CHAPTER 5. FAUNA OF BOTTOMLAND HARDWOOD ZONES 



Bottomland hardwood forests support a 

 diverse fauna that matches the floristic 

 and hydrologic complexity which is so 

 characteristic of these communities. The 

 moisture gradient and hydroperiods of 

 floodplains provide a habitat continuum 

 for a wide range of aquatic to terrestrial 

 to aerial species. The fauna is here also 

 treated within the zonal concept. Because 

 of the large numbers of taxa, only abun- 

 dant or dominant animals or groups can be 

 mentioned. (For further information, see 

 Wharton et al. 1981.) Some overlap among 

 zones occurs, especially between Zones IV 

 and V, which share many species. The 

 mobility of many species and their over- 

 lapping distribution in response to vary- 

 ing environmental regimes make combining 

 discussions of faunal assemblages in Zones 

 II and III useful. It should be recog- 

 nized that placing an animal in one or 

 even two zones does not necessarily 

 restrict it to these areas. Floodplain 

 inhabitants are opportunists, and many 

 move freely into irregularly flooded or 

 dry areas over the year. 



FAUNA OF ZONES II AND III 



Invertebrates 



Given the diversity of vegetational 

 dominance types in Zone II, it is not sur- 

 prising to find that faunal components 

 also vary. In terms of fauna, the environ- 

 ment of a tupelo gum-cypress forest with 

 hydroperiods approaching a year is mark- 

 edly different fron, a similar forest in a 

 tidal area with daily water level fluctua- 

 tion or a forested site with permanently 

 saturated soils. An example of this phe- 

 nomenon is illustrated in Figure 45 for a 

 coastal section of the blackwater Suwannee 

 River (FL). The tree associations within 

 Zone II of the Suwannee change with dis- 

 tance from the coast in response to less- 

 ening tidal influences (i.e., to the 

 extent of daily inundation and salini- 

 ties). The vegetative changes are changes 

 in species morphology as well as species 



replacements. The coastal forest comprises 

 dwarfed swamp tupelo, pumpkin ash, sweet 

 bay, cabbage palm, and cypress which 

 transform upstrean^ to an association of 

 taller Ogeechee tupelo, water tupelo, 

 pumpkin ash, and cypress. The faunal 

 associations change abruptly from a brack- 

 ish water snail-fiddler crab community 

 ( Neretina - Uca ) to a freshwater snail - 

 crayfish community ( Vivipara -Ca mbarus ) at 

 the point upstream where natural levees 

 first occur. 



Macroinvertebrates dominate Zone II 

 and the wetter depressions and pools of 

 Zone III. Parsons and Wharton (1978) doc- 

 umented a cyclic sequence of dominant 

 macroinvertebrates in isolated pools (Fig- 

 ure 46) (Zone III) in Piedmont flood- 

 plains: initially stoneflies dominated, 

 followed sequentially by the isopod 

 Asellus sp. and amphipod Hy alel la azteca , 

 snail oligochaete worms and midge fly lar- 

 vae, and finally an association of sphae- 

 riid clams ( Sphaerium and Mu sculium ). 

 Sklar and Conner (1979) found an almost 

 equal distribution of aniphipods, oligo- 

 chaetes, gastropods, and turbellarians 

 (densities of 10,700/m2) on vegetation in 

 a tupelo gum-cypress association. Beck 

 (1977) found that detrital substrates, 

 such as Zone II soils, were extremely pro- 

 ductive, averaging 2885 organisms/m' in a 

 large alluvial system (Atchafalaya Basin, 

 LA). The dominant macroinvertebrates were 

 a tubificid annelid ( Peloscolex multi- 

 setosus ), an isopod ( Lirceus lineatus ), an 

 amphipod ( Gammarus tiqrinusX a mayfly 

 ( Caenis ), a phantom midge larva ( Chaoborus 

 punctipennis ), a chironomid (Ch ironomus ), 

 a pulironate snail ( Physa ), and a finger- 

 nail clam ( Pisidium ). Ziser (1978) found 

 an average density of 1296 organisms per 

 100 g of duckweed and water hyacinths in a 

 Louisiana swamp. The dominants were the 

 naidid worm ( Dero ), three snails ( Physa , 

 Ferrissia and Promenetus ), an oribatid 

 mite ( Hydrozetes ), two" damsel flies 

 ( Enallagma , Ischnura ), a back swimmer 

 ( NeopTea striola ), a'nd midge and biting 

 midge larvae. 



84 



