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Graduate Research Fellowship
Dynamics of upland and wetland subshrubs at the salt marsh-coastal sage scrub ecotone

Matthew James
Graduate Research Fellow 1997-1998
Tijuana River Reserve
University of Wisconsin

Lycium californicum, a perennial subshrub not considered a wetland species, grows preferentially in the salt marsh-coastal sage scrub ecotone in southern California. This species has not been given consideration in the conservation or restoration of this now rare and threatened habitat. Transect and nearest-neighbor sampling regimes revealed that Lycium is growing at intermediate elevations compared to an upland subshrub, Eriogonum fasiculatum, (which grows at higher elevations) and an obligate wetland subshrub, Salicornia subterminalis, (which grows at lower elevations). The distribution of Lycium is that of an ecotone species (i.e., a species that occurs in an ecotone and is rare or absent from adjacent habitats). The possible influence of selected abiotic factors (salinity, waterlogging and drought) in controlling the elevational limits of the three previously mentioned species was investigated. Salicornia is restricted from higher elevations because it requires saturated soil to establish. Greenhouse experiments showed that Lycium seedlings could not tolerate sea water wetting of the soil (100% mortality) while adults did (100% survival). Therefore, Lycium probably only establishes where salinity remains low until the plant can mature. Eriogonum cannot tolerate salt water wetting of the soil as seedlings (100% mortality) or adults (100% mortality) and is limited to higher elevations where flooding probably never occurs. Lycium shows high tolerance to drought and so the upper limit of Lycium is likely controlled by competition with other upland species. Lycium showed significantly more use by birds and small mammals than Eriogonum at Tijuana Estuary. Lycium can establish well (~80% survival) in a restoration context from cuttings (easy to propagate, need irrigation), or from seedlings (difficult to propagate, do not need irrigation).
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