Diameter Distribution and Litterfall Dynamics of Dominant Tree Species in Manokwari Lowland Fallow Ecosystems, Indonesia

Abstract

In the lowlands of Manokwari, West Papua, Indonesia, shifting cultivation is still a prevalent practice among local Papuan communities. The secondary succession on abandoned shifting cultivation lands warrants investigation, given that these lands are typically reused for agriculture after a period of fallow. Key parameters for assessing the succession process include vegetation structure and litter production; however, information on these aspects in Manokwari, West Papua, remains limited. This research examined the distribution of stem diameters and developed a model for litterfall types across three different ages—age 5 year (LB-5), 10 (LB-10) and age 15 year (LB-15) in the lowland tropical ecosystems of Manokwari. Vegetation analysis with nested plots and litter trap methods were employed. Litterfall modeling utilized pseudo replication principles, combining principal component analysis and non-metric multidimensional scaling (NMDS) based on Bray-Curtis’ similarity. Results showed distinct distribution patterns and diameter classes for each dominant type. Dominant species in LB-5 and LB-10 accumulated stem diameters below 25 cm, whereas LB-15 exhibited a more complex distribution with stem diameters exceeding 50 cm. Species such as Macaranga aleuritoides, Macaranga tanarius, Kleinhovia hospita, and Ficus nodosa exhibited higher diameter growth rates at early successional stages (e.g., age/DBH), indicating their fast-growing nature. The litterfall model explained 99.9% of data variability. LB-5 showed positive correlation with leaf litterfall production, while LB-10 and LB-15 correlated with branch, twig, and reproductive organ litterfall. This study demonstrates that vegetation structure and composition significantly influence litterfall quality, emphasizing the importance of long-term litterfall modeling.