Biological Considerations in the Utilization of Racosperma Auriculiforme and Racosperma Mangium in Tropical Countries with Empha
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2 42 l ForestJournal ScienceTropica f o 6(4): 422-443 BIOLOGICAL CONSIDERATION UTILIZATIOE TH N SI N OF RACOSPERMA AURICULIFORME AND RACOSPERMA MANGIUM TROPICAN I L COUNTRIES WITH EMPHASIS ON ZAIRE P.D. Khasa*, Centre, Recherche,de. Biologieen Forest/ere, Faculte Foresterie.de Geomatique,de et Universite. Lavtil, Sle- Foy, Quebec, G1K 7P4, Canada G. Vallee Direction de. Recherche,la Ministere Forelsdes Quebec,du rue,700 Einstein,2 Ste-Fo\, Quebec CAPW8, 3 Canada & J. Bousquet+ Centre Recherchede. Biologieen Forestiere,, Faculte, Foresteriede Geomatique,,de, et Universite Laval, Ste- Foy, Quebec GlK 7P4, Canada Received July 1992 _____________ ______________ ___ _ ______ KHASA, P.D., VALLEE, G. & BOUSQUET, J. 1994. Biological considerations in the utilization of Racospenna auriculiforme and R. mangium in tropical countries with emphasis on Zaire. Racusperma miriculiforme (.Acacia auriculiformis) and R. mangium (A. mangiuw), two fast-growing species belonging to the Leguminosae family, have been introduced into Zair r industriaefo l fuelwood plantation r socia wels fo s a s a l agroforestry purposes repore W . r current herou n eo t knowledg biologicae th n eo l consideration e utilizatioth n si f boto n h specie tropican i s l countries with emphasis n Zaireo e taxonomTh . d ecologyan y , reproductive biolog d breedinyan g systems,, genetic diversity, biolic interactions, silvicultur d presenean t use f theso s e species c examinedar . Because these species will pla a ymajo r rol n reforestatioi e n programme e nexth tr fo decades developinn i s g countries suc s Zairea h e th , necessit genetie th r fo yc improvemen f theso t e specie s wel a ss adaptability a l , site trial d silvicultnraan s l requirement e discussear s n relatioi de increasth o t nf o e plantation productivity. Keywords: Acacia - biotic interactions - genetic diversity - luelvvood plantations, reproductive biology - taxonomy - silviculture - social agroforestry - Zaire KHASA , VALLEED. BOUSQUET,]P ,& . ,G . 1994. Pertimbangan-pertimbangan dari segi biologi dalam pengurusan Racospertna auriculiforme . mangiumR n da i d * Present address: Department de Biologie, Faculte des Sciences, B.P. 190, Universite, de Kinshasa, Zaire * Author for correspondence: Fax: (418) 656-3551; Tel: (418) 656-5085 3 42 Journal of Tropical Forest 3 Science44 - (4)2 6 42 : negera-negara tropika dengan penekanan kepada negara Zaire. Dua spesies dari famili Leguminose, iaitu Racosperma auriculiformis (Acacia auriculiformis). R n da mangium (A. mangium), telah diperkenalkan di Zaire untuk industri ladang kayu jugn da a i untuap k perhutanan tani sosial i siniD ., kami melaporkan dengan pengetahuan semasa kami, tentang perimbangan biologi penggunaan kedua-dua spesies ini di negara-negara tropika dengan memberi tumpuan kepada negara Zaire. Taksonomidanekologi,pembiakan biolog sisten da i m pembiakbaikan,kepelbagaian genetik, interaksi biotik, silvikultu penggunaan rda n semasa kesemua spesie dikajii sin . Keperluan untuk memperbaiki genetik spesie i sertin s a kebolehsesuaian da n keperluan silvikultur yang berkaitan dengan peningkatan produktiviti ladang dibincangkan i adalaIn . h keranakedua-dua spesie akai sin n memainkan peranan utama dalam program-program penghutanan semula dalam dekad-dekad yang akan datang di negeri-negeri membangun scperti Zaire. Introduction n manAi s y tropical Sub-Saharan African countries, shiftin d moderan g n agriculture, fuelwood gathering foresty , firedr d savannas n i an s d selectivan , e logging system have been e maireporteth ne b cause o t d f o losf foresso s t biodiversity in Zaire (Khasa et al, in preparation). In order to overcome the problems associated with forest depletion and to maintain a sufficient supply of woo r fuelwooddfo , timber d chemicalsan , , reforestation with fast-growing tree species is being intensified in many tropical countries. It is estimated that in Sub- Saharan Africa, at least 25 million ha of plantations and woodlots with fast-growing tree e requiresar satisfo dt e demanth y r fuelwoofo d othed an d r rural needs (Schonau 1990). Most forest tree plantation tropican si l countries consis exotif to c fast-growing tree species (Evans 1982, Zobel et al. 1987). Their growth and yields generally exceed those of natives, attaining for instance 30 m3 ha'1 y~l or more with Eucalyptus in Congo at 7- y rotation (Vigneron & Delwaulle 1990). However, the monoculture of exotics is often criticized, because of apparent lack of adaptation e exoticoth f s use theid dan r susceptibilit pestso yt betteA . r knowledge th f eo performanc adaptatiod ean exoticf no thein environmentsw i ne r s therefori s e crucial before proceedin largo gt e scale introductions same th t e A .time longe th , - term environmental impact introductioe th f so exoticf no oftee sar n unknown. This may be depicted by the slow decomposition of litter of introduced Casuarina equisetifolia along the coast of Senegal. Native species might represent a logical