Preliminary Biomass Estimation and UAV Image Exploration of In-situ Phyllanthus rufuschaneyi in Sabah Ultramafic Soils Alexius Korom 1 2*, Nur Ain Munirah Amaruddin 3, Evy Michelle Emison 3, Rimi Repin 4, John Sugau 5 and Imam Purwadi 6
1Faculty of Plantation and Agrotechnology, Universiti Teknologi MARA Sabah Branch, Kota Kinabalu, Malaysia
2TANiLAB, Universiti Teknologi MARA Sabah Branch, Kota Kinabalu, Malaysia
3Centre of Postgraduate Studies, Universiti Teknologi MARA Sabah Branch, Kota Kinabalu, Malaysia
4Sabah Parks, Kota Kinabalu, Malaysia
5Forest Research Centre, Sabah Forest Department, Sandakan, Malaysia
6Botanickel Sabah, Malaysia
Abstract
Phyllanthus rufuschaneyi is a recently identified nickel hyperaccumulator with promising potential for agromining in ultramafic regions of Sabah, Malaysia. This study reports preliminary findings from a field campaign aimed at: a) understanding the relationship between biomass and selected biophysical parameters, and b) exploring the potential detection of the spatial distribution of individual biomass using UAV images. The study site is located at the degraded ultramafic soil area in Garas Hill of Ranau district, Sabah. A total of 36 destructive treelet samples and one plot of 10x10 meters field measurements, consisting of 90 readings, were conducted to quantify fresh and dry biomass and record plant characteristics. Samples were selected based on height, ranging from 103 to 620 cm at approximately 1-meter intervals. The dataset consists of measurements such as plant height, canopy size, and various biomass weights of components: leaves, rachises, trunk and roots. Initial analysis shows the power function demonstrated the highest predictive capacity, with an R^2 value of 0.913-0.927 for height, followed by trunk diameter (R^2 of 0.823-0.892), canopy size (R^2 of 0.552-0.655) and root length (R^2 of 0.417-0.614), suggesting potential for predictive modelling. Concurrently, aerial data were captured at a flying altitude of 130 meters using a DJI Phantom 4 Pro UAV to assess the plot-level spatial patterns. Based on early manual observations, ideal dimensions for the detection of individuals or clumping trees are exhibiting a height of at least 300 cm, a crown diameter of 100 cm or greater, and an estimated biomass equal to or exceeding 3000 grams. Although complete biomass modelling is still underway, these early results demonstrate the feasibility of integrating ground measurements with aerial data for biomass estimation of Phyllanthus rufuschaneyi, laying the foundation for non-destructive monitoring and sustainable metal cropping systems.
