- be highest
, Relative dominance = 0.042 , CVI = 0.882 and IVI = 2.84 %. Chromolaena odorata, Nephrolepis pumicicola, Nephrolepis biserrata were frequent with Nephrolepis pumicicola having the highest density ( 3.35 %) and 13.87 % relative density. Alstonia boonei and Maytenus sp. had the lowest densities. Shannon-weaver diversity (H1) and Simpson diversity indices are 3.58 and 22.863 respectively. The physico-chemical parameters of the soil from the edges and the centre of the lava were analysed. Colour ranged from very dark grey (5y 3/1), in the centre, to dark reddish brown (5y 3/3, 5y 3/4). The topsoil was mostly made up of organic matter. The soils were acidic (pH from 4.62 - 5.31 ), soil sand content was highest at the right edges (56.5%) and lowest at the centre (16.8%). Total Nitrogen was found to be highest on the lava centre, ( 3.53 %), and lowest at the right edge ( 1.65 %) while the total phosphorus was highest at the left edge ( 27.15 ) and lower (19.3) on the centre; being relatively higher The principal component analysis showed that PC1 (69.3%) is most strongly affected by total Nitrogen, exchangeable cations, CEC, organic carbon and organic matter, while PC2 ( 30.70 %) is strongly associated with total phosphorus ( Bray II) and sand silt content. These are the main factors that influence vegetation growth on this lava. Resumen La vegetación en el flujo de lava de 1922 del Mt. Camerún, fue estudiado entre 2001-2002 para investigar la riqueza de especies y el estado de suelo. Se encontraron 102 especies de plantas de 47 familias, incluyendo 21 especies de árboles en 13 familias, 13 arbustos pertenecientes a siete familias, 20 hierbas en 10 familias, siete trepadoras en cinco familias, 17 helechos en ocho familias, cinco briofitos, cuatro líquenes, 13 especies de orquídeas y dos en hongos. Las orquídeas representan la familia más importante de hierbas, mientras que las Rubiaceas son la familia más rica de árboles. Se encontró un total de 106 árboles con dap de 1-10 cm., y un dap medio de 6.65 cm., y un total de área basal (AB) de 1885.3 cm2. Syzygium guineense tuvo la AB más alta (769.68 cm2), la densidad relativa más alta ( 16.807 %), dominancia relativa (40.83%) y CVI (57.638%) con índice de valor de importancia (IVA) = 68.24%. Alchornea cordifolia con BA = 537.21cm2 , densidad relativa de =

- be one
%) mientras que el fósforo estuvo mas alto en el lado izquierdo ( 27.15 %) y mas bajo (19.3%), una cantidad mas alta que en suelos normales de Camerún (12 - 16%). Introduction Mt Cameroon is located in the Gulf of Guinea at the South West Province of Cameroon. Its longest axis, as shown in [[Figure 1]], about 45 km long and 30 km wide runs SW to NE between latitudes 3°57' to 4°27'N and longitudes 8°58' to 9°24'E, with the main peak at 4°7'N and 9°10'E (Tchouto, 1996 ; Suh et al., 2003 ). It is considered to be one of the most active volcanoes in Africa, having erupted eight times within the past 100 years ( 1909 , 1922 , 1925 , 1954 , 1959 , 1982 , 1999 and 2000 ). Soils on Mt Cameroon are mostly of recent age and derived from active volcanic rocks. They are generally fertile but have a poor moisture retaining capacity (Cheek, 1992 ). The soil temperature, measured at depths of 10 cm, varies from 25°C (at 200 m) through 20°C (at 1100 m) to 15°C at 2200 m above sea level (Payton, 1993 ). The region has two main seasons: a wet mm, near Ekona on the leeward side, to 9086 mm at Debundscha on the windward side of the mountain. This is the wettest place in Africa (Fraser et al., 1999 ). Mean monthly temperatures, at sea level, vary from 19°C to a maximum at 30°C during the months of March and April (Fraser et al.,

- En 1993 be because