alternativ unfortunatelyt ebu , little researc bees hha n devote theo dt their me fo rus in reforestatio land nan d reforestatio tropice th n ni s (Butterfield 1990). Eucalyptus spp. and Pinus spp. are generally selected for exotic monocultures severad an l industrial tree planting programme timber s fo puld ran p production have been established with these species (Martin 1987, Campinho Ikemors& i 1989, Moutanda 1990, Schonau 1990, Vigneron & Delwaulle 1990). However, polar and non-polar allelochemicals fro e leavemth f Eucalyptuso s have been showo nt inhibit growth of annuals, to decrease biodiversity in the area of eucalypt forest, causo t d e an economic los o agriculturat s l crops (Kohl Sing& i h 1990). These problems are also exacerbated by the high competitiveness of some Eucalyptus specie nutrientr sfo d watean s r (Martin othee 1987)th n r handO . , Pinus radiata has been used successfully in, silvopastoral systems by the forest industry in the journal of Tropical Forest Science 6(4): 422 - 443 southern temperate zones of New Zealand, Chile and Australia (Knowles el. al. 1990). Several shrub treed san s fro e genermth a Acacia sensu lato, Calliandra, Cassia, Gmeiina, Gliricidia , Lcucaena, and Tectona have been used in tropical countries for fuelwood plantation agroforestrd san y purposes (National Academ f Scienceyo s 1980, National Research Council 1983). Fast-growing leguminous, actinorhizal, othed an r nitrogen-fixing tree oftee sar n preferre ruran di l community plantations for agroforestry systems theio t parn e i ,r abilittdu improvo yt nitrogee eth n status of soils in symbiotic association with either Rhizobium, Bradyrhizobium, Azorhizobiurn, Sinorhizobium, Pholorhizobium, or Frankia (Baker 1990, Brewbaker et al. 1990, Sprent & Sutherland 1990), and also due to the increase in the uptake of immobile nutrients, especially phosphorus, in symbiotic association with endomycorrhi/al and/orectomycorrhi/alfungi (Khasarfrt/. 1990,1992,Bolan 1991,Molinar 1992). al t fe . Many of these species are early colonizers of cleared or disturbed sites, being mycorrhi/al dependen becomind tan g less importan lesd san t competitiv sois ea l fertility increases (Molina et al. 1992). They play a major role in soil nitrogen accretio organin i d nan c matter accumulation, contributin earlo gt y soil develop- ment (see Baker 1990). Of the exotic leguminous plants selected as multi-purpose trees for planting in the tropical countries, Racosperma auriculiforme (Cunn. ex Benth.) Pedley (Acacia auriculiformis) mangium. R d an (Willd.) Pedley, comb. nov mangium). A ( . oftene ar cite havins da highese gth t priority (National Academ Sciencef yo s 1980, National Research Council 1983, Turnbull 1987, 1991) presene Th . t review focusee th n so biological considerations in the utilization of both species in tropical countries with emphasis on Zaire. Their taxonomy and ecology, reproductive biology and breeding systems, genetic diversity, biotic interactions, silvicultur used e ean sar discussedIntroductio. n of Racosperma auriculiforme and R. mangium into Zaire R. auriculiforme and R. mangium have been introduced as plantation species into many countries of tropical Asia, America, and Africa (Catinot 1984, Turnbull 1987, 1991, Boland et al. 1990, Souvannavong 1990). Trial plots have been estab- lished in some western, central, southern African countries (Table 1), and in other countrie f tropicaso l AsiAmericad aan . Accordin Kankolonggo t Kamd oan i (1989), R. auriculiforme was introduced into Zaire in 1967 as part of a programme funde Fooe Agriculturd th dy an d b e Organizatio Unitee th f no d e Nationth d an s United Nations Development Programme (FAO/UNDP). R. mangium was intro- duced into Zair Kinzone n 197th i e t 9a o arboretum situatenortheasm k 0 d15 t from Kinshasa. However seee th , d origin botf so h introduced Racosperma species were not recorded. Because of the outstanding amenity attributes of R auriculiforme (Jim 1990) fe,a w hectare urbaf so n plantin around an gn i d Kinshasa City have been established, mainly for ornamentation and energy biomass production. Zairen I , reforestation activities have been supervise Service th y db e National de Reboisement (SNR) since 1978. In 1979, the Centre Forestier Kinzono 5 42 Journal of Tropical Forest Science 3 44 6(4)- 2 42 : Table 1. Some African countries where Racosperma auriculiforme and R. mangium have been introduced . auriculiformeR . mangiumR Country West Africa s ye s ye Benin Ivor)' Coast yes Niger yes Nigeria yes Sierra Leone vcs East Africa Kenya yes s ye s ye Tan/ania s ye Uganda Centra] Africa Burundi yes Cameroon yes yes Congo yes yes Zaire ves ves Southern Africa s ye Malawi Zimbabwe yes s ve South Africa initiate introductioe dth f exotino c species suc thoss ha Racosperma,f eo Eucalyptus, d Pinusan n Kinzoni o arboretu e Batekth n o me Plateau. From 197o 9t 1985,about 300 ha were planted, including R. auriculiforme, Cassia siamea, Eucalyptus camaldulensis, Millettiad an laurentii. 1985n I funa , d named "Fonde sd Reconstitu-tion du Capital Forestier" (FRCF) was created in order to promote reforestation activities throughout the country.