Solar-Induced Chlorophyll Fluorescence: Enabling Early Warning of Soil Salinization

土(tǔ)壤鹽漬(zì)化，是指(zhǐ)土(tǔ)壤(rǎng)底層或地(dì)下水(shuǐ)中(zhōng)的可(kě)溶(róng)性鹽(yán)分(fēn)隨水(shuǐ)分上(shàng)升至地(dì)表，水分蒸發(fā)後，鹽(yán)分在(zài)表層土壤(rǎng)中積累的(dí)過(guò)程。這就像海(hǎi)水(shuǐ)曬(shài)鹽一樣(yàng)，水分(fēn)被(bèi)“曬幹"了(liǎo)，鹽分卻(què)留了下(xià)來(lái)。土壤鹽漬化是影響農業(yè)生產和生態(tài)健康(kāng)的全球(qiú)性(xìng)問題(tí)。

Soil salinization refers to the process in which soluble salts from the soil subsurface or groundwater migrate upward with water to the soil surface. After the water evaporates, the salts accumulate in the topsoil. This is similar to sea salt production: the water is "dried out," but the salts remain. Soil salinization is a global issue affecting agricultural production and ecological health.

土壤鹽漬(zì)化(huà) / Soil Salinization

鹽脅(xié)迫的負麵影響主要(yào)體現在四(sì)個(gè)方(fāng)麵(miàn)：

·水分虧(kuī)缺與滲(shèn)透脅(xié)迫：土壤(rǎng)鹽分升(shēng)高導致水勢降(jiàng)低，阻(zǔ)礙(ài)根係(xì)吸水(shuǐ)，引發滲透脅(xié)迫，造成(chéng)植株生(shēng)理缺水(shuǐ)。

·離子(zǐ)毒(dú)害：過量(liáng)鈉離(lí)子(zǐ)和氯離(lí)子侵(qīn)入細胞(bāo)，破壞膜(mó)結構和酶活性，幹擾正常代謝。

·氧(yǎng)化(huà)脅(xié)迫(pò)：鹽誘導(dǎo)活性(xìng)氧(yǎng)（ROS）大量產(chǎn)生(shēng)，引(yǐn)發膜脂過氧(yǎng)化，細胞結(jié)構受損，丙(bǐng)二(èr)醛(quán)（MDA）含量上升。

·光(guāng)合作(zuò)用抑製(zhì)：鹽(yán)脅迫降低葉綠素(sù)含量
，改變(biàn)色素組成(chéng)，直接削(xiāo)弱光(guāng)係(xì)統(tǒng)II（PSII）效率(shuài)，抑製(zhì)光合碳同(tóng)化。

The negative impacts of salt stress are mainly manifested in four aspects:

·Water Deficit and Osmotic Stress: Increased soil salinity lowers water potential, hindering water uptake by roots and causing osmotic stress, which leads to physiological water deficiency in plants.

·on Toxicity: Excessive sodium and chloride ions enter cells, disrupting membrane structures and enzyme activity, thereby interfering with normal metabolic processes.

·Oxidative Stress: Salt stress induces the overproduction of reactive oxygen species (ROS), triggering membrane lipid peroxidation, damaging cell structures, and increasing malondialdehyde (MDA) content.

·Inhibition of Photosynthesis: Salt stress reduces chlorophyll content, alters pigment composition, directly impairs the efficiency of photosystem II (PSII), and suppresses photosynthetic carbon assimilation.

其(qí)中，光合作用的變(biàn)化尤(yóu)為(wéi)關(guān)鍵。而(ér)日光誘導葉綠(lǜ)素熒(yíng)光（SIF）作為(wéi)光(guāng)合作(zuò)用的“副(fù)產物"，能(néng)夠靈(líng)敏地捕捉(zhuō)到(dào)鹽脅(xié)迫(pò)下光(guāng)合(hé)機構的(dí)早(zǎo)期(qī)響應(yīng)。

例如，受鹽脅迫(pò)的(dí)植物葉(yè)片(piàn)往往出(chū)現葉(yè)綠素含量(liáng)下降(jiàng)
，光合(hé)活性會(huì)下(xià)降，SIF信號也隨之減弱(ruò)，這(zhè)種變(biàn)化(huà)比傳統的植被(bèi)指數(shù)（如NDVI）更(gēng)早(zǎo)
，更(gēng)靈敏，因為植被指數(shù)通(tōng)常(cháng)反映(yìng)的是冠層結構(gòu)或(huò)色(sè)素含量的(dí)變(biàn)化，而這些(xiē)變化(huà)往往在脅迫(pò)發生(shēng)一段(duàn)時間後(hòu)才顯(xiǎn)現。

Among these, changes in photosynthesis are particularly critical. As a byproduct of photosynthesis, sun-induced chlorophyll fluorescence (SIF) can sensitively capture the early responses of the photosynthetic apparatus under salt stress.

