observed for low intensity rockplow- 

 ing without subsequent farming 

 effects. In this case, all vestiges 

 of the natural prairie community 

 were removed and a secondary succes- 

 sional community, consisting of a 

 few abundant annuals and perennials, 

 occupies the site. Close inspection 

 of this recovery community reveals 

 that none of the pre-existing 

 populations except for arrowhead 

 ( Sagittaria lancifolia ) survived. 

 Cattail ( Typha latifolia ), which was 

 rare in the pre-farming community, 

 is found to be the dominant grami- 

 noid species. The successional 



species that were dominating the 

 farmed site include: primrose wil- 

 low ( Ludwiqia peruviana ), willow 



( Salix caroliniana ) , loosestrife 



( Lythrum lineare ), marsh fleabane 

 ( Pluchea odorata ), bushy beardgrass 

 ( Andropoqon qlomeratus ), saltbush 

 ( Baccharis halimifolia ) , narrow- 

 leaved primrose willow ( Ludwiqia 

 octovalvis ) , giant goldenrod 



( Solidaqo sempervirens ) , and hemp 

 vine ( Mikania babatifolia ) . 



The striking contrast between 

 the two recovery communities that 

 develop following agricultural 



disturbances indicates that while a 

 low level of isolated disturbance to 

 the natural prairie vegetation is 

 not highly detrimental, a more in- 

 tensive use of a pattern combining 

 several episodes of rockplowing with 

 a single season of tomato farming 

 results in the total obliteration of 

 the natural prairie vegetation. It 

 appears that the spontaneous recov- 

 ery of the muhly prairie vegetation 

 will not occur. Furthermore, the 

 site appears to be open to coloni- 

 zation by one or more of the exotic 

 tree species within the near future. 



Grove plantings are becoming an 

 increasingly more frequent type of 

 land use throughout the agricultural 

 portion of the study area. The 



major grove crops are citrus ( Citrus 

 spp.), avocado ( Persea americana 

 varieties), mango ( Manqifera indica 

 varieties), and a wide range of 

 ornamental trees and shrubs planted 

 in field nurseries. Typically, 



grove plantings are generated on 

 rockplowed lands that have been pre- 

 viously farmed for tomatoes, beans, 

 squash, or other truck crops, and 

 only rarely have natural communities 

 been directly converted to a grove 

 situation. 



A grove planting differs from 

 an annual crop system in several 

 respects. The most pronounced dif- 

 ference is that in grove plantings, 

 the mounds upon which the trees are 

 planted are several times higher and 

 wider than those of a tomato or 

 squash field. This mounding pro- 

 duces an area in where the furrows 

 support a more hydric plant commu- 

 nity and the mounds support a more 

 mesic community than was present in 

 either the natural community or that 

 developed on the abandoned farm 

 field. The mound vegetation con- 

 sists principally of ruderal spe- 

 cies including: bushy beardgrass 

 ( Andropoqon qlomeratus ), saltbush 

 ( Baccharis halimifolia ), Brazilian 

 pepper ( Schinus terebinthifolius ) , 

 potato tree ( Solanum erianthum ), 

 lantana ( Lantana montevidensis ) , 

 milkweed vine ( Sarcostemma clausa ), 

 santa maria ( Parthenium hystero - 

 phorus ) , and beggar tick ( Bidens 

 pilosa ) . The furrow vegetation 



consists primarily of: arrowhead 



( Sagittaria lancifolia ) , marsh 



fleabane ( Pluchea odorata ), fog bit 

 ( Lippia stoechadifolia ) , soft rush 

 ( Juncus polycephalus ) , and matter 

 figwort ( Bacopa monnieri ). 



The exotic tree Brazilian pep- 

 per ( Schinus terebinthifolius ), is 

 commonly present in most if not all 

 groves regardless of the age of the 

 grove. The actual numbers of this 



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