Phenological response patterns of forest communities to annual weather variability at long-term ecological monitoring sites in Western Himalaya

•In this paper, we report periodicity of phenophases (e.g., timing of bud-break and leafing, leaf-drop, flowering and fruiting) vis-a-vis climatic conditions in 28 tree species (142 individuals), 58 shrub and 72 herb species' populations in four semi-deciduous and evergreen forests along an elevational transect (680–1860 m asl) by establishing long-term ecological monitoring (LTEM) sites continuously for 23 months during 2018–2020.•In this study we presented (i) long-term ecological monitoring (LTEM) sites for continuous monitoring of phenological events of tree, shrub and herb layer of dominant forest types in the Western Himalayan region, and (ii) phenological response patterns of forest vegetation to annual variability in meteorological conditions for enhanced understanding on response of vegetation to climate change.•Understanding intensity and direction of on-going and potential changes of climate on vegetation responses that influence the structure and functioning of forest ecosystem attributes are important. This work is significant because in the absence of LTEM sites in the Himalayan region, studies on responses of forest vegetation to climate change remains least attempted, thereby creating major knowledge gap. This paper presents the periodicity of phenophases in 28 tree species (142 individuals), 58 shrub, and 72 herb species' populations for 23 months (during 2018–2020) vis-a-vis weather variability in four semi-deciduous and evergreen forests along an altitudinal transect (680–1860 m asl) in long-term ecological monitoring (LTEM) sites in Western Himalaya. Across these forests, atmospheric temperature, relative humidity, and annual rainfall declined significantly with increasing elevation. The autumn to winter period (October-February) of 2019 was characterized by higher temperature (0.49 °C), rainfall (48.5 mm), and relative humidity (9%) in comparison to 2018. Vegetative bud-break, leafing and leaf drop occurred predominantly in the spring season (March-April) followed by flowering and fruiting through summer until the onset of the rainy season. All the phenophases occurred in 3–4 episodes of varying magnitudes year-round, except for a few months during the rainy season. The year 2019 was characterized by earliness in bud-break and leafing by over 2 weeks as compared to 2018. This may be attributed to the greater elevation-dependant warming as reflected by the shallow mean annual temperature lapse rate (−0.36 ± 0.2 °C/100 m) observed for th