Applications of Sun-Induced Chlorophyll Fluorescence in Forest Health Monitoring

日光誘導(dǎo)葉綠素?zé)晒馐侵钢参锶~綠素在吸收太陽(yáng)輻射后重新發(fā)射出的光子，該過(guò)程與光合作用密切相關(guān)，因此通過(guò)測(cè)量日光誘導(dǎo)葉綠素?zé)晒猓ㄏ挛暮?jiǎn)稱SIF）能夠直接反演植被的光合效率、生理狀態(tài)及其對(duì)環(huán)境脅迫的響應(yīng)。

SIF的核心優(yōu)勢(shì)在于它直接來(lái)源于光合作用過(guò)程，可更準(zhǔn)確地反映植被的光合活性與碳吸收能力；同時(shí)，其對(duì)環(huán)境脅迫高度敏感，一旦植物遭受脅迫，光合系統(tǒng)的變化會(huì)迅速體現(xiàn)于SIF信號(hào)中，使其成為早期脅迫檢測(cè)的有效指標(biāo)。

Sun-Induced Chlorophyll Fluorescence (SIF) refers to photons re-emitted by plant chlorophyll after absorbing solar radiation. This process is closely related to photosynthesis; therefore, measuring SIF enables direct retrieval of vegetation's photosynthetic efficiency, physiological status, and responses to environmental stress.

The core advantage of SIF lies in its direct origin from the photosynthetic process, allowing it to more accurately reflect vegetation’s photosynthetic activity and carbon uptake capacity. At the same time, it is highly sensitive to environmental stress. Once plants experience stress, changes in the photosynthetic system are rapidly reflected in the SIF signal, making it an effective indicator for early stress detection.

SIF在森林健康監(jiān)測(cè)中，主要有以下應(yīng)用：

SIF has the following main applications in forest health monitoring:

1.評(píng)估森林光合效率和GPP / Assessing Forest Photosynthetic Efficiency and GPP

通過(guò)SIF數(shù)據(jù)，可以估算森林的GPP。研究表明，基于2000–2015年中國(guó)西南地區(qū)多生物群系數(shù)據(jù)發(fā)現(xiàn)，在森林、草地、農(nóng)田、灌叢和荒漠五種生態(tài)類型中，SIF與GPP均呈顯著線性關(guān)系，決定系數(shù)r²不低于0.91。

SIF data can be used to estimate forest Gross Primary Productivity (GPP). Research based on multi-biome data from Southwest China between 2000 and 2015 showed that across five ecosystem types—forest, grassland, farmland, shrubland, and desert—SIF and GPP exhibited a significant linear relationship, with a coefficient of determination (r²) no less than 0.91.

2000~2015年間，不同生物群落類型的月平均SIF、月平均NDVI與GPP的線性回歸模型

Linear regression models of monthly mean SIF, monthly mean NDVI, and GPP across different biome types during 2000–2015.

2.識(shí)別森林病害、干旱脅迫及植被健康狀況 / Identifying Forest Diseases, Drought Stress, and Vegetation Health Status

森林健康受到多種因素的影響，包括病蟲(chóng)害、干旱、污染等。病蟲(chóng)害、干旱等脅迫會(huì)導(dǎo)致降低葉綠素含量、破壞光合結(jié)構(gòu)或氣孔關(guān)閉，使SIF信號(hào)減弱；健康森林則因光合效率高而SIF值高，衰退或受損森林則相反。

因此，持續(xù)監(jiān)測(cè)SIF即可早期捕捉病蟲(chóng)害和干旱的發(fā)生，又能綜合評(píng)估森林的整體健康狀況與活力，為精準(zhǔn)防控及抗旱管理提供及時(shí)依據(jù)。

一項(xiàng)研究以棉花黃萎病為案例，發(fā)現(xiàn)病害初期，SIF變化主要由光合生理參數(shù)驅(qū)動(dòng)（貢獻(xiàn)度>70%）。隨著病害加重，冠層結(jié)構(gòu)變化（如葉片脫落、冠層結(jié)構(gòu)稀疏）導(dǎo)致的非生理因素貢獻(xiàn)度提升47.7%，最終主導(dǎo)SIF變化。

Forest health is affected by various factors, including pests, diseases, drought, and pollution. Stressors such as pests, diseases, and drought can reduce chlorophyll content, damage photosynthetic structures, or cause stomatal closure, thereby weakening the SIF signal. Healthy forests exhibit high SIF values due to high photosynthetic efficiency, while declining or damaged forests show the opposite.

Therefore, continuous SIF monitoring can not only capture the onset of pests and drought at an early stage but also comprehensively assess the overall health and vitality of forests, providing a timely basis for precise prevention, control, and drought management.

A case study on cotton Verticillium wilt found that in the early stage of the disease, changes in SIF were mainly driven by photosynthetic physiological parameters (contribution > 70%). As the disease progressed, the contribution of non-physiological factors (e.g., leaf abscission and canopy thinning) increased by 47.7%, eventually dominating the changes in SIF.

