also produce large sporo-carps (5-10 mm diameter) containingmany spores on roots. These fungispread in soil by root contact, movingwater, insects, or mammals. Most endo-mycorrhizal fungi of trees belong to thefamily Endogonaceae. Several genera andspecies have been identified; many moreundoubtedly exist (Gerdemann andTrappe, 1974). They are so widespreadthat it is extremely difficult to find nat-ural soils anywhere in the world that donot contain them. In the absence of ahost, the spores of these fungi are able tosurvive for many years in the soil. Basedon the limited amount of research doneon endomycorrhizal fungi, most speciesappear to have very broad host ranges.For example, Glomus mosseae (= Endogonemosseae) will form endomycorrhizae withcotton, corn, pepper, soybeans, sorghum,and other agronomic crops, as well assycamore, sweetgum, citrus, peach, andblack locust.

ECTENDOMYCORRHIZAEAnother class of mycorrhizae are

ectendomycorrhizae which are of lesserecological importance than the otherclasses. They have the features of bothecto- and endomycorrhizae. Ectendo-mycorrhizae have a limited distributionin forest soils and are primarily found onroots of normally ectomycorrhizal foresttrees. Very little is known about thespecies of fungi involved or their signifi-cance to tree growth, since only limitedresearch has been attempted on them.

Ectomycorrhizal fungi are beneficialto the growth and development of trees.For some trees, such as Pinus, they areindispensable for growth under naturalfield conditions. Trees with abundantectomycorrhizae have a much larger,physiologically active, root-fungus sur-face area for nutrient and water absorp-tion than do trees with few mycorrhizae.This increase in surface area comes notonly from the multi-branching habit ofmost ectomycorrhizae, but also from theextensive vegetative growth of hyphae ofthe fungus symbionts from the ectomy-corrhizae into the soil. These extrama-trical hyphae function as additional nu-trient and water-absorbing entities. Ecto-mycorrhizae are able to absorb and ac-cumulate in the fungus mantles nitrogen,phosphorus, potassium, and calcium morerapidly and for longer periods of timethan nonmycorrhizal feeder roots. Thefungi of ectomycorrhizae assist in thedegradation of certain complex mineralsand organic substances in soil and renderessential nutrients from these materialsavailable to the tree. Ectomycorrhizaealso appear to increase tolerance of treesto drought, high soil temperatures, soiltoxins (organic and inorganic), and ex-tremes of soil pH caused by high levels ofsulfur or aluminum. Ectomycorrhizaefunction as biological deterrents to infec-tion of feeder roots by root pathogens,such as species of Pythium and Phyto-phthora. Induced hormone relationshipsin ectomycorrhizae by fungal symbiontsextend the longevity (length of physiolog-ical activity) of these roots as comparedto nonmycorrhizal roots.

Very little research has been accom-plished on the value of endomycorrhizaeto forest trees. Available research results


indicate that endomycorrhizae are moreefficient nutrient-abosrbing roots than arenonmycorrhizal roots. This applies es-pecially to the absorption and utilizationof phosphorus. The extensive networkof hyphae of these fungi growing fromendomycorrhizae exploit large volumesof soil that are rarely exploited by non-mycorrhizal roots. It is not known forcertain if some trees are dependent onendomycorrhizae for growth as Pinusspecies are on ectomycorrhizae, however,recent evidence obtained from researchat the Athens, Ga. laboratory indicatesthat sweetgum may need endomycor-rhizae in order to become establishedafter seed germination and to grownormally.

