severe on seedlings and young transplants. Established plants seem to be 

 able to tolerate much higher salinities at least for short periods of 

 time. 



Core Sound and the southern part of Pamlico are particularly vulner- 

 able to this phenomena since the southwesterly winds normally prevailing 

 here during the warm part of the year result in low water levels. It 

 occurs also in northern Pamlico where low water results from northeasterly 

 winds. Heavy salt concentrations, even to the extent of a white crust on 

 the soil surface, have been observed. This condition develops at Oregon 

 Inlet, particularly in April and early May when northeasters of several 

 days duration are not uncommon. At such times the effect on young seed- 

 lings is quite severe. 



While seedling stands are occasionally killed completely by salt 

 damage, the more frequent effect is a temporary dieback, thinning and 

 stunting. The less severe effect may be due to an intermediate salt 

 concentration or to shortening or interruption of the buildup period by 

 rain showers or wind shifts. This probably happened at the field-scale 

 seeding on South Island (Drum Inlet) during the 1973 growing season. 

 Early seedling emergence on most of this site was good, and by early May 

 a very dense stand seemed ensured. However, by early July many seedlings 

 had died and the remaining plants were stunted and exhibited the general 

 appearance we associate with salt damage -- dead leaves and varying degrees 

 of tip burn of living leaves. Spot checks of salinity were made on about 

 every site visit throughout the summer. All readings were approximately 

 sea strength, although plant appearances suggested that some additional 

 salt damage had occurred, probably on more than one occasion. When the 

 planting was sampled 5 November for estimates of aboveground and below- 

 ground production, salinity determinations were made at each sample site. 

 The mean for the 48 samples was 40 parts per thousand (sound water = 35 

 parts per thousand in this vicinity) . 



Stand losses that appear to be related to salt buildup have also been 

 observed in well established plantings, occurring as small irregular spots. 

 These have been identified at The Straits on recently dredged material, 

 highly variable in texture, and at Drum Inlet on recently dredged material 

 containing a high proportion of sand. 



The damage always appeared the year after transplanting, and was first 

 observed at The Straits in the summer of 1971. Five sampling stations 

 were established and these were sampled three times (Tab. 18). 



Wherever salinities of the soil solution exceeded 45 parts per thou- 

 sand, dieback of S. alterniflora leaves was observed; in more severe cases, 

 entire plants were dead. 



A similar pattern appeared at Drum Inlet in the spring of 1973 on plots 

 transplanted to S. alterniflora in May 1972. Eight sampling stations were 

 established in May and followed through August (Tab. 19). 



74 



