814 research outputs found
Characterizing the Impacts of the Invasive Hemlock Woolly Adelgid on the Forest Structure of New England
Climate change is raising winter temperatures in the Northeastern United States, both expanding the range of an invasive pest, the hemlock woolly adelgid (HWA; Adelges tsugae), and threatening the survival of its host species, eastern hemlock (Tsuga canadensis). As a foundation species, hemlock trees underlie a distinct network of ecological, biogeochemical, and structural systems that will likely disappear as the HWA infestation spreads northward. Remote sensing can offer new perspectives on this regional transition, recording the progressive loss of an ecological foundation species and the transition of evergreen hemlock forest to mixed deciduous forest over the course of the infestation. Lidar remote sensing, unlike other remote sensing tools, has the potential to penetrate dense hemlock canopies and record HWAâs distinct impacts on lower canopy structure. Working with a series of lidar data from the Harvard Forest experimental site, these studies identify the unique signals of HWA impacts on vertical canopy structure and use them to predict forest condition. Methods for detecting the initial impacts of HWA are explored and a workflow for monitoring changes in forest structure at the regional scale is outlined. Finally, by applying terrestrial, airborne, and spaceborne lidar data to characterize the structural variation and dynamics of a disturbed forest ecosystem, this research illustrates the potential of lidar as a tool for forest management and ecological research
Complexity and Dynamics of Semi-Arid Vegetation Structure, Function and Diversity Across Spatial Scales from Full Waveform Lidar
Semi-arid ecosystems cover approximately 40% of the earthâs terrestrial landscape and show high dynamicity in ecosystem structure and function. These ecosystems play a critical role in global carbon dynamics, productivity, and habitat quality. Semi-arid ecosystems experience a high degree of disturbance that can severely alter ecosystem services and processes. Understanding the structure-function relationships across spatial extents are critical in order to assess their demography, response to disturbance, and for conservation management. In this research, using state-of-the-art full waveform lidar (airborne and spaceborne) and field observations, I developed a framework to assess the complexity and dynamics of vegetation structure, function and diversity across spatial scales in a semi-arid ecosystem.
Difficulty in differentiating low stature vegetation from bare ground is the key remote sensing challenge in semi-arid ecosystems. In this study, I developed a workflow to differentiate key plant functional types (PFTs) using both structural and biophysical variables derived from the full waveform lidar and an ensemble random forest technique. The results revealed that waveform lidar pulse width can clearly distinguish shrubs from bare ground. The models showed PFT classification accuracy of 0.81â0.86% and 0.60â0.70% at 10 m and 1 m spatial resolutions, respectively. I found that structural variables were more important than the biophysical variables to differentiate the PFTs in this study area. The study further revealed an overlap between the structural features of different PFTs (e.g. shrubs from trees).
Using structural features, I derived three main functional traits (canopy height, plant area index and foliage height diversity) of shrubs and trees that describe canopy architecture and light use efficiency of the ecosystem. I evaluated the trends and patterns of functional diversity and their relationship with non-climatic abiotic factors and fire disturbance. In addition to the fine resolution airborne lidar, I used simulated large footprint spaceborne lidar representing the newly launched Global Ecosystem Dynamics Investigation system (GEDI, a lidar sensor on the International Space Station) to evaluate the potential of capturing functional diversity trends of semi-arid ecosystems at global scales. The consistency of diversity trends between the airborne lidar and GEDI confirmed GEDIâs potential to capture functional diversity. I found that the functional diversity in this ecosystem is mainly governed by the local elevation gradient, soil type, and slope. All three functional diversity indices (functional richness, functional evenness and functional divergence) showed a diversity breakpoint near elevations of 1500 m â 1700 m. Functional diversity of fire-disturbed areas revealed that the fires in our study area resulted in a more even and less divergent ecosystem state. Finally, I quantified aboveground biomass using the structural features derived from both the airborne lidar and GEDI data. Regional estimates of biomass can indicate whether an ecosystem is a net carbon sink or source as well as the ecosystemâs health (e.g. biodiversity). Further, the potential of large footprint lidar data to estimate biomass in semi-arid ecosystems are not yet fully explored due to the inherent overlapping vegetation responses in the ground signals that can be affected by the ground slope. With a correction to the slope effect, I found that large footprint lidar can explain 42% of variance of biomass with a RMSE of 351 kg/ha (16% RMSE). The model estimated 82% of the study area with less than 50% uncertainty in biomass estimates. The cultivated areas and the areas with high functional richness showed the highest uncertainties. Overall, this dissertation establishes a novel framework to assess the complexity and dynamics of vegetation structure and function of a semi-arid ecosystem from space. This work enhances our understanding of the present state of an ecosystem and provides a foundation for using full waveform lidar to understand the impact of these changes to ecosystem productivity, biodiversity and habitat quality in the coming decades. The methods and algorithms in this dissertation can be directly applied to similar ecosystems with relevant corrections for the appropriate sensor. In addition, this study provides insights to related NASA missions such as ICESat-2 and future NASA missions such as NISAR for deriving vegetation structure and dynamics related to disturbance
ë€ì€ ê·ëȘš LiDAR ë°ìŽí°ë„Œ íì©í ëììíêł ê”ŹìĄ° ë° ì°êČ°ì± íê°
íìë
ŒëŹž(ë°ìŹ) -- ììžëíê”ëíì : íêČœëíì íëêłŒì ìĄ°êČœí, 2021.8. ìĄìê·Œ.Integrated multiscale light detection and ranging (LiDAR) datasets are required for managing urban ecosystems because 1) LiDAR datasets can represent various spatial structures across the urban landscape and 2) the multitemporal LiDAR approach can derive the changes of urban landscape structures. This dissertation aimed to find the various spatiotemporal availabilities (i.e., from the tree-level spatial scale to the city-level regional scale with the multitemporal approach) of LiDAR or laser scanning (LS) datasets for monitoring urban ecosystems in the following three chapters.
