<S1-12> Biotic and abiotic factors influencing the seedling dynamics of four dipterocarp species

Abstract

Identification of the factors influencing seedling dynamics is crucial for improved understanding of the mechanisms underlying the coexistence of trees in species-rich tropical rainforests. Both biotic and abiotic factors are known drivers of tree seedling establishment; however, interspecific differences in seedling survival and growth responses to these factors have not been thoroughly investigated. We monitored 1, 038 current-year seedlings of Shorea laxa, Shorea beccariana, Dipterocarpus globosus, and Dryobalanops aromatica for eight months in each of the 20-m grids in the 4-ha Crane Plot following a mast fruiting event in 2013-2014 in the Lambir Hills National Park, Sarawak, Malaysia. Biotic (initial height, conspecific seedling density, dipterocarp seedling density) and abiotic (canopy openness, soil water content) factors were measured during the 8-month monitoring period. The survival proportion and growth rate of current-year seedlings were significantly different among species. The survival proportion of D. globosus was 44.0 %; those of S. laxa, S. beccariana, and D. aromatica were > 55 % (56.9-69.5 %). The growth rate of D. aromatica was the lowest among the species. Our modeling analyses selected different biotic and abiotic drivers of seedling survival and growth among the species. We suggest that interspecific differences in the effects of biotic and abiotic factors influencing seedling dynamics may underlie the coexistence of tree species in this forest.