In 631 MASTREE+ seed, fruit and cone series of 20–69 years, year-to-year variability did not change from the first to the second half with equal study weights and did not follow local warming

Question: did masting (year-to-year variability of plant reproduction) increase over time, as Pearse et al. (2017) reported, or decrease with summer warming, as the beech masting-breakdown studies reported? Approach: we used 631 continuous seed, fruit and cone series of 20 to 69 years from the open MASTREE+ V2 database (229 species, 99 studies, 1874-2022). In each series, we compared the coefficient of variation (CV) of the first half with the CV of the second half. We used study bootstrap intervals, a year-shuffle permutation null, and GHCN-CAMS warm-season temperature of the cue year. Results: with equal weight for each study, CV changed by +0.6% (95% interval -5.0% to +6.8%; permutation p = 0.83). Proportional variability and crop-failure frequency also did not change. With equal weight for each species, CV increased by 5.2% (+0.6% to +10.0%). One study (Lope, Gabon; 47 species) caused this increase: its mean fruiting decreased by 69% and its CV increased by 29%. Without this study, the species-weighted change was 0.0%. The change in log CV did not decrease where the cue-year summers became warmer (median +0.37 C; slope +0.049 per C, -0.073 to +0.120). In 52 European beech series after 1980, UK and Polish series became less variable, but Italian and French series became more variable (study mean +2.2%, -8.1% to +14.6%). A calendar-decade analysis gave +6.9% per decade with pooled series. Within series, one Polish survey had 70% of the weight, and with equal study weights the slope was -0.8% per decade (-5.6% to +4.4%). Limitation: the halves are on average 16 years apart, and the series use different methods and units. Thus the test cannot exclude small changes or opposite regional changes. We did not use the full data or the exact methods of the earlier studies.

mast seeding · masting breakdown · seed production · interannual variability · coefficient of variation · MASTREE+ · climate change · Fagus sylvatica · tree reproduction · time series · GHCN-CAMS