Local positive feedback and the persistence and recovery of fringe Avicennia marina (Forssk.) Vierh. mangroves
Huisman, T.J. ; Langevelde, F. van; Boer, W.F. de - \ 2009
Wetlands Ecology and Management 17 (2009)6. - ISSN 0923-4861 - p. 601 - 611.
early-life history - early growth - ecosystems - restoration - australia - establishment - regeneration - propagules - patterns - forests
While mangrove restoration efforts are reasonably successful, failure often occurs in high wave energy situations. Due to differences in wave energy, seedling mortality rates vary strongly with position on the intertidal flat between high water spring and high water neap elevations. However, a local positive feedback can be present between the pneumatophores of adult mangroves and the survival of mangrove seedlings to trigger recovery. In this study, a mangrove population of Avicennia marina is modelled to determine the effects of seedling mortality and local positive feedback on mangrove recovery. The model uses life history data and dispersal to simulate population dynamics. The mangrove range limits are determined by high water spring and high water neap levels. The results indicate that within these limits mangrove populations with life-history parameter values as derived from literature are indeed capable of fast growth under conditions with low seedling mortality. Local positive feedback has then a small positive influence on population recovery after mangrove loss. If, however, mortality rates increase, such as in high wave energy situations, the importance of a positive feedback increases. The model shows that a positive feedback may, given high seedling mortality rates, be an important factor for mangrove recovery. While a positive feedback may enable mangrove persistence in unfavourable conditions, destruction of adult mangroves can remove the positive feedback, which would render the system uninhabitable and practically prohibits reforestation of such areas. The model results and the presence of positive feedbacks and their importance for population dynamics in harsh conditions indicate that investigating and understanding possible feedbacks could be crucial for successful restoration efforts
Differences in regeneration between hurricane damaged and clear-cut mangrove stands 25 years after clearing
Ferwerda, J.G. ; Ketner, P. ; McGuiness, K.A. - \ 2007
Hydrobiologia 591 (2007)1. - ISSN 0018-8158 - p. 35 - 45.
marina forsk vierh - avicennia-marina - rhizophora-apiculata - natural regeneration - seedling growth - predation - forest - salinity - establishment - propagules
The effect of human disturbance on mangrove forest may be substantially different from the effects of natural disturbances. This paper describes differences in vegetation composition and structure of five vegetation types in two mangrove areas near Darwin, Australia, 25 years after disturbance. The vegetation in clear-felled forest showed more adult Avicennia marina than in the hurricane-affected forest, and a virtual absence of A. marina juveniles and saplings. This indicates that A. marina will be replaced by other species in the canopy, showing a multi-phase vegetation development in mangrove forest after human disturbance. The mechanism of disturbance and the conditions after clearing therefore affects the vegetation composition for at least 25 years after this disturbance took place.