Tracking phenology and phytomass using oblique repeat photography and kite aerial photography in Arctic wetlands

Background/Question/Methods

The extreme arctic environment often limits our ability to take repeat observations using most airborne and satellite systems and thus makes it difficult to track seasonal changes over large temporal and spatial scales. In addition, plot-level measurements are often time consuming and logistically difficult in these harsh environments. To overcome these constraints, this study evaluated the effectiveness of two new cost-effective methods of remotely assessing seasonal phenological and biomass changes of aquatic plants: (1) oblique repeat photography and (2) kite aerial photography (KAP). We validated the effectiveness of these near-surface methods by determining relationships between remotely sensed greening and ground-based spectral measurements and plant biomass for both Carex aquatilis and Arctophila fulva, important mediators of carbon fluxes and energy balance in the Arctic.

Results/Conclusions

The green excess index (2G/R+B), calculated using both methods, was a good predictor of NDVI and aboveground biomass. The vertical approach of KAP was able to track spatial variability in greening and senescing, while the emergence and flowering of both species was best captured by the oblique photography. Our data support the effectiveness of oblique repeat photography and KAP to assess spatial and seasonal changes in plant phenology and biomass. These methodological advances will lead to high-resolution descriptions of intra- and inter-annual variation in aquatic plant productivity.