For example, salt-stressed plants often exhibit decreased chlorophyll content and reduced photosynthetic activity, accompanied by a decline in SIF signals. These changes occur earlier and are more sensitive than traditional vegetation indices (such as NDVI), as vegetation indices typically reflect alterations in canopy structure or pigment content, which often become apparent only after the stress has persisted for some time.

日光誘導(dǎo)葉綠素(sù)熒(yíng)光(guāng)的(dí)產生 / Generation of Solar-Induced Chlorophyll Fluorescence

西(xī)北(běi)農林科(kē)技(jì)大學(xué)基(jī)於全(quán)球(qiú)OCO-2的SIF產(chǎn)品(pǐn)（GOSIF）的SIF觀(guān)測時間序列（2000 ∼ 2020）的標(biāo)準(zhǔn)化日致(zhì)葉綠(lǜ)素流失指(zhǐ)數（SIFI）來建立土(tǔ)壤(rǎng)鹽(yán)度(dù)模型(xíng)。下圖是該(gāi)課題組(zǔ)得(dé)出的(dí)SIF觀測對(duì)土(tǔ)壤鹽度(dù)估(gū)算的(dí)評價。

Using the standardized SIF-based loss index (SIFI) derived from the global OCO-2 SIF product (GOSIF) time series (2000–2020), researchers from Northwest A&F University developed a model for estimating soil salinity. The figure below shows the evaluation of SIF observations for soil salinity estimation by this research team.

(a)是典(diǎn)型區域(yù)和非(fēi)典型區域的分(fēn)布；(b)是SIF觀(guān)測(cè)對受(shòu)鹽(yán)影響土(tǔ)壤的(dí)分類(lèi)精(jīng)度(dù)；(c)∼(d)為SIF觀測(cè)的(dí)分(fēn)類結果(guǒ)。

(a) Distribution of typical and atypical regions; (b) Classification accuracy of SIF observations for salt-affected soils; (c)‒(d) Classification results based on SIF observations.

新(xīn)疆(jiāng)的科研(yán)機構(gòu)也(yě)利用日光誘(yòu)導葉(yè)綠素熒光來(lái)捕(bǔ)捉新疆(jiāng)和(hé)中亞(yà)地區的(dí)植物(wù)對鹽(yán)脅(xié)迫(pò)的反應。

Research institutions in Xinjiang have also utilized sun-induced chlorophyll fluorescence to monitor plant responses to salt stress in Xinjiang and Central Asia.

標準化(huà) SIFI 指標對八種代(dài)表(biǎo)性(xìng)土(tǔ)地覆蓋類型的(dí)相(xiāng)對(duì)建(jiàn)模貢(gòng)獻(xiàn)

Relative modeling contributions of the standardized SIFI indicator for eight representative land cover types.

SIF對早期脅迫(pò)的高(gāo)度敏感(gǎn)性(xìng)，使其成(chéng)為(wéi)監測鹽(yán)脅迫的(dí)有效工具，主要體現在(zài)以下方麵(miàn)：

·早(zǎo)期預警(jǐng)與精準管理：SIF可實現早期脅迫(pò)區(qū)域(yù)識別，幫助管(guǎn)理者及(jí)時調(tiáo)整灌溉
，施(shī)用土(tǔ)壤(rǎng)改良(liáng)劑(jì)或(huò)更換耐鹽(yán)品(pǐn)種(zhǒng)，減(jiǎn)輕產(chǎn)量(liáng)損失。

·耐鹽品種選育(yù)：通(tōng)過(guò)無(wú)損監(jiān)測(cè)不同(tóng)品種在鹽條件下的響應，可高(gāo)效篩(shāi)選出光合(hé)效率穩定的(dí)耐鹽材(cái)料，加(jiā)速抗(kàng)逆(nì)育種進(jìn)程(chéng)。

·科(kē)學研(yán)究與(yǔ)模型融合：SIF可(kě)與多源遙(yáo)感數(shù)據(jù)及生(shēng)態模型（如SCOPE
，VISIT-SIF）結合(hé)，深化(huà)鹽脅(xié)迫(pò)下(xià)作(zuò)物(wù)生理(lǐ)響應(yīng)機製的(dí)認識，推動脅(xié)迫生理(lǐ)學發展。

The high sensitivity of SIF to early-stage stress makes it an effective tool for monitoring salt stress, mainly demonstrated in the following aspects:

·Early Warning and Precision Management: SIF enables the identification of stress-affected areas at an early stage, helping managers adjust irrigation, apply soil amendments, or switch to salt-tolerant varieties in a timely manner to mitigate yield losses.

