Top Canopy Height and Stem Size Variation Enhance Aboveground Biomass across Spatial Scales in Seasonal Tropical Forests

Zhenhua Sun, Arunkamon Sonsuthi, Tommaso Jucker, Arshad Ali, Min Cao, Feng Liu, Guanghong Cao, Tianyu Hu, Qin Ma, Qinghua Guo, Luxiang Lin*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

2 Citations (Scopus)

Abstract

Tropical forests are biologically diverse and structurally complex ecosystems that can store a large quantity of carbon and support a great variety of plant and animal species. However, tropical forest structure can vary dramatically within seemingly homogeneous landscapes due to subtle changes in topography, soil fertility, species composition and past disturbances. Although numerous studies have reported the effects of field-based stand structure attributes on aboveground biomass (AGB) in tropical forests, the relative effects and contributions of UAV LiDAR-based canopy structure and ground-based stand structural attributes in shaping AGB remain unclear. Here, we hypothesize that mean top-of-canopy height (TCH) enhances AGB directly and indirectly via species richness and horizontal stand structural attributes, but these positive relationships are stronger at a larger spatial scale. We used a combined approach of field inventory and LiDAR-based remote sensing to explore how stand structural attributes (stem abundance, size variation and TCH) and tree species richness affect AGB along an elevational gradient in tropical forests at two spatial scales, i.e., 20 m × 20 m (small scale), and 50 m × 50 m (large scale) in southwest China. Specifically, we used structural equation models to test the proposed hypothesis. We found that TCH, stem size variation and abundance were strongly positively associated with AGB at both spatial scales, in addition to which increasing TCH led to greater AGB indirectly through increased stem size variation. Species richness had negative to negligible influences on AGB, but species richness increased with increasing stem abundance at both spatial scales. Our results suggest that light capture and use, modulated by stand structure, are key to promoting high AGB stocks in tropical forests. Thus, we argue that both horizontal and vertical stand structures are important for shaping AGB, but the relative contributions vary across spatial scales in tropical forests. Importantly, our results highlight the importance of including vertical forest stand attributes for predicting AGB and carbon sequestration that underpins human wellbeing.

Original languageEnglish
Article number1343
JournalPlants
Volume12
Issue number6
DOIs
Publication statusPublished - Mar 2023

Bibliographical note

Funding Information:
This study is supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB31000000), the Joint Fund of the National Natural Science Foundation of China-Yunnan Province (Grant No. U1902203), Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (Grant No. 151C53KYSB20200019), and the CAS 135 program (Grant No. 2017XTBG-T01). Arshad Ali is supported by Hebei University (Grant No. 521100221033).

Publisher Copyright:
© 2023 by the authors.

Keywords

  • aboveground biomass (AGB)
  • mean top of canopy height (TCH)
  • stand structural attributes
  • tropical forest
  • UAV LiDAR-based canopy structure

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