Chapter 2: Collecting tree inventory data in urban areas is important for managing green areas. Surveying using airborne laser scanning (ALS) is effective for collecting urban tree structures but less efficient regarding the economic costs and its operation. Terrestrial laser scanning (TLS), and mobile laser scanning (MLS) datasets could have the potential in complementing those of ALS in the respect to efficiency. However, to the best of my knowledge, there were limited studies for seeking the similarities and variations among the canopy metrics derived from various LiDAR platforms. In Chapter 2, I compared structural canopy metrics among ALS, TLS, and MLS datasets in the urban parks. The purpose of Chapter 2 was to test whether the estimates of tree metrics differed depending on single or clustered trees and to test whether the errors in LiDAR-derived metrics were related to the tree structures. Small, urban parks were selected for surveying trees using the three LiDAR platforms. The ALS datasets were acquired on 14 May, 2017. The TLS and MLS datasets were acquired from 10â11 May, 2017, and 21â25 April, 2020, respectively. The tree point clouds were classified into single and clustered trees. The structural metrics were compared in each pair (i.e., ALS and TLS, ALS and MLS, and TLS and MLS pairs). The heights related metrics (e.g., percentile heights and the distribution of the heights values), the complexity metric (e.g., the Rumple index) and area were calculated for comparisons. The root mean square error (RMSE), bias, and the Pearsonâs correlation coefficient (r) were calculated to evaluate the difference in each metric among the LiDAR platforms. The results showed that ZMAX, max and mean CHM, and area showed good consistencies (RMSE% 0.900). Especially, the biases of CHM-derived metrics did not present significant differences (p > 0.05) regardless of single or clustered trees. Moreover, the biases from the comparisons in each pair showed linear relations with the tree heights and vertical canopy complexity (i.e., Pearsonâs correlation coefficient showed significant; r >0.29, p < 0.05). My results could be references when combining multiple LiDAR systems to estimate the canopy structures of urban park areas.
Chapter 3: Understanding forest dynamics is important for assessing the health of urban forests, which experience various disturbances, both natural (e.g., treefall events) and artificial (e.g., making space for agricultural fields). Therefore, quantifying three-dimensional (3D) changes in canopies is a helpful way to manage and understand urban forests better. Multitemporal ALS datasets enable me to quantify the vertical and lateral growth of trees across a landscape scale. The goal of Chapter 3 is to assess the annual changes in the 3-D structures of canopies and forest gaps in an urban forest using annual airborne LiDAR datasets for 2012â2015. The canopies were classified as high canopies and low canopies by a 5 m height threshold. Then, I generated pixel- and plot-level canopy height models and conducted change detection annually. The vertical growth rates and leaf area index showed consistent values year by year in both canopies, while the spatial distributions of the canopy and leaf area profile (e.g., leaf area density) showed inconsistent changes each year in both canopies. In total, high canopies expanded their foliage from 12 m height, while forest gap edge canopies (including low canopies) expanded their canopies from 5 m height. Annual change detection with LiDAR datasets might inform about both steady growth rates and different characteristics in the changes of vertical canopy structures for both high and low canopies in urban forests.
Chapter 4: Although many studies have considered urban structure when investigating urban ecological networks, few have considered the 3D structure of buildings as well as urban green spaces. In Chapter 4, I examined an urban ecological network using the 3D structure of both green spaces and buildings. Using breeding-season bird species observations and ALS data collected, I assessed the influence of 3D structural variables on species diversity. I used correlation analyses to determine if vertical distribution, volume, area, and height of both buildings and vegetation were related to bird species diversity. Then I conducted circuit theory-based current flow betweenness centrality (CFBC) analysis using the LiDAR-derived structural variables. I found that the volumes of buildings and 8â10 m vegetation heights were both highly correlated with species richness per unit area. There were significant differences between 2D and 3D connectivity analysis using LiDAR-derived variables among urban forest patches, boulevards, and apartment complexes. Within urban forest patches and parks, 3D CFBC represented canopy structural characteristics well, by showing high variance in spatial distributions. The 3D CFBC results indicated that adjacent high-rise buildings, dense apartment complexes, and densely urbanized areas were isolated, as characterized by low centrality values, but that vegetation planted in open spaces between buildings could improve connectivity by linking isolated areas to core areas. My research highlights the importance of considering 3D structure in planning and managing urban ecological connectivity.
