Stand age drives changes in the biodiversity and microclimate of oil palm plantations

Tree plantation age strongly dictates its environment. As they mature, the canopy closes and habitat complexity tends to increase, which in turn affects biodiversity. However, for oil palm, one of the most important and widespread tree plantations, we lack a detailed understanding of how this process affects microclimate and biodiversity. We therefore compiled environmental and biodiversity data of oil palm plantations that were repeatedly sampled over a 6 year period in Malaysian Borneo. Using these data, we made a chronosequence of the microclimate and biodiversity of oil palm plantations between the ages 5 and 18. We found that oil palm plantations increasingly buffer temperature and humidity over time, becoming cooler and less dry. Animal responses differed between taxa: spider and beetle abundance increased, ant abundance decreased, and mammal and dung-beetle abundances stayed constant. The diversity of beetles in general increased and family-level community composition changed, while dung-beetle and mammal diversity stayed constant. Some taxa are therefore likely limited by the harsh microclimate of young plantations, while increased habitat complexity and fruit and leaf production in older plantations could also drive increased abundances of other taxa. Our results reveal that oil palm plantations undergo considerable changes, even over a decade after establishment. Correspondingly, plantation age should be considered in studies into oil palm plantations impact on climate and biodiversity, and landscape level diversity could be increased by allowing multiple oil palm stand-ages to co-exist.