DOI: 10.5061/dryad.80gb5mm1g
title: The structural and functional impacts of invasive <em>Psidium cattleianum</em> in forests on the Island of Hawaiʻi

description: During the past century, the proliferation of invasive species has
 contributed to the loss of biodiversity and ecosystem degradation. In
 forests, invasive tree species can alter ecosystem function, but the
 underlying mechanisms of these changes are not fully understood. We use
 the ongoing invasion of P. cattleianum on the Island of Hawaiʻi to test
 the hypotheses that invasive structural changes drive changes to forest
 evapotranspiration (ET). The aim of our study is first to quantify the
 structural changes to native ʻōhiʻa -dominated forest impacted by a
 gradient of P. cattleianum invasion. Our results suggest that invasive P.
 cattleianum causes significant changes to the vegetation density and
 structure of native forest on the Island of Hawai’i, including increased
 vegetation area index (VAI), decreased mean leaf height, and decreased
 structural heterogeneity. Second, we strove to understand the functional
 implications of structural changes through a biophysical modeling
 simulation, testing the sensitivity of ET to canopy structure under
 contrasting scenarios. Modeling the functional impact of structural
 change, we found that plots with P. cattleianum invasion importance value
 (IVinv) above 0.35 have a higher likelihood to increase ET compared to
 plots with P. cattleianum invasion less than 0.35 IVinv. Modeled increases
 in ET due to invasion ranged from 19% and 123% relative to native
 transects. The large variation in ET increases is caused by structural
 variation because the modeling scenarios did not include potential species
 differences in leaf physiology. Diagnostic scenario modeling shows the
 effect size of increased leaf area on modelled ET is constrained by the
 structural arrangement, i.e., vertical distribution, of the increased
 vegetation. Thus, an invasion structure that increases vegetation density
 in taller, more sunlit forest strata will lead to a greater increase in ET
 compared to an invasion structure that increases vegetation density in the
 shaded forest understory. Overall, we conclude that the vertical
 distribution of vegetation is an important factor shaping the impact of
 invasive P. cattleianum on the forest water balance. This dryad repository
 contains:  Point clouds of forest structure derived from
 terrestrial LiDAR for each sample site (.las files). The vegetation area
 index (VAI) for each 1 m3 voxel corresponding to each point cloud dataset
 (.csv files).
description: # The structural and functional impacts of invasive *Psidium cattleianum*
 in forests on the Island of Hawaiʻi Dataset DOI:
 [10.5061/dryad.80gb5mm1g](10.5061/dryad.80gb5mm1g) ## Description of the
 data and file structure ### Files and variables #### There are 25 .csv
 files listed below: 191105_coopercenter_native1_georef_.csv
 191108_coopercenter_mixed1_georef_c.csv
 191207_olaahwy11_invasive1_georef_c.csv
 191207_olaahwy11_invasive2_georef_c.csv
 191202_olaa_mixed_20to40_georef_cla.csv
 191211_laupahoehoe_invasive_0to20_r.csv
 191210_olaa_mixed_0to20_georef_clas.csv
 191120_olaa_native2_georef_classifi.csv
 191120_olaa_native1_georef_classifi.csv
 191219_Laupahoehoe_native_0to22_reg.csv
 200105_kalopa_native2_registered_ge.csv
 191229_havo_nativeec_registered_geo.csv
 191227_havo_mixed_registered_georef.csv
 191105_coopercenter_native2_georef_.csv
 191213_laupahoehoe_invasive_20to40_.csv
 191111_coopercenter_invasive1_geore.csv
 191223_Laupahoehoe_native_22to40_re.csv
 191108_coopercenter_mixed2_georef_c.csv
 191215_laupahoehoe_mixed2_registere.csv
 200103_havo_invasive_registered_geo.csv
 191215_laupahoehoe_mixed1_registere.csv
 191111_coopercenter_invasive2_geore.csv
 200106_kalopa_mixed_registered_geor.csv
 200105_kalopa_native1_registered_ge.csv
 200107_kalopaanalogue_invasive_regi.csv #### Description of .csv files:
