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Retrieval of forest canopy height in a mountainous region with ICESat-2 ATLAS

Forest Ecosystems 2022年第4期9卷 491-502页

作者： Shiyun Pang Guiying Li Xiandie Jiang Yaoliang Chen Yagang Lu Dengsheng Lu State Key Laboratory for Subtropical Mountain Ecology of the Ministry of Science and Technology and Fujian Province Fujian Normal UniversityFuzhou350007China Institute of Geography Fujian Normal UniversityFuzhou350007China Institute of East China Inventory and Planning National Forestry and Grassland AdministrationHangzhou310019China

Forest canopy height is one of the important forest parameters for accurately assessing forest biomass or carbon sequestration. ICESat-2 ATLAS provides the potential for retrieval of forest canopy height at global or regional scale, but the current canopy height product (ATL08) has coarse resolution and high uncertainty compared to airborne LiDAR-derived canopy height (hereafter ALCH) in mountainous regions, and is not ready for such applications as biomass modeling at finer scale. The objective of this research was to explore the approach to accurately retrieve canopy height from ATLAS data by incorporating an airborne-derived digital terrain model(DTM) and a data-filtering strategy. By linking ATLAS ATL03 with ATL08 products, the geospatial locations,types, and (absolute) heights of photons were obtained, and canopy heights at different lengths (from 20 to 200 m at 20-m intervals) of segments along a track were computed with the aid of airborne LiDAR DTM. Based on the relationship between the numbers of canopy photons within the segments and accuracy of ATLAS mean canopy height compared to ALCH, a filtering method for excluding a certain portion of unreliable segments was *** method was further applied to different ATLAS ground tracks for retrieval of canopy heights and the results were evaluated using corresponding ALCH. The results show that the incorporation of high-precision DTM and ATLAS products can considerably improve the retrieval accuracy of forest canopy height in mountainous *** the proposed filtering approach, the correlation coefficients (r) between ATLAS canopy height and corresponding ALCH were 0.61–0.91, 0.65–0.92, 0.68–0.94 for segment lengths of 20, 60, and 100 m, respectively;RMSE were 1.90–4.35, 1.55–3.63, and 1.34–3.23 m for the same segment lengths. The results indicate the necessity of using high-precision DTM and using the proposed filtering method to retrieve accurate canopy height from ICESat-2 ATLAS in mountainous re

关键词： Airborne LiDAR canopy height ICESat-2 ATLAS Mountainous region Segment filtering

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维普期刊数据库

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Influence of voxel size on forest canopy height estimates using full-waveform airborne LiDAR data

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Forest Ecosystems 2020年第3期7卷 392-403页

作者： Cheng Wang Shezhou Luo Xiaohuan Xi Sheng Nie Dan Ma Youju Huang College of Resources and Environment Fujian Agriculture and Forestry UniversityFuzhou350002China Key Laboratory of Digital Earth Science Institute of Remote Sensing and Digital EarthChinese Academy of SciencesBeijing100094China Guangxi Zhuang Autonomous Region Institute of Natural Resources Remote Sensing Nanning530023China

Background: Forest canopy height is a key forest structure parameter. Precisely estimating forest canopy height is vital to improve forest management and ecological modelling. Compared with discrete-return LiDAR(Light Detection and Ranging), small-footprint full-waveform airborne LiDAR(FWL) techniques have the capability to acquire precise forest structural information. This research mainly focused on the influence of voxel size on forest canopy height ***: A range of voxel sizes(from 10.0 m to 40.0 m interval of 2 m) were tested to obtain estimation accuracies of forest canopy height with different voxel sizes. In this study, all the waveforms within a voxel size were aggregated into a voxel-based LiDAR waveform, and a range of waveform metrics were calculated using the voxelbased LiDAR waveforms. Then, we established estimation model of forest canopy height using the voxel-based waveform metrics through Random Forest(RF) regression *** and conclusions: The results showed the voxel-based method could reliably estimate forest canopy height using FWL data. In addition, the voxel sizes had an important influence on the estimation accuracies(R2 ranged from 0.625 to 0.832) of forest canopy height. However, the R2 values did not monotonically increase or decrease with the increase of voxel size in this study. The best estimation accuracy produced when the voxel size was 18 m(R2= 0.832, RMSE = 2.57 m, RMSE% = 20.6%). Compared with the lowest estimation accuracy, the R2 value had a significant improvement(33.1%) when using the optimal voxel size. Finally, through the optimal voxel size, we produced the forest canopy height distribution map for this study area using RF regression model. Our findings demonstrate that the optimal voxel size need to be determined for improving estimation accuracy of forest parameter using small-footprint FWL data.

