4.4 Conclusions and implications for rainforest restoration in the Australian Wet Tropics
Although site and provenance effects were important in determining tree survival and growth across our 16 study species, evidence for local adaptation was mixed. For most species the lowland provenance performed better than the upland provenance regardless of site, and provenance differences were generally stronger in faster growing species. This highlights the complexity and context-dependency of local adaptation in tropical rainforest trees, challenging the ‘local is best’ strategy for sourcing seed for restoration plantings (Cooper et al. 2018). Our findings suggest that using lowland provenances, regardless of site, could optimize initial plant growth in some species. Restoration practitioners might consider expanding the sources of seed, particularly in higher altitude sites like the Atherton Tablelands, to meet seed demands and enhance genetic diversity and adaptive capacity. However, risks associated with both local and mixed provenancing approaches are well-documented (Jordan et al 2024). Future research at this site includes investigating whether observed growth responses evident here can be explained by variation of physiological traits, or whether trade-offs exist with growth and tolerance to heat (Middleby et al. 2024b) or drought stress. We urge researchers and practitioners in this region to focus on generating the necessary information for informed decision-making.