Phenophases, Climate change, Forest management, Yamuna Nagar.

Phenology is the study of regular occurrences in the life cycle of living organisms influenced by seasonal and yearly climate variations. Phenological stages arise from a combination of biological rhythms and environmental influences. These factors over the course of evolution have led species to adapt to various climatic conditions (Orlandi et al., 2007). A number of studies on phenophases of plants have been carried out by different workers in different regions of the world (Kaur et al., 2013; Liu et al., 2023; Kanwar and Sharma 2023). According to Chhetri et al. (2020), an understanding of the diversity of phenological patterns, which show variations in the timing of phenophases in the different plant species, is essential for determining the status and development of trees throughout the year.  Plants depend on one or more of the factors for their phenological processes with the changing environmental conditions. Keerthana et al. (2022) in their study on Glycine max (L.) Merrill observed that increasing the seed-space during sowing improves phenology and seed quality. In a study on Lupinus perennis L., Pushpa et al. (2022) found that application of Gibberellic acid improves the phenology of flowering and yield of the plant. In another study on tropical forests, Numata et al. (2022) concluded that the phenological processes across different species in various ecosystems showed variable responses. 

Phenological patterns in tropical plants are typically linked to the distinct seasonal rainfall patterns, characterized by sharply contrasting wet and dry seasons (Marques et al., 2004). Nanda et al. (2017) in a study on tropical evergreen forests observed that rainfall had a notably negative impact on both vegetative and reproductive phenological events. All phenophases of these phenologies, except for leaf senescence, displayed significant seasonal patterns. Identifying a specific relationship with air temperature makes it possible to regulate the species composition and quantity when establishing this type of plantation. Kopp et al. (2020) examined a large number of plants and their phenology in certain regions of North America. They found that there was a sensitive relationship between temperature and the flowering of plants. They also suggested that further studies are required to establish the effect of global warming on plant phenology. The progression of phenophases and the timing and length of plants' phenological cycles are consistently influenced by seasonal climate variations, such as the regular alternation of seasons with differing day lengths, temperatures, and precipitation levels (Adamenko et al., 2023).

Due to climate change, seasonal perennial plants face several physiological challenges. Identifying and understanding the timing of physiological stress tolerance can offer managers a valuable tool for adapting to and reducing the effects of expected change in climate (Grossman, 2023).  Ibáñez et al. (2010), from their study, concluded that it is utmost important to study multiple plant species in different geographical conditions so as to express change in phenological behaviour of plants. Climate change is shifting the timing of biological events in species, yet the ecological and conservation impacts of these changes remain underestimated (Mendes et al., 2023).

 The effects of climate change on plant phenology are being increasingly studied, but most of the research tends to overlook woody species (Verbényiné Neumann et al., 2023). According to Pancharoen et al. (2021), urban forests are vital for reducing urban heat and influencing the microclimate, which can affect tree phenology. Mrekaj et al. (2024) in their study on forest trees of Slovakia concluded that temperature was the main factor influencing different phenophases of the plants. Bartosova et al. (2025) compared the phenology of crops and wild plant species in Central Europe. They concluded that studies on natural vegetation can give better information regarding phenological changes due to shifting climate patterns. Using remote sensing technology, Kleinsmann et al. (2023), studied the phenological behaviour of different plants and concluded that tracking of the phenomena is crucial for gaining insights into ecosystem dynamics and evaluating how they respond to climate change. A detailed study of these interactions can form the basis for urban planners to choose the most suitable trees for the plantation activity. 

Study site. The present study has been conducted on some important tree species in district Yamика Nagar of Haryana (Figure 1). The district lies between 29° 55' to 30° 28' North latitudes and 77°09' to 77°36’ East longitudes at 274 meters AMSL (DCOH, 2011). The climate of the study area is subtropical, with the majority of rainfall taking place in the monsoonal season. The hot summers start  from April  and go up to June. This is followed by the arrival of the South-West monsoon that lasts up to the month of September. A Period from October to November is called post-monsoon (Autumn) and the winters start from December to February. A transition period is there in the month of  March called the spring season. The annual rainfall during the study period has been recorded as 855 mm (Fig. 2 ) for the calendar year, with the highest peak of 270 mm in September 2024. The average minimum and maximum monthly temperature were recorded in January (6℃) and May (46℃), respectively. The meteorological data has been collected from the office of the district administration and the weather stations of Saraswati Sugar Mill at Yamuna Nagar, Haryana. 

Fig. 1. Map of the Study Area.

