To Everything There Is a Season: Summer-to-Winter Food Webs and the Functional Traits of Keystone Species
To Everything There Is a Season: Summer-to-Winter Food Webs and the Functional Traits of Keystone Species
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DOI：
10.1093/icb/icx119
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发表时间：
2017-11-01
影响因子：
2.6
通讯作者：
Boutin, Stan
中科院分区：
文献类型：
--
作者：
Humphries, Murray M.;Studd, Emily K.;Boutin, Stan
从营养的角度来看，气温和光周期的季节性增加作为植物初级生产、草食动物二级生产和食肉动物第三级生产的自下而上的脉冲传播。然而，食物网的季节性不仅反映了温度和光周期的非生物变化，而且反映了生物群落的组成及其对这种变化的功能反应。一些植物和动物--在这里被称为季节性专家--在冬季通过迁徙或各种形式的新陈代谢停止(例如衰老、滞育和冬眠)与食物网脱钩，而一些植物和常驻动物--在这里被称为季节性多面手--在冬季仍然存在并以营养方式耦合。对冬季有不同反应的物种的共存引入了相互作用强度的季节性变化，导致夏季到冬季营养组织的差异。秋季的降温和日长的缩短阻碍了初级生产力，并暗示了季节性食草动物的脱钩，使得多面手食肉动物将捕食集中在少数多面手食草动物身上，这些多面手食草动物在冬季仍然驻留，活跃，容易被捕食，这些草食动物本身以冬季可用的少数多面手植物结构为食。因此，这种自下而上的脉冲在夏季在许多物种中传播，包括高生产力的季节性专家，在冬季逆转为强大的自上而下的调节，这是头重脚轻的，集中在少数多面手食草动物及其冬季食物中。中型多面手食草动物在冬季仍然活跃，容易被捕食，很可能是季节性食物网中的关键物种，因为它们提供了将夏季初级生产力转化为肉食动物冬季食物的基本生态系统服务。对北部森林和从北极到热带季节梯度的陆地哺乳动物及其季节性营养状况的经验研究表明，季节性专门化在草食动物、体型较小的地区和中等季节性的地区比在食肉动物、体型较大的地区和夏季很短或很长的地区更常见。更好地了解季节性环境中的食物网，包括它们对气候变化的脆弱性和恢复力，需要从多个季节的角度来看。
From a trophic perspective, a seasonal increase in air temperature and photoperiod propagates as bottom-up pulse of primary production by plants, secondary production by herbivores, and tertiary production by carnivores. However, food web seasonality reflects not only abiotic variation in temperature and photoperiod, but also the composition of the biotic community and their functional responses to this variation. Some plants and animals-here referred to as seasonal specialists-decouple from food webs in winter through migration or various forms of metabolic arrest (e.g., senescence, diapause, and hibernation), whereas some plants and resident animals-here referred to as seasonal generalists-remain present and trophically coupled in winter. The co-occurrence of species with divergent responses to winter introduces seasonal variation in interaction strengths, resulting in summer-to-winter differences in trophic organization. Autumn cooling and shortening day length arrests primary productivity and cues seasonal herbivores to decouple, leaving generalist carnivores to concentrate their predation on the few generalist herbivores that remain resident, active, and vulnerable to predation in winter, which themselves feed on the few generalist plant structures available in winter. Thus, what was a bottom-up pulse, spread among many species in summer, including highly productive seasonal specialists, reverses into strong top-down regulation in winter that is top-heavy, and concentrated among a small number of generalist herbivores and their winter foods. Intermediate-sized, generalist herbivores that remain active and vulnerable to predation in winter are likely to be keystone species in seasonal food webs because they provide the essential ecosystem service of turning summer primary productivity into winter food for carnivores. Empirical examination of terrestrial mammals and their seasonal trophic status in the boreal forest and across an arctic-to-tropics seasonality gradient indicates seasonal specialization is more common among herbivores, small body sizes, and in regions with intermediate seasonality, than among carnivores, large body size, and regions where summers are very short or very long. Better understanding of food webs in seasonal environments, including their vulnerability and resilience to climate change, requires a multi-season perspective.