Many factors affect mycorrhizal de-velopment. In discussing them it isnecessary to separate those which affectthe tree from those which affect thefungal symbionts. The main factors in-fluencing the susceptibility of tree rootsto mycorrhizal infection appear to bephotosynthetic potential and soil fer-tility. High light intensity and low tomoderate soil fertility enhance the de-gree of mycorrhizal development, whereasthe other extreme of these conditions, i.e.,low light intensity (below 20% of full sun-light) and excessively high soil fertilityreduce, or may even eliminate, mycor-rhizal development. These factors ap-pear to influence the biochemical statusof feeder roots, such as controlling levelsof reducing sugars or the synthesis of newfeeder roots, which are prerequisites tosymbiotic infection. Roots growing rap-idly due to high soil fertility may actuallyoutgrow their fungal symbionts. Gen-erally, any soil or above-ground conditionwhich influences root growth also in-fluences mycorrhizal development to onedegree or another. Factors which affectthe fungal symbionts directly are thosewhich regulate survival or growth of in-fective propagules or vegetative growthof the symbionts on roots. Extremes ofsoil temperatures, pH, moisture, etc., andpresence of antagonistic soil microorgan-isms can affect the symbionts and therebyinfluence the mycorrhizal potential of thesoil.

Several excellent texts have been pub-lished in recent years which compre-

hensively cover the different mycorrhizalassociations (Harley, 1969; Marks andKozlowski, 1973; Hackskaylo and Tomp-kins, 1973). •

MYCORRHIZAE ANDAFFORESTATION PRACTICESOver 3,000 papers have been published

on mycorrhizae of plants and most ofthese relate to forest trees (Hacskaylo andTomplins, 1973). Much of this researchhas been very basic and has broadenedour understanding of their complexity inforest soil ecosystems. Various studieshave shown that a prerequisite to growthof many forest trees is the presence ofectomycorrhizae on their roots. Thismeans that certain trees, such as Pinus,have an obligate requirement for ecto-mycorrhizae and cannot grow normallywithout them. This basic informationshows that ectomycorrhizae formed byany fungus is better than no ectomycor-rhizae at all on tree roots, especiallypines. This point has practical signifi-cance to afforestation programs withnormally ectomycorrhizal trees in areasof the world where their symbiotic fungido not occur naturally. Mikola (1969)has demonstrated that there must be aparallel introduction of the essentialectomycorrhizal fungi if afforestationwith these trees {Pinus in particular) isto succeed. There are many areas of theworld where indigenous ectomycorrhizaltrees and their symbiotic fungi do notoccur naturally. In these areas, i.e., thehigh Andes of Peru (Marx, 1976a),Puerto Rico (Vozzo and Hacskaylo,1971), Africa (Gibson, 1963), Australia(Bowen et al., 1973), Asia (Oliveros,1932), subalpine areas of Austria (Moser,1963), former agricultural soils of Poland(Dominik, 1961), oak shelterbelts in thesteppes of Russia (Imshenetskii, 1967),former treeless areas of the United States(Hatch, 1937), forestation attempts wereeither total or near failures until ecto-mycorrhizal infection occurred on treeroots. Symbiotic root infection was in-sured either by introductions of pure cul-tures of the fungi, soil containing ecto-mycorrhizal fungi, or manipulation of soilcontaining low levels of indigenous sym-biotic fungi to encourage ectomycorrhizaldevelopment.


Natural soils of the world which havesupported vegetation in the past have notbeen reported void of endomycorrhizalfungi. The broad host range of mostspecies of endomycorrhizal fungi nor-mally ensures endomycorrhizal develop-ment on desirable plants. Failure inafforestation of normally endomycorrhizaltrees due to a deficiency of endomycor-rhizal infection, therefore, has not beenreported.

MYCORRHIZAE ANDREVEGETATION OF

STRIP-MINED LANDSIn observing the physical disruption of

overburden strata during strip-miningoperations, it becomes quite apparentthat the resulting surface material doesnot physically, chemically, or biologicallyresemble any other landscape in theworld. Physically, the surface materialis often very rocky, steeply sloped, anddepending on its mineral composition,has variable weathering rates. This ma-terial may be quite dark in color andabsorb sufficient radiant energy to causehigh surface temperatures. Chemically,the surface material may contain highlevels of sulfur, aluminum, manganese,etc., which are limiting to plant growth.The material may contain only smallquantities of the essential elementsfor normal plant growth. Biologically,any macro- or microbiological systemwhich existed in the surface soil prior tostripping may now be buried dozens offeet under the stripped overburden.Some of the original topsoil may be mixedthroughout the stripped profile, but evenunder these conditions the surface ma-terial is nearly a biological desert in com-parison to the biological status of theoriginal profile.

