PARENT SESSION
Contributed Oral Session 58: Forest Ecology: Riparian Areas
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal
Unexpected response of terrestrial litter beetles to riparian zones of first order streams in Australian wet eucalypt forest.
Baker, Sue*,1, 2, Richardson, Alastair1, Barmuta, Leon1, Thomson, Russell1, 3, 1 University of Tasmania, Hobart, Tasmania, Australia2 CRC for Sustainable Production Forestry, Hobart, Tasmania, Australia3 Menzies Research Institute, Hobart, Tasmania, Australia
ABSTRACT- Unlike streams in drier areas, obvious bands of riparian vegetation do not border first order streams in Eucalyptus obliqua forest, a wet forest ecosystem common in Tasmania, Australia. We aimed to ascertain the presence, and measure the extent, of riparian effects on litter-dwelling beetles. Beetles were collected using 100 m long transects of pitfall traps at right angles to four streams. Multivariate analyses and generalised linear models of abundance and species richness examined beetle patterns. Beetle response varied between the study sites, and site differences were stronger than riparian influences in structuring the beetle community. The strength and nature of the riparian responses varied between streams, but was strongest (approx. 100 m) at the largest stream and weakest (extending 5 m) at the smallest stream. Abundance of beetles, especially of commonly trapped species, was lower adjacent to three of the four streams, while the total abundance of rarely trapped beetles was not affected. Species richness was also lower adjacent to one stream. This riparian response of lower abundance adjacent to streams was unusual. We expected either no response based on vegetation patterning, or greater abundance and species richness near streams since riparian zones are often considered to be of higher diversity/richness. The explanation for this finding remains unclear; pitfall depletion was ruled out, and measured habitat variables were not consistently related to riparian plots in ordinations. Our findings indicate that riparian areas are not necessarily of higher habitat quality, and in fact may have lower habitat quality in some instances. Our results also illustrate that litter beetles do not show a uniform response to all first order streams. Some streams will have stronger riparian characteristics as a result of topography, microclimate or geomorphology. The tendency to concentrate most reserve corridors along riparian areas may not be optimal for conservation.
Key words: riparian, litter beetles, abundance, richness