In this dissertation, the availability of integrated multiscale LiDAR datasets was found via three standalone studies. It was revealed that 3D information could enhance the quality of urban landscape monitoring and ecological connectivity analysis by elaborately explaining spatial structures. However, the spatiotemporal scales of each standalone study were limited to the city scale and to five years. The recently launched Global Ecosystem Dynamics Investigation (GEDI) would help to solve these limitations. Furthermore, the GEDI dataset could help researchers understand the relationship between ecosystem structures and their functions.ëłž íìë
ŒëŹžì ë€ìí ìêł”ê° ì€ìŒìŒìì ëììíêł ëȘšëí°ë§ì ìí LiDAR ë°ìŽí°ì íì©êłŒ ìíì ì믞 ëì¶ì êŽí ëŽì©ì ë€ëŁŹë€. LiDARë Light Detection and Rangingì ìœìŽëĄ, LiDAR ìŒììì ë°ìŹë ë ìŽì ê° ëìì ëëŹí ë€ ë°ìŹëìŽ ëìì€ë ë ìŽì ì ìžêž°ì ìê°ì êłì°íìŹ ëìì ììč ì ëłŽë„Œ 3ì°šì ì ê”° ë°ìŽí°ëĄ ëłííŽìŁŒë ë„ëí ìêČ©íìŹ ëê”ŹìŽë€. LiDAR ìêČ©íìŹ ëê”Źì ë±ì„ìŒëĄ ìì°êłŒ ëìì 3ì°šì êł”ê°ì 볎ì ì·šëìŽ êž°ë„íŽì§ì ë°ëŒ, ììì§ì 3ì°šì êł”ê°ì 볎ì ìëŹŒ ìą
ìŹìŽì êŽêł ëì¶, ìêłìŽ LiDAR ë°ìŽí°ë„Œ íì©í ë
čì§ ëȘšëí°ë§ ì°ê”Ź ë±ìŽ ìŽë€ì§êł ìë€. ëí íêł” LiDAR(ALS), ì§ì LiDAR(TLS), ìŽëí LiDAR(MLS) ë± ë€ìí LiDAR ìì€í
ì ê°ë°ëĄ ì°ê”Ź ëȘ©ì ì ìë§ì ìêł”ê° íŽìëì 3ì°šì êł”ê°ì ëłŽë„Œ ì·šëí ì ìêČ ëìë€. ëłž íìë
ŒëŹžììë ëìë
čì§ë„Œ ëììŒëĄ LiDAR ìêČ©íìŹ ëê”Źì ë€ìí ìêł”ê° ì€ìŒìŒ ì ì© ìžĄë©Žìì, Chapter 2 íêł”, ì§ì, ìŽëí LiDAR ìì€í
ìŹìŽ ìëȘ©ê”ŹìĄ°êŽë š ëłìë€ì ìŒìčì± íê°, Chapter 3 ìêłìŽ ë¶ìì í”í ëìë
čì§ ëí ëȘšëí°ë§, Chapter 4 ëìì ìíì ì°êČ°ì± ë¶ìì ì§ííìë€.
Chapter 2: ëìì ìëȘ©ì ëłŽë„Œ ì·šëíë êČì ëìë
čì§ êŽëŠŹì ììŽ íìì ìŽë€. LiDAR êž°ì ì ë°ëŹëĄ ëììëȘ©ì 3ì°šì ì ëłŽë„Œ ì·šëí ì ìêČ ëììŒë©°, ìŽë„Œ í”íŽ ìëȘ©ëìŽì ìëȘ©ê”ŹìĄ°, ì§ì ë°ìŽì€ë§€ì€ ë±ì ëì ì íëëĄ ì°ì¶í ì ìêČ ëìë€. íêł” LiDARë ëì ëČìì êł”ê°ì ëłŽë„Œ ëì ì íëëĄ ìžĄì íë íčì±ì ì§ë
ì°ëŠŒ ëȘšëí°ë§ ë¶ìŒìì íë°í íì©ëêł ìë€. íì§ë§ íêł” LiDAR ë°ìŽí°ì ì·šëì íêł”êž° ìŽì©ëč, ì„ëčêŽë š ë§ëí ëčì©ìŽ ë°ìíêł ìŽì©ì ììŽ ì 돞ì±ì ìê”Źíë©° ëìì ì ê”°ë°ëê° ìëì ìŒëĄ ëźë€ë ëšì ì ì§ëë€. ë°ë©Ž ì§ì LiDARì ìŽëí LiDARë ìŽì©íêž° ížëŠŹíêł ëì ì ê”°ë°ëë„Œ ì¶ë „íë€ë ì ìì íêł” LiDARì ëšì ì ê·čëł”í ì ìë€. ìŽìČëŒ ë€ìí LiDAR ìì€í
ì ë±ì„êłŒ ìŽë„Œ íì©í ìíêł ëȘšëí°ë§ ì°ê”Ź ìëê° ìŠê°íë©Žì LiDAR ìì€í
ê° íšìšì ìž ìŽì©êłŒ ë°ìŽí°ì 볎ì ë°©ëČë€ìŽ ìê”Źëêł ìë€. íì§ë§ íìŹêčì§ ALS, TLS, MLSì 3ê°ì ìì€í
