Reproductive Ecology and Propagation of Fig Trees (Ficus spp.) as Framework Trees for Forest Restoration

ABSTRACT: Fig trees (Ficus spp.) have been promoted as framework species for tropical forest restoration, because they are considered to be keystone species. This study investigated the reproductive ecology, propagation and planting techniques for seven Asian dioecious Ficus species, which will enable their inclusion in forest restoration plantings: Ficus auriculata, F. fulva, F. hispida, F. oligodon, F. semicordata, F. triloba and F. variegata.

At the population-level, most species produced figs all year round, but fig abundance varied seasonally. Maximum production of ripe figs by female trees of most species occurred in the rainy season (May-August, except for F. triloba), whilst the main fig crop of male trees peaked 1-3 months before female trees. Four species F. auriculata, F. fulva, F. oligodon and F. variegata had critical bottleneck periods for wasp survival, especially during the rainy season, when the wasp-producing figs of male trees were least abundant. At the level of individual trees, considerable variation in phenology was evident among species. Only F. hispida and F. semicordata had completely within-tree asynchronous phenologies (receptive- and releasing/ripening-phases present simultaneously within individual tree crowns).

Most pollinators and non-pollinators were specific to single host fig species. However, F. hispida was pollinated by two pollinator species, whilst F. auriculata and F. oligodon shared the same pollinator. The effects of habitat fragmentation on the numbers of foundresses and seeds of most selected Ficus species was unclear, because pollinator wasps were highly efficient at locating their host Ficus spp., even isolated trees, in highly disturbed habitats and transported pollen to them over much longer distances than anticipated.

The most efficient method of producing Ficus spp. planting stock for forest restoration projects was from seed. Propagation from cuttings was much less successful. Seedlings produced from seed had the highest rates of growth and survival both in the nursery and in field trials. In field trials, use of planting stock from seed was also more cost-effective than direct seeding and vegetative propagation.

The study generated scientifically-based recommendations that will be useful for development of efficient forest restoration programs that maintain keystone resources in tropical forest ecosystems such as i) optimum time/place for seed collection, and optimum planting sites for each species ii) recommendations on the propagation and planting of dioecious fig species, and iii) forest restoration plans, to sustain the obligate ecological relationships between fig-trees and their pollinators. Most tested Ficus tree species acted as excellent framework species, thus they should be grown and planted in broad-scale restoration activities across the Asia Pacific region