Table 3.8. Early information on dune vegetation at Silver Strand, the beach that extends north from 

 Tijuana Estuary (from Purer 1936b). Species present in 1936 and their common names are 

 listed. Taxonomy follows Munz (1974) and (USDA 1982). 



Species 



Common name 



Notes on distribution 



Ambrosia maritima 



Abronia umbellata 

 Ambrosia chamissonis 

 Atriplex leucophylla 



Cakile edentula a 

 Camissonia cheiranthifolia 



ssp. suffruticosa dune primrose 



Carpobrotus aequilaterale seafig 



Mesembryanthemum nodiflorum 

 M. crystallinum ice plant 



Rhus integrifolia lemonadeberry 



Rhus laurina b 



ragweed "one of the most conspicuous plants... 



forms extensive mats along the dunes 



as well as inland. ..where the sand is unstable" 

 sand verbena "grows in more stabilized place in the sand 



strand. ..forming extensive mats" 

 dune ragweed "holds a conspicuous and important place... 



in unstabilized areas" 

 salt bush "forms hummocks of sand. ..associated with 



Abronia and Ambrosia" 

 sea rocket "finds itself at home. ..close to the ocean" a 



"flourishes on the [plain] of the strand" 

 "a conspicuous feature of the landscape" 

 "quite well distributed" 

 "forms large mats" 

 "growing extensively on the strand 

 in many places... growth is considerably 

 stunted. ..to a mere few inches" 

 laurel sumac "growing to some 10 feet in height" 



a This species has been entirely replaced by C. maritima, which was absent in 1936. 

 b Noted as present at Silver Strand Beach State Park, but not necessarily on the dune. 



plants of hottentot-fig compared to conditions 

 under native vegetation. In the laboratory, 

 the dune beetles do not eat the hottentot-fig. 

 In the field, dune beetles and other native 

 insects are less abundant under exotic 

 vegetation. Temperatures are cooler under 

 the hottentot-fig than under the native 

 vegetation, which may slow insect 

 development. Because the phenology 

 (development phases) of some exotic plants 

 differs from that of native plants, this may 

 also affect insects. The sea rocket is eaten by 

 dune beetles, but the plant does not live long 

 enough to support insect growth to maturity 

 (K. Williams, SDSL), pers. comm.). 

 Revegetation of denuded areas must employ 

 native plant species in order to maintain the 

 native flora and fauna (Chapter 6). 



Insects are important components of the 

 dune habitat. Several threatened species are 

 found at the Tijuana Estuary dunes (Nagano 

 1982). The globose dune beetle (Coelus 

 globosus; Figure 3.27), inhabits foredunes 

 and sand hummocks. It burrows beneath the 

 surface of the sand and is most common under 

 native dune vegetation; it is absent from areas 

 covered by hottentot-fig. This beetle is a 

 candidate for Federal listing and is threatened 

 with trampling by humans, vehicles, and 

 horses. 



Tiger beetles are threatened by loss of 

 habitat at Tijuana Estuary and elsewhere. The 

 sandy beach tiger beetle (C. hirticollis 

 gravida) and the sand dune tiger beetle (C. 

 latesignata latesignata; Figure 3.27) are 



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