Effects of avian seed dispersers and the exclusion of small edaphic mammals on riparian plant community restoration

Riparian zones are some of the most species diverse, complex habitats in existence.  Anthropogenic disturbances result in extensive biological degradation of these systems.  Unfortunately, restoration of riparian zones has been limited especially in urban settings where they are expected to fulfill ecological, recreational, and cultural functions. My studies investigate the utilization of bird perches and rodent exclusion fences as methods of increasing seed bank by attracting seed dispersing birds and preventing seed loss due to granivory and herbivory in a local urban riparian habitat.  During 2005, baseline assessments of plant density and biodiversity were conducted.  Treatments applied included (1) addition of a perch, (2) addition of a fence, (3) addition of both a perch and fence, and (4) no additions (control).  Assessments were repeated in 2006.  Preliminary analysis of 2005 and 2006 data showed a 28% decrease in biodiversity and a 44% decrease in plant density.  Festuca rubra (red fescue), a native plant, was the dominant species in both years with an increase in density of 6% in 2006.  Aster vimineus (small white aster), another native plant, had a 7 % increase in density from 2005 to 2006 making this plant the second most dominant species in 2006.  Changes in diversity and density may be related to experimental manipulations, especially the decrease in granivory and herbivory due to rodent exclusion.  If these treatments effectively increase the viable seed bank, favoring the establishment of later native secondary successional plant species, these low-cost techniques could be utilized for restoration of our urban riparian areas.