Abstract
Cyclical fluctuations in reproductive output are widespread among perennial plants, from multi-year masting cycles in forest trees to alternate bearing in horticultural crops. In natural systems, ecological drivers such as climate and pollen limitation can result in synchrony among plants. Agricultural practices are generally assumed to outweigh ecological drivers that might synchronize alternate-bearing individuals, but this assumption has not been rigorously assessed and little is known about the role of pollen limitation as a driver of synchrony in alternate-bearing crops. We tested whether alternate-bearing perennial crops show signs of alternate bearing at a national scale and whether the magnitude of national-scale alternate bearing differs across pollination syndromes. We analysed the Food and Agriculture Organization of the United Nations time series (1961–2018) of national crop yields across the top-producing countries of 27 alternate-bearing taxa, 6 wind-pollinated and 21 insect-pollinated. Alternate bearing was common in these national data and more pronounced in wind-pollinated taxa, which exhibited a more negative lag-1 autocorrelation and a higher coefficient of variation (CV). We highlight the mutual benefits of integrating ecological theory and agricultural data for (i) advancing our understanding of perennial plant reproduction across time, space and taxa, and (ii) promoting stable farmer livelihoods and global food supply.This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.
Highlights
Variation in plant reproduction is central to processes from forest dynamics to farmer livelihoods [1,2]
The validation exercise confirmed that the FAO time series were well-aligned with published reports on national shocks to production across pollination syndrome and countries
As long cycles could be an artefact of the detrending method, we inspected their occurrence across each (GAM, locally estimated scatterplot smoothing (LOESS) and differencing) by counting the crop–country combinations that exhibited a significant positive lag followed by a significant negative lag and returned to a positive lag in which the lag was greater than 1 year
Summary
Variation in plant reproduction is central to processes from forest dynamics to farmer livelihoods [1,2]. Despite evidence of similar plant-level mechanisms in masting and alternate bearing [4,18,19,20,21], ecological research on the synchrony of mast-seeding has largely ignored, or explicitly excluded, alternate-bearing crops ([13]; though notable exceptions include work on citrus and pistachio [22,23,24]) This may be because breeding and management actions are generally assumed to outweigh any natural conditions that could result in alternate bearing at farm-, region- or nationwide scales [2,13,25,26]. We assess (i) whether these crops are alternate bearing at national scales and (ii) whether patterns differ across pollination syndromes and are consistent with findings in masting systems [5,6,13] For this analysis, we use data from the Food and Agriculture Organization of the United Nations (FAO) [29]. After assessing these patterns at national scales, we discuss the socio-ecological implications of our findings and explore future research directions
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