Inter-specific competition between seeds and seedlings of two confamilial tropical trees

Abstract

Inter-specific competition among species in a mixed species plantation is inevitable, and the degree of competition for available resources determines the success of species co-existence. Different species compete and interact for resources at different physiological and developmental stages. However, most research has investigated inter-specific competition at the mature stage. We examined seed germination and seedling growth of two confamilial species, Albizia saman and Albizia lebbeck, and explored inter-specific competition at their early life stages, grown in a mixture of different proportions of seeds and seedlings through a series of replacement experiment. The experiment included germination and height growth tests for each species on its own, as well as three mixtures of species with ratios of 25:75, 50:50 and 75:25. We found that the germination speed and percentage, the probability of seedling emergence, and the seedling height were significantly higher in A. saman than in A. lebbeck. Moreover, in mixtures, we observed that A. saman exhibits higher germination speed and percentages compared to A. lebbeck. The increase in seedling height did not vary significantly among treatments when the seedlings of the studied species were mixed in different proportions. However, both species showed an apparent benefit when growing together, which was significantly influenced by A. saman in terms of inter-specific competition indexes. The knowledge of the early growth performance of these species and their inter-specific competition presented in this study may influence recruitment success and will be useful in understanding the population dynamics in the case of a mixed species plantation. Furthermore, our study suggests that there could be an impact of species mixture on the regeneration or recruitment process, even when the species are confamilial. Therefore, this information could be useful for selecting suitable species mixtures in any afforestation and reforestation activities.