The status of the mycorrhizal potentialof the new surface material is of concernto us. The literature is well documentedwith descriptions of the various physicaland chemical properties of strip-minedlands (Hutnik and Davis, 1973). Thequestions I shall attempt to answer are—Can indigenous and recolonizing my-corrhizal fungi survive these "soil" prop-erties? Are myeorrhizae essential to allplants which may naturally or artificiallyrevegetate this surface material ? Is there

significant potential for ecological selec-tion among the vast number of species ofmycorrhizal fungi to assure that adapt-able ones will maintain themselves onroots of plants in these disturbed sites?

Ectomycorrhizal Associations.—Therehas been only limited research on mycor-rhizal associations of plants on strip-mined lands and mining wastes. Sch-ramm (1966) published a classic piece ofwork on plant colonization of anthracitewastes in Pennsylvania. He concludedthat early ectomycorrhizal developmentwas essential for seedling establishmentof Betula lenta, B. populifolia, Pinusrigida, P. virginiana, Populus tremuloides,Quercus rubra, and Q. velutina on thiswaste material. The only generally suc-cessful original plant colonists of thisbare and predominantly nitrogen-defi-cient waste were either nitrogen-fixingplants or certain ectomycorrhizal treespecies. Schramm suggested that dueto their year-round effectiveness, ever-green trees (pines) should receive specialattention, and furnished strong evidencein support of his conclusions. Seedlingsfrom either wind-blown or artificallyplanted seed of these tree species that didnot have ectomycorrhizae were chloroticand soon died. The majority of surviv-ing seedlings, and especially those grow-ing well, were heavily ectomycorrhizal.The main basidiomycetes observed bySchramm that developed near the sur-viving tree seedlings were Inocybe lacera,Thelephora terrestris, Pisolithus tinctorius,Amanita rubescens, and Sclerodermaaurantium which form ectomycorrhizaeon trees (Trappe, 1962). These obser-vations by Schramm add additional evi-dence to that which has been already dis-cussed on the need of these tree speciesfor ectomycorrhizal associations.

Schramm (1966) traced the extensivelydeveloped mycelial strands formed by P.tinctorius from ectomycorrhizae of thesevarious tree species through large wastevolumes to the base of its basidiocarp.These mycelial strands arc somewhatunique in that they are large and brilliantgold-yellow in color and were easilytraced through the contrasting dark an-thracite wastes. Some strands weretraced through waste material as far as

No. G MYCORRHIZAE AND RECLAMATION 293

15 ft from the seedlings to the basidiocarpThe ectomycorrhizae formed by Pisoli-thus were also yellow-gold in color andprolifically branched. He associated P.iinctorius ectomycorrhizae with the mostvigorously growing seedlings. In mostcases, it was the first symbiont on seed-ling roots. The other species of ecto-mycorrhizal fungi appeared on roots andproduced basidiocarps primarily afterlitter had accumulated under the seedlingcanopy. These observations tentativelyconfirmed that P. tinctorius was the fun-gal symbiont forming the gold-yellowectomycorrhizae on these tree species.Earlier, Bryan and Zak (1961) "synthe-sized" ectomycorrhizae with P. tinctoriuson Pinus echinata seedlings in aseptic cul-ture. This pine species, however, wasnot encountered by Schramm in Penn-sylvania.

