Widespread leaf phenology change detected by the leaf-age-dependent leaf area index (Lad-LAI) in pantropical evergreen broadleaf forests

doi:10.1093/jpe/rtag164

J Plant Ecol ›› Advance articles DOI:10.1093/jpe/rtag164

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Widespread leaf phenology change detected by the leaf-age-dependent leaf area index (Lad-LAI) in pantropical evergreen broadleaf forests

Hao-Ran Xu^1,#, Xue-Qin Yang^2,#, Mei Wang^1,*, Xin-Yue Fu¹, Jie Tian¹, Xiu-Zhi Chen¹

¹ Guangdong Province Data Center of Terrestrial and Marine Ecosystems Carbon Cycle, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, School of Atmospheric Sciences, Sun Yat-Sen University and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519082, China
² Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong, China
^* Correspondence: Mei Wang Email: wangm377@mail2.sysu.edu.cn Tel & Fax: + 86 19176748218
^#Hao-Ran Xu and Xue-Qin Yang contributed equally to this work

Received:2026-02-11 Accepted:2026-06-23 Published:2026-07-17
Supported by:
This work was supported by the Science and Technology Program of Guangdong Province (No. 2024B1212070012), the National Key R&D Program of China (No. 2024YFF1306601), and the General Program of Guangdong Provincial Natural Science Foundation (No. 2024A1515012731)

基于叶龄依赖型叶面积指数（Lad-LAI）检测的热带常绿阔叶林叶片物候的广泛变化

Abstract

Abstract: Leaf phenology in tropical evergreen broadleaf forests (EBFs) often exhibits weak seasonality, making it challenging to detect the start of season (SOS) and end of season (EOS) from satellite-based vegetation indices particularly challenging. Leaf age structure describes the seasonal variability in canopy leaves of different age cohorts (young, mature, old) and for characterizing leaf phenology in tropical EBFs. Here, we built a methodological framework to produce a 0.25° leaf phenology dataset for tropical EBFs across 30°S–30°N using a leaf-age-dependent leaf area index product (Lad-LAI) for 2001–2023. SOS and EOS from the new dataset showed strong agreement with PhenoCam-derived metrics and good correlations with EVI-, NIRv-, and kNDVI-derived metrics. Across continents, the Amazon exhibited relatively later SOS dates, mainly during DOY 210–330, and earlier EOS dates, mainly during DOY 60–210. Conversely, the Congo and tropical Asia were characterized by relatively smaller SOS and larger EOS. Notably, SOS increases while EOS decreases progressively from northern to southern latitudes, showing contrasting latitudinal patterns. From 2001 to 2023, tropical EBFs experienced a widespread advance in SOS, which was most pronounced in the Congo region, with an average rate of -1.39 days yr^-1. In contrast, EBFs mostly experienced a delay in EOS, which was strongest in tropical Asia, with a mean delay rate of 2.12 days yr^-1. Consequently, the growing season (EOS minus SOS) increased significantly across all three continents. Overall, our leaf-age-dependent phenology dataset provides fundamental data for leaf phenology monitoring, carbon-cycle modeling, and climate-change impact predictions in tropical EBFs.

Using a leaf-age-dependent leaf area index product, this study generated a 2001–2023 leaf phenology dataset for tropical evergreen broadleaf forests. The dataset captures key phenological transitions consistent with in situ camera observations and satellite vegetation index metrics, and reveals pronounced spatial heterogeneity in both the occurrence and temporal trends of leaf phenology across tropical regions.

Key words: leaf phenology, leaf age, leaf onset, leaf senescence, growing season, tropical evergreen broadleaf forests

摘要：
热带常绿阔叶林（evergreen broadleaf forests,EBFs）的叶物候通常季节性较弱，因而基于卫星植被指数识别的生长季开始时间（start of season,SOS）和结束时间（end of season,EOS）具有较大挑战。叶龄结构能够刻画冠层中不同叶龄组分，包括幼叶、成熟叶和老叶的季节性变化，为表征热带EBFs的叶物候过程提供了新的信息来源。本研究基于叶龄依赖型叶面积指数产品（leaf-age-dependent leaf area index product,Lad-LAI），构建了一套叶物候提取方法框架，生成了2001-2023年覆盖30°S-30°N热带EBFs、空间分辨率为0.25°的叶物候数据集。结果表明，该新数据集提取的SOS和EOS与PhenoCam观测数据提取的物候指标具有较强一致性，并与基于EVI、NIRv和kNDVI提取的物候指标具有良好的相关性。在大陆尺度上，亚马逊地区的SOS相对较晚，主要集中在DOY 210-330，而EOS相对较早，主要集中在DOY 60-210。相比之下，刚果和热带亚洲地区表现出较早的SOS和较晚的EOS。沿纬度梯度，SOS由北向南逐渐增大，而EOS则逐渐减小，二者呈现相反的纬向变化特征。2001-2023年期间，热带EBFs的SOS整体呈提前趋势，其中刚果地区最为显著，平均变化速率为-1.39天yr^-1。相较而言，EOS整体呈推迟趋势，其中热带亚洲地区推迟最为明显，平均变化速率为2.12天yr^-1。受SOS提前和EOS推迟的共同影响，三个区域的生长季长度，即EOS与SOS之差，均呈显著增加趋势。总体而言，本研究构建的叶龄依赖型物候数据集为热带常绿阔叶林叶物候监测、碳循环模拟以及气候变化影响预测提供了重要基础数据。

关键词: 叶物候, 叶龄, 展叶, 叶片衰老, 生长季, 热带常绿阔叶林

Hao-Ran Xu, Xue-Qin Yang, Mei Wang, Xin-Yue Fu, Jie Tian, Xiu-Zhi Chen. Widespread leaf phenology change detected by the leaf-age-dependent leaf area index (Lad-LAI) in pantropical evergreen broadleaf forests[J]. J Plant Ecol, DOI: 10.1093/jpe/rtag164.

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Widespread leaf phenology change detected by the leaf-age-dependent leaf area index (Lad-LAI) in pantropical evergreen broadleaf forests

基于叶龄依赖型叶面积指数（Lad-LAI）检测的热带常绿阔叶林叶片物候的广泛变化

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