cE3c-Centre for Ecology, Evolution and Environmental Changes & CHANGE, Global Change and Sustainability Institute, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, Piso 5, 1749-016 Lisboa, Portugal; Centre for Applied Ecology "Prof. Baeta Neves" (CEABN- InBIO), School of Agriculture, University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon, Portugal.
Centre for Applied Ecology "Prof. Baeta Neves" (CEABN- InBIO), School of Agriculture, University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon, Portugal.
Sci Total Environ. 2024 Jan 10;907:167835. doi: 10.1016/j.scitotenv.2023.167835. Epub 2023 Oct 14.
Masting, the synchronized production of variable quantities of seeds, is a global phenomenon in diverse ecosystems, including treed grazing systems where trees and grazing animals coexist. This phenomenon can be interspersed with years of extreme crop failure, whose frequency and unpredictability are increasing. Yet, the combined impact of crop failure and grazing on seed dispersal and seed-to-seedling transition remains poorly understood. To address this concern, we investigated rodent-mediated cork-oak (Quercus suber) acorn predation, dispersal, and seedling emergence in cattle grazed and non-grazed areas in central Portugal during years with contrasting masting seasons. We found that the acorns supplied in the crop failure year were dispersed more rapidly and over longer distances than those supplied in the crop success year when other acorns were naturally available. The crop failure year also had 83 % more dispersal events and 84 % more predated acorns than the reproductive success year. However, the higher acorn predation was offset by a 2.4-fold higher percentage of unpredated dispersed acorns recruiting into seedlings. Both years ended up recruiting a similar number of seedlings. Acorns emerged seedlings 3.4 times farther in the crop failure year than in the crop success year. Cattle grazing was the main constraint on seed dispersal distance by rodents, reducing it by 53 %. Our study provides empirical evidence that cattle grazing modulates how an extreme crop failure year can surprisingly be an opportunity for the few existing acorns to have seedlings established farther apart than in a crop success year. If we are to better manage and preserve the high conservation and socio-economic value of Mediterranean cork oak woodlands in the face of climate change, we must prioritize fecund trees and carefully manage seed dispersal factors such as cattle grazing, particularly during years of crop failure.
结实（即同步产生不同数量的种子）是一个全球性现象，存在于多种生态系统中，包括树木和放牧动物共存的放牧林地系统。这种现象可能会与多年的极端作物歉收交错出现，而且其频率和不可预测性都在增加。然而，作物歉收和放牧对种子传播和种子到幼苗的转变的综合影响仍知之甚少。为了解决这一问题，我们调查了啮齿动物对栓皮栎（Quercus suber）橡实的捕食、传播和幼苗出现情况，研究地点在葡萄牙中部的放牧和非放牧地区，这些地区在结实年份和不结实年份的结实季节差异很大。我们发现，在作物歉收年份提供的橡实比在其他橡实自然供应的作物丰收年份提供的橡实传播得更快、更远。此外，在作物歉收年份，发生了 83%更多的传播事件，被捕食的橡实数量比繁殖成功年份多了 84%。然而，较高的橡实捕食率被未被捕食的分散橡实的 2.4 倍高比例所抵消，这些橡实进入了幼苗。这两年最终招募的幼苗数量相似。在作物歉收年份，橡实长出的幼苗比在作物丰收年份远 3.4 倍。在作物歉收年份，牛放牧是啮齿动物种子传播距离的主要限制因素，使传播距离减少了 53%。我们的研究提供了经验证据，表明牛放牧会调节极端作物歉收年份的情况，使少量现存的橡实有机会在幼苗之间建立得比在作物丰收年份更远。如果我们要更好地管理和保护地中海栓皮栎林地的高保护和社会经济价值，以应对气候变化，我们必须优先考虑多产的树木，并仔细管理种子传播因素，如牛放牧，特别是在作物歉收年份。