rainfall, temperature and distance from the seacoast (Payton, Throughout the year, the temperature is between 22°C - 30°C in Debundscha at an altitude of about 20 m asl. In Idenau at 40 m asl it ranges between 20°C - 30°C (Fraser et al., 1998 ; Tchouto, 1996 ). This may be because there is a gentle breeze blowing from the sea and that the air movements are very slow, thus modifying the temperature. Cable and Cheek ( 1998 ) reported that there are no hurricanes in this region. Table 6a: Eigen-analysis of the Correlation Matrix 1922 Lava

- be as
Where C2 = sand C9 = Org. Matter (%) C16 = S/CECE (%) C3 = Total silt C10 = Tot. N (g/kg) C17 = CEC 7 C4 = Clay C11 = C/N C18 = Brays P2 (ppm) C5 = pH H2O C12 = Ca C19 = P-ret (%) C6 = pH KCl C13 = Mg C20 = Soluble Fe (g/kg) C7 = pH NaF C14 = K C21 = Liberated Fe C8 = Org. C (%) C15 = Na C22 = Amorphous Fe C23 = Amorphous Al The mean annual relative humidity, on this Southwestern flank ranges between 75 % and 80 %. Generally , the climate is of the equatorial regime covering the entire land of the Atlantic oceanic plain. Rosevear conducted the first recolonization study on lava flows on Mt Cameroon in 1936 and 1937 on the 1922 eruption, fourteen years after it occurred (cited by Keay, 1959 ). Eighty years after the eruption, it is observed that the vegetation has moved from the mosses, lichens and ferns as observed by Rosevear, to a dominant shrubby forest with 74 flowering plant species belonging to 29 families, the family Orchidaceae being the most dominant. This is in contrast with the findings of Ndam et al. ( 2002 ), who stated after a survey, conducted in 1995 , that in the third stage of succession , 90% of orchids disappear. The vegetation presently comprises of a semi- dense, forest 4-5 m tall with emergent that are 10- 25 m tall. The co-dominant trees (about 40% of all those greater than 6 cm dbh recorded, and generally the tallest of all trees present) are Syzygium guineense var . littorale and Alchornea cordifolia. Fraser et al., ( 1999 ) and Ndam, ( 2000 ) reported the presence of Syzygium guineense, during their 1995 survey. Lannea was not observed during this survey. This may be as a result of logging for fuel wood, which has already started on the lava flow (fig 5). The main trees and large shrubs, in descending order of importance (% of all trees between 1-10 cm dbh) are Syzygium guineense ( 16.81 %), Alchornea cordifolia ( 15.97 %) and Tarenna conferta ( 14.29 %). Seedlings of Tarenna conferta, in shrub surveys conducted done by Fraser et al., 1999 and Ndam et al., 2002 , were shown to dominate those of smaller woody plants. Some of the species found in the centre of the lava flow were not present on the edges. Plant diversity was higher in the centre than the edges. This may be as a result of the lava flow being surrounded by palm plantations (Elaies guineensis) and also because of the age of the lava

- En 1987 be expected
(Déreulle et al., Shannon- Weaver and Simpson's Diversity Indices show that plant diversity is high as should be expected . They are 3.58 and 22.86 respectively, higher than those determined by Ndam et al. ( 2002 ) on the same lava in 1995 ( 3.1057 and 16.4201 respectively). This shows that plant diversity has increased. The Basal Area of 0.785m2/h was far less than that observed by Ndam ( 1998 ). This may be as a result of the logging for fuel wood that is going on in the area. Species richness was highest on the edges probably because at this stage of succession , new species colonize from the edges. Thebaud and Stersberg ( 1997 ), while studying species colonization of 15, 48, 91 year old lava flows at Grand Bruté, la Reunion , observed that dispersal on the15 year old lava flow was stochastic but found that large sized plants on the old lava flows (e.g. 91 years) tended to grow from the edge at a very slow rate (less than 1 m per year). They also observed that most colonizing species are wind -dispersed. A similar observation was reported by Ndam et al., ( 2002 ) on the 1922 lava flow and by Robyns( 1932 ) in Kiva and Krakatua . This could also be due to the thickness of the