关键词： Voxel size Airborne LiDAR Full-waveform Forests canopy height

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Morphological and physiological differences in heteromorphic leaves of male and female Populus euphratica Oliv.

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Journal of Arid Land 2022年第12期14卷 1456-1469页

作者： LI Xiu ZHAI Juntuan LI Zhijun College of Life Sciences and Technology Tarim UniversityAlar 843300China Key Laboratory of Protection and Utilization of Biological Resources in Tarim Basin of Xinjiang Production&Construction Corps Alar 843300China

Leaf traits can directly reflect the adaptation strategies of plants to the ***,there is limited knowledge on the adaptation strategies of heteromorphic leaves of male and female Populus euphratica *** response to individual developmental stages(i.e.,diameter class)and canopy height *** this study,morphological and physiological properties of heteromorphic leaves of male and female *** were *** showed that both male and female *** exhibited increased leaf area(LA),leaf dry weight(LDW),leaf thickness(LT),net photosynthetic rate(P_(n)),transpiration rate(T_(r)),stomatal conductance(g_(s)),proline(Pro),and malondialdehyde(MDA)concentration,decreased leaf shape index(LI)and specific leaf area(SLA)with increasing diameter and canopy *** water potential(LWP)increased with increasing diameter,LWP decreased significantly with increasing canopy height in both sexes,and carbon isotope fraction(δ^(13)C)increased significantly with canopy height in both sexes,all of which showed obvious resistance ***,males showed greater LA,LT,P_(n),T_(r),and Pro than females at the same canopy height,and males showed significantly higher LA,SLA,LT,P_(n),T_(r),g_(s),and MDA,but lower LWP and δ_(1)3C than females at the same canopy height,suggesting that male *** have stronger photosynthetic and osmoregulatory abilities,and are sensitive to water ***,difference between male and female *** is closely related to the increase in individual diameter class and canopy *** summary,male plants showed higher stress tolerance than female plants,and differences in P_(n),g_(s),T_(r),Pro,MDA,δ_(13)C,and LWP between females and males were related to changes in leaf morphology,diameter class,and canopy *** results of this study provide a theory for the differences in growth adaptation strategies during individual development of ***.

关键词： arid area canopy height dioecious plants morphology physiological characteristics

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Leaf Longevity in a Timberline Tree Species Juniperus saltuaria in the Sergymla Mountains,Southeastern Tibet

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Journal of Resources and Ecology 2022年第1期13卷 34-40页

作者： ZHANG Lin YANG Liu GUO Ying SHEN Wei CUI Guangshuai State Key Laboratory of Tibetan Plateau Earth System Resources and EnvironmentInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China Muoto Observation and Research Center for Earth Landscape and Earth System Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Leaf longevity is an important adaptive strategy that allows plants to maximize photosynthetic carbon *** to the difficulty of identifying overwintering bud scars and distinguishing the age sequence of twigs,leaf longevity is rarely studied in Cupressaceae species,which further limits our understanding of the leaf economic spectrum (LES) for these ***,we investigated the leaf longevity,as well as mass-based leaf nitrogen concentration (N;),of Juniperus saltuaria at different canopy heights for both subalpine and alpine timberline forests in the Sergymla Mountains,southeastern *** found that the mean leaf longevity was 4.2±1.2 years,and overall it did not differ significantly between different *** the vertical profiles of juniper canopies,the leaf longevity did not reflect a linear *** increasing leaf longevity,N;showed declining *** further analyzed the relationship between leaf longevity and the corresponding length of green twigs,and found that the length of green twigs could only explain 1%-3%of the variation in leaf longevity,indicating that the length of green twigs is a poor predictor for the variation in leaf *** summary,for the *** species in timberline or nearby subalpine forests,the effects of elevation and canopy depths on leaf longevity are minor,and the leaf trait analysis is in accordance with the prediction of LES.

关键词： canopy height elevation leaf nitrogen concentration length of green twigs Cupressaceae

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