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Asynchronous canopy physiological and structural cycles reveal complex bimodal seasonality in the Congo rainforest

Xie, Qi ; Tian, Feng LU ; Tagesson, Torbern LU ; Wang, Lanhui LU orcid ; Fensholt, Rasmus ; Tong, Xiaoye ; Jin, Hongxiao LU ; Ma, Xuanlong ; Cai, Zhanzhang LU orcid and Dou, Yujie , et al. (2026) In Agricultural and Forest Meteorology 384.
Abstract

Tropical rainforests have complex responses to seasonal climatic variations. Compared to the Amazon and Asian rainforests, the Congo rainforest exhibits a more widespread bimodal seasonal pattern, yet it remains understudied. Here, we use three independent satellite-based vegetation indices to investigate the seasonal variations of the Congo rainforest, including solar-induced chlorophyll fluorescence (SIF), the two-band enhanced vegetation index (EVI2), and vegetation optical depth (VOD), which represent vegetation canopy photosynthesis, greenness, and water content, respectively. We find widespread asynchronous bimodal seasonality among the three vegetation indices, suggesting alternating physiological and structural variations of the... (More)

Tropical rainforests have complex responses to seasonal climatic variations. Compared to the Amazon and Asian rainforests, the Congo rainforest exhibits a more widespread bimodal seasonal pattern, yet it remains understudied. Here, we use three independent satellite-based vegetation indices to investigate the seasonal variations of the Congo rainforest, including solar-induced chlorophyll fluorescence (SIF), the two-band enhanced vegetation index (EVI2), and vegetation optical depth (VOD), which represent vegetation canopy photosynthesis, greenness, and water content, respectively. We find widespread asynchronous bimodal seasonality among the three vegetation indices, suggesting alternating physiological and structural variations of the Congo rainforest. These bimodal seasonality shifts are driven by temporally diverse environmental factors. The variations in photosynthesis are predominantly driven by temperature from January to June of the first growing season, and by precipitation and temperature from July to December of the second growing season. The bimodal seasonal pattern of vegetation greenness is primarily constrained by precipitation across most of the region. In contrast, variations in vegetation water content are closely related to terrestrial water storage, with a temporal lag of 1 to 2 months. These findings highlight the intertwined seasonality of the vegetation canopy traits and their environmental controls in the Congo rainforest, providing an improved understanding of the vegetation-climate feedback for predicting rainforest responses to climate change.

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Contribution to journal
publication status
published
subject
keywords
Bimodal seasonality, Canopy dynamics, Congo rainforest, Solar-induced chlorophyll fluorescence, Two-band enhanced vegetation index, Vegetation optical depth
in
Agricultural and Forest Meteorology
volume
384
article number
111186
publisher
Elsevier
external identifiers
  • scopus:105035233831
ISSN
0168-1923
DOI
10.1016/j.agrformet.2026.111186
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2026 Elsevier B.V.
id
14b96ade-ee12-41dd-a247-0f1208da9b44
date added to LUP
2026-06-05 09:14:28
date last changed
2026-06-08 10:15:32
@article{14b96ade-ee12-41dd-a247-0f1208da9b44,
  abstract     = {{<p>Tropical rainforests have complex responses to seasonal climatic variations. Compared to the Amazon and Asian rainforests, the Congo rainforest exhibits a more widespread bimodal seasonal pattern, yet it remains understudied. Here, we use three independent satellite-based vegetation indices to investigate the seasonal variations of the Congo rainforest, including solar-induced chlorophyll fluorescence (SIF), the two-band enhanced vegetation index (EVI2), and vegetation optical depth (VOD), which represent vegetation canopy photosynthesis, greenness, and water content, respectively. We find widespread asynchronous bimodal seasonality among the three vegetation indices, suggesting alternating physiological and structural variations of the Congo rainforest. These bimodal seasonality shifts are driven by temporally diverse environmental factors. The variations in photosynthesis are predominantly driven by temperature from January to June of the first growing season, and by precipitation and temperature from July to December of the second growing season. The bimodal seasonal pattern of vegetation greenness is primarily constrained by precipitation across most of the region. In contrast, variations in vegetation water content are closely related to terrestrial water storage, with a temporal lag of 1 to 2 months. These findings highlight the intertwined seasonality of the vegetation canopy traits and their environmental controls in the Congo rainforest, providing an improved understanding of the vegetation-climate feedback for predicting rainforest responses to climate change.</p>}},
  author       = {{Xie, Qi and Tian, Feng and Tagesson, Torbern and Wang, Lanhui and Fensholt, Rasmus and Tong, Xiaoye and Jin, Hongxiao and Ma, Xuanlong and Cai, Zhanzhang and Dou, Yujie and Feng, Luwei and Eklundh, Lars}},
  issn         = {{0168-1923}},
  keywords     = {{Bimodal seasonality; Canopy dynamics; Congo rainforest; Solar-induced chlorophyll fluorescence; Two-band enhanced vegetation index; Vegetation optical depth}},
  language     = {{eng}},
  month        = {{06}},
  publisher    = {{Elsevier}},
  series       = {{Agricultural and Forest Meteorology}},
  title        = {{Asynchronous canopy physiological and structural cycles reveal complex bimodal seasonality in the Congo rainforest}},
  url          = {{http://dx.doi.org/10.1016/j.agrformet.2026.111186}},
  doi          = {{10.1016/j.agrformet.2026.111186}},
  volume       = {{384}},
  year         = {{2026}},
}