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The dynamics of the ecosystem structure over time will be used to determine the character and importance the ecosystem functions such as herbivory. Structural development of the vegetation and herbivory are an easy tools for evaluation the maturity of the ecosystem. The objective of this study was to determine how vegetation structure and herbivory as regulatory function change as ecosystems develop with age. The study was conducted in a restricted silvofishery zone managed by resort forest stakeholder (RPH) Poponcol, Perhutani Unit III West Java in Subang, from January to December 2011. Within this area can be found Rhizophora sp. mangrove stands which have been purposely planted so that their ages are known with certainty. Comparisons were made among five stands of different ages, stands planted in 2007 (4 years), 1999 (12 years), 1990 (21 years), 1982 (29 years), and 1973 (38 years). Structural parameters (tree density, height, DBH (diameter at breast height) and biomass) were observed in three plots measuring 10 m x 10 m in each age stand. While herbivory were recorded through direct observation. We found that vegetation structure differed among stand ages (P <0.05). At the youngest stand (4 years), average tree height measured 1.56±0.33 meters, DBH 2.92±0.23 cm,, and biomass 1.45 kg m-2; whereas at the oldest stand (38 years), average height measured 8.13±5.65 meters, DBH 16.29±7.23 cm, and biomass 108.62 kg m-2. The highest tree density was found at age 4 years (800 trees ha-1) and the lowest at age 29 years (333 trees ha-1). On the other hand, stand age had no effect on the level of insect herbivory (P> 0.05). Lowest herbivory levels were observed in age 4 years (7.4%) and highest in 12 years (11.3%). The general conclusion of this study is that planting age (as substitute for time) affected the complexity of certain parameters of ecosystem structure and ecosystem function. Vegetation structure varied among stands with indication of increasing complexity with age, whereas herbivory did not show a clear pattern among stands. Results indicate complex relationship patterns which are not always obvious proportional, especially for herbivory as a regulatory functional parameters.
Keywords : structure, vegetation, herbivory, mangrove, Rhizophora |
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