Tracking vegetation phenology of pristine northern boreal peatlands by combining digital photography with CO 2 flux and remote sensing data

[摘要] Vegetation phenology, which refers to the seasonal changes inplant physiology, biomass and plant cover, is affected by many abioticfactors, such as precipitation, temperature and water availability.Phenology is also associated with the carbon dioxide (CO 2 ) exchangebetween ecosystems and the atmosphere. We employed digital cameras tomonitor the vegetation phenology of three northern boreal peatlands duringfive growing seasons. We derived a greenness index (green chromaticcoordinate, GCC) from the images and combined the results with measurementsof CO 2 flux, air temperature and high-resolution satellite data(Sentinel-2). From the digital camera images it was possible to extractgreenness dynamics on the vegetation community and even species level. Thehighest GCC and daily maximum gross photosynthetic production (GPP max )were observed at the site with the highest nutrient availability and richestvegetation. The short-term temperature response of GCC depended ontemperature and varied among the sites and months. Although the seasonaldevelopment and year-to-year variation in GCC and GPP max showedconsistent patterns, the short-term variation in GPP max was explainedby GCC only during limited periods. GCC clearly indicated the main phases ofthe growing season, and peatland vegetation showed capability to fullycompensate for the impaired growth resulting from a late growing seasonstart. The GCC data derived from Sentinel-2 and digital cameras showedsimilar seasonal courses, but a reliable timing of different phenologicalphases depended upon the temporal coverage of satellite data.

[学科分类] 大气科学