ì í”íŽ ì·šëë ìëȘ© ì ëłŽë„Œ ìëĄ ëčê”íêł , ìëĄ ëìČŽê°ë„í ìëȘ©ì ëłŽë„Œ ëì¶í ì°ê”Źë ë§ìŽ ì§íë ë° ìë€. ë°ëŒì ëłž íìë
ŒëŹžì Chapter 2ììë ALS, TLS, MLS í”íŽ ì·šëë ëìì ìëȘ©ì ëłŽë„Œ ìëĄ ëčê”íìŹ ìŒìčì±ì íê°íêł , ìŽë í ìëȘ©ê”ŹìĄ°êŽë š ì§íê° ìž LiDAR ìì€í
ìŹìŽìì ëìČŽê°ë„íì§ ë€ëŁšêł ìë€. ìžë¶ì ìŒëĄ Chapter 2ë ìëȘ©ê”ŹìĄ°êŽë š ì§íê° ëšëȘ©ì°šìêłŒ ê”°ì§ì°šì, ìëȘ©ê”ŹìĄ°ì ë°ëŒ ALS, TLS, MLS ìì€í
ìì ì°šìŽê° ë°ìíëì§ì ëí ëŽì©ì ëŽêł ìë€. ìČìì ëìêł”ì 9ê°ììì ALS ë°ìŽí°ë 2017ë
5ì 14ìŒ, TLS ë°ìŽí°ë 2017ë
5ì 10ìŒêłŒ 11ìŒ, MLS ë°ìŽí°ë 2020ë
4ì 21ìì 25ìŒ ì·šëëìë€. ì·šëë ë°ìŽí°ì
ì ìêŽì êČčìčš ìŹë¶ì ë°ëŒ ëšëȘ©êłŒ ê”°ì§ìŒëĄ ë¶ë„ëììŒë©°, 3ê°ì íìŽ(ALS-TLS, MLS-TLS, ALS-MLS)ëĄ ìêŽì íŒìŒíìŒ ëìŽ, ìêŽëł”ìĄì±, ë©Žì ë±ì ìëȘ©ê”ŹìĄ°êŽë š ëłìë€ì 1:1 ëčê”íìë€. íêł” LiDAR ë°ìŽí°ë„Œ í”íŽ ëì¶ë ìëȘ©ê”ŹìĄ°êŽë š ëłìë€ì ì°žìĄ°ëĄ íìŹ íê· ì êł±ê·Œì€ì°š(RMSE), íží„(bias), íŒìŽìš ìêŽêłì(r) ë±ì êłì°íêł ìž LiDAR ìì€í
ìŹìŽì ìŒìčì±ì íê°íìë€. íê° êČ°êłŒ ZMAX, CHMêŽë š ìêŽëìŽ êŽë š ëłìë€, ê·žëŠŹêł ìêŽë©Žì ìŽ ëì ìŒìčì±ì 볎ìë€(RMSE% 0.900). íčí CHMì í”íŽ ëì¶ë ìêŽëìŽ êŽë š ëłìë€ì ëšëȘ©êłŒ ê”°ì§ìì ìžê°ì LiDAR ìì€í
ê° í”êłì ìž ì°šìŽë„Œ 볎ìŽì§ ììë€(p > 0.05). ë°ë©Ž íŒìŒíìŒ ìêŽëìŽì íê· ìêŽëìŽ ë±ì ë§€ì° ëźì ìŒìčì±ì ëíëìŒë©°, ìž íìŽìì ëì¶ë íží„ì ìêł , ìêŽëł”ìĄì±êłŒ ìœí ì íêŽêłë„Œ ëíëë€(r >, p < 0.05).
Chapter 3: ìêŽëíë ìČì 걎ê°ì±ì ë°ìíë€. íčí, ìì°ì ·ìžìì ìž ê”ëì ìíŽ ë°ìí ìČíì ìČ ëŽë¶ì ëčì íŹêłŒìš, ìšë, ì”ë ë±ì ìí„ì ëŒìł ìŁŒëł íêČœì ëłíë„Œ ìŒêž°íë€. ë°ëŒì ìČíì íì§íêł ëȘšëí°ë§íë êČì ìČì ëíë„Œ ìŽíŽíëë° ììŽ ë§€ì° ì€ìíë€. íêł” LiDAR ìŒìë„Œ íì©í êČœì° ìì±ìììŽë íêł”ìŹì§ ë± 2ì°šì ë°ìŽí°ëĄ íì§íêž° ìŽë €ìŽ ìČí ëë ê°ë°©êł”ê°ì íì§ì ìêŽì 3ì°šì íìì ì·šëìŽ ê°ë„íë€. Chapter 3ììë 2012ë
ëë¶í° 2015ë
ë 4ê°ë
ì íêł” LiDARë„Œ íì©íìŹ ìì°í ëìêł”ì(ëŽìì°)ì ìêŽêłŒ ìČíì ìíì ìì§ì ëłíììì ì¶ì íìë€. ìêŽì ëìŽ 5më„Œ êž°ì€ìŒëĄ ììž”ë¶ì íìž”ë¶ ìêŽìŒëĄ ë¶ë„ëììŒë©°, ìêŽëìŽëȘšëž(canopy height model, CHM)ì ìì±íìŹ ì°ê°ëłíë„Œ íì§íìë€. ì°ê”ŹêČ°êłŒ ììž”ë¶ ë° íìž”ë¶ ìêŽì ìì§ìì„ëêłŒ ìœë©Žì ì§ìë ìŒì í ì°ê° ëłíììì ëłŽìž ë°ë©Ž, ìíì ëłíì ìœë©Žì ë°ëë ë¶ê·ìčì ìž ì°ê° ëłíììì 볎ìë€. ì ë°ì ìŒëĄ ììž”ë¶ ìêŽì ëìŽ 12mìì ìžĄë°©í„ ìì„ì íë êČìŒëĄ ëíëŹìŒë©°, íìž”ë¶ ìêŽ ì€ ìČíììë ëìŽ 5mìì ìžĄë°©í„ ìì„ìŽ íë°íêČ ëíëŹë€. LiDAR ë°ìŽí°ì ì°ê° ëłí íì§ë„Œ í”íŽ ìì°ì ìŒëĄ íì±ë ìČíì êČœì° ìì„êłŒ ê”ë ìžĄë©Žìì ë§€ì° íë°í ëíê° ë°ìíêł ììŒë©°, ìžìì ìŒëĄ íì±ë ê°ë°©êł”ê°ì êČœì° ìêŽì ëíê° ë€ì ìčšìČŽëšì ëì¶íìë€.
