Thomas Evert, Jansen Merel, Chiriboga-Arroyo Fidel, Wadt Lúcia H O, Corvera-Gomringer Ronald, Atkinson Rachel Judith, Bonser Stephen P, Velasquez-Ramirez Manuel Gabriel, Ladd Brenton
Bioversity International, Lima, Peru.
Department of Environmental Systems Science, Institute of Terrestrial Ecosystems, Ecosystem Management, ETH Zürich, Zurich, Switzerland.
Front Plant Sci. 2021 Mar 31;12:621064. doi: 10.3389/fpls.2021.621064. eCollection 2021.
Ecosystem services of Amazonian forests are disproportionally produced by a limited set of hyperdominant tree species. Yet the spatial variation in the delivery of ecosystem services by individual hyperdominant species across their distribution ranges and corresponding environmental gradients is poorly understood. Here, we use the concept of habitat quality to unravel the effect of environmental gradients on seed production and aboveground biomass (AGB) of the Brazil nut, one of Amazonia's largest and most long-lived hyperdominants. We find that a range of climate and soil gradients create trade-offs between density and fitness of Brazil nut trees. Density responses to environmental gradients were in line with predictions under the Janzen-Connell and Herms-Mattson hypotheses, whereas tree fitness responses were in line with resource requirements of trees over their life cycle. These trade-offs resulted in divergent responses in area-based seed production and AGB. While seed production and AGB of individual trees (i.e., fitness) responded similarly to most environmental gradients, they showed opposite tendencies to tree density for almost half of the gradients. However, for gradients creating opposite fitness-density responses, area-based seed production was invariable, while trends in area-based AGB tended to mirror the response of tree density. We conclude that while the relation between environmental gradients and tree density is generally indicative of the response of AGB accumulation in a given area of forest, this is not necessarily the case for fruit production.
亚马逊森林的生态系统服务不成比例地由一小部分优势树种提供。然而，对于单个优势树种在其分布范围内以及相应环境梯度下生态系统服务提供的空间变化，我们了解得还很少。在这里，我们使用栖息地质量的概念来揭示环境梯度对巴西坚果种子产量和地上生物量（AGB）的影响，巴西坚果是亚马逊地区最大且寿命最长的优势树种之一。我们发现一系列气候和土壤梯度在巴西坚果树的密度和适合度之间产生了权衡。对环境梯度的密度响应符合简森 - 康奈尔假说和赫姆斯 - 马特森假说下的预测，而树木适合度响应则符合树木在其生命周期内的资源需求。这些权衡导致了基于面积的种子产量和AGB的不同响应。虽然单株树木的种子产量和AGB（即适合度）对大多数环境梯度的响应相似，但对于近一半的梯度，它们与树木密度呈现相反的趋势。然而，对于产生相反适合度 - 密度响应的梯度，基于面积的种子产量是不变的，而基于面积的AGB趋势往往反映树木密度的响应。我们得出结论，虽然环境梯度与树木密度之间的关系通常表明了给定森林区域内AGB积累的响应，但果实产量不一定如此。