Phenology. The phonological events of 12 tree species have been recorded from villages Parwalo (P), Buria (B), Manakpur (M) and Jaroda (J). These selected plants belong to 12 genera and 8  families (Tabel 1). The  sites  of study area were  chosen as there  was  a wide diversity of tree species. Different phenological activities were recorded  for the calendar year 2024. The  phenophases  included -Leaf budding (Lb), Leaf flush (Lf), Senescence of leaves (Sl), Complete leaf fall (Cl ), Flower budding (Fb), Flowering  (Fl), Fruiting  (Fr), Fruit maturation (Fm), fruit fall (Ff) and last years fruit fall (Ffl) as shown in Table 2. Visits were paid to the site fortnightly but weekly during the period of higher activity from Feb to May to record the phenological events. 

Fig. 2.  Record of monthly temperature and rainfall of the study area during 2024.

The phenological observation for 12 trees in the year 2024 has been recorded in Table 2. Most of the trees under study were found to be in the stage of leaf senescence or completely leafless in the month of January 2024. Towards the second half of February, Leaf buds were reported in 83%  of the trees, and leaf flush also started in the last week of the month in 41.7 plant species (Fig. 3). The months of March and April were having  the highest numbers of activities like leaf flush, flower budding and flowering. In April 91.6% of the species were in the flowering phase, and 6 species had started the process of fruiting. In May 2024, all the tree species were in the fruiting phase and that continued in June with almost half of the species. Fruits started maturing in the month of June, and the phenomenon lasted till August. The fruit fall took place in July and August in Azadirachta indica A.Juss.,  Cordia myxa L., Melia azedarach L., Toona ciliata  M.Roem., Ficus religiosa L., Syzygium cumini (L.) Skeels and Dalbergia sissoo Roxb. ex DC.

For the members of the family Meliaceae the process of leaf flush, flowering and fruiting was first noticed in Melia azedarach L. followed by Toona ciliata  M.Roem. and Azadirachta indica A.Juss., while in the family Fabaceae the order was Dalbergia sissoo Roxb. ex DC., Albizia lebbeck (L.) Benth and Delonix regia (Bojer ex Hook.) Raf. Senescence started in most of the plants towards the end of the rainy season in the second half of September  and continued till the end of the year as the winters arrived.  In Jacaranda mimosifolia D.Don, Terminalia bellerica (Gaertn.) Roxb and the  members of the family Fabaceae the fruits were still attached to the plants in the cold winter seasons when the senescence of leaves was taking place.  In case of Pterospermum acerifolium (L.) Willd. the  last year's fruits started dehiscing while the next year flowering, and fruiting was taking place in the month April and May. 

From this study it was observed that the peak season for most of the physiological activities, including leafing, flowering, and fruiting, was from March to May. This observation is similar to some other phenological studies  (Chhetri et al., 2020; Kaur et al., 2013). Fruit maturation took place in most of the plants during the rainy season. As the winters approach, there is a decline in temperature and day length and the process of leaf senescence starts  in most of the plants.  A few studies on senescence as reported by some workers (Wang et al., 2023; Wang et al., 2025), have shown temperature to be the factor responsible for this process. 

Table 1:  List of tree species selected for the study of phenological events.

Fig. 3.  Important Phenological patterns (%) of the selected plants during January to December 2024.

Table 2:  Phenophases of selected  plant species during the study period from January to December 2024.

ABBREVIATIONS:  Lb-   Leaf budding                   Fr- Fruiting

                                     Lf-   Leaf flush                         Fm- Fruit maturity     

                                    Sl - Senescence of leaf              Ff- Fruit fall

                                    Fb-Flower budding                   Ffl- Fruit fall of last year   

                                    Fl-Flowering                             Cl-Complete leaf fall

The impacts of global warming are now being felt and some studies have observed a change in the phenology of plants and higher temperature is the major contributor (Mrekaj et al., 2024). In a warmer world, the seasons of spring, summer and autumn may change and alter the phenological processes in plants. Therefore, such studies are important to understand the phenological shift due to climate change. 

This study can provide a baseline to monitor the effects of climate change on tree species in Yamuna Nagar. It may help in biodiversity conservation by identifying sensitive species and improving forest and agroforestry practices. Understanding phenology can also support urban planning by selecting suitable trees for green spaces. Future work could expand to remote sensing, climate modelling, and citizen science initiatives. Overall, the findings can guide local policies on environmental management and climate adaptation.

Varsha Nigam, Amarjit Singh and Gian Bhushan  (2025). Exploring the Phenological Patterns of Selected Tree Species in District Yamuna Nagar, Haryana. Biological Forum, 17(5): 58-62.