Chapter 4ë ëì ëŽ ê±ŽëŹŒêłŒ ë
čì§ì 3ì°šì ê”ŹìĄ°ë„Œ ì
ë „ìëŁëĄ íì©íìŹ ëìì ìíì ì°êČ°ì±ì íê°íë ì°ê”Źë„Œ ë€ëŁŹë€. ëì ëŽ ìíì ì°êČ°ì± ëì¶êłŒ êŽë ší ì°ê”Źë ëìì ë
čì§ì íí ë±ì ìŁŒì ëłìëĄ íìŹ ì§íìŽ ëêł ìë€. ê·žëŹë 3ì°šìì ìž íčì±ìž ëì ê±ŽëŹŒì ë¶íŒ, ìëȘ©ì ìì§ì ìž ê”ŹìĄ° ë±ì êł ë €í ì°êČ°ì± ë¶ìì ë§ìŽ ì§íë ë° ìë€. ì°ê”Ź ëìì§ë ìČìì ììČì ì€ìŹìŒëĄí 4 km Ă 4 km ì§ììŒëĄ, 2015ë
ì ì·šëë íêł” LiDARì ê°ì íŽ ì·šëë ìĄ°ë„ ìą
ìĄ°ìŹ ë°ìŽí°ë„Œ íì©íìŹ 1)ëì ëŽ ê±ŽëŹŒêłŒ ë
čì§ì 3ì°šì ê”ŹìĄ°ì ìĄ°ë„ ìą
ë€ìì± ìŹìŽ êŽêłë„Œ ìŽíŒêł , 2)ìĄ°ë„ ìą
ë€ìì±êłŒ ìêŽêŽêłë„Œ ê°ì§ë 3ì°šì ê”ŹìĄ°ëłìë„Œ íì©íìŹ ì ë„íëŠêž°ë° 맀ê°ì€ìŹì± ì°êČ°ì± ë¶ì(CFBC)ì ì§ííìë€. ì°ê”ŹêČ°êłŒ 걎ì¶ëŹŒì ë¶íŒì ìëȘ©ëìŽ 8-10mì ë
čì§ ë¶íŒëčê° ë©Žì ëč ìĄ°ë„ ìą
íë¶ëì ì€íŒìŽë§ ìììêŽêŽêłìì ëì ìêŽêŽêł(Ï> 0.6)ë„Œ ëíëë€. ì°êČ°ì± ë¶ìì êČ°êłŒë ì
ë „ëłìì êł”ê°ì°šì(2D ë° 3D)ì ë°ëŒ ë€ë„ŽêČ ëíëŹë€. íčí ëììČ, ëëĄëł, ìíížëšì§ëŽ ë
čì§ ë±ìì 2D êž°ë° CFBCì 3Dêž°ë° CFBCë í”êłì ìŒëĄ ì ì믞í ì°šìŽë„Œ 볎ìë€. ëí ëìë
čì§ì 3D êž°ë° CFBCì êČœì° ê°ì ë
čì§ ë©Žì ììë ìêŽì ê”ŹìĄ°ì ìž íčì±ì ë°ëŒ ëì ì°šìŽê° ëíëšì íìžíìë€. 3D CFBC ë¶ìêČ°êłŒë„Œ í”íŽ êł ìž” ê±ŽëŹŒ ìŁŒëłë¶, êł ë°ë ìíížëšì§, êł ë° ìê°íì§ì ë±ìŽ ëźì ì€ìŹì±ì ëłŽìŹ êł ëŠœì§ììŒëĄ ëíëŹìŒë©°, ê±ŽëŹŒ ìŹìŽ êł”ì§ ëŽ ììì ì°êČ°ì±ìŽ êł ëŠœë ì§ìêłŒ í”ìŹì§ìì ì°êČ°íë êž°ë„ì ëíëë€.
