Comparative growth performance of different Casuarina species and provenance at Lushoto in the West Usambara mountains, Tanzania

Abstract

Variation in growth charactristics, coppicing ability and understory vegetation development was assessed in four Casuarina species (C. equisetifolia, C. junghuhniana, C. cunnighamiana and C. oligodon) grown in Lushoto in the West Usambara Mountains (WUM), Tanzania. The performance of the four species as well as of 12 provenances, including 5 landraces within some of the species was studied. Tree survival was assessed at 36 months; stem height, diameter at breast height (dbh), volume, biomass, cop pieing ability and understorey vegetation development were assessed at 78 months. Survival was significantly lower in C. equisetifolia (79%) than in other species (>97%). There were significant differences in growth between species, with C. junghuhniana and C. oligodon outperforming the others, and C. cunnighamiana outyielding C. equisetifolia. Only C.junghuhniana and C. cunnighamiana coppiced, while understorey biomass was significantly higher under C. equisetifolia than under C. oligodon. There were significant differences in growth between provenances within species, with growth of new provenances often exceeding that of the local land races. The potential for fuel wood production and soil N-enrichment through foliage addition also exhibited inter-specific and intra-specific variation. There is great opportunity to significantly improve the productivity, and at the same time broaden the genetic base of Casuarinas through species and provenance selection for planting in the highland areas of the WUM. However, while exploiting the productive potential of Casuarinas, there is need to build sufficient information regarding their side effects on conservation of natural ecosystems, and local community's views on how to minimise the problem.