III. EVALUATING SITE SUITABILITY 



1, Factors Influencing Planting Success . 



A number of factors are known to influence planting success. The follow- 

 ing is a state-of-the-art discussion of these factors. 



a. Soils . 



(1) Type. A few salt marsh species are confined to certain soil 

 types or conditions. Gulf cordgrass, for example, occurs almost exclusively 

 on soils high in clay or underlain by clay at shallow depths. However, most 

 other salt marsh plants exhibit a wide tolerance of substrates. They may be 

 found growing on mineral soils ranging from coarse sands to heavy clays and on 

 peats and mucks of widely varying nutrient content and degree of decomposi- 

 tion. This does not mean that soils are unimportant to marsh establishment 

 and growth. Soil characteristics affect marsh planting in at least three 

 respects — substrate stability, nutrient supply, and ease of planting. 



Even under the most favorable conditions, transplants require several 

 weeks to anchor themselves and still more time to develop an appreciable 

 protective effect. Substrate is important to this process. Consequently, 

 planting in loose sands is a poor risk if the site is likely to be subjected 

 to high wave activity during the establishment period. Even when net erosion 

 may be minimal, substrate movement or wave action may dislodge the transplants 

 before they can become fully anchored. The threat of substrate movement is 

 less critical in cohesive soils which tend to be more stable. 



A limited nutrient supply is much more common to plantings on eroding 

 shorelines than to plantings in sheltered areas or on dredged materials. 

 Also, unlike other plantings, nutrient deficiencies on eroding shorelines are 

 not necessarily confined to the more sandy materials. Soil materials exposed 

 by erosion will usually be representative of subsoils of the adjacent uplands. 

 These are often the highly weathered soils which are low in nutrients. Some 

 of the most acute deficiencies, particularly of phosphorus, may occur on com- 

 pact, cohesive soils (Broome, Seneca, and Woodhouse, in preparation, 1983). 

 Further, the mechanics of correcting nutrient deficiencies become more compli- 

 cated in compact soils. While the method of fertilizer placement is usually 

 not critical on sands, it may make the difference between success and failure 

 on clays or packed sandy loams (Broome, Seneca, and Woodhouse, in preparation, 

 1983). 



Nutrient supply in organic soils is highly variable. Some peats are 

 extremely deficient and as a consequence are very difficult to sustain plant 

 growth; others are very well supplied with nutrients and are excellent mediums 

 for marsh growth. The nature and origin of the soils in a region will often 

 provide general guidance as to the probability of fertilizer needs. For 

 example, young soils formed from moderately weathered materials, such as occur 

 in the Mississippi Delta, are much less likely to be deficient in nutrients 

 than the much older, highly weathered sediments that predominate along much of 

 the Atlantic coast. 



Soil characteristics can be of vital importance because of their influence 

 on the marsh planting process, particularly on eroding shorelines. It is 



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