ìŽ íìë
ŒëŹžì ìëĄ ë€ë„ž LiDAR ìì€í
ì íì©íìŹ ëšëȘ©, êČœêŽ ì§ìëšì ë± ë€ìí êł”ê° ì€ìŒìŒììì ëìêČœêŽê”ŹìĄ° ë¶ì, ëìë
čì§ê”ŹìĄ°ì í ì§ìŽì© ë±ì ë°ë„ž ìê°ì ëłíìì, ëìêČœêŽê”ŹìĄ°ê° ê°ì§ë ìíì ì믞 ë±êłŒ êŽë šë ëŽì©ì ë€ëŁšêł ìë€. í„í Global Ecosystem Dynamics Investigation(GEDI) 믞ì
ì ë°ìŽí°ë„Œ íì©íìŹ ëłž íìë
ŒëŹžìì ë€ëŁšë ì§ìê·ëȘšì ì°ê”Źë„Œ ê”ê°ëšì, ëë„ëšì ë±ìŒëĄ íì„í ì ìì êČìŽë©° ìŽë„Œ í”íŽ ëììíêł ê”ŹìĄ°ì ê·ž êž°ë„ ìŹì êŽêłë„Œ ìŽíŽíëë° ëìì ì€ ì ìì êČìŽë€.Chapter 1. Introduction 1
1. Background 1
1.1. Urbanization and the importance of urban green spaces 1
1.2. Urban landscape and Light detection and ranging application 1
2. Purpose 6
Chapter 2. Comparing tree structures derived among multiple LiDAR systems in urban parks 10
1. Introduction 10
2. Methods and materials 12
2.1. Study site and tree classification 12
2.2. LiDAR survey and processing 14
2.3. Deriving the structural variables of the parks 17
2.4. Assessing the accuracy of the LiDAR-derived indices 18
3. Results 19
3.1. Comparing height metrics among the three LiDAR systems 19
3.2. Comparing CHM-derived canopy height metrics from each LiDAR systems 22
3.3. Comparing the area and the Rumple index determined using the LiDAR systems 23
4. Discussion 25
4.1. LiDAR configurations and data acquisition time intervals 25
4.2. Uncertainty of the structural indices derived from the three LiDAR systems 28
Chapter 3. Urban forest growth and gap dynamics detected by yearly repeated airborne LiDAR 31
1. Introduction 31
2. Methods and Materials 33
2.1. Field survey 33
2.2. Canopy opening detection 34
2.3. Airborne LiDAR dataset acquisition and registration 35
2.4. Generation of height models and change detection 36
2.5. Gap detection and classification 38
2.6. Estimating changes of vertical canopy distribution and canopy complexity 38
3. Results 39
3.1. Pixel and hexagon height model-based change detection 39
3.2. Continuous one-year vertical growth area 41
3.3. Open canopy change detection 42
3.4. Changes in vertical canopy structures in High Canopy and Open Canopy 43
4. Discussion 45
4.1. What are the differences between the canopy structural changes derived from annual change detections and three-year interval change detection? 45
4.2. What are the characteristics of the structural changes according to the different canopy classes (e.g., high canopies and low canopies) in the urban forest? 46
Chapter 4. LiDAR-derived three-dimensional ecological connectivity mapping 49
1. Introduction 49
2. Materials and Methods 51
2.1. Study area and avian species observation 52
2.2. Airborne LiDAR acquisition, preprocessing and classification and deriving structural variables 53
2.3. Correlation analysis and selection of structural variables 55
2.4. 2D and 3D ecological networks 55
3. Results 56
3.1. Avian species survey 56
3.2. Correlation analyses and variable selection 56
3.3. Connectivity analysis results 58
3.4. Correlation between connectivity results with bird species diversity 59
3.5. Differences between 2D- and 3D-based CFBCs 60
4. Discussion 61
4.1. Vegetation and building structures and bird species diversity 61
4.2. 3D-based connectivity results 62
4.3. Differences between 2D and 3D network analyses 64
4.3.1. Forest and artificial green area 65
4.3.2. Roads and residential areas 66
Appendix 67
Chapter 5. Conclusion 70
1. Combination with multiple LiDAR data for surveying structures of urban green spaces 70
2. Multi-temporal urban forest gap monitoring 71
3. Ecological connectivity analysis using LiDAR 71
4. LiDAR application to Urban ecosystem monitoring 72
5. Expanding spatiotemporal scale and further works 73
Acknowledgments 75
Reference 76
Abstract in Korean 85ë°
The Burning Bush: Linking LiDAR-derived Shrub Architecture to Flammability
Light detection and ranging (LiDAR) and terrestrial laser scanning (TLS) sensors are powerful tools for characterizing vegetation structure and for constructing three-dimensional (3D) models of trees, also known as quantitative structural models (QSM). 3D models and structural traits derived from them provide valuable information for biodiversity conservation, forest management, and fire behavior modeling. However, vegetation studies and 3D modeling methodologies often only focus on the forest canopy, with little attention given to understory vegetation. In particular, 3D structural information of shrubs is limited or not included in fire behavior models. Yet, understory vegetation is an important component of forested ecosystems, and has an essential role in determining fire behavior.
In this dissertation, I explored the use of TLS data and quantitative structure models to model shrub architecture in three related studies. In the first study, I present a semi-automated methodology for reconstructing architecturally different shrubs from TLS LiDAR. By investigating shrubs with different architectures and point cloud densities, I showed that occlusion, shrub complexity, and shape greatly affect the accuracy of shrub models.
In my second study, I assessed the 3D architectural drivers of understory flammability by evaluating the use of architectural metrics derived from the TLS point cloud and 3D reconstructions of the shrubs. I focused on eight species common in the understory of the fire-prone longleaf pine forest ecosystem of the state of Florida, USA. I found a general tendency for each species to be associated with a unique combination of flammability and architectural traits. Novel shrub architectural traits were found to be complementary to the direct use of TLS data and improved flammability predictions.
