摘要：Vegetation influences the stability of slope by both hydrological events and mechanical reinforcement of the soil. The magnitude of such effects is subject to the root system growth, which in turn is a purpose of the genetic properties of the species and site appearances. In this study, we investigated the root distribution of Macaranga tanarius (L.) Müll. Arg. as a native species in Malaysia, with an aim to rise our knowledge on root area ratio distribution inside the soil. Concerning the estimation of root distribution within the soil, we assessed the root area ratio (the proportion between the area occupied by the roots in a slice area of soil) according to its depth for four samples in the rainforest. Results show that the root area ratio (RAR) declined with depth, and the higher RAR values were calculated in the higher layers. RAR values were between 0.950% and 18.477%. There is a plentiful diversity of root density in depth classes. Also, the result showed that about 50% of the roots are located in the first 10 cm layer, and about 87% of roots were in the fine root diameter (>2 mm). There is not a significant difference between RAR and soil depth. Spearman correlation showed no significant and negative correlation between RAR and depth. The maximum RAR percentage was in the first layer 0-10 cm (44.59%). Also, the results showed that the amount of RAR decreased with depth in fine roots (d<2mm), but RAR in thin roots (2
