Understanding and modelling the dynamics of data point clouds of relative growth rate and plant size

•Relative growth rate (RGR) allows comparison between contrasting type of organisms.•The pattern of decreasing RGR with increasing size is known as ontogenetic drift.•The linear RGR-size relationships of repeated surveys form the ontogenetic drift.•Unfavourable environmental conditions reduce the strength of the ontogenetic drift.•Slopes of semi-major axes of the RGR-size change signs when smaller trees cease to dominate growth.