- En 1983 be
lava at the centre compared to the edges (Fitton et al. The Dendogram produced from the similarity indices shows that plants of the same species and life forms were found both on the edges and in the centre. Although the lava is chemically uniform, its structure can be variable resulting in differences in the colonization process (Bachelery,

- En 1981 be that
). Another possible reason given earlier by Robyns ( 1932 ) for these differences could be that erosion from adjacent land, deposits soil on the edges of lava flows, favouring the development of species that are not adapted to grow on the dry rock environment. This is in contrast with our findings. Species diversity is higher in the centre of the 1922 lava flow as a result of differences in the soil parameters. The amounts of organic matter and organic carbon from analyses were highest in the centre ( 19.10 and 11.10 % respectively). On the edges they were 4.07 and 7.1 % respectively. The main reason for the contrast of our findings with earlier reports may be that the lava is moving towards a more mature structure. The climatic conditions of the area could also be wielding an influence. According to Fraser et al. ( 1998 ), the area has the highest amount of rainfall in the country. This , coupled with the high temperature and humidity, leads to rapid decomposition of organic matter resulting in fast soil formation. The topography (gentle sloping and flat) and lava type (pahoe-pahoe) also influence disintegration of the surface rock and soil formation. It could be said that the successional pathway on lava flow starts with lichens and mosses, followed by a second stage characterised by the presence of all other life forms, with woody species and climbers being the least abundant or even absent. Lava Profile The profile of the lava flow is divided into 2 horizons. The topsoil is 10 cm dbh did not conform to this observation. Comparing the observed data on species composition, basal area and plant density on the lava with those of other researchers showed some differences, which may be attributed to the logging for fuelwood -already taking place there . This means that colonization may be very difficult to assess. The edaphic factors; climate (temperature between 19°C - 34°C), rainfall (between 227 - 9086 mm) and soil, play a very vital role on the plant colonization process. Also , the type and number of plant species tend to improve the nutrient level of the soil although the plants are selective to the type and amount of nutrients utilized. The soil pH is slightly acidic and tends to break down parent rock materials. Growing roots of trees also tend to break down the parent materials releasing nutrients. From our results it was found that soil texture, total Phosphorus, total Nitrogen, Organic matter, cation exchange capacity (CEC), exchangeable cations soil pH and Phosphorus retention strongly affect the plant colonization process on the lava flows of Mt Cameroon. Acknowledgements laboratory analysis were carried out), and the Limbe Botanic and Zoological Garden (who made available facilities for use during this research). References Allison, F.E. ( 1973 ). Soil Organic Matter and Its Role in Crop Production. eds. Sci Pub. Co. New York : pp 346-359, 417 - 444. Alvarado , A. et S.W. Buol 1985 . Field estimation of Phosphate retention by Andepts. Journal of the Soil Science Society of America 49: 911-914. Anderson, D.W. et D.C. Coleman 1985 . The dynamics of organic matter in grassland soils. Journal of Soil Water Conservation. 