DOI: 10.5061/dryad.tmpg4f55v
title: Data from: Tracking shifts in forest structural complexity through space and time in human-modified tropical landscapes

description: Habitat structural complexity is an emergent property of ecosystems that
 directly shapes their biodiversity, functioning and resilience to
 disturbance. Yet despite its importance, we continue to lack consensus on
 how best to define structural complexity, nor do we have a generalised
 approach to measure habitat complexity across ecosystems. To bridge this
 gap, here we adapt a geometric framework developed to quantify the surface
 complexity of coral reefs and apply it to the canopies of tropical
 rainforests. Using high-resolution, repeat-acquisition airborne laser
 scanning data collected over 450 km2 of human-modified tropical landscapes
 in Borneo, we generated 3D canopy height models of forests at varying
 stages of recovery from logging. We then tested whether the geometric
 framework of habitat complexity – which characterises 3D surfaces
 according to their height range, rugosity and fractal dimension – was able
 to detect how both human and natural disturbances drive variation in
 canopy structure through space and time across these landscapes. We found
 that together, these three metrics of surface complexity captured major
 differences in canopy 3D structure between highly-degraded, selectively
 logged and old-growth forests. Moreover, the three metrics were able to
 track distinct temporal patterns of structural recovery following logging
 and wind disturbance. However, in the process we also uncovered several
 important conceptual and methodological limitations with the geometric
 framework of habitat complexity. We found that fractal dimension was
 highly sensitive to small variations in data inputs and was ecologically
 counteractive (e.g., higher fractal dimension in oil palms than old-growth
 forests), while rugosity and height range were tightly correlated (r=0.75)
 due to their strong dependency on maximum tree height. Our results suggest
 that forest structural complexity cannot be summarised using these three
 descriptors alone, as they overlook key features of canopy vertical and
 horizontal structure that arise from the way trees fill 3D space.
    
description: For details of the methods used to generate the data see Rosen et
 al. (2024) Ecography, 10.1111/ecog.07377 
description: # Tracking shifts in forest structural complexity through space and time
 in human-modified tropical landscapes ``` data_code_archive/ |-----data/ |
 |-----new_standardised_chms/ # &lt;- ready to use canopy height models. |
 |-----sensitivity_polygons_2023/ # &lt;- shapefile containing the polygons
 needed for the sensitivity analysis. | |-----SAFE forest classification/ #
 &lt;- raster and .xlsx file classifying SAFE landscape by habitat type. |
 |-----Danum_boundary_extent/ # &lt;- shapefile of Danum CHM boundary
 extent. | |-----SAFE_boundary_extent/ # &lt;- shapefile of SAFE CHM
 boundary extent. | |-----Maliau_boundary/ # &lt;- shapefile of Maliau CHM
 boundary extent. | |-----whole_landscape/ # &lt;- shapefile containing
 gridded polygons used in the whole landscape analysis. |
 |-----Land_use_gradient/ # &lt;- shapefile containing polygons used in the
 space-for-time analysis. | |-----other_metrics/ # &lt;- rasters of plant
 area density (PAD) for each of the sites. | |-----2014_2016_logged/ #
 &lt;- shapefile containing polygons for the temporal analysis. |
 |-----2013_2020_recovery/ # &lt;- shapefile containing polygons for the
 temporal analysis. | \-----2014_2020_old_growth/ # &lt;- shapefile
 containing polygons for the temporal analysis. |-----R code/ |
 |-----surface_geometry_functions.R # &lt;- main functions used for
 calculating R, D and deltaH. | |-----alternative_metrics_functions.R #
 &lt;- functions for calculating alternative structural metrics, compared
 in SI. | |-----plotting_functions.R # &lt;- functions for plotting. |
 |-----calculate_RDH_borneo.R # &lt;- calculate RDH across a land-use
 gradient of forest disturbance or across time. |
 |-----RDH_whole_landscape.R # &lt;- calculate RDH across the entire SAFE
 and Danum landscapes. | |-----calculate_RDH_sensitivity_analysis.R # &lt;-
 calculate RDH for sensitivity analysis. | |-----PCA.R # &lt;- PCA
 analysis. | |-----analysis.R # &lt;- t-tests comparing RDH in forests vs.
 non-forests. | |-----calculate_alternative_metrics.R # &lt;- calculate
 alternative metrics for comparison with R, D and H (in SI). |
 |-----calculate_percentage_na_rasters.R # &lt;- calculate percentage of
 NAs in each CHM. | |-----whole_landscape_plot.R # &lt;- plot Figure 4. |
 |-----sensitivity_analysis_plots.R # &lt;- plot Figure 3. |
 |-----temporal_plots.R # &lt;- plot Figure 5. |
 |-----plot_CHMs_temporal_changes.R # &lt;- plot Figure 6. |
 |-----testing_CHM_resolution.qmd # &lt;- testing impact of CHM resolution
 on RDH estimates. Figures for SI. | \-----testing_method_changes.qmd #
 &lt;- testing impact of various changes to the geometric theory.
 \-----README.md ```