研究目的
To investigate relations of half-hourly and daily carbon dioxide (NEE and GPP) and water vapour flux with spectral reflectance data.
研究成果
The research demonstrates significant correlations between spectral data and greenhouse gas fluxes, with higher correlations for carbon dioxide than water vapour, and better results using spectral indices and daily timestamps. This supports the potential for upscaling flux estimates using remote sensing, though challenges remain in accounting for respiration components in net fluxes.
研究不足
The study is limited to a specific wetland site (alkaline fen in Biebrza Valley) and two growing seasons, which may not represent all wetland types or climatic conditions. The use of quadratic functions for correlations might not capture all nonlinear relationships, and the reliance on spectral data may not fully account for ecosystem respiration effects on net fluxes.
1：Experimental Design and Method Selection:
The study involved parallel measurements of greenhouse gas fluxes and canopy reflectance using the eddy-covariance technique and spectrometers. Statistical analyses included linear, quadratic, exponential, and logarithmic functions to relate fluxes to reflectance and spectral indices at half-hour and daily timestamps.
2：Sample Selection and Data Sources:
Data were collected from an alkaline fen in the Upper Biebrza Basin, NE Poland, during the growing seasons of 2015 and 2016. The site is part of the Biebrza National Park, characterized by peat soils and wetland vegetation.
3：The site is part of the Biebrza National Park, characterized by peat soils and wetland vegetation.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a Li-7200 infrared gas analyzer (Licor, USA), WindMasterPro sonic anemometer (Gill, UK), two USB2000+ spectrometers with cosine correctors, and a micrometeorological station. Software used were EddyPro? (LI-COR, USA) for flux calculations and R REddyProc package for gap-filling and partitioning.
4：Experimental Procedures and Operational Workflow:
Fluxes were measured at 10 Hz using eddy-covariance, with half-hour fluxes calculated and quality-checked. Reflectance was measured in the 400-1000 nm range, filtered for time, physical range, and clearness index, and used to compute spectral indices. Daily means and sums were derived from half-hour data.
5：Data Analysis Methods:
Correlation coefficients were calculated between fluxes and reflectance/spectral indices using quadratic functions (found to have the highest correlations), with statistical significance assessed (p-value < 0.05).
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