|Role of folivory in mangrove ecosystem functioning - identifying the key functional group|
Nguyen, T.T. (2014). Role of folivory in mangrove ecosystem functioning - identifying the key functional group. MSc Thesis. VUB/ULB/Universiteit Gent/Universiteit Antwerpen: Brussel, Gent, Antwerpen. 16, 67 pp.
Herbivory in general and folivory in particular is normally underestimated in mangroves. The aim of this study is to assess the role of folivory in mangrove ecosystem functioning by estimating level of folivory and identifying the key functional feeding guild. Leaf samples of fourteen mangrove species were taken from three study sites in two mangrove bio-geographical regions (USA and South Africa as the subtropical regions and Sri Lanka as the tropical area). Level of folivory is expressed as the percentage of damaged leaves and percentage of leaf area loss, which were estimated by visual observation and using ImageJ software. Six feeding guilds were identified by comparing with references. A number of statistical tests such as Kruskal-Wallis, Wilcox, t-test, Wald’s test were applied to the percentage of leaves damaged and leaf area loss data in order to see whether there is a significant difference in folivory rate between sites, feeding guilds and mangrove species. The results show that there is approximately 50% of leaves were attacked by folivores and roughly 2.8% leaf area was lost due to folivory in all study areas. Leaf chewers are detected as a dominant feeding guild with the presence in a majority of damage (about 70%). Among all mangrove species, Laguncularia racemosa suffers the highest destruction with 91.3% of the attacked leaves and an average 11.3% leaf area loss while Excoecaria agallocha, in contrast, suffers the least from folivory with an average of 20% damaged leaves and 0.3% area loss. Since the amount of leaf fall can affect the quantity as well as the quality of material that is transferred to marine environment, the fact that 50% of leaves were attacked demonstrated that folivory plays a crucial role in the ecosystem functioning of mangroves by utilizing above-ground production. Studies in a longer period of time are recommended to assess long term effect of folivory.