·Breeding Salt-Tolerant Varieties: By non-destructively monitoring the responses of different varieties under saline conditions, photosynthetically efficient and salt-tolerant materials can be efficiently screened, accelerating the process of stress-resistant breeding.

·Scientific Research and Model Integration: SIF can be integrated with multi-source remote sensing data and ecological models (e.g., SCOPE, VISIT-SIF) to deepen the understanding of crop physiological responses under salt stress and advance stress physiology research.

目(mù)前，SIF的(dí)監(jiān)測(cè)已(yǐ)從實驗室走(zǒu)向(xiàng)田(tián)間(jiān)實際(jì)應用。

以我(wǒ)司(sī)推出(chū)的(dí)係(xì)列日光(guāng)誘導(dǎo)葉(yè)綠素熒(yíng)光監(jiān)測係(xì)統(tǒng)為例(lì)，用戶無需自行搭建(jiàn)復(fù)雜模(mó)型與(yǔ)反演流(liú)程，即可直接(jiē)獲取(qǔ)精(jīng)準(zhǔn)的SIF產額(é)及光合作用(yòng)效(xiào)率(shuài)數(shù)據。

我(wǒ)們提(tí)供多種(zhǒng)部署形態：在綫式監測係統(tǒng)可安裝於地麵塔台(tái)，實(shí)現(xiàn)無(wú)人值(zhí)守
，連續監測(cè)並(bìng)自動(dòng)回傳數據至雲(yún)平(píng)台；無(wú)人(rén)機載係統(tǒng)則支持(chí)靈(líng)活(huó)機(jī)動
，高空(kōng)間(jiān)分辨(biàn)率(shuài)的(dí)田間巡測。無(wú)論哪種方式，都能(néng)幫助(zhù)用戶快(kuài)速
，定量(liáng)地(dì)評(píng)估(gū)鹽脅(xié)迫對(duì)植物光合功能的具體抑製程度(dù)，為精準農(nóng)業提供穩(wěn)定可靠的(dí)數(shù)據(jù)底(dǐ)層(céng)。

Currently, SIF monitoring has transitioned from the laboratory to practical field applications.

For instance, our company's series of sun-induced chlorophyll fluorescence monitoring systems allow users to directly obtain accurate SIF yield and photosynthetic efficiency data without the need to build complex models or inversion processes.

We offer multiple deployment options: online monitoring systems can be installed on ground-based towers for unattended, continuous monitoring with automatic data transmission to cloud platforms; UAV-mounted systems support flexible, high-spatial-resolution field surveys. Both approaches help users quickly and quantitatively assess the extent of salt stress-induced inhibition of plant photosynthetic function, providing a stable and reliable data foundation for precision agriculture.

ABN-SIF係列 / ABN-SIF Series

總之，日光誘導(dǎo)葉(yè)綠(lǜ)素熒光技術(shù)為鹽漬化監測(cè)與(yǔ)管理提(tí)供(gōng)了強有力的工具(jù)。它早(zǎo)期
，靈敏反映(yìng)光合生(shēng)理變化，支持精(jīng)準農業
，耐(nài)鹽(yán)育種與大(dà)尺度生態(tài)監測(cè)，為(wéi)保(bǎo)障糧(liáng)食安全提(tí)供重要(yào)科技(jì)支(zhī)撐(chēng)。

In summary, sun-induced chlorophyll fluorescence technology provides a powerful tool for monitoring and managing soil salinization. It offers early and sensitive detection of photosynthetic physiological changes, supports precision agriculture, salt-tolerant breeding, and large-scale ecological monitoring, and delivers crucial technological support for ensuring food security.

案例來源 / Sources ：

1. Du, R., Xiang, Y., Chen, J., Lu, X., Wu, Y., He, Y., Xiang, R., Zhang, Z., & Chen, Y. (2024). Potential of solar-induced chlorophyll fluorescence (SIF) to access long-term dynamics of soil salinity using OCO-2 satellite data and machine learning method. Geoderma, 444, 116855.

2. Cui, K., Ding, J., Wang, J., Tan, J., Han, L., & Li, J. (2025). Potential of solar-induced chlorophyll fluorescence for monitoring long-term dynamics of soil salinity in Central Asia the Xinjiang Region China. Frontiers in Plant Science, 16.