Ecology and Development Series No. 10, 2003 - ZEF

Impacts of human use on the forest vegetationTable 5.11. Differences in basal area among the forest categories, using paired t-test.Levels of significance denoted by * = P < 0.05, ** = P < 0.01, *** = P < 0.001and NS = no significant difference.1 2 3 4 5Mean BA (m 2 /ha) 46.2 37.6 43.4 27 231 NATFOR2 SECFOR NS3 SEMIFOR-NEW NS NS4 SEMIFOR-OLD * NS *5 SEMIFOR-PLAN ** ** ** NSFrom the managed forest categories, the BA of the SEMIFOR-NEW is notsignificantly different from that of the undisturbed forests, i.e., the NATFOR and theSECFOR (Table 5.11; P > 0.05). In absolute figures, the mean BA of SEMIFOR-NEW iseven higher than that of SECFOR. The BA of the SEMIFOR-PLAN is highly significantlydifferent from that of the other forest categories except for the SEMIFOR-OLD, while theBA for SEMIFOR-OLD is significantly different from that of the NATFOR andSEMIFOR-NEW, but not significantly different from the SECFOR. Two of the managedforests, the SEMIFOR-OLD and the SEMIFOR-PLAN, had quite lower BA compared tothe undisturbed forests and the SEMIFOR-NEW.5.4 DiscussionSimplification of ecosystems is a typical characteristic of ecological modification by humanbeings (Western 2001). Through simplification of a complex ecosystem, people maximizeproduction of a specific utility in the ecosystem. The current study on Yayu forest revealsthat managing forests for coffee production has changed several vegetation characteristics.The changes are grouped into three and discussed in this section. The three majordifferences observed among the different forests categories are in: (a) species diversity andcomposition; (b) population structure of the retained plant species and (c) structure of theforest as a whole.90