The inherent complexity of shrub architecture and uncertainty in the TLS point cloud make scaling up from an individual shrub to a plot level a challenging task. Therefore, in my third study, I explored the effects of lidar uncertainty on vegetation parameter prediction accuracy. I developed a practical workflow to create synthetic forest stands with varying densities, which were subsequently scanned with simulated terrestrial lidar. This provided data sets quantitatively similar to those created by real-world LiDAR measurements, but with the advantage of exact knowledge of the forest plot parameters, The results showed that the lidar scan location had a large effect on prediction accuracy. Furthermore, occlusion is strongly related to the sampling density and plot complexity.
The results of this study illustrate the potential of non-destructive lidar approaches for quantifying shrub architectural traits. TLS, empirical quantitative structural models, and synthetic models provide valuable insights into shrub structure and fire behavior
Assessing the utility of geospatial technologies to investigate environmental change within lake systems
Over 50% of the world's population live within 3. km of rivers and lakes highlighting the on-going importance of freshwater resources to human health and societal well-being. Whilst covering c. 3.5% of the Earth's non-glaciated land mass, trends in the environmental quality of the world's standing waters (natural lakes and reservoirs) are poorly understood, at least in comparison with rivers, and so evaluation of their current condition and sensitivity to change are global priorities. Here it is argued that a geospatial approach harnessing existing global datasets, along with new generation remote sensing products, offers the basis to characterise trajectories of change in lake properties e.g., water quality, physical structure, hydrological regime and ecological behaviour. This approach furthermore provides the evidence base to understand the relative importance of climatic forcing and/or changing catchment processes, e.g. land cover and soil moisture data, which coupled with climate data provide the basis to model regional water balance and runoff estimates over time. Using examples derived primarily from the Danube Basin but also other parts of the World, we demonstrate the power of the approach and its utility to assess the sensitivity of lake systems to environmental change, and hence better manage these key resources in the future
Assessing wood properties in standing timber with laser scanning
Managed forests play crucial roles in ongoing climatic and environmental changes. Among other things, wood is capable of sinking and storing carbon in both standing timber and wood products. To promote these positive effects, more precise planning is required that will ensure sustainable forest management and maximal deposition of harvested wood for long-term applications. Information on wood properties plays a key role; i.e. the wood properties can impact the carbon stocks in forests and the suitability of wood for structural timber.
With respect to the theoretical background of wood formation, stem, crown, and branching constitute potential inputs (i.e. wood quality indicators) to allometric wood property, tree biomass, and wood quality models. Due to the complex nature of wood formation, measurements of wood quality indicators that could predict wood properties along the relevant directions of variation have previously been elusive in forest inventories. However, developments in laser scanning from aerial and terrestrial platforms support more complex mapping and modeling regimes based on dense three-dimensional point clouds.
The aim here was to determine how wood properties could be estimated in remote-sensing-aided forest inventories. For this purpose, methods for characterizing select wood quality indicators in standing timber, using airborne and terrestrial laser scanning (ALS and TLS, respectively) were developed and evaluated in managed boreal Scots pine (Pinus sylvestris L.) forests. Firstly, the accuracies of wood quality indicators resolved from TLS point clouds were assessed. Secondly, the results were compared with x-ray tomographic references from sawmills. Thirdly, the accuracies of tree-specific crown features delineated from the ALS data in predictive modeling of the wood quality indicators were evaluated.
The results showed that the quality and density of point clouds significantly impacted the accuracies of the extracted wood quality indicators. In the assessment of wood properties, TLS should be considered as a tool for retrieving as dense stem and branching data as possible from carefully selected sample trees. Accurately retrieved morphological data could be applied to allometric wood property models. The models should use tree traits predictable with aerial remote sensing (e.g. tree height, crown dimensions) to enable extrapolations.
As an outlook, terrestrial and aerial remote sensing can play an important role in filling in the knowledge gaps regarding the behavior of wood properties over different spatial and temporal extents. Further interdisciplinary cooperation will be needed to fully facilitate the use of remote sensing and spatially transferable wood property models that could become useful in tackling the challenges associated with changing climate, silviculture, and demand for wood.Hoidetuilla metsillÀ on useita tÀrkeitÀ rooleja muuttuvassa ilmastossa ja ympÀristössÀ. Puu sitoo ja varastoi hiiltÀ niin kasvaessaan, kuin pitkÀikÀisiksi puutuotteiksi jalostettuna. NÀiden vaikutusten huomioiminen metsÀnhoidossa vaatii tarkkaa suunnittelua, jolla varmistetaan metsÀnhoidon ja puunkÀytön kestÀvyys. Tieto puuaineen ominaisuuksista on keskeisessÀ osassa, sillÀ ne vaikuttavat hiilivarastojen suuruuteen metsissÀ, sekÀ puun kÀytettÀvyyteen pitkÀikÀisenÀ rakennesahatavarana. Puunmuodostuksen teoreettisen taustan mukaisesti, runko, latvus ja oksarakenne ovat potentiaalisia selittÀviÀ muuttujia (eli puun laatuindikaattoreita), kun mallinnetaan puuaineen ominaisuuksia, puubiomassaa ja puun laatua. Puunmuodostuksen monimutkaisuudesta ja moniulotteisesta vaihtelusta johtuen, tarvittavien laatuidikaattorien mittaaminen osana metsÀvarojen inventointia ja riittÀvÀllÀ yksityiskohtaisuudella on ollut aiemmin mahdotonta. Monialustaisen laserkeilauksen kehittyminen kuitenkin tukee aiempaa monipuolisempien kartoitus- ja mallinnusjÀrjestelmien rakentamista, jotka perustuvat tiheisiin kolmiulotteisiin pistepilviin.
