upper zone. Based on the first 3 years of stand development on this site, 

 it is evident from the standpoint of vegetative cover, substrate stabili- 

 zation, and primary productivity, that marsh development following trans- 

 planting can be quite rapid. Productivity was 7,000 kilograms per hectare 

 the second year and reached 10,000 kilograms per hectare in the third 

 year which compares with 5,100 and 16,000 for the short and tall height 

 forms in the long established natural marshes of Oak Island (discussed 

 later in Section VI, Tab. 40). Cover, as reflected in number and size 

 of stems, and production increased between the second and third year, but 

 the rate of increase slowed. Belowground growth expanded much more than 

 did top growth during the third year. However, these data may be decep- 

 tive, since this may mean an accumulation of another season's growth 

 added to that of the first 2 years. If this is the correct interpreta- 

 tion, the annual rate of production belowground appears to be slowing also. 

 There may be further increases in vegetative material in the root zone, 

 but it is difficult to comprehend how it can continue to expand at the 

 present rate without much deeper penetration into the substrate. We have 

 seen no evidence of change in this respect from the first year. 



Distribution of roots and rhizomes by depths was examined at Snow's 

 Cut in 1972. It was feasible to take cores to a depth of about 30 centi- 

 meters, but only at low tide. There was little penetration of roots and 

 rhizomes below this depth, and no adequate method of sampling below 30 

 centimeters was found. Cores almost invariably broke off at the point of 

 sharp decrease in belowground growth which occurred around 25 to 30 

 centimeters below surface. 



Cores collected in 1972 were divided into the to 10- and 10 to 

 30-centimeter depth segments, and the roots separated from rhizomes. 

 The depth division was selected because belowground plant material was 

 more dense in the upper 10 centimeters. About two-thirds of the roots 

 collected are distributed in the upper 10 centimeters; the remainder 

 occurring in the 10-to 30-centimeter zone (Tab. 21). Rhizomes were more 

 evenly distributed between the two zones. There was a distinct tendency 

 toward less total belowground growth as the period of inundation increased. 



Sampling variation is high with coefficients of variability of 37.5 

 to 84.3 percent. Consequently, differences would have to be quite large 

 to be detectable. 



Estimates of rate of spread were obtained at Snow's Cut at the end of 

 the third growing season. The lateral rate of spread was from 0.9 to 1.5 

 meters per year (Tab. 22; Fig. 41). Data on downslope spread were avail- 

 able from only one plant source (Ocracoke) at one elevation. Since 

 lateral spread for all plantings at this location was uniform across the 

 four zones of inundation and of the same general magnitude as the single 

 downslope expansion determination, we assume that the latter would be 

 very similar to the lateral spread at all elevations within this range 

 (2 to 12 hours inundation). 



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