Schramm's work strongly suggests thatonly a few ectomycorrhizal fungi arecapable of ecologically adapting to soilconditions on the anthracite wastes.High soil temperatures could be a limitingfactor in specific mycorrhizal establish-ment. Marx and coworkers (1970) foundthat P. tinctorius formed more ectomycor-rhizae on P. taeda seedlings at a constantsoil temperature of 34° C than it formedat either 14, 19, 24, or 29°C. Thelephoraterrestris did not form ectomycorrhizae at34°C soil temperature and it formed morebetween 14 and 24°C than at 29°C. T.terrestris is one of the major ectomycor-rhizal fungi on pine seedlings in nurseriesthroughout the United States, whichprobably accounts for its presence onplanted coal spoils. It was on the seed-ling roots from the nursery prior toplanting on the spoil. In a later studywith these fungi, Marx and Bryan (1971)found P. taeda seedlings with Pisolithusectomycorrhizae survived and grew aswell at 40°C as they did at 24°C. Seed-lings with Thelephora ectomycorrhizae orthose without ectomycorrhizae did notsurvive well and did not exhibit growthat 40°C. These results may explain whyPisolithus is the primary symbiont onyoung volunteer seedlings on anthracitewastes. Schramm (1966) recorded soiltemperatures between 35°C and 65°C inwTastes at a depth of 2}-4 inches. PerhapsPisolithus was dominant because high

soil temperatures restricted earlier estab-lishment of the other fungi.

Prompted by Schramm's report andour findings on soil temperature, exami-nations were made in 1971 of variousstrip-mined wastes in the East. Our re-sults were only observational, but wethought them to be significant. Wefound Pisolithus basidiocarps and itsunique, gold-yellow ectomycorrhizae andmycelial strands to be the predominant,if not the only, ectomycorrhizal fungus onroots of Pinus virginiana, P. taeda, P.resinosa, and several Betula spp. on coalwastes in Indiana, Pennsylvania, Ohio,Virginia, West Virginia, Kentucky, Ten-nessee, and Alabama, as well as P.echinata and P. taeda on strip-minedkaolin wastes in Georgia. Some of thesewastes had a soil reaction as low as pH2.9, although most were between pH 3.5and 5.5. Pisolithus has also been re-ported on coal wastes associated with B.lenta, B. pendula, B. populifolia, Populusgrandidenta, P. tremuloides, and Salixhumilis in West Germany (Meyer, 1968),Pinus banksiana in Missouri (Lampkyand Peterson, 1963), and Pinus spp. inIndiana and Tennessee (Hile and Hennen,1969).

On a coal waste near Fabius, Alabama,over 3,000 Pisolithus basidiocarps wereobserved under planted P. taeda in anarea of less than j ^ acre. From themature basidiocarps in this area we col-lected over 1,300 g of dry basidiospores.There are approximately 1.1 billionspores per gram. These and otherbasidiospore collections have proved func-tional as inoculum for ectomycorrhizaldevelopment on pines (Marx, 1976b).

I previously discussed evidence whichproved that any ectomycorrhizae on rootsof trees such as Pinus are better than noectomycorrhizae at all. It appears thatone more premise can be made—certainspecies of ectomycorrhizal fungi are morebeneficial to tree growth than others.Based on Schramm's observations andour reports, it appears that Pisolithusmay be more beneficial to the establish-ment of Pinus and Betula species on strip-mined lands and wastes than are otherspecies of ectomycorrhizal fungi. Makingthe assumption that Pisolithus ectomy-corrhizae are instrumental in tree estab-


lishment and maintenance on strip-minedwastes, research was begun to developtechniques to "tailor" seedlings in thenursery with Pisolithus ectomycorrhizae.The working premises were simple—Whywait for natural means to establish Pi-solithus on colonizing trees? Could treesurvival and growth be improved byhaving Pisolithus ectomycorrhizae pre-formed on the seedlings in the nurseryprior to planting on the strip-minedlands ? Recently, techniques were devel-oped for this "tree tailoring" concept(Marx and Bryan, 1975) which wereeffective on several species of pines inconventional tree nurseries (Marx et al.).1976c). Briefly, the techniques involvedthe production of pure culture, vege-tative mycelial inoculum of P. tincto-rius in a vermiculite-peat moss-nutrientsubstrate, or the use of basidiosporesmixed with a physical carrier, such asmoist vermiculite. Either inocula wasused to infest artificially fumigated nur-sery soil and no further modifications ofstandard nursery practices were neces-sary. Effective soil fumigation (methylbromide), done shortly before soil infesta-tion, and the maintenance of reasonablelevels of soil fertility through the growingseason appear to be the two prerequisitesfor successful "tailoring" of pine seedlingswith Pisolithus. These techniques alsohave been used successfully with otherectomycorrhizal fungi, such as Thele-phora terrestris and Cenococcum grani-forme.

