An Evaluation of Bess Beetles (Passalidae) and Their Resource Base in a Restored Andean Forest

Abstract

Degraded lands in the Colombian Andes have been restored by means of monospecific tree plantations of native and exotic species, and by abandoning lands to natural regeneration. Both methods rapidly produce a vegetation cover that helps to stabilize soils, but the value of resulting ecosystems for wildlife needs to be evaluated. We assessed the effects of these two restoration methods on the diversity and abundance of bess beetles (Passalidae), which are important deadwood recyclers. We quantified coarse woody debris (logs and branches >10 cm diameter) and associated passalid beetle fauna in 40-year-old Andean alder ( Alnus acuminata) plantations, adjacent natural regeneration and old-forest remnants, at 2430 m of elevation in the Central Andes. The three forest types contained the same number of logs per unit area, but wood volume was lower in alder stands than in natural forest types. Old-forest remnants contained a higher number of occupied logs and individual beetles per transect and per unit wood volume than the two other habitats. We found six species of beetle, three of which were found in the three habitats and the other three in one habitat each. Forest remnants and natural regeneration had four species each, whereas alder plantations had three species. Although beetle abundance was lower in alder stands, in the small-scale mosaic found at this site alder plantations behaved similarly to secondary forest and merged as part of the local habitat heterogeneity. Whether these results apply to larger and more isolated plantations remains to be established.