PhD ceremony Ms. H. Beukema: Biodiversity in rubber agroforests

PhD ceremony: Ms. H. Beukema, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Biodiversity in rubber agroforests

Promotor(s): prof. J. van Andel, prof. M.J.A. Werger

Faculty: Mathematics and Natural Sciences

The thesis of Hendrien Beukema is an assessment of the role of rubber (Hevea brasiliensis) agroforests in the conservation of lowland rain forest species in Sumatra. Primary forest and monoculture rubber plantations were included in this study to provide reference systems for biodiversity and rubber production values.

Jungle rubber gardens are low-input rubber agroforests that structurally resemble secondary forest and in which wild species are tolerated by the farmer. With the disappearance of undisturbed lowland rain forest habitat the question arises whether disturbed habitat maintains some of the characteristics and functions of the original forest. In rubber plantations, 98% of trees were rubber trees, whereas on average only 41% of trees in jungle rubber agroforests were rubber trees. New data was collected on biodiversity of terrestrial and epiphytic pteridophytes, and compared to existing data on trees and birds. Age of jungle rubber plots varied from 9 to 74 years, while the age of rubber plantation plots was 5–19 years old.

The understorey environment of jungle rubber supported intermediate numbers of ‘forest species’, and several species of terrestrial pteridophytes can be used as indicator species for forest disturbance and forest regeneration. Although species conservation in jungle rubber is limited by management practices and by a slash-and-burn cycle for replanting of about 40 years, this forest-like land use does support species diversity in an impoverished landscape increasingly dominated by monoculture plantations. Older jungle rubber agroforests have a higher conservation value, but they also tend to be less productive for the farmer.