SIF (Sunlight Induced Chlorophyll Fluorescence) is like a precise doctor, using a professional "stethoscope" to directly capture the real pulse of vegetation photosynthesis. As a natural optical signal of photosynthesis, the intensity of SIF directly reflects the intrinsic "physiological activity" of the plant, not just the apparent "greenness". This ability to directly detect the physiological state of plants makes SIF technology show unique advantages in early warning of stress, accurate yield estimation and carbon sink accounting, providing a new technical way for agricultural management, ecological monitoring and carbon cycle research.
From the Protected Area of Closed Forest in Baotou, Inner Mongolia, to the Field Scientific Observatory of Karst Ecosystems in Guanling, Guizhou, to the Modern Agricultural Weather Field in Hebi, Henan, a set of high-precision daylight-induced chlorophyll fluorescence spectroscopy system with fully independent intellectual property rights is continuously serving many typical ecological and agricultural research scenarios in China, providing reliable data support for vegetation photosynthesis monitoring.
Technical Advantage: Accurately Capturing the "Pulse" of Photosynthesis
The system adopts advanced optical design and signal processing technology with the following features:
Spectral range:650 - 800 nm, accurate coverage of key fluorescence absorption lines such as O₂-A, O₂-B, etc.
Precision spectral acquisition:0.3 nm spectral resolution with 0.1 nm sampling interval for clear resolution of oxygen absorption line features
Excellent signal-to-noise performance:1000:1 signal-to-noise ratio ensures reliable extraction of weak fluorescent signals
Stabilizing environmental adaptation:Semiconductor and air-cooled synergistic temperature control to ensure long-term stable operation in the field
Wide dynamic range:5000:1 dynamic range to adapt to various lighting conditions
Intraday trends
(Sample 1 of the Regional Scale Automatic Ecological Observation of the Hulunbeier Grassland, Inner Mongolia, July 1, 2022)
II. Accuracy guarantee and verification system
We have established a complete laboratory and field calibration process to ensure accurate and reliable data:
Laboratory absolute radiation calibration:Before each instrument is shipped, absolute radiation calibration is carried out in a darkroom environment using an integrating sphere and a standard lamp, which has been calibrated by the China Academy of Measurement Sciences to ensure the accuracy of the physical value of the data.
Factory calibration and quality control:The system integrates automatic optical path switching function, and dark current collection and standard whiteboard reference measurement are carried out before leaving the factory, which effectively suppresses instrument drift and environmental interference.
Validated against international brands:In order to evaluate the performance objectively, we conducted a comparison test with Ocean Optics spectrometer under the same conditions. The results show that the system has reached a comparable level in terms of signal-to-noise ratio, stability and consistency of fluorescence inversion, and has reliable data comparability.
Statistically significant agreement between the domestic spectrometer and the imported Ocean Optics QE Pro in general, with a correlation of 92% (R2 = 0.85) especially in the far-red band (O2B)
III. Typical application cases
Agricultural Meteorological Observation Station, Hebi City, Henan Province, China
Crops at the Hebi station are planted in a two-season planting pattern, and during the installation period (mid- to late May) were in the later part of the growing season for winter wheat, which was harvested on or around June 10 and then planted with corn.
The equipment at the Hebi station was set to work from 10:00 a.m. to 14:00 p.m. with a 10-minute sampling frequency from May 20 to June 3, and since June 4, the sampling frequency has been set to 5 minutes, so that the theoretical measurements of the data volume per day are 24 and 48, respectively. The actual valid data of the device is ≥98%, indicating that the device can collect and transmit data stably.
The time of the nadir of the SIF observation coincides exactly with the date of wheat harvesting in the field, and the sudden decrease in SIF reflects well the actual situation of rapid wheat harvesting.
The trend of climate camera (vegetation index) observations in the same period showed that although the NDVI bottomed out at a date similar to the wheat harvest date, the downward trend was more gentle than that of SIF, and was not as sensitive as that of SIF in reflecting the vegetation harvest (mutation) situation.
This was clearly reflected in the slow change and rapid increase in SIF during both the beginning growth phase (early July) and the rapid growth phase (mid-July) of the corn.
Trends in SIF and vegetation index (NDVI) values were generally consistent, with the SIF date differing from the NDVI date by only 1 day in the timing of the start of the rapid maize growth period.
The vegetation indices show that corn did not have a significant lifting period until the beginning of DOY = 194 days (July 14), a date that is essentially the same as the July 15 date observed by the SIF.
In the winter wheat-corn rotation system at Hebi Station in Henan Province, the SIF measurement system operated stably and received complete data. The system accurately captured the sharp decline in SIF caused by wheat harvesting, and the response was sharper than that of the vegetation index; at the same time, it clearly recorded the dynamic changes in SIF during the seedling emergence and rapid growth stages of maize, which was highly consistent with the results of the monitoring of the vegetation index.
This case shows that the SIF equipment has reliable physiological response detection capability and accurate capture of vegetation dynamics, providing solid data support for agricultural monitoring and ecosystem research.
IV. Outlook
At present, the system has been put into operational operation in several field stations and agrometeorological stations, providing continuous and stable data support for related research. In the future, we will continue to deepen the research and application of SIF measurement technology to further expand the adaptability and stability of the system in multiple ecosystems and complex environments.
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