October 1998 event and continued throughout 1999, 

 which had several months of consistent rainfall. 



Monanthocloe littoralis - At Station III, Monanthodoe 

 littoralis cover remained relatively constant (13% to 

 21%) over the study period (Figure 6-9d). Cover 

 exhibited only minor decreases in cover in response to 

 the July 1997 event (7% decline) and a 4% decrease 

 after the October 1998 event. 



Salicornia bigelovii - At Station III, Salicomia higelovii 

 was practically non-existent throughout the study 

 period, with only 1% cover in June 1998 and 3% cover 

 in June 1999 (Figure 6-9e). 



Bare Area — Bare area cover at Station III gradually 

 increased 1 5% from the beginning to the end of the 

 study period, but changes did not appear to be 

 mediated by hydrographic events (Figure 6-9f). 



large-scale whole transect 

 Analyses: Leaf Area Index 



Leaf area index , a non-destructive means of estimating 

 total vegetation foliage density, exhibited considerable 

 temporal and spatial variability within and between 

 sampling transects. Measurements are reported as total 

 transect values. Average LAI values for the transects 

 exhibited seasonal peaks in the summer and declines in 

 the fall and winter (Figure 6-10) and displayed a similar 

 trend at all three stations. However, values at the three 

 stations differed in range and magnitude. At the 

 Reference Station, values range from 0.60 to 1.99 and 

 had an average of 1.42 compared to a range of 0.89 to 

 1.34 and an average of 1.13 at Station II. Values at 

 Station III were higher than the other two stations, 

 ranging from 1.64 to 2.43, with an average of 2.02. At 

 the three stations, peaks in LAI occurred in September 

 and November 1996, following a two-month period 

 with over 22.5 cm (9 inches) of rain. LAI then 

 declined in February 1997, which was a period with 

 litde rainfall. Values increased and peaked in January 

 1998, another period following a three-month period 

 of over 30 cm (12 inches) rain. The third major peak 

 shared by the three stations was in June 1999, which 

 followed a four-month period with over 30 cm rain. 



This spring also followed the October 1998 event. 

 The greatest decline in LAI occurred in September 

 1999 and coincided with a large increase in bare area. 

 The decline occurred several weeks after a tidal surge 

 due to Hurricane Bret flooded the transects and 

 drowned much of the vegetation. In general, large 

 decreases in LAI coincided with increases in bare area. 



Small-Scale Analyses 



Percent Cover 



Changes in the percent cover of individual species were 

 e\'ident during sampling periods before and after 

 composite hydrographic events (Table 6-5). 



Spring Cover — Analysis of GIS maps created from 

 springtime percent cover at the Reference Station 

 indicated that bare area cover appeared to be greatest 

 following fall periods with little precipitation 

 independent of amount of spring precipitation 

 (Figures 6-1 lb and 6-1 le). Salicomia bigelovii increases 

 occurred when fall and spring precipitation were high 

 (Figure 6- lid), and Monanthocloe littoralis cover and bare 

 area decreased with increases in S. bigelovii. The maps 

 indicate that S. bigelovii invaded previously bare areas. 



At Station II, maps indicate that bare area was greatest 

 following fall periods with no flow events and/ or littie 

 precipitation. In June 1997 (Figure 6- 12b), bare area 

 was greatest compared to other springs. Prior to this 

 spring, there was litde fall rain and no flow. May 1996 

 and June 1998, springs foOowing falls with heavy rain 

 but no flow event, had less bare area than June 1997 

 but more than either June 1999 or June 2000. In the 

 falls prior to June 1999 and 2000, there were 

 freshwater diversions and heavy precipitation. 

 Salicomia bigelovii cover was greatest in June 1999, 

 having greater than 50% cover over 59% of the 

 transect (Table 6-5). Cover was also high in June 2000, 

 with 49% of the transect having greater than 50% 

 cover. The maps show that S. bigelovii invasion 

 occurred in previously bare areas. The maps further 

 indicate that 'Qatis maritima cover decreased after 

 flooding events (Figures 6- 12c and 6-1 2d). 



Chapter Six ♦ 6-21 