TÀmÀn työn tavoitteena oli mÀÀritellÀ, kuinka puuaineen ominaisuuksia voidaan arvioida kaukokartoitusta hyödyntÀvÀssÀ metsÀvarojen inventoinnissa. TÀtÀ tarkoitusta varten kehitettiin menetelmiÀ puun laatuindikaattorien mittaamiseksi hoidetuissa mÀnniköissÀ (Pinus sylvestris L.) lento- ja maastolaserkeilauksen avulla, ja arvioitiin niiden toimivuutta. Ensin arvioitiin laatuindikaattorien mittatarkkuus pistepilvissÀ. Toiseksi verrattiin pistepilvimittauksia röntgentomografiamittauksiin teollisilla sahoilla. Kolmanneksi arvioitiin lentolaserkeilauksella tuotettujen latvuspiirteiden tarkkuutta laatuindikaattorien ennustamisessa.
Tuloksien perusteella pistepilvien laatu ja pistetiheys vaikuttivat merkittÀvÀsti mitattujen laatuindikaattorien tarkkuuteen. Puuaineen ominaisuuksien arvioimisessa, maastolaserkeilausta tulisi kÀyttÀÀ työkaluna mahdollisimman yksityiskohtaisten runko- ja oksikkuustietojen kerÀÀmiseen tarkkaan valikoiduista nÀytepuista. Tarkasti mitatut laatuindikaattorit voivat selittÀÀ puuaineen ominaisuuksia mallinnuksessa. KÀytettyjen mallien tulisi perustua laatuindikaattoreille, jotka voidaan ennustaa lentolaserkeilausaineistosta (esim. puun pituus ja latvuksen mittasuhteet), jotta ennusteet ovat yleistettÀvissÀ laajoille alueille.
Tulevaisuudessa, maasta ja ilmasta tehtÀvÀllÀ kaukokartoituksella voi olla tÀrkeÀ rooli puuaineen ominaisuuksien aikaan ja paikkaan sidotun vaihtelun tutkimuksessa. LisÀÀ poikkitieteellistÀ työtÀ tarvitaan, jotta kaukokartoitusta ja puuaineen ominaisuuksia ennustavia spatiaalisia malleja voidaan tÀysimittaisesti hyödyntÀÀ kiihtyvÀn ilmastonmuutoksen, muuttuvan metsÀnhoidon ja lisÀÀntyvÀn puunkÀytön tuomien haasteiden kohtaamisessa
Spaceborne Lidar in the Study of Marine Systems
Satellite passive ocean color instruments have provided an unbroken ~20-year record of global ocean plankton properties, but this measurement approach has inherent limitations in terms of spatial-temporal sampling and ability to resolve vertical structure within the water column. These limitations can be addressed by coupling ocean color data with measurements from a spaceborne lidar. Airborne lidars have been used for decades to study ocean subsurface properties, but recent breakthroughs have now demonstrated that plankton properties can be measured with a satellite lidar. The satellite lidar era in oceanography has arrived. Here we present a review of the lidar technique, its applications in marine systems, a prospective on what can be accomplished in the near future with an ocean- and atmosphere-optimized satellite lidar, and a vision for a multi-platform virtual constellation of observational assets enabling a 3-dimensional reconstruction of global ocean ecosystems
A backpack-mounted omnidirectional camera with off-the-shelf navigation sensors for mobile terrestrial mapping: Development and forest application
The use of Personal Mobile Terrestrial
System (PMTS) has increased considerably for mobile mapping applications
because these systems offer dynamic data acquisition with ground
perspective in places where the use of wheeled platforms is unfeasible,
such as forests and indoor buildings. PMTS has become more popular with
emerging technologies, such as miniaturized navigation sensors and
off-the-shelf omnidirectional cameras, which enable low-cost mobile
mapping approaches. However, most of these sensors have not been
developed for high-accuracy metric purposes and therefore require
rigorous methods of data acquisition and data processing to obtain
satisfactory results for some mapping applications. To contribute to the
development of light, low-cost PMTS and potential applications of these
off-the-shelf sensors for forest mapping, this paper presents a
low-cost PMTS approach comprising an omnidirectional camera with
off-the-shelf navigation systems and its evaluation in a forest
environment. Experimental assessments showed that the integrated sensor
orientation approach using navigation data as the initial information
can increase the trajectory accuracy, especially in covered areas. The
point cloud generated with the PMTS data had accuracy consistent with
the Ground Sample Distance (GSD) range of omnidirectional images (3.5â7
cm). These results are consistent with those obtained for other PMTS
approaches.
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Keywords:
personal mobile terrestrial system; omnidirectional cameras; low-cost sensors; forest mapping; PMTS data quality
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