## 5 The State of Phenological Monitoring in India  
India is a country that has enormous diversity and endemism of plant species, with a total forest cover of 713,789 sq. km, which is about 21.71% of its total geographical area [62]. According to [PERSON] and [PERSON], Indian forests have been classified into 16 different forest types and 255 sub-forest types [63]. Each of these forest and sub-forest types exhibits a distinct phenological behavior, necessitating enhanced phenological monitoring in Indian forests. Currently, forest phenological monitoring in India is mainly carried out using traditional ground observations and satellite remote-sensing techniques [20; 64; 65]. Ground-based phenological studies mainly focused on deciduous forests (tropical moist deciduous forests and tropical dry deciduous forests) and evergreen forests (tropical wet evergreen forests) [66; 67; 68; 69] and a few on tropical and subtropical moist forests in the north-east of India [70; 71; 72] (Figure 5). The first-ever formal (from the available literature) phenological study in India was conducted from 15 April 1975 to 20 December 1976 and from 14 February 1978 to 15 September 1979 in the dry deciduous forests of Bandipur [64]. Figure 4: Distribution of published PhenoCam-based studies as per IPCC AR6 regions. However, only a few studies have been published for phenological observations over a long period (more than five years), such as the study by [PERSON] & [PERSON] at Pakke Wildlife Sanctuary and Tiger Reserve, Arunachal Pradesh, which lasted six years from 1997 to 1999 and 2009 to 2011, and the study by [PERSON] & [PERSON] at Mudumalai Dry Forests, Tamil Nadu, which lasted from 2000 to 2008 [73; 74]. Even though India has 37 (Figure 6, Table S3) distinct ground-based phenology observation sites, it has been reported that there are only six long-term forest phenology monitoring sites in India (most of them are ongoing, and only a few are published): Mudumalai-Tamil Nadu (30 years), Pakke Tiger Reserve-Arunachal Pradesh (1997-2000 and 2009-ongoing), dry forest in Rishi Valley-Andhra Pradesh (10 years), Kalakkad Mundanthurai Tiger Reserve-Tamil Nadu (20+ years), Anamalai Hills-Tamil Nadu (4 years) and dry tropical forest in Nigdale-Maharashtra (7 years) [75]. In addition, India has a long-term, large-scale citizen science initiative for plant monitoring called SeasonWatch. Hitherto, SeasonWatch ([[https://www.seasonwatch.in/](https://www.seasonwatch.in/)]([https://www.seasonwatch.in/](https://www.seasonwatch.in/)), accessed on 15 October 2023) has registered over 24,617 plants and collected over 6.6 lakh observations on the phenology of these trees. In addition to this, several satellite-based phenological monitoring studies have been conducted since 1980 [76; 77; 78]. However, nationwide ground validation is not possible for satellite-based phenological products due to a lack of ground observations. The published literature provides information for ground validation in a few locations; however, it is difficult to identify the exact date of the year (DOY) from these linguistic distributions (such as early spring, the end of the dry period, and the post or pre-monsoon period). In addition, most of the ground-based phenological studies in India have monitored the major nine phenological stages in the cycle, such as leaves (bud stage, mature, abscission), flowers (bud stage, anthesis, abscission), and fruit (bud stage, maturation, and abscission). However, it is impossible to monitor all these nine phenological stages with a high level of accuracy using satellite data, which is one of the significant limitations of satellite remote sensing in phenology monitoring. Scientists have employed near-surface digital cameras to circumvent these impediments for phenological monitoring. [PERSON] et al. (2021) installed a camera in the Western Himalayas to track Betula, utilize phenological temporal trends, and record snow cover patterns [79].