40: 211-216. Bachelery, P. 1981 . Le Piton de la Fonraise (Ile dela Peunion), Etude volcanique Structural, et pedologique. PhD dissertation University of Clement - Ferand, France . Benl, G. 1976 . Studying fern in the Cameroon: The lava ferns and their occurrence on Cameroon Mountains. Fern Gazette , 11(4): 207-215. Black, C. 1968 . Soil Plant Relationships. Wiley and Sons , New York . Blakemore, L.C.; P.L. Searle et B.K. Daly. 1981 . Soil Bureau Laboratory Methods. A Method for Chemical Analysis of Soils. W.Z. Soil bureau. Sci. Rep. 10A DSIRO, new. Blakemore, L.C.; P.L. Searle et B.K. Daly 1987 . Method for Chemical Analysis of Soils. New Zealand Soil Bureau of Science Rep . 80. Soil Bureau , Lower Hutt , New Zealand. Bullock, J. 1996 . Plants, Furzebrook Research Station, NERC Institute of Terrestrial, Wareharm, Dorset BH20 5AS, United Kingdom , In Sutherland (ed) Ecological Census Techniques. A Handbook. Cambridge University Press, pp 111-138 Cable, S. et M. Cheek. 1998 . The Plants of Mt Cameroon -A Conservation Check List. RBG Kew , London . pp 19 Cheek, M. 1992 . A Botanical Inventory of Mabeta-Moliwe Forest . Report to ODA/MCP, Royal Botanic Gardens, Kew , Britain. pp 122. Cottenie, A.; L. Kiekens; M. Verloo; G. Velghe et R. Camerlynck. 1982 ). Chemical Analysis of Soils and Plants . Ghent . Belgium. 40pp. De Coninck, F. 1978 . Physico-chemical Aspects of Pedogenesis. ITC, State University, Gent , Belgium Déruelle, B.; C. Moreau et N. Nkonguin. 1983 . Sur la récente eruption du Mount Cameroon . C.r. Academic Science. Paris Série II 296(2) 807-812. Déruelle, B.; J. N'ni et R. Kambou. 1987 . Mount Cameroon : an active volcano of the Cameroon line. Journal of African Earth Science. 6(2): 197- 214. FAO-UNDP/ IRA -Ekona. 1977 . Soils and soil fertility management of the lands of Ekona banana estate. CDC Technical Report. Ekona, Cameroon, pp 84. FAO-UNDP/ IRA -Ekona. 1989 . Soil survey and land evaluation of Ekona banana estate. CDC Technical Report. Ekona, Cameroon, pp 170. Fitton, J.G.; C.R.J. Kilburn; M.F. Thirlwall et D.J. Hughes. 1983 . 1982 Eruption of Mount Cameroon , West Africa . Nature 306/5941: 327-332 Fowler, J.; L. Cohen et P. Jarvis. 1998 . Practical statistics for field biology 2nd Ed. Open University Press, England . Pp 259

- ens di
N Co Form of o de dispersa l Convolvulace 1 ae Ipomoea batatas (L.) Lam. Ip Clim Animal ba ber Convolvulace 2 ae Ipomoea involucrata P. Beauv. Ip Clim Animal in ber Convolvulace 3 3 ae Ipomoea sp. Ip Clim Animal sp ber Dilleniaceae 1 4 Tetracera alnifolia Willd. Te Clim Animal ae ber Leeaceae 1 5 Leea guineensis G. Don Le Clim Animal qu ber Passiflorace 1 6 ae Adenia lobata (Jacq.) Engl. Ad Clim Wind lo ber Rubiaceae 8 7 Mussaenda tenuiflora Benth. Mu Clim Wind te ber Aspleniaceae 1 8 Asplenium barteri Hook . As Fern Wind ba Dryopteridac 1 9 eae Ctenitis dimidiata (Mett. Ex Ct Fern Wind Kuhn)Tardieu di Hymenophylla 10 ceae Trichomanes africanum Christ. Tr Fern Wind af Hymenophylla 2 11 ceae Trichomanes borbonicum Bosch Tr Fern Wind bu Oleandraceae 12 Arthropteris cameroonensis Alston Ar Fern Wind ca Oleandraceae 13 Nephrolepis biserrata (Sw.) Ne Fern Wind Schott bi Oleandraceae 4 14 Nephrolepis cordiflora Ne Fern Wind co Oleandraceae 15 Nephrolepis pumicicola Ballard Ne Fern Wind pu Ophioglossac 16 eae Ophioglossum reticulatum L. Op Fern Wind re Polypodiacea 4 17 e Anapeltis lycopodioides (L.) An Fern Wind J.Sm. ly Polypodiacea 18 e Microgramma