The present study shows the phenological events such as leaf fall, flushing, flowering and fruiting of some tree species of Pali region which is located in south western side of Rajasthan. The region is dominated by some tree species such as Anogessus latifolia, Acacia leucophloea, Boswellia serrata and Bombex ceiba. Phenological events are closely related to ecoclimatic factors like temperature, moisture and humidity of the region. Phenological observation of different tree species were recorded periodically throughout the study. Single peak for each event occurring one after another was observed for most of the tree species. Phenological observation during present investigation showed leaf fall in January- February, leaf fall and flowers in March-April followed by fruiting in April-June.

Phenological study has not been carried out properly from the study area, hence the record provided here may be utilized for further climate change assessment.

Numataet al. (2003) showed that the flower production of tropical canopy trees was triggered by prolonged drought, high, solar radiation, and abnormally low temperature.  Kikuzawa and Lechowicz (2010) concluded that phonological studies are also important to understand ecosystem processes such as plant growth pattern, biomass production, plant water stress. Fu et al. (2015) have been founded the effects of global warming on plant phonological traits. Boesch (2013) studied the long-termchanges in fruit phenology of West African tropical rain forest and observed   decrease in rainfall have a negative impact on fruit phenology. Nakar and Jadeja (2014) studied the phenology of two Bombacaceae members from Girnar reserve forest, Gujrat. Tripathi (2018) studied the phenology of some dominant tree species of Ajmer region of Rajasthan. Negi et. al. (2021) studied the effect of atmospheric warming on phonological earliness and length of growing season in Himalayan trees. Mittal et. al. (2021) studied the patterns of phenological characteristics of tree species of Kumaun Himalayan region. Singh et. al. (2023) observed phenological variations with respect to climatic variables of moist temperate forest tree species of Western Himalaya.

Site of study and Methodology-

Pali is located between 24 °45’ to 26°45’ north latitude and 72°48’ to 74°2’ east longitudes. The area of the district may be called sub mountainous and has undulated plains with scattered hills.  This district is surrounded by Aravali range on its south east. The climate of the district is dry and has extremes of temperature. It is hot during summer and very cold during winter. The winter season is from November to March and is followed by the summer from April to June. The period from July to mid-September forms the south west monsoon season and mid-September to October is the post monsoon season. January is the coldest month list. The mean daily maximum temperature is 34.1°c and minimum is 19.0°C. The average maximum rainfall is 153.7 mm and average maximum relative humidity is 85.5% maximum rainfall is recorded in the month of August and maximum relative humidity is record in the month of September. For detailed phenological observation a list of forest tree species of Pali was prepared.

Phenology of trees is a major determinant of forest dynamics especially in the seasonal zone. Different phonological condition such as leaf shedding and flushing affect both climatic and soil below the canopies similarly, flowering and fruiting affect the mean of dispersal, germination and establishment of seeds and subsequently the regeneration capacity of tree species. Phenological changes depend on macroclimate modified by physiographic and edaphic conditions.

In the present investigation Phenological observation on leaf fall, leaf flushing, flowering, and fruiting were observed for various tree species of Pali and monthly observation were recorded (Table-1) Majority of tree species recorded in the present investigation are deciduous and shed their leaves at least once in a year. Generally peak of leaf fall was observed in January and February. In most of the tree like Albizia, Prosopis, Dalbergia, Boswellia leaf fall was confined to winter to spring while the peak period of leaf falls in evergreen trees like Acacia nilotica, Ziziphus, Azadirachta, Maytenus was spring followed by summer season. Increased drought conditions enhance the leaf fall and cause synchronization of the development. Borchert(1978) observed that subsequent leafing is the result of change in the internal root-shoot relationship. Reports on maximum leaf fall during driest period of the year are frequent (Shukla and Ramakrishan,1982). Because of extremes of climatic fluctuations and seasonal periodicity, most of the tree species of this area show leaf-fall and flushing in the same period. Though 80% ofthe tree genera completed their bud burst by the end of April, while for rest of the period it was comparatively low. Similar trend of flushing and production in dry condition before the rains was recorded by many workers (Shukla and Ramakrishan,1982; Sundriyal(1990). These events are dependent on photoperiodic conditions e.g. Increase in dry length induce the leaf flushing (Janz en,1976). In majority of trees leaf fall is followed by flowering. It was observed that most of the tree species bloom once a year, but periodicity of flowering before rainy season has been reported for many trees (Medway, 1972). Observations recorded during the present investigation suggest that extreme variability in moisture, temperature and photo period directs the flowering of many trees. Similar observation on flowering has been documented by Oplaret.al. (1976). A member species has shown dropping of flowering in April which is followed by fruiting. Fruit ripening and shedding after October was very low. Similar result was reported by Sundriyal,1990 and Tripathi 2018. Phenology of trees is strongly driven by environmental factor such as temperature and moisture.

Usingphenological information of trees, a fruiting calendar can be created to select species,quality, quantity and to plan effective harvesting. Phenological data are also useful for further studies like ecological restoration and biodiversity conservation. Phenologicalstudies can help to solve problems of propagation.

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