资源环境科技发展态势分析平台

Concerns exist over the continual decline of marula trees (Sclerocarya birrea subsp. caffra), a large ecologically and economically important tree species in southern Africa, primarily as a consequence of impact by African elephants (Loxodonta africana) and poor regeneration. We assessed changes to marula tree population structure in a protected area that was only recently opened to elephants. Jejane Private Nature Reserve (JPNR) has been subjected to elephants from the Greater Kruger National Park (Greater KNP) since 2013, as it was fenced off beforehand. A previous survey of the marula population in JPNR was done in 2009 and again in 2016. Therefore this study aimed to (i) assess elephant-induced impact and mortality levels on the previously surveyed JPNR marula tree population, (ii) compare these levels with previously recorded impact and mortality levels on marula trees across the Greater KNP, and (iii) assess manila seed predation and seedling recruitment in JPNR. The resurveyed marula population had declined by 23.8% post-elephant movement into JPNR, with the highest annual mortality rates (AMR) and elephant impact scores for trees in the 5-8 m height class. The JPNR marula tree AMR of 8.1% was higher than that of Greater KNP (4.6%). Only two marula seedlings were found across all transects, whilst 84.2% of all endocarps' locules had seeds missing, with bite marks present on 42.3% of all endocarps. This suggests potential high levels of seed predation and a lack of seedling recruitment. The concern over the impact by elephants on adult marula trees is therefore escalated as a consequence of the lack of regeneration, primarily because of seed and seedling predation. Management policies should be focused on protection methods for individual trees, seedlings and seeds, together with a large scale artificial surface water management plan to manipulate herbivore densities and pressures on marula tree populations. (C) 2017 Elsevier B.V. All rights reserved.