owariensis (Desv.) Mi Fern Wind Alston ow Polypodiacea 19 e Microsorum punctatum (L.) Copel. Mi Fern Wind pu Polypodiacea 20 e Microsorum scolopendria Mi Fern Wind (Burm.f.)Copel sc Selaginellac 1 21 eae Selaginella sp. Se Fern Wind sp Vittariaceae 22 Antrophyum mannianum Hook . An Fern Wind ma Vittariaceae 3 23 Loxogramme abyssinica Lo Fern Wind (Baker)M.G.Price ab Vittariaceae 24 Loxogramme lanceolata(Sw.)C.Presl Lo Fern Wind la Fungi 25 Unidentified 0 Fung Wind i Fungi 2 26 Unidentified 0 Fung Wind i Commelinacea 1 27 e Commelina diffusa Burm.f. Co Herb Animal di Compositae 28 Chromolaena odorata (L.)R.M. King Ch Herb Wind etH.Robinson od Compositae 29 Crassocephalum crepidioides Cr Herb Wind (Benth.) S.Moore cr Compositae 30 Emilia coccinea ( Sims .)G. Don Em Herb Wind co Compositae 5 31 Melanthera scandens (Schumach.et Me Herb Wind Thonn.)Roberty sc Compositae/A 32 steraceae Ageratum conyzoides L. Ag Herb Wind co Cyperaceae 1 33 Mariscus alternifolius Sensu Ma Herb Animal Hooper al Euphorbiacea 5 34 e Phyllanthus amarus Schumach. et Ph Herb Animal Thonn. am Fabaceae 3 35 Pueraria phaseolioides (Roxb) Pu Herb Animal Benth. ph Fabaceae 2 36 Centrosema virginiana (L.) Benth. Ce Herb Animal vi Gramineae 5 37 Hyparrhenia rufa (Nees) Stapf. Hy Herb Wind ru Gramineae 38 Panicum maximum Jacq. Pa Herb Wind ma Gramineae 39 Paspalum conjugatum Berg Pa Herb Wind co Gramineae 40 Pennisetum hordeoides (Lam.) Pe Herb Wind Steud. ho Gramineae/Po 41 aceae Axonopus compressus (Sw.) P. Ax Herb Wind Beauv. ca Labiatae/Lam 42 iaceae Solenostemon monostachyus So Herb Wind (P.Beauv.) Briq. mo Marantaceae 1 43 Megaphrynium macrostachyum Me Herb Animal (Benth.) Milne-Redh. ma Melastomatac 44 eae Dissotis rotundifolia(Sm.)Triana Di Herb Animal ro Piperaceae 1 45 Piper umbellatum L. Pi Herb Animal um Rubiaceae 46 Diodia sarmentosa Sw. Di Herb Animal sa Lichens 47 Coccocarpia sp. Co Lich Wind sp ens Lichens 48 Dictyonema sp. Di Lich Wind sp ens Lichens 49 Leptogium sp. Le Lich Wind sp ens Lichens 4 50 Parmelia laevigata Pa Lich Wind la ens Musci 51 Campylopus dusenii C.M Ca Moss Wind du Musci 52 Campylopus horridus Welw.etDuby Ca Moss Wind ho Musci 53 Ectropothecium afro-molluscum Ec Moss Wind (C.M) Broth.Keay mu Musci 54 Ectropothecium regulare Ec Moss Wind (Brid.)Jaeg re Musci 5 55 Sematophyllum calspitosum (Sw) Se Moss Wind Mitt Sensu lato H.n.Dixon ca Orchidaceae 56 Ancistrochilus rothschildianus An Orch Wind O' Brien ro id Orchidaceae 57 Ancistrorhynchus cephelotes An Orch Wind ce id Orchidaceae 58 Angraecum birrimense Rolfe An Orch Wind bi id Orchidaceae 59 Bulbophyllum bifarium Hook.f. Bu Orch Wind bi id Orchidaceae 60 Bulbophyllum calvum Summerh Bu Orch Wind ca id Orchidaceae 61 Bulbophyllum calyptratum Kraenzl. Bu Orch Wind ca id Orchidaceae 62 Bulbophyllum intertextum Lindl. Bu Orch Wind in id Orchidaceae 63 Bulbophyllum josephii (Kuntze) Bu Orch Wind Summerh. var . josephii jo id Orchidaceae 64 Bulbophyllum simonii Summerh. Bu Orch Wind si id Orchidaceae 1 65 Hebenaria sp. 3 He Orch Wind sp id Orchidaceae 66 Polystachya affinis Lindl. Po Orch Wind af id Orchidaceae 67 Polystachya tessellata Lindl. Po Orch Wind te id Orchidaceae 68 Polystachya laxiflora Lindl. Po Orch Wind Costaceae 1 69 Costus afer Ker Gawl . Co Shru Animal af b Euphorbiacea 70 e Croton gratissimus Burch. cr Shru Animal hi b Guttiferae/C 71 lusiaceae Psorospermum staudtii Engl. Ps Shru Wind st b Malavaceae 1 72 Urena lobata L. Ur Shru Animal lo b Melastomatac 73 eae Dissotis erecta (Guill. et Di Shru Animal Perr.)Dandy er b Melastomatac 3 74 eae Tristemma hirtum P.Beauv. Tr Shru Animal hi b Mimosoidae 75 Mimosa pudica L. Mi Shru Animal pu b Rubiaceae 76 Hymenodictyon biafranum Hiern Hy Shru