Department of Geography and Environmental Science, University of Reading, Whiteknights, RG6 6DW, UK; Department of Geography, University of Exeter, Streatham Campus, Exeter EX4 4QE, UK.
University of Waterloo, ON N2L 3G1, Canada.
Sci Total Environ. 2021 Apr 20;766:142613. doi: 10.1016/j.scitotenv.2020.142613. Epub 2020 Oct 1.
Estimates of peatland carbon fluxes based on remote sensing data are a useful addition to monitoring methods in these remote and precious ecosystems, but there are questions as to whether large-scale estimates are reliable given the small-scale heterogeneity of many peatlands. Our objective was to consider the reliability of models based on Earth Observations for estimating ecosystem photosynthesis at different scales using the Forsinard Flows RSPB reserve in Northern Scotland as our study site. Three sites across the reserve were monitored during the growing season of 2017. One site is near-natural blanket bog, and the other two are at different stages of the restoration process after removal of commercial conifer forestry. At each site we measured small (flux chamber) and landscape scale (eddy covariance) CO fluxes, small scale spectral data using a handheld spectrometer, and obtained corresponding satellite data from MODIS. The variables influencing GPP at small scale, including microforms and dominant vegetation species, were assessed using exploratory factor analysis. A GPP model using land surface temperature and a measure of greenness from remote sensing data was tested and compared to chamber and eddy covariance CO fluxes; this model returned good results at all scales (Pearson's correlations of 0.57 to 0.71 at small scale, 0.76 to 0.86 at large scale). We found that the effect of microtopography on GPP fluxes at the study sites was spatially and temporally inconsistent, although connected to water content and vegetation species. The GPP fluxes measured using EC were larger than those using chambers at all sites, and the reliability of the TG model at different scales was dependent on the measurement methods used for calibration and validation. This suggests that GPP measurements from remote sensing are robust at all scales, but that the methods used for calibration and validation will impact accuracy.
基于遥感数据估算泥炭地碳通量是对这些偏远而珍贵的生态系统进行监测方法的有益补充，但由于许多泥炭地的小规模异质性，对于大规模估算的可靠性存在疑问。我们的目标是考虑使用苏格兰北部福斯湾流动皇家鸟类保护协会保护区作为研究地点，基于地球观测的模型在不同尺度上估算生态系统光合作用的可靠性。在 2017 年生长季节监测了保护区内的三个地点。一个地点是近自然的毯子沼泽，另外两个地点是在商业针叶林采伐后恢复过程的不同阶段。在每个地点，我们测量了小（通量室）和景观尺度（涡度协方差）的 CO 通量，使用手持式分光计测量小尺度光谱数据，并从 MODIS 获得相应的卫星数据。使用探索性因子分析评估了影响小尺度 GPP 的变量，包括微地形和优势植被物种。使用土地表面温度和遥感数据中绿色度的指标测试和比较了 GPP 模型与室和涡度协方差 CO 通量；该模型在所有尺度上都取得了很好的结果（小尺度上的皮尔逊相关系数为 0.57 至 0.71，大尺度上为 0.76 至 0.86）。我们发现，尽管与含水量和植被物种有关，但微地形对研究地点 GPP 通量的影响在空间和时间上是不一致的。在所有地点，EC 测量的 GPP 通量都大于腔室测量的 GPP 通量，不同尺度上 TG 模型的可靠性取决于校准和验证中使用的测量方法。这表明，遥感的 GPP 测量在所有尺度上都是可靠的，但校准和验证中使用的方法会影响准确性。
