DOI: 10.5751/es-01206-090211
¤ Open Access
Using the Species–Area Relationship to Set Baseline Targets for Conservation
This paper demonstrates how the power form of the Species-Area Relationship (SAR) can be used to set conservation targets for land classes using biodiversity survey data. The log-transformation of the power model is a straight line; therefore, if one knows the average number of species recorded per survey site and can estimate the true species number present in the land class, using EstimateS software, it is possible to calculate the slope of the curve, or z-value. The z-value is the exponent in the power model and it can then be used to estimate the proportion of area required to represent a given proportion of species present in any land class. This application of the SAR is explored using phytosociological releve data from South Africa's Succulent Karoo biome. We also provide suggestions for extrapolating the estimated z-values to other land classes within a bioregion that lack sufficient survey data, using the relationship between z-values and remotely determined landscape variables such as habitat diversity (topographic diversity) and geographic location (latitude and longitude). The SAR predicts that for most Succulent Karoo vegetation types a conservation target of 10% of the land area would not be sufficient to conserve the majority of species. We also demonstrate that not all land classes are equal from a plant biodiversity perspective, so applying one target to all land classes in a region will lead to significant gaps and inefficiencies in any reserve network based on this universal target.
DOI: 10.4312/dela.41.10.183-201
¤ Open Access
Tafoni – predstavitev značilnosti reliefne oblike
V članku so predstavljeni tafoni in alveole, plitve vdolbine v skalah in skalnatih stenah. Pojavljajo se v različnih podnebjih in kamninah, nastali naj bi z votlinastim preperevanjem. V slovenski geografski literaturi zasledimo pojem tafon redko, samo v povezavi z drugo reliefno obliko – spodmoli. Namen članka je na podlagi obstoječe tuje literature predstaviti glavne značilnosti tafonov, vpeljati nekaj novih pojmov, predstaviti dileme v zvezi z njimi in opredeliti razlike s spodmoli.