Using easily accessible digital photography to monitor phenology of boreal peatland vegetation impacted by linear disturbances

Abstract:

Plant phenology is a useful metric for understanding disturbance impacts on ecosystem functioning. Tree removal and ground disturbance following the creation of linear features such as seismic lines, long linear forest clearing used for geologic exploration, can impact vegetation communities through changes in productivity and shifts in composition. Here, we develop a simple approach to monitor growing season phenology by quantifying vegetation ‘greenness’ using easily accessible digital photography. The objectives of this study were 1) to evaluate variation in vegetation greenness between disturbed and undisturbed boreal sites using the Green chromatic coordinate (g_cc) index and 2) evaluate if variation in greenness is related to differences in plant species composition. This study was undertaken at three boreal peatland sites (two bogs and one fen) in northern Alberta, Canada. Weekly photographs were taken between May 12^th to August 22^nd, 2019. The photographs effectively quantified the temporal variation in greenness at all three sites. The disturbed bog sites were, on average, greener than natural bog sites across the whole growing season. Conversely, at the fen, natural sites were greener than disturbed sites in the spring, but by summer both areas had similar greenness levels. Preliminary results indicate that variation in greenness is driven more by changes in plant species composition than loss of plant cover at the plot scale between disturbed and natural sites. In particular, there has been a shift from a natural feather moss/lichen dominated system to a Sphagnum dominated system at the bog sites while the disturbed fen sites have become dominated by sedges and willows compared to the feather moss dominated natural sites. This work highlights the ease of use and application of digital photography to successfully quantify phenological changes in boreal peatland vegetation communities.