實(shí)驗(yàn)期間非生理因子、SIF、SIF_PAR及生理參數(shù)的日變化特征；

非生理因子：NIRv、FCVI、RENDVI，生理因子：ΦF；

T1-T2和T2-T3由溫降事件劃分，T3–T4 由定期灌溉事件劃分。

VW1代表急性脅迫，VW3代表整個(gè)實(shí)驗(yàn)期持續(xù)緩慢發(fā)病，最終達(dá)到重度脅迫水平；VW4代表全程緩慢發(fā)病但脅迫程度較輕。

Daily variation characteristics of non-physiological factors, SIF, SIF_PAR, and physiological parameters during the experimental period;
Non-physiological factors: NIRv, FCVI, RENDVI; physiological factor: ΦF;
T1–T2 and T2–T3 are divided by temperature drop events, while T3–T4 are divided by periodic irrigation events.
VW1 represents acute stress; VW3 represents persistent slow progression throughout the experimental period, ultimately reaching severe stress levels; VW4 represents slow progression throughout with relatively mild stress levels.

該發(fā)現(xiàn)可直接遷移至森林健康監(jiān)測(cè)：當(dāng)森林遭受真菌、病原菌或昆蟲(chóng)侵襲時(shí)，早期可通過(guò)SIF異常降低快速鎖定受害區(qū)域；中后期結(jié)合結(jié)構(gòu)參數(shù)（如NIRv）可區(qū)分生理衰退與冠層結(jié)構(gòu)破壞的貢獻(xiàn)，從而精準(zhǔn)評(píng)估病害等級(jí)并制定針對(duì)性防治策略。

These findings can be directly applied to forest health monitoring: when forests are infested by fungi, pathogens, or insects, early SIF reduction can quickly identify affected areas. In mid-to-late stages, combining structural parameters (e.g., NIRv) can help distinguish the contributions of physiological decline and structural damage to the canopy, enabling accurate assessment of disease severity and formulation of targeted control strategies.

3.為長(zhǎng)期森林生態(tài)動(dòng)態(tài)研究提供數(shù)據(jù)支持 / Providing Data Support for Long-Term Forest Ecological Dynamics Research

森林生態(tài)系統(tǒng)是一個(gè)復(fù)雜的動(dòng)態(tài)系統(tǒng)，受到氣候變化、人為干擾等多種因素的影響。通過(guò)長(zhǎng)期的SIF數(shù)據(jù)積累，可以研究森林生態(tài)系統(tǒng)的動(dòng)態(tài)變化規(guī)律，為森林管理和保護(hù)提供科學(xué)依據(jù)。例如，通過(guò)分析SIF的時(shí)間序列數(shù)據(jù)，可以了解森林的物候變化、生長(zhǎng)速率、對(duì)氣候變化的響應(yīng)等。

Forest ecosystems are complex and dynamic systems influenced by various factors such as climate change and human activities. Long-term SIF data accumulation allows the study of dynamic changes in forest ecosystems, providing a scientific basis for forest management and conservation. For example, analyzing SIF time-series data can reveal forest phenological changes, growth rates, and responses to climate change.

SIF的測(cè)量方法 / SIF Measurement Methods

為充分發(fā)揮SIF在森林健康監(jiān)測(cè)中的上述應(yīng)用價(jià)值，離不開(kāi)精準(zhǔn)、穩(wěn)定的測(cè)量手段。

愛(ài)博能研發(fā)生產(chǎn)的日光誘導(dǎo)葉綠素?zé)晒?SIF)監(jiān)測(cè)系統(tǒng)（ABN-SIF系列），利用植物冠層的光譜信息，自動(dòng)測(cè)量日光誘導(dǎo)葉綠素?zé)晒獾葏?shù)。該系統(tǒng)采用高分辨率、高靈敏度和高穩(wěn)定性的國(guó)產(chǎn)光譜儀，支持在線或機(jī)載觀測(cè)方式，能夠提供高頻、準(zhǔn)確的數(shù)據(jù)輸出，助力植物光合作用狀態(tài)和長(zhǎng)勢(shì)的實(shí)時(shí)監(jiān)測(cè)與分析。

To fully leverage the above applications of SIF in forest health monitoring, accurate and stable measurement methods are essential.

The Sun-Induced Chlorophyll Fluorescence (SIF) monitoring system (ABN-SIF series) developed and produced by Aiboneng uses spectral information from the plant canopy to automatically measure parameters such as SIF. Equipped with a high-resolution, high-sensitivity, and high-stability domestically produced spectrometer, the system supports online or airborne observations and delivers high-frequency, accurate data output, facilitating real-time monitoring and analysis of plant photosynthetic status and growth trends.

案例來(lái)源 / Sources：

Jia, L., He, Y., Liu, W., Li, Y., & Zhang, Y. (2023). Drought did not change the linear relationship between chlorophyll fluorescence and terrestrial gross primary production under universal biomes. Frontiers in Forests and Global Change, 6, Article 1157340.

Zhou, J., et al. (2024). Roles of physiological and nonphysiological information in sun-induced chlorophyll fluorescence variations for detecting cotton verticillium wilt. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 17, 8835–8850.