 **Naming convention:** The first 6 digits indicate the date the data was
 collected in yymmdd format. The name after the first underscore
 corresponds to the study site. The label after the second underscore
 corresponds to the transect type (native, mixed, or invasive) and number
 (some transects had to be split into 2 sections). If the name specifies a
 number range (i.e. 0to20), that indicates the portion of the 40m transect
 the data represents (in m). The remaining descriptive words in the file
 names include abbreviations of "georeferenced",
 "classified", and "registered". These are processing
 steps that apply to all the datasets and do not identify any important
 differences among datasets. Words were cut off according to a limit on
 file name characters. **Description:** The .csv files contain a 3D
 voxelized matrix in which the transect's point cloud has been
 summarized into cubic meter voxels. The vegetation area index is the
 normalized LiDAR point density found in each cubic meter voxel. These .csv
 files are the input data processed by forestR to derive structural summary
 metrics.  ##### Variables * : An index column * X: The value corresponds
 to x (m) in a 3D grid * Y: The value corresponds to y (m) in a 3D grid *
 Z: The value corresponds to z (m) in a 3D grid * V1: The vegetation area
 index (VAI) (dimensionless), the normalized LiDAR point density in each
 cubic meter voxel. #### There are 25 .las files listed below:
 191108_coopercenter_mixed2_georef_c.las
 191105_coopercenter_native2_georef_.las
 191105_coopercenter_native1_georef_.las
 191111_coopercenter_invasive2_geore.las
 191111_coopercenter_invasive1_geore.las
 191202_olaa_mixed_20to40_georef_cla.las
 191108_coopercenter_mixed1_georef_c.las
 191207_olaahwy11_invasive1_georef_c.las
 191120_olaa_native2_georef_classifi.las
 191120_olaa_native1_georef_classifi.las
 191210_olaa_mixed_0to20_georef_clas.las
 191219_Laupahoehoe_native_0to22_reg.las
 191223_Laupahoehoe_native_22to40_re.las
 191213_laupahoehoe_invasive_20to40_.las
 191207_olaahwy11_invasive2_georef_c.las
 191211_laupahoehoe_invasive_0to20_r.las
 191215_laupahoehoe_mixed2_registere.las
 191215_laupahoehoe_mixed1_registere.las
 200105_kalopa_native1_registered_ge.las
 200105_kalopa_native2_registered_ge.las
 191229_havo_nativeec_registered_geo.las
 200103_havo_invasive_registered_geo.las
 191227_havo_mixed_registered_georef.las
 200107_kalopaanalogue_invasive_regi.las
 200106_kalopa_mixed_registered_geor.las #### Description of .las files:
 **Naming convention:** The first 6 digits indicate the date the data was
 collected in yymmdd format. The name after the first underscore
 corresponds to the study site. The label after the second underscore
 corresponds to the transect type (native, mixed, or invasive) and number
 (some transects had to be split into 2 sections). If the name specifies a
 number range (i.e. 0to20), that indicates the portion of the 40m transect
 the data represents (in m). The remaining descriptive words in the file
 names include abbreviations of "georeferenced",
 "classified", and "registered". These are processing
 steps that apply to all the datasets and do not identify any important
 differences among datasets. Words were cut off according to a limit on
 file name characters. **Description:** The .las files contain the point
 clouds derived from terrestrial laser scanning (TLS) for each transect.
 These .las files have been normalized, thinned, and georeferenced
 according to the processing steps outlined in the supplement to the
 manuscript. These .las files are the input data required to derive the
 voxelized .csv files described above. ## Code/software .csv files can be
 opened using Google Sheets or other open-source software.  .las files can
 be opened with free software such as .lastools or Cloud Compare. ## Access
 information Other publicly accessible locations of the data: * N/A Data
 was derived from the following sources: * Field collection