Termites facilitate root foraging by trees in a Bornean tropical forest

Plants can develop novel adaptations for nutrient acquisition in nutrient-limited ecosystems. These adaptations include colonization by roots of tree trunks and logs that can act as nutrient reservoirs. Termites may facilitate this root colonization by digging tunnels and accelerating decomposition in logs and tree trunks. We measured the frequency with which above-ground tree root colonization co-occurs with the presence of termites or their tunnels inside living trees above 20 cm dbh (n = 178) and dead tree trunks and logs at least 15 cm in diameter (n = 146) in a Bornean tropical forest. Roots above the soil surface co-occur with termite tunnels 39% more frequently than expected by chance in trunks of living trees and 17% more frequently than expected by chance in logs. By categorizing logs according to hardness through ease of penetration, we found that softer logs at a late stage of decay did not show co-occurrence of termite activity and roots to the same extent as harder logs. This suggests that trees forage where termites have removed physical barriers to colonization. In this fashion, termites may accelerate nutrient cycling in tropical rain forests.