Biodiversity index of fruit trees cultivated by communities around marginal land in Jombang Regency, East Java Province, Indonesia

Marginal land conditions are a major problem in reducing the level of diversity of species due to decreased soil, climate, and water quality and topography. This study aims to analyze the diversity index and the dominance of fruit tree species cultivated by surrounding communities. The research method uses nested sampling in 4 (four) sub-districts, each of which is taken three sample villages and each of them is made of three transect plots measuring sample plots 20 × 20 m 2 (trees), 10 × 10 m 2 (poles), and 5×5m 2 (sapling). Data analysis using the Biodiversity R application program with version R 3.6.1. The results of the analysis of the growth rates of the best tree species were found in Ploso Regency because they had the highest growth rates of trees, poles, and saplings. The diversity of fruit tree species is based on the distribution of the highest H index value of 1.47 and the lowest of 0.58 and includes areas that have an abundance of moderate species. Fruit tree species that have the highest importance value index are Mangifera indica (mango) 70.26% with a tree density of 139 individuals per hectare, then Dimocarpus longan (longan) 40.24% with a tree density of 153 individuals per hectare. The results of this study indicate that the community structure of fruit trees in degraded lands is more dominated by plants from the Sapindaceae and Anacardiaceae families which generally grow spread in the 4 sub-districts studied.