Integrated use of field sensors, PhenoCam, and satellite data for pheno-phase monitoring in a tropical deciduous forest of Dalma Wildlife Sanctuary, Jharkhand, India: initial results from the Indian Phenology Network

Abstract

Plant phenology regulates ecosystem functions at diverse scales but is impacted by micro and macro climatic variations, and climate change. In India, precise estimations of pheno-phase transition dates remain scarce at different spatial and temporal scales, necessitating comprehensive research efforts. This study aims to gather continuous intra-day ground data about vegetation and climate conditions using PhenoCam (optical RGB and IR images) along with meteorological sensors, at Dalma Wildlife Sanctuary (DWS), Jharkhand. To derive phenological metrics, different indices were computed from images captured by PhenoCam sensors and Satellite derived Normalized Difference Vegetation Index (NDVI). Since the PhenoCam covers diverse vegetation species in the frame, the analysis was performed over three specific subset Region of Interests (ROI): Bombax ceiba (Semal) tree, background cluster of vegetation and a sample tree. MODIS NDVI data revealed that most of the area is highly deciduous with major greening in the 1st half of April and senescence during 2nd half of March. The study found that Green Chromatic Coordinate Index (G_CC) and Blue Chromatic Coordinate Index (B_CC) results could reveal greening and senescence phases correctly. The timing of start of leaf flush (SOLF), end of leaf flush (EOLF) and end of leaf maturity (EOLM) estimated based on inflection point method from Pheno-Cam images are: for Semal tree: 5th April, 2nd May, 10th June, 2022; for background vegetation: 15th March, 28th March and 2nd May, 2022; and for sample tree: 15th March, 28th March and 25th April, 2022, respectively. The dates of SOLF differed in 2023 and it occurred twice for Semal and background vegetation: for Semal tree: 20th February and 3rd April 2023, and for background vegetation: 20th January and 8th March, 2023, respectively. The rate of leaf flush and rate of leaf maturity was not similar in different years as the rates were much higher in 2023 than in 2022. The temperature and rainfall during winter and spring played an important role in greening, senescence, and its sustenance. These findings revealed the micro-climatic effect on plant phenology in the Dalma Wildlife Sanctuary, as well as the importance of integrating PhenoCam and satellite data in accurate monitoring of phenological phases.