even after major hydrographic events, may be 

 indicative of increased tidal influence, as this station 

 was closer to Nueces Bay. The smaller responses seen 

 in S. bigelovii cover at the Reference Station and Station 

 III compared to the response seen at Station II after 

 the 1998 event appear to be precipitation-mediated and 

 limited by a lack of freshwater inundation. 



Small scale GIS analyses indicated that the 

 establishment of Salicomia bigelovii corresponded to a 

 decrease in bare area at the Reference Station and 

 Station II. At Station II, decreases in bare area were 

 proportional to increases in cover. LAI maps 

 produced from the small scale analyses further 

 supported the increase in vegetation at both the 

 Reference Station and Station II during spring 1998 

 and 1999. Weilhoefer (1998) and Dunton et al. (2000) 

 have previously dociimented establishment and 

 expansion of vegetation cover and subsequent decrease 

 in bare area after freshwater inundation in the lower 

 Nueces Delta. Decreases in bare area could have direct 

 affects on the functionality of the marsh. 



Other studies have noted that halophyte species, which 

 can occupy bare areas following disturbance events 

 through sexual (seed) reproduction, can act to reduce 

 soil salinity concentrations by shading the soil surface 

 and by actively uptaking salts. The reduction in soil 

 salinity eventually allows the establishment of 

 dominant and persistent perennial species (Bertness 

 etal. 1992). The establishment of these species is 

 necessary as they pro\ade stable habitat for many for 

 many small organisms, including crabs, molluscs and 

 small terrestrial animals such as rats. The marsh 

 vegetation also serves as habitat and food for a variety 

 of permanent and migratory birds (Henley and 

 Rauschbauer 1981). Successful long-term 

 establishment provides large amounts of plant biomass 

 to the detrital food-web, which can then be utilized by 

 microorganisms and other small animals such as snails 

 (Marples 1966). This is an especially important role of 

 annual plants because all of their aimual biomass 

 production eventually becomes detritus. Marsh 

 vegetation contribution to the detrital food-web is 

 essential as it serves as a critical link between primary 

 and secondary trophic levels (Burkholder and 

 Burkholder 1956; Odum and Wilson 1962; Teal 1962). 



Vegetative occupation of bare space is critical as the 

 vegetation acts to stabilize marsh sediments, thereby 

 sheltering the metropolitan area of Corpus Christi 

 from extensive flood damage and erosion. Without 

 vegetation expansion into bare space, the functionality 

 of the marsh would be compromised. 



hatis maritima cover at the Reference Station and 

 Station III changed seasonally, with peak cover in the 

 summer and declines in the winter. This seasonal 

 trend appears to be due to natural variation and 

 corresponds to observations made by Weilhoefer 

 (1998) in the lower Nueces Delta. B. maritima is a 

 highly salt tolerant perennial succulent, which may 

 explain its high cover during the summer. The plant 

 expanded in cover during the spring and early summer 

 when soil salinity levels were usually low and was then 

 able to maintain a high cover during the summer 

 months, although active growth may not have occurred 

 during the hot, dry season. The greatest percent cover 

 observed at the three stations, however, was during the 

 summer of 1997, following a spring with over 52.1 cm 

 (20.7 inches) of precipitation. The rain was steady over 

 a five-month period and was not due to a major 

 hydrographic event. No other spring during the study 

 period experienced a similar rainfall pattern. Although 

 B. maritima is capable of surviving at elevated salinity 

 concentrations, increases in cover occur when gradual 

 freshwater inputs alleviate soil salinity levels. 



After a major composite hydrographic event in 

 July 1997, percent cover of hatis maritima temporarily 

 increased in August but then declined at all three 

 stations. After the summer 1997 event, the following 

 fall, winter and spring were relatively dry, potentially 

 keeping cover low at all three stations during June 

 1998. Cover increased again in June 1999 at die 

 Reference Station and Station III; cover remained low 

 for over two years at Station II. The continual 

 suppression of B. maritima growth at Station II might 

 reflect this species intolerance to waterlogging and 

 anaerobic soils. Freshwater-mediated decreases have 

 been noted in a species with similar morpholog}', 

 Salicomia virginica (Zedler and Beare 1986; Weilhoefer 

 1998). Continual flooding occurred during the 

 fall 1998 and diroughout 1999. At Station II, the 

 vegetation began at the mean water line, so, after 



Chapter Six ♦ 6-47 



