Basic and Applied Ecology vol:15 issue:4 pages:288-296
Tree species regeneration determines future forest composition and dynamics, but is often severely hampered in forest relicts. To study succession, long-term studies or simulation models are used but data, knowledge or resources to run such models are often scarce in remote areas or developing countries. We propose and implement a regional and a local species accounting equation which parameters can be derived from a single inventory and include the co-occurring events extinction, colonization and recruitment. To parameterize the species accounting equations, we compared the tree species presence among the seedling, sapling and mature tree layer of 82 plots in 12 remaining Afromontane cloud forest relicts in Taita Hills, Kenya. A simultaneous ordination of the seedling, sapling and mature tree layer data revealed that species extinctions, colonizations and recruitments initiated species shifts. A potential extinction debt of 9 % of the species pool was found in all the remaining forest relicts. Surprisingly, the smallest forest relicts harboured an important component of the tree species diversity, but rather in the regeneration layer than in the mature tree layer. In some forest relicts, up to 30 % of the species pool was only present as persistent seedling or sapling, which we defined as potential recruitment credit. The extinction rates were larger than the recruitment rates, which could result in a future species richness decline of 17 % and 34 % of the small and large forest relicts, respectively. The regional and the local species accounting equations provide a time and resource effective tool and give an improved understanding of the conservation status and possible future succession dynamics of forest relicts, which can be particularly useful in a context of participatory monitoring.