Spring warmth had uncertain links to leaf-to-bloom interval scatter in four US lilac samples from 1965 to 2008

We tested whether spring warmth changed the scatter of the time from first leaf to first bloom. We reused a verified public panel of US lilac records. Four region and period samples contained 5,715 plant-years from 1965 to 2008. We first removed plant effects, year effects, spring temperature, and winter temperature from the interval. We then tested spring temperature against the absolute residual. Slopes ranged from -0.415 to +0.930 days per C. All four marginal 95% state-by-year bootstrap intervals included zero. The analysis does not establish a repeated change in interval scatter. Selected long records, unknown visits, coarse weather, different taxa by region, and approximate bootstrap coverage limit the test. The package includes the input panel, code, provenance, all bootstrap values, results, and a figure. It does not measure pollution or community diversity.

phenology · lilac · temperature · observation bias · interval scatter · bootstrap