The Ecology of Hydric Hammocks - USGS National Wetlands ...

hammocks and in loblolly pine-domi -natd hammnrkq. Cr27i179 hy cattle nrferal hogs can greatly influence theplant species composition of hydrichammock. Hogs avidly consume mast,infl uenci ng oak regenerati on, andtheir rooting for tubers, roots, andsmall invertebrates severely disturbsthe soil. Cattle compact the soil andreduce browse and groundcover vegetation,including hardwood regeneration(Figure 37). Where cattle density ishigh. hydric hammock may resemble amanicured lawn with an occasional tree(often live oak). The dominance ofcabbage palm and live oak in some hydrichammocks, for example the OrangeLake forest, probably is perpetuatedby preferential consumption of hardwoodseedlings and saplings by grazers.The major natural disturbances inhydric hammocks are floodins. fire,grazing, and wind. Browsing by nativewild3 ife. main1 v deer, influences theabundance and composition of groundcover,tree seedl ings, and shrub vegetation.Gaps from fallen trees arefound in all hydric hammocks, but theyare especial ly common in coastal areasvulnerable to hurricanes (Figure 38).Succession, whether on naturallycleared or on harvested sites, has notbeen documented in hydri c hammocks.However. some trends can be predictedbased upon species differences inshade to1 erance, re1 ati ve growth rate,longevity, requirements for seed1 ingestabl ishment, and ability to sproutfollowing disturbance (Putnam et a?.1960; Fowells 1965; McKnight et a7.1981). The composition of the regeneratingforest is affected by a numberof factors including the type, severity,and extent of disturbance, thecomposition of the pre-disturbanceFigure 37. A grazing exclosure in Gulf Hammock demonstrates the effects of cattle and deer on theground cover of hydric hammock. Wood fern is a predominant species both inside and outside theexclosure, but its height is greatly reduced by grazers.