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Litter Decomposition and Ectomycorrhiza in Amazonian Forests

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Litter Decomposition and Ectomycorrhiza in Amazonian Forests Litter decomposition and Ectomycorrhiza in Amazonian forests 1. A comparison of litter decomposing and ectomycorrhizal Basidiomycetes in latosol­ terra-firme rain forest and whité podzol campinarana Rolf Singer ( *) lzonete de Jesus da Silva Araujo (*) Abstract lNTRODUCTION Application of a mycosociological method (adaptation of the Lange method) in Central lt had been assumed that ectomycorrhiza Amazonia produced the following results: In the in the neotropics ls restricted to 1) secondary­ white-sand podzol campinarana type of forests the forest and partially destroyed or damaged dominant trees are oblígatorily ectotrophically tropical and subtropical forests (cicatrizing mycorrhizal; litter is accumulatea as raw humus mycorrhiza), 2) to the natural vegetation above as a consequence of ectotroph dominance; fewer a certain altitude in the Andes and pre-Andine leaf inhabiting litter fungi occur in the dry as tropical-montane zone, 3) plantations of intro­ well as the wet seasons tha..'1 are counted in the latosol terra-firme rain forest, and the fungi duced ectomycorrhizal trees, inoculated with of that category are most strongly represented eccomycorrh1za or carryng spores or mycelium ("F-dominance") by other species here than in the with seeds or seedlings, 4) possible scattered terra-finne stands tested. The ectomycorrhizal trees occurrences restricted to certain genera of and !ungi are enumerated. On the other hand, in Cormophyta [Salíx was suggested), not being the terra-finne forest, ectotrophically mycorrhizal dominant in the tropical rain forest (Singer, !ungi did not occur in the test plots. The trees are 1963; Singer & Morello, 1960). This assumption, almost all non-ectomycorrhizal in primary terra­ firme forest; here, litter doE-s not appreciably if correct, would , mean that the neotropical accumulate as a deep raw humus layer because the humid lowland cannot be expected to produce considerably higher number o! leaf inhabiting litter anything in the way of a t rue ectotroph forest !ungi (ratios o! 4:1 to 4 .2:1 in favor cf terra-finne) excepting secondary forests (capoeira), plan­ and greater diversification (a larger number of tations and possibly forests containing species) is potentially capable o! reducing more scattered non-dominant ectotrophic elements. than the yearly leaf-fall. In this study, a group of !ungi was · mainly considered which is not This would mean that there is a basic differ­ represented in laboratory litter decomposition ence in the composition of the neotropical and experiments. However, a comparison with un­ the paleotropical lowland rain forests. published and published data shows that otir results However, recent observations by Kreisel satisfactorily match the experimental and phyto­ sociological data obtained both with other classes ( 1971) and Fiard (personal communication) o! microorganisms and wíth observations in other indicate that in the Gulf area certain types of regions. The quantity o! litter decomposing !ungi forest contain ectotrophically mycorrhizal in the folücolous group depends mainly on tne elements {Coccoloba in Cuba, Torrubía in amount o! precipitation during the last few days Martinique). before counting. This does not hold for all llgnicolous f ungi.. The reasons for this as well a.s Our own recent investigations in the Lower the mechanisms by which the ectomycorrhizae may Rio Negro region of Central Amazonia show. reduce litter decomposition rate:; and influence the thât certain vegetation types (campina, campi­ nutrient cycling patterns are disc-ussed. The most nar·ana, igapó) are rich in ectomycorrrhiza­ important genera of Basidiom,ycetes involved in forming fungi, e. g. Boletaceae (Singer, 1978a). litter decomposition in the Lower Rio Negro forest associations are enumerated. Possible economic Thus, in both hemispheres, certain tropical significance of introducing ectotrophs in the terra­ soils require for the formation of any kind of firme forest is indicated. forest the presence of ectomycorrhiza. Canse- ( • ) - Instituto Nacional de Pesquisas da Amazônia, Mall'aus . ACTA AMAZONICA 9(1) : 25-41. 