Comparisons between original and current composition of indigenous tree species around Mount Kenya

摘要

As the ecology and distribution of most tree species remain poorly understood, biogeographical maps offer spatial surrogates for analysis of biodiversity patterns. We used a 1 : 250,000 potential natural vegetation map to compare the current indigenous tree species composition of 250 0.5-ha quadrats surveyed around Mount Kenya (1999-2004) with the original species composition of ten potential natural vegetation types (PNVTs). The original 1960 vegetation map was based on intensive fieldwork and detailed aerial photographs by Trapnell et al. For each PNVT, we compiled original species lists from literature and herbarium voucher information. The percentage of species that overlap between the current list and the original list ranged from 30% to 75% for seven frequent PNVTs, but was only above 45% for dry Combretum savanna (DC). When only investigating the six to ten species with highest frequencies, these species were shared 70-100% for the four forest PNVTs, 90% for lowland Acacia-Commiphora, 67% for evergreen and semi-evergreen bushland and 50% for DC savanna. To promote agroecosystem diversification, ecological and socio-economic reasons for low current frequencies of most indigenous tree species need to be better understood.