The introduction of Pisolithus into nur-sery soils has significantly improved pineseedling quality in the nursery. Growthincreases of between 100-150% after onegrowing season in the nursery have beenencountered with seedlings of P. taeda,P. strobus, and P. virginiana (in theSouth) following successful soil infestationand ectomycorrhizal development byPisolithus. After a few more years ofresearch, ectomycorrhizal deficiencies innurseries of many acres may be correctedby using pure cultures of highly bene-ficial symbionts. In the past these de-ficiencies were corrected by the additionof forest litter and humus to the nurserysoil. This practice inadvertently intro-duced a considerable number of pests,such as weeds and disease-causing organ-

isms, into certain nurseries. Currently,Pisolithus is being tested in tree nurseriesin Australia, Mexico, East Africa, Switz-erland, and France, as well as in differentparts of the United States. The practic-ability of introducing Pisolithus and otherectomycorrhizal fungi into the near-sterile root substrate of containerizedseedlings is also being examined. Pre-liminary information suggests that growthin containers and field performance ofthese seedlings can be improved withspecific ectomycorrhizae (Marx and Bar-nett, 1974). This application to con-tainerized tree stock could be as relevantas it is to standard nursery-grown seed-lings, since it is anticipated that in thenear future container stock will accountfor as much as 20% of the seedlings usedin reforestation in North America. Con-tainer-grown stock also has promise forreforesting strip-mined lands.

Since the techniques to "tailor" seed-lings with Pisolithus ectomycorrhizaehave only recently been developed, verylittle seedling performance information isavailable. In a greenhouse pot study,Nicholas (1971) found that Pisolithusectomycorrhizae improved growth ofBetula pendula and Pinus resinosa seed-lings in variously amended bituminouscoal spoils in comparison to seedlingswithout Pisolithus. Unfortunately, histest seedlings were not grown under thebest of conditions during synthesis ofectomycorrhizae due to problems ex-perienced in the mycorrhizal growth roomlocated at the Athens, Ga. facility.

Since the winter of 1973, members ofthe Athens, Ga. Project have outplantednearly 25,000 pine trees with specificectomycorrhizae from Pennsylvania toFlorida. These test plantings are locatedon strip-mined coal and kaolin spoils,eroded Copperhill, Tennessee, and routinereforestation sites. The field results lookvery promising, but due to the young ageof the plantings, problems with field de-sign, destruction of certain plots by cattleand trailbikes, and lack of winter hardi-ness of Georgia-grown seedling stockplanted in the North, they can only bediscussed in general terms. With fewexceptions, seedlings of P. taeda, P.virginiana, P. echinata, P. clausa, P.resinosa and P. elliottii var. elliottii with


Pisolithus ectomyeorrhizae survived andgrew better than seedlings with ectomy-eorrhizae formed by other ectomycor-rhizal fungi. The few exceptions can beexplained on the basis of seedling condi-tion and degree of ectomycorrhizal de-velopment at the time of planting. Incertain tests, basidiospores of Pisolithuswere placed on roots of standard nurserystock that had Thelephora terrestris ecto-myeorrhizae prior to planting on coalwastes. Some Pisolithus ectomyeorrhizaedeveloped from basidiospore inoculumand stimulated seedling height growth asmuch as 30 percent in comparison toseedlings without Pisolithus.