1979 -25 quently, the anectotrophic "hyiaea" is inter­ domycetes, Zygomycetes, etc., as well as mittent, with interspersed islands of ectotroph bacteria, Myxomycetes, and Actinomycetes. forests where climatic or edaphic (in Amazo­ worms, Arthropods, higher animais) under nia mainly the latter) conditions make it various conditions of tropical forests has, as impossible for anectotrophic trees to obtain far as we are aware, never been made, and sufficient mineral nutrition unless ectotrophs with the methods available, meets with some dominate to such a degree as to change the difficulties. microbiology of the soil completely and intro­ Under these circumstances it was felt that duce what has come to be cailed direct cycling a method had to be found that at least provides (Went & Stark, 1968) or "short-cycling" (Har­ quantitative data on the Basidiomycetes, their iey, 1977) of mineral nutrients. numbers, diversity, habitat requirements and lhe proposal (Singer, 1964) to reclassify dependency on meteorological conditions, their the forest types of the world in such a way capacity of forming ectomycorrhiza, their fru­ that they are first and basically divided into iting periodicity, in fact ali data that could not two main groups [1) - ectotroph and anec­ be obtained in laboratory studies. This method totrophic forests - has been ignored by forest had already been introduced (Moser-method in ecologists, first because of misunderstandings Europe, North, and South America; Lange­ with regard to the term "ectotroph" on the method in Europe) and had now to be adapted part o-f some mycorrhiza-speciaiists (Meyer, to the conditions of the lowland tropical rain 1973) and secondly because understandably forest. The method chosen - the Lange the mycological literature is not adequately methoci - was expected to provide the desired accessible to ali forest ecologists and phyto­ data and permit comparisons between the 2 sociologists ( ) • latosol -terra firme rain forest and the podzol The necessity to accept the importance ot white-sand campinarana . basidiomycetous components of the eco­ systems and the usefulness of terms de­ MATERIALS AND METHODS scribing unequivocally the fungus-cormophyte symbiotic associations at the levei of the The Lange method ( 1948) was introduced individual (ectotroph) and the plant-fungus for the study of fungus sociology in Danish community (ectrotroph forest) has, in the Sphagneta whereby, in contrast to the Moser menntime, become ever more obvious and the method (1959), permanent 1x1 m squares present study wi 11 show that, without them, an were marked and fructifications periodic3lly undcrstanding of the phenomena observed is counted. In ou r case one 5x5 m square was nearly imposs1ble. marked in the primary latosol terra firme forest With regard to litter decomposition, the 30 km north of Manaus (immediately adjacent role of the Basidiomycetes is generally under­ to a hectare of a fully studied (Prance et. al., stood but rarely presented in quantitative form, 1976) forest reserve at EMBRAPA) and regu­ principally becauae earlicr investigators were larly observed (in 6-11 day intervals) 37 times hampered by the intricacies of the taxonomy during a whole year. Furthermore two 5x1 m involved. On the other hand the experimental rectnngular test lots, one in latosol terra firme methods tend to minimize the part played by forest at km 45 of the Manaus-Caracaraí Road Basidiomycetes since in litter samples their and another immediately adjacent in the Re­ growth under laboratory conditions is sup­ serva Biológica de Campina INPA-SUFRAMA, pressed. A convincing study, or even estimate with three countings (two, at different seasons of the relative numbers and efficiency of litter of the year coordinated with countings, the decomposing organisms (Basidiomycetes, same day, in the latosol terra firme forest) . other Eu-Mycetes including Hypho-and En- The campinarana forest, the relatively most ( 1 ) - An ectotroph forest is one in which the dominant trees are obligatorily ectomycorrhizal. An anectotrophic forest is one in which the dominant trees are not obligatorily ectomycorrhizal. ( 2) - • Despite this massive documentation plant scientists commonly seem to little heed the phenomenon [mycor­ rhiza] and its implications unless they are studying mycorrhizae per se" J . M . Trappe & R. D. Fogel (1977). 26- Singer & Araujo thoroughly studied one in the Lower Rio Negro clays with exceptional temperaturas or air (Andcrson, 1978; Anderson et a/., 1975; Lis­ humidity measured were marked as such for bôa, 1975; Prar.ce, 1975) is located between later reference. The precipitation data for the the entrance to the Reserva and the transition test lot at EMBRAPA were obtained hom the to the more open, true campina-vegetation meteorological station of EMBRAPA (\ess than further east. In the following text we shall 1 km away) until October 1977, and from then refer to this lot and the corresponding cam­ on from that of Ducke Forest (INPA), little pinarana vegetation in other Rio Negro locali­ more than 3 km away. During this latter period ties as CR and to the latosol terra firme rain very minor rainfall may have been local, but forest as TF. any major rainfall and most minor ones were The fungi were counted accordlng to the sufficiently widespread so that the figures carpophores observed and were w ithout diffl­ registered at Ducke Forest should be con­ culty divrded
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