干旱区生态环境知识资源中心

Calorific values of six indigenous species and four exotics were determined for components such as stump, main stem, tree top, branches, foliage and bark. Tree species selected were: Acacia nilotica, Azadirachta indica, Casuarina equisetifolia, Dalbergia sissoo, Prosopis cineraria, Zizyphus mauritiana (all indigenous); Acacia auriculiformis, A. tortilis, Eucalyptus camaldulensis and E. tereticornis (all exotics). Studies indicated that indigenous tree species are better suited as fuelwood species as they contain high-density wood, low ash content and low nitrogen percentage. The most promising species were A. nilotica, C. equisetifolia and Z. mauritiana. The tree components among the groups (indigenous and exotics) and within the species differed very significantly (P < 0.01) in calorific values. The calorific means ranged from 18.7 to 21.77 MJ/kg for the indigenous tree species, and 16.3 to 20.0 MJ/kg for the exotic tree species. The fuelwood value index (FVI) was also worked out, taking into account the calorific value and density of the wood as positive characteristics, and high water content and high ash content as negative characteristics. It was observed that the FVI of the indigenous tree species was high.