Last winter, pine seedlings grown inthe Athens' nursery with either Pisolithusor Thelephora ectomyeorrhizae wereplanted on strip-mined coal sites in Ken-tucky, Virginia and Ohio. The Ken-tucky site had been planted to pine fivetimes previously on a yearly basis withnearly complete failure each year. Inour planting on this site, survival of P.virginiana seedlings with Thelephora ecto-myeorrhizae was only 1.5 percent. Sur-vival of seedlings with Pisolithus ecto-myeorrhizae was 45.5 percent. Theseseedlings grew significantly in one grow-ing season and Pisolithus has completelycolonized the roots and adjacent soil vol-umes. The Virginia site was not con-sidered a major problem area and sur-vival and growth of P. taeda seedlingswere better than on the Kentucky site.Pisolithus ectomyeorrhizae increased sur-vival of these seedlings by 11%, andheight and stem diameter by 21% and26%, respectively, in comparison to seed-lings with Thelephora ectomyeorrhizae.In the Ohio planting near New Straits-ville, Pisolithus ectomyeorrhizae in-creased survival of loblolly pine seed-lings by 34% and Virginia pine seedlingsby 36% over similar seedlings ectomycor-rhizal with Thelephora.

An inherent difficulty in research ofthis nature has become apparent to usand that is maintaining the integrity ofthe specific ectomycorrhizal associationon these sites. Pisolithus recolonizesroots of test seedlings from naturalsources so rapidly that valid growth com-parisons between seedlings initially withand without Pisolithus is verv erratic.

Quite often, over one-half of the seedlingswithout Pisolithus at planting will havevariable quantities of Pisolithus ecto-myeorrhizae by the end of the firstgrowing season on site.

Preliminary field results look promis-ing, but are not in themselves conclusive.Much more research remains to be done.The results, however, point out thepotential benefits of specific ectomyeor-rhizae on seedlings for specific sites.Many reforestation sites, including strip-mined lands, are characterized by soilfactors which exert selective pressure onsymbiotic fungi. Fungi which can toler-ate these factors and are ecologicallyadapted to these sites, should be used to"tailor" seedlings prior to planting. Per-haps in this manner a persistent andphysiologically active root system can beassured. This feature in itself mayremedy some of the problems encoun-tered in the past on the reclamation ofthese adverse sites. The same principleof symbiont selection and tailoring mayalso have application in the reforestationof more routine sites.

HOST RANGE AND GEOGRAPHICDISTRIBUTION OF

PISOLITHUS TINCTORIUSThere has been a great deal of interest

generated throughout the world on thepractical use of Pisolithus in re- andafforestation efforts on a variety of sites.Because of this interest and the obviousimplications of plant quarantine in into-ducing Pisolithus to other areas, attemptshave been made to obtain informationfrom the literature and correspondenceregarding its host range and geographicdistribution. After a brief search, itbecame apparent that Pisolithus has anearly worldwide distribution. It hasbeen found in Europe, Asia, Africa, Cen-tral and South America, and in the Mid-dle East. It has been reported in 22states throughout the United States. Itstree host range is also quite impressive:Thirty-five species or varieties of pines,three species of Betula, two species ofEucalyptus, two species of Populus, andsix species of Quercus have either beenexperimentally confirmed as hosts ofPisolithus or have been associated withthis fungus consistently in the field. It


possible that "tailoring" these tree specieswith Pisolithus in the nursery or in con-tainers may also improve their survivaland growth in the field.

Endomycorrhizal A ssociations.—Therehas been only limited research on endo-mycorrhizae of plants on strip-minedwastes. Daft et al. (1974) found abun-dant endomycorrhizae on roots of avariety of herbaceous plants, includinggrasses, on anthracite and bituminouscoal wastes in Pennsylvania and bitumi-nous wastes in Scotland. They identifiedand collected spores of Gigaspora gigantea( = Endogone gigantea) from the Penn-sylvania wastes and found that theywould infect and stimulate growth ofcorn plants in spoil material. In addi-tion to G. gigantea, other species of Endo-gonaceae were also found. They con-cluded that endomycorrhizae may beessential for the survival and growth ofherbaceous plants on coal wastes.

Two of my associates (W. C. Bryanand W. J. Otrosina.) have made observa-tions on the incidence of endomycorrhizaeon herbaceous plants on strip-mined land.On both artificially and naturally revege-tated coal spoils in Kentucky and Vir-ginia, as well as kaolin spoils in Georgia,they found a variety of wild and culturedgrasses to be endomycorrhizal to onedegree or another. They observed thatnot all seedlings of some grasses haveendomycorrhizae on the same site.Planted and volunteer trees, such assycamore, sweetgum, maples, and blackalder, were also heavily endomycorrhizal.In all likelihood, the endomycorrhizal in-fection on the planted trees was on theroots prior to planting on the spoil, how-ever, the significance is that these endo-mycorrhizae persisted.

