Tree biodiversity in Bornean lowland forest: What are the key species for forest city development in the new capital city of Indonesia?

PLOS ONE | https://doi.org/10.1371/journal.pone.0320489 April 8, 2025 11 / 19 PLOS ONE Tropical urban tree selection improving quality of life and human health and prosperity [40,41,42]. Therefore, biodiversity should become the main indicator for successful forest city development in IKN. This research found that the landscape around the proposed IKN contained high tree species richness, particu- larly in less-disturbed forested areas such as Samboja Research Forest and Sungai Wain Protec- tion Forest. Previous research also found that Samboja Research Forest had the second highest plant diversity across forests in Indonesia with 553 identified tree species [20]. Of the 13 Dip- terocarpaceae genera found in Kalimantan, only the monospecific genera Neohopea and Upuna were not found in this study area. However, there are records from Kartawinata et al. [20] of the presence of Upuna at Samboja Research Forest based on an inventory in 2004. Whilst the Dipterocarpaceae was the dominant family as expected [6,7,8], the Euphorbia- ceae, Malvaceae and Phyllanthaceae were also abundant in the landscape. These families are known to be characteristic of lowland evergreen rain forest in Kalimantan. In a rehabilitation context, fast-growing pioneer tree species (such as members of the Euphorbiaceae) can make the micro-climate shadier, thus allowing better growth of shade-tolerant species [43,44]. The pioneer tree species with short lifespans live up to around 30 years [45], then allowing shade-tolerant species to form the subsequent canopy. Priority species

The development of IKN is within the framework of a forest city, namely a city designed on a landscape basis placing forest ecosystems at the centre of urban spatial planning and facilitat- ing the life of urban communities [46]. To revitalize green open areas and to implement the forest city concept, replacement of Eucalyptus spp. with native species from Borneo is needed. The high score given to conservation status and endemicity shows the spirit of IKN develop- ment by prioritizing rare and endangered tree species to support recovery of Borneo’s tropical forests. To rehabilitate forest ecosystems, appropriate species selection is fundamental to its success. Species selected should be native [47,48,49] and have high survival rates [50]. In addi- tion, fast-growing species can be added to the species selected, but we should pay attention to the trade-offs related to life-history strategies since fast-growing species have short lifespans [51]. The advantage of planting fast-growing species in the initial step of rehabilitation is the ability of these species to rapidly form canopy cover [47], thereby creating microclimates suitable for the growth of shade-tolerant species as noted above. Several studies recommend combining trees with a diversity of traits in rehabilitation, such as pioneer species and climax species [52], or fast-growing native tree species and slow-growing native tree species [49]. There is also increasing recognition that tree selection should be not only be considered in

terms of ecosystem recovery but also for local communities. Therefore, selected trees should have economic benefits and improve local livelihoods [27,53,54]. Rank Species Total Score Priority 45 Knema pallens, Knema percoriacea, Myristica villosa, Palaquium stenophyllum 0,771 3rd 46 Artocarpus rigidus 0,762 3rd 47 Lithocarpus gracilis 0,750 3rd 48 Macaranga beccariana 0,744 3rd 49 Durio oxleyanus 0,730 3rd 50 Rubroshorea leprosula* 0,723 3rd Remarks: *Seed sources are available in IKN. https://doi.org/10.1371/journal.pone.0320489.t005 Table 5. (Continued)