Seed collection practices in tropical rainforest restoration and implications for provenance research

Abstract

The dramatic increase in scale of ecological restoration required to meet future global targets will require enormous quantities of seed and propagule material. Tropical forests - which are often identified as priority regions for large-scale restoration - often experience substantial fragmentation and degradation, processes which may reduce the availability and genetic quality of seeds and propagules. Hence, trade-offs between cost, quantity, and genetic quality occur due to financial and logistical constraints on collection and production of plant material. Seed provenance, i.e. their ecological origin, may play a crucial role in determining the success of restoration efforts and may be directly influenced by said trade-offs. Here we examined the geographical and environmental ranges over which seeds are collected in three revegetation nurseries in tropical Australia. Our results showed that seed collections from 2012 to 2018 were overwhelmingly conducted within 10 km of the collecting nursery, concentrated in sites that were easier to access, and in areas in which the surrounding remnant forest cover was low. Additionally, seed collections were conducted predominantly in sites that were hotter than the average climate conditions surrounding the nurseries, and that – at the species level – seed collection locations frequently represented the hotter end of a species thermal range. We discuss these results in light of their effects on restoration stocks, particularly how biases in seed collection may influence the composition of species included in restoration as well as the resulting seedling genetic and phenotypic range. How such biases have affected restoration outcomes, however, remains poorly understood.