Earl F. Aldon (USDA, Forest Service,Rocky Mountain Forest and Range Ex-periment Station, Alburquerque, NewMexico 87101, personal communication)found that endomycorrhizae significantlyincreased survival and growth of the four-wing saltbush (Altriplex canescens) onstrip-mined coal spoils in New Mexico.Size index (height X stem diameter) of themycorrhizal seedlings was 231 and only91 for the nonmycorrhizal seedlings afterthe second year on the spoil site.

Since some endomycorrhizal infectionis apparent on wild grasses and volunteertrees on spoil material, the logical ques-tion to ask is, what was the source of theinitial inoculum? As mentioned earlier,endomycorrhizal fungi do not havehighly effective means of dissemination.Most geographic spread of these fungi isthought to be slow and mainly by movingwater or, soil, insects, birds, and perhapsmammals (including man). Their pres-ence on strip-mined lands may be ac-counted for through contamination ofoverburden material with the originaltopsoil. If some plants are dependenton, or at least stimulated by, endomycor-rhizal infection, then perhaps by increas-ing the amount of available inoculum,either artificially or naturally, revegeta-tion of spoil material with these plantsmay be enhanced.

It appears that research on the valueof endomycorrhizae to survival andgrowth of plants, including trees, on strip-mined lands should be concentrated ontesting a variety of fungi which persist onthe spoil. In this manner, perhaps anecologically adapted endomycorrhizalfungus can be found which may have asimilar potential to that of the ectomycor-rhizal fungus Pisolithus tinctorius. Ap-parently there are a multitude of speciesof endomycorrhizal symbionts of her-baceous plants from which the potentialchoice can be made (Nicolson, 1967). Itwould be extremely interesting to deter-mine the value of endomycorrhizae topioneer plants. Are they pioneer plantsbecause they do not require endomycor-rhizae for normal growth? If sufficientquality and quantity of endomycorrhizalinoculum were present in spoil materialwould the same succession of herbaceousspecies prevail? There is tremendouspotential for practical research on thisaspect of endomycorrhizal associations.

LITERATURE CITEDBowen, G. D., C. Theodorou and M. F. Skinner.

1973. Towards a mycorrhizal inoculationprogramme. Proc. Amer.-Australian ForestNutr. Conf., Canberra, 1971.

Bryan, W. C. and B. Zak. 1961. Syntheticculture of mycorrhizae of southern pines.Forest Sci. 7:"123-129.

Daft, M. J., E. Hacskaylo and T. H. Nicholson.1975. Arbuscular mycorrhizas in plants col-onizing spoils in Scotland and Pennsylvania.


Symposium on Endotrophic Mycorrhizas,Univ. of Leeds, (July 1974)/ AcademicPress, N.Y.

Dominik, T. 19(51. Experiments with inocu-lation of agricultural, land with microbialcenosis from forest soils. Prace Inst. Bad.Lesn. No. 210, p. 103.

Gerdemann, J. W. and J. M. Trappc. 1974.The Endogonaceae in the Pacific Northwest.Mycologia Memoir No. 5, p. 7(5.

Gibson, I. A. S. 19(53. Einc mitteilung uberdie Kiefernmykorrhiza in der Walden Kenias.In Mycorrhiza. W. Rawald and H. Lyr, eds.p. 49. Fischer, Jena.

Hacskaylo, E. and C. M. Tompkins. 1973.World literature on mycorrhizae. Cont. ofReed Herbarium, No. XXII. The Paul M.Harrod Co., Baltimore.

Harley, J. L. 19(59. The biology of mycor-rhiza. Leonard Hill Publ. London. 344pp.

