Estudo da vegetação e da herbivoria através da instalação de quadrículas definitivas na Reserva Especial de Maputo

Abstract

This study of the impact of elephants on vegetation was carried out between January and April 1999 in the Maputo Special Reserve. Its objectives were to install study units that are the definitive grids, describe the specific composition, its biomass and cover, study the interaction between elephants and vegetation, quantify the damage caused and create a database for future comparisons on the effect of herbivory on vegetation. Twelve squares with dimensions ranging from 386 to 455m2 were installed in the study area. In the 12 squares, herbaceous and woody species were identified, based on these species, the specific woody and herbaceous composition was determined. The determination of woody biomass was made based on the formulas from heights and diameters at breast height, having obtained greater woody biomass in the sandy forest. Using the “Point intercept” method, it was possible to determine the specific herbaceous composition of the different squares in the two vegetation communities. Six squares of 20X20m are sufficient to obtain the specific wooly and herbaceous composition representative of each vegetation community. In the two vegetation communities the sandy forest had 95 woody species and 49 herbaceous species; and the western sandy forest mosaic had 107 woody species and 83 herbaceous species. The forest mosaic had an average density of 9224 trees per hectare and the sandy forest 8454 trees. The woody plant biomass of the two vegetation communities does not differ significantly, being approximately 56 ton/ha in the sandy forest and 32 ton/ha in the western sandy forest mosaic. The contribution of herbaceous species in the different grids in the two vegetation communities is different, having presented 51,870g/m2 of biomass in the sandy forest and 84,386g/m2 in the western sandy forest mosaic.

. The percentage of woody vegetation cover in the two vegetation communities does not differ, it is 350% in the forest and 358% in the mosaic. The western forest mosaic is the site that registered high damage compared to the sandy forest, however no differences were observed between the two communities. Thus, at a significance level of 5%, the initial hypothesis that the damage caused by elephant herbivory is greater in the sandy forest than in the western sandy forest mosaic was rejected. The initial hypothesis was proved that the damage is greater in the squares that are located in the vicinity of water sources. No significant differences were found between the amount of feces found in the two vegetation communities, so the sandy forest and the sandy forest mosaic showed the same preference for the elephant. Out of a total of 4492 trees identified in the twelve (12) squares, fifty (50) were damaged. Elephant damage to the vegetation of the Maputo Special Reserve is low in the order of 1.10% and more localized in branches and aged between 1 to 2 years and greater than 2 years, it can be assumed that the carrying capacity has not yet been achieved. .