Heinemeyer Andreas, Holmes Thomas, Jones Anthony, Liu Bing, Daff Jason
University of York, Stockholm Environment Institute (York Centre), Wentworth Way, Heslington, York, YO10 5NG UK.
University of York, Department of Biology, Wentworth Way, Heslington, York, YO10 5DD UK.
J Anal Sci Technol. 2025;16(1):31. doi: 10.1186/s40543-025-00496-y. Epub 2025 Aug 4.
Manual chamber-based carbon flux measurements are frequently used to capture terrestrial carbon cycle processes over vegetated areas. Light response curves, achieved by sequential shading, enable obtaining model parameters of light compensation points, maximum photosynthetic rates and dark respiration. However, light conditions in the field are sometimes, or in higher northern latitudes frequently limited, especially in darker seasons and areas with frequent cloud and fog, which questions the robustness of fitted model parameters. Artificial light therefore offers a crucial way to assess and address these potential limitations, especially recent advances in LED lights with improved wavelength spectra and irradiance. However, previous LED lights were fixed on the chamber top, blocking out natural light, heavy and with a high-power demand unsuitable for remote field deployment. Here we tested a handheld LED torch as a flexible, low-power and low-weight option. We investigated the wavelength spectrum and photosynthetically active radiation (PAR) output under controlled conditions and applied it under light limiting field conditions. Increased PAR from short-term measurements did not increase chamber temperature significantly but improved confidence in fitted light response curves, especially for situations with higher flux variability.
基于气室的手动碳通量测量经常用于获取植被覆盖区域的陆地碳循环过程。通过顺序遮光获得的光响应曲线能够得到光补偿点、最大光合速率和暗呼吸的模型参数。然而，实地的光照条件有时会受到限制，在较高的北纬地区则经常受限，尤其是在较暗的季节以及云雾频繁的地区，这使得拟合模型参数的稳健性受到质疑。因此，人工光提供了一种评估和解决这些潜在限制的关键方法，特别是近年来具有改进波长光谱和辐照度的LED灯取得了进展。然而，以前的LED灯固定在气室顶部，会遮挡自然光，重量大且功率需求高，不适合远程实地部署。在这里，我们测试了一种手持式LED手电筒，它是一种灵活、低功率且重量轻的选择。我们在受控条件下研究了其波长光谱和光合有效辐射（PAR）输出，并将其应用于光照受限的实地条件下。短期测量中PAR的增加并没有显著提高气室温度，但提高了对拟合光响应曲线的置信度，特别是对于通量变异性较高的情况。