Wind bi b Rubiaceae 77 Oldenlandia lancifolia Ol Shru Animal (Schumach.) DC . la b Rubiaceae 78 Pauridiantha venusta N.Halle Pa Shru Animal ve b Rubiaceae 79 Tarenna conferta (Benth.)Hiern Ta Shru Animal co b Rubiaceae 80 Tarenna sp. Ta Shru Animal sp b Rubiaceae 81 Tricalysia discolor Brenan Tr Shru Animal di b Anacardiacea 1 82 e Magifera indica L. Ma Tree Animal in Apocynaceae 1 83 Alstonia boonei De Wild. Al Tree Animal bo Cecropiaceae 84 Cecropia cecropioides Ce Tree Animal ce Cecropiaceae 85 Cecropia peltata Ce Tree Animal pe Cecropiaceae 3 86 Musanga cecropioides R.Br. ex Mu Tree Animal Tedlie ce Celastraceae 1 87 Maytenus sp. Ma Tree Animal sp Ericaceae 1 88 Agauria salicifolia (Comm.ex Ag Tree Animal Lam.)Hook.f.ex Oliv. sa Euphorbiacea 89 e Alchornea cordifolia (Schum. $ Al Tree Animal Thonn.)Mull.Arg. co Euphorbiacea 90 e Bridelia micrantha Br Tree Animal (Hochst.)Baill. mi Euphorbiacea 91 e Macaranga occidentalis Ma Tree Animal (Mull.Arg.)Mull.Arg. oc Fabaceae 92 Desmodium adscendens (Sw.) DC . De Tree Animal var.adscendens ad Guttiferae/C 2 93 lusiaceae Harungana madagascariensis Lam. Ha Tree Bird Ex Poir. ma Mimosaceae 94 Albizia zygia ( DC .)J.F.Macbr. Al Tree Wind zy Moraceae 3 95 Ficus conraui Warb. Fi Tree Animal/B co ird Moraceae 96 Ficus lutea Vahl Fi Tree Animal/B Moraceae 97 Ficus sur Forssk. Fi Tree Animal/B su ird Myrtaceae 3 98 Psidium guajava L. Ps Tree Animal qu Myrtaceae 99 Syzygium guineense (Wild.) DC Sy Tree Animal gu Myrtaceae 10 Syzygium sp. Sy Tree Animal 0 sp Palmae 1 10 Elaies guineensis Jacq. El Tree Animal/R 1 gu odents Ulmaceae 1 10 Trema orientalis (L.)Blume Tr Tree Animal 2 or

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71: Nye, P.H. 1961 . Organic and nutrient cycles under a moist tropical forest. Plant and Soil 13: 33-346. Payton, R.W. 1993 . Ecology, Altitudinal Zonation and Conservation of Tropical Rainforest of Mount Cameroon . Final Project - Report R4600 , ODA , London Robyns, W. 1932 . La Colonization Vegetale des Laves Recentes du Vocan Rumoka (Laves de katerujzi). Inst. Roy. Col. Belge, sed. Sci Nat . Med mem, in 8°1(1): 34pp. Sanchez, A.P. 1976 . Properties and Management of Soils in the Tropics. John Wiley and Sons. pp 135-159. Suh, C.E.; S.N. Ayonghe et E.S. Njumbe 2001 . Neotectonic Earth Movements Related to the 1999 Eruption of Cameroon Mountain, West Africa . Episodes 24:9-13 Suh, C.E.; R.S.J. Sparks ; J.G. Fitton; S.N. Ayonghe; C. Annen; R. Nana et A. Luckman 2003 . The 1999 and 2000 Eruptions of Mount Cameroon ; Eruption Behaviour and Petrochemisty of Lava. Bulletin of Volcanicity 65:267-281. Tchouto, P. 1996 . Forest Inventory Report of the Proposed Etinde Rainforest Reserve. Mount Cameroon Project , S.W.P. Cameroon. Thébaud, C. et D. Strasberg 1997 . Plant Dispersal in Fragmented Landscapes: A Field Study of Woody Colonization in Rainforest Remnants of the Mascarene Archipelago. In: Laurence, W.F. et R.O. Bierregaard (eds) Tropical Forest Remnants: Ecological, Management and Conservation of fragment communities. University of Chicago Press, Chicago . Pp 321 -332. Tisadale, L.S.; L.N. Werner et D.B. James 1985 . Soil Fertility And fertilizers. Mac Pub. Co; USA . 754p. Uehara, G. et G.P. Gillman 1981 . The mineralogy, Chemistry, Physics of Tropical Soils with Variable Charge Clays . Westview Press. Boulder , Colorado , 170p. Wada, K. 1977 . Allophane and Imogolite . In: J.B. Dixon et S.B Weed (eds). Minerals in soil environment. Soil Sci. Soc. Amer. Madison, Wiscosin. pp 60 -638. Wada, K. et N. Gunjigake 1981 . Active Aluminium, Iron and Phosphate Adsorption in Andosols. Soil Science 128: 331-336. Wilson, E.O. 1992 . The Diversity Of life - Allen Lava . The Penguin Press . pp 424.