Like many perennial crops, coffee exhibits alternate bearing, a pattern of reproduction in which high-yielding years are followed by low-yielding ones. Alternate bearing threatens farmer livelihoods, yet little is known about the underlying mechanisms in coffee or the potential for farm management to mitigate it. The resource budget model, an ecological theory positing endogenous resource tradeoffs as the driver of reproductive variability, could help fill this gap. On three coffee farms in Santa María de Dota, Costa Rica, we manipulated relative fruit load, fertilizer levels, and shade cover to test whether the model’s core assumptions (i.e., that fruiting depletes resources and limits investment in subsequent reproduction) can elucidate patterns of alternate bearing in coffee, and to assess whether these patterns are impacted by farm management practices. Coffee plants exhibited within-year and between-year tradeoffs of a high fruit load that scaled from decreased bean size during the same season to fewer fruited nodes and fruits per node in both old and new cohorts of branches during the subsequent season. Stem nitrogen concentration was also depleted in response to high fruit loads and recovered during the subsequent season of low fruiting. The findings provide novel evidence that tradeoffs of a high fruit load are manifested in several reproductive traits at both the branch- and plant-level and offer initial support for the resource budget model in the system. While both moderate shade and increased fertilizer levels tended to improve reproductive traits, a lack of interactive effects between either management treatment and the relative fruit load treatment suggests that they do little to mitigate the reproductive tradeoffs underlying alternate bearing.

像许多多年生作物一样，咖啡也表现出交替的生育能力，这是一种高产年份紧随其后的低产年份。交替轴承威胁着农民的生计，但人们对咖啡的潜在机制或农场管理缓解它的潜力知之甚少。资源预算模型是一种将内生资源权衡作为生殖变异性驱动因素的生态理论，可以帮助填补这一空白。在哥斯达黎加圣玛丽亚德多塔的三个咖啡农场，我们操纵了相对果实负荷、肥料水平和遮荫，以测试模型的核心假设（即结果会耗尽资源并限制后续繁殖的投资）是否可以阐明在咖啡中交替出现，并评估这些模式是否受到农场管理实践的影响。咖啡植物表现出高果实负荷的年内和年间权衡，从同一季节的豆子大小减少到随后季节新老分枝组中每个节点的结果节点和果实减少。茎杆氮浓度也因高果实负荷而耗尽，并在随后的低结果季节恢复。这些发现提供了新的证据，表明高果实负荷的权衡体现在分枝和植物水平的几个生殖性状中，并为系统中的资源预算模型提供了初步支持。虽然适度遮荫和增加施肥水平都倾向于改善生殖性状，