Tracking biological footprints of climate change using flowering phenology of the geophytes: Pancratium tenuifolium and Scadoxus multiflorus.

Drought-adapted geophytes are responding to the effects of climate change in arid and semi-arid environments. In this study, herbarium and historical rainfall data were used to examine the impact of rainfall changes on flowering trends of Pancratium tenuifolium Hochst. ex A.Rich and Scadoxus multiflorus (Martyn) Raf. subsp. multiflorus. Flowering was delayed by approximately 7 days per decade for P. tenuifolium during the period 1930 to 2018 and by approximately 14 days per decade for S. multiflorus subsp. multiflorus during the period 1924 to 2008. Scadoxus multiflorus subsp. multiflorus delayed the day of flowering by approximately 0.3 days per millimetre increase of rainfall, with Pancratium tenuifolium showing a non-significant response to summer rainfall during the same period. Overall, a linear mixed-effects model revealed that the day of flowering was delayed by approximately 8 days per degree rise in latitude and advanced by approximately 9 days per degree rise in longitude. Additionally, summer rainfall had significant effects on the day of flowering with a 1-mm increase in summer rainfall delaying the day of flowering by approximately 0.16 days. These changes in flowering times may ultimately alter the distribution of geophytes in Namibia.