COS 129-3 - Beyond forestry plantations: understanding biodiversity retention in pine and eucalyptus dominated lanscapes

Abstract: Worldwide most forestry plantations are managed as monocultures of fast-growing species, covering large areas. In Chile, forest plantations of exotic tree species currently cover >3 million ha, principally with Pinus radiata and Eucalyptus spp. In the coastal range of Chile (35-38° S), plantation establishment has generated areas in which natural Nothofagus dominated forests had became “islands” of biodiversity, surrounded by an “ocean” of plantations. An understanding on how these remnant natural patches contribute to biodiversity retention is needed. Natural forest patches retain native plants within, but can also influence nearby areas into the plantation matrix. We evaluated the attributes of natural Nothofagus patches among pine and eucalyptus plantations, that contribute in retaining plant biodiversity within adjacent plantations. Using as study area of ~250,000 ha in the coastal range of South central Chile (°38 S), we (a) quantified the frequency by size, shape and isolation of Nothofagus forest patches among plantations at landscape level. Afterwards, we selected 18 Nothofagus forest patches adjacent to pine (n=9) and eucalyptus (n=9) plantations, including a wide range of sizes for fieldwork. We sampled vegetation, site, forest structure, soil properties and other variables considering 162 plots (5 x 5 m) set in transects from the Nothofagus patches, 140 m into the adjacent plantations. We (b) analyzed natural forest attributes that influenced plant species richness and cover below pine and eucalyptus; and (c) we assessed plantation attributes that promote establishment of native species on its understory.

Nothofagus patches varied in size (0.5 to > 200 ha), but most presented < 8 ha. Plant diversity underneath pines and eucalyptus did not differed dramatically from that of natural forest patches and was primarily explained by plantation attributes than by the adjacent forest attributes. Native tree regeneration density was slightly higher in the understory of pine plantations than below eucalyptus, although native species richness was significantly greater on the eucalyptus understorey.

Conserving and restoring natural forest patches within forestry plantation landscapes can play a key role for biodiversity retention. We discuss current knowledge on fragmented ecosystems including the role that natural forest patches can play for plantation conversion, and the need of novel approaches for pine and eucalyptus management.