The early colonizers of desert soils
1 The early colonizers : Some of the early colonizers including small ephemerals include: Polygala erioptera DC.; Polycarpaea corymbosa (L.) Lamk. ; Gisekia phamacioides L ; Mollugo cerviana (L.) Ser. ; Side ovals Forsk. ; Corchorus tridens L. ; Triumfetta pentandra A. Rick. ; Indigofera essiliflora DC. ; I. linnaei Ali. These plant species have their value as initial colonizer and are not suitable as biomass resource because" their yield potential is very low. These early colonizers provide helpful association for any subsequent plant to come in the succession like Artemisia scoparia Waldst. ; Farsetia hamiltonii Royle. ; Tephrosia purpurea (L.) Pers ; Citrullus colocynthis (L.) Schrad.; Boerhavia diffuse L. and other herbs. Among the shrub species which came in the next season Leptadenia pyrotechnica (Forsk.) Decene.; Calotropis procera (Ait.) RBr.; Side cordifolia L. ; Crotalaria burhia Buch. - Ham. ; Verbesina encelioides (Cav.) Benth. & Hook. and grass Saccharum munja L. were abundant. In the second year of growth the tree species became dominant and undergrowth diminished to some species. The important tree species included Acacia torti/is (Forsk.) Hayne. ; Acacia nilotica (L.) Wind.ex. Del. ; Leucaena /eucocephala (Lam.) de WItt. ; Acacia senega/ (L.) Willd.; Prosopis chi/ensis Stuntz.. 3.2 Initial association: Initial plant formed association and appeared to benefit with each other. These association included Calotropis procera (Ait) RBr. with nitrogen fixing Crotalaria burhia Buch-Ham. Besides this at a later stage the nitrogen fixing Tephrosia purpurea (L.) Pers. was largely predominant with other plant like Verbesina encelioides (Cav.) Benth. & Hook. Artemisia scoparia, Waldst; Sericostoma pauciflorum stock; Sida corditolia L.; Crota/aria burhia Buch.-Ham.; Boerhavia diffuse L. The biomass productivity ranged from 0.5 tonnes per ha. (Citrullus colocynthis), to 52 tonnes dry matter per he. per annum (Saccharum munja). A combination of these plant could be used to form a three tier system to colonize the wasteland and get productive biomass as an alternative model to the hydrocarbon yielding plants (6). 3.3 Some other association: Boemavia diffuse, Citrullus colocynthis, Artemisia scoparia largely cover the ground throughout the year due. to their xerophytic adaptation make good association with these plants R. purpurea, V. encelioides, S. pauciflorum, C. bilmia, C. bonplandium, S. cordifolia, H. marifolium, P. angustifolia, P. corymbosa, E. hirta.