2019 Volume 61 Issue 1 Pages 1-13
Spatial assessment of nitrogen content in canopy leaf is important to understand the spatial variability of nitrogen cycle in forest ecosystem, because leaf nitrogen closely relate to quality and quantity in litterfall, nutrient cycle and plant nutrient uptake. This study aims to develop and analyze the assessment method to estimate spatial distribution of nitrogen content in canopy leaf in natural forest with heterogeneous species composition and complexed canopy structure using unmanned aerial vehicle (UAV) with digital camera through Structure from Motion (SfM). The study was conducted in a natural cool-temperate mixed forest in Uryu experimental forest, Hokkaido University located in northern Hokkaido, Japan. Digital image for single leaf in dominated 8 tree species (2 evergreen coniferous and 6 deciduous broad-leaved species) and Sasa dwarf bamboo as understory vegetation were taken to analyze the relationship to leaf nitrogen content using various RGB indicators. There were significant correlations between RGB indicators and leaf nitrogen content in coniferous and broad-leaved tree (with Sasa understory), respectively. We developed a method to estimate the spatial distribution of each vegetation using the aerial digital images taken from UAV derived digital surface model (DSM) and their seasonal differences between leave on and off periods. Spatial distribution of nitrogen content in canopy leaf was mapped from the relationship between the RGB indicators and leaf nitrogen content on the vegetation map. From this result, spatial dynamics in nitrogen cycling of forest ecosystem can be visualized and mapped out to help to understand detail locational difference.