Hatch, A. B. 1937. The physical basis ofmycotrophy in the genus Pinus. Black RockForest Bull. (5: 1-1(58.

Mile, Nancy and J. F. Hennen. 19(59. In vitroculture of Pisolithus tinctorius mycelium.Mycologia (51: 195-198.

Hutnik, R. J. and G. Davis (eds.). 1973.Ecology and reclamation of devatated land.Vols. 1 and 2. Gordon and Breach, pub-lishers. 538 pp. and 504 pp.

Imshenetskii, A. A. (ed.). 1967. Mycotrophyin Plants. Isr. Program Sci. Transl, Jeru-salem. (Original in Russian, Izd. Akad.Nauk SSSR, Moscow, 1955.)

Lampky, J. R. and J. E. Peterson. 1963.Pisolithus tinctorius associated with pines inMissouri. Mycologia 55: 675-678.

Marks, G. C. and T. T. Kozlowski (cds.). 1973.Ectomycorrhizae: Their ecology and phy-siology. Academic Press, New York. 444pp.

Marx, D. H. 1976a. Mycorrhizae of exotictrees in the Peruvian Andes and synthesis ofectomycorrhizae on Mexican Pines. ForestSci. (In Press).

1976b. Synthesis of ectomycorrhizaeon loblolly pine seedlings with basidio-spores of Pisolithus tinctorius. Forest Sci.(In Press).

and J. P Barnett. 1974. Mycorrhizaeand containerized forest tree seedlings.North American Containerized Forest Tree

Seedling Symposium, Denver, Colo., [August26-29, 1974J.

and W. C. Bryan. 1975. Growthand ectomycorrhizal development of loblollypine seedlings in fumigated soil infested withPisolithus tinctorius. Forest Sci. 21: 245-254.

-, \V. C. Bryan and C. E. Cordcll. 1976c.Growth and ectomycorrhizal developmentof pine seedlings in soils of three state nurs-eries infested with Pisolithus tinctorius.Forest Sci. (In Press).

••- and W. C. Bryan. 1971. Influence ofectomycorrhizae on survival and growth ofaseptic seedlings of loblolly pine at hightemperatures. Forest Sci. 17: 37-41.

-— —, W. C. Bryan and C. B. Davey. 1970.Influence of temperature on aseptic synthesisof ectomycorrhizae by Thelephora terrestrisand Pisolithus tinctorius on loblolly pine.Forest Sci. 16: 424-431.

Meyer, F. H. 19(58. Mykorrhiza. In Halden-begrunung im Ruhrgebiet., Mellinghoff, K.,Schriftenr, eds. Siedlungsverb. Ruhr Kohl-enbezirk 22: 118-123.

Mikola, P. 1969. Mycorrhizal fungi of exoticforest plantations. Karsteina 10: 1(59-175.

Moser, M. 1963. Die Bedeutung der mykor-rhiza bei Aufforstung unter besondererBerucksichtigung von Hochlagen. In My-korrhiza. W. Rawald and H. Lyr, eds.Fischer, Jena. p. 407.

Nicholas, A. K. 1971. Ectomycorrhizal es-tablishment and seedling response of vari-ously treated deep-mine coal refuse. MS.Thesis, Dept. of Forestry and Wildlife, Penn.State Univ.

Nicholson, T. H. 1967. Vesicular-arbuscularmycorrhiza—a universival plant svmbiosis.Sci. Prog. Oxf. 55: 561-581.

Oliveros, S. 1932. Effect of soil inoculationson the growth of Benquet pine. MakilisgEcho 11: 205.

Schramm, J. E. 196(5. Plant colonizationstudies on black wastes from anthracite min-ing in Pennsylvania. Amer. Philoso. Soc. 56:1-194.

Trappe, J. M. 1962. Fungus associates ofectotrophic mycorrhizae. Botanical Rev.28: 538-606.

Vozzo, J. A. and E. Hacskaylo. 1971. Inocu-lation of Pinus carribaea with ectomycor-rhizal fungi in Puerto Rico. Forest Sci. 17:239.

mycorrhizae and establishment of trees on strip-mined land

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