Climate changes and trends in phenology of Cassia fistula L. in Agra (India)—1965-2019

Abstract

Aim. The phenological observations help in identifying how plant species respond to regional climatic changes in particular such as ambient temperature. The study of trends in phenology of Cassia fistula L. (Caesalpiniaceae, Fabaceae) to climate changes in Agra (India) was the aim of the researches. Methods. The data on the average annual temperature in India and Agra were collected for 1965 to 2019 from the Meteorological Department. Commencement of leaf fall, time of new flush of leaves, flowering period (initiation, full bloom, and end) and the rest of phenophases in trees planted at Raja Balwant Singh College (Agra, Uttar Pradesh, India) were recorded from 25 marked trees during 1965–2019. Results. In C. fistula trees leaf fall started in the second and third week of February. Trees became completely leaf-less at the beginning of March. Flowering commenced in the first week of March, and the trees were in full bloom during the second week of March. Flowering continued till the beginning of May, and it was over in the second week of June. Fruiting commenced in December and continued till April. The timing of phenological events was consistent in 1965–2000. However, after 2001, there was a gradual shift recorded, and the shift was evident in 2009–2019. During the period 1965–2008, the average annual temperature ranged between 23.23o–25.13oC there was a liner increase in the temperature. The increase in average yearly temperature became more pronounced in 2009, and this trend is rising in temperature continued till 2019. In Agra in 2009–2019, temperature increase by 0.75–1.0oC had been recorded. The shift of phenoevents in C. fistula is correlated with the rise in annual average temperature. Conclusions. The shift in the timing of various phenoevents is the trees of C. fistula at Agra (India) are influenced by the change in the climate and rise in temperature. It is suggested that a phenological model should be developed to estimate the impact of climate change on fruit trees, horticultural plants and crops development in different regions of India.