Contemporary defaunation has profound ecological consequences ranging from local or even global co‐extinctions of interacting species to the loss of ecosystem functions and services critical for humanity. Other components of global change (climate change, introduced pests, land use changes) are also harming ecosystem functioning by augmenting tree mortality worldwide. Defaunation and increased tree mortality often coincide in many human‐altered ecosystems but whether they interact, leading to non‐additive effects on ecosystem functioning, remains largely unknown. However, under some ecological circumstances, the decline or extirpation of one species due to defaunation can be neutralized by increases in the abundance of some functionally similar species (i.e. ‘density compensation’). We combined long‐term field data with individual‐based modelling to investigate the potential interactive effects of seed disperser loss, increased tree mortality and density compensation on seed dispersal in a heterogeneous landscape. Our simulation experiments showed that both stressors markedly limit not only the quantity of seed dispersal but also its quality since the impact on seed dispersal strongly varied among habitat types that differ strikingly in suitability for tree establishment. Density compensation had a marked positive effect on seed dispersal which, however, was largely limited under increased tree mortality. The combined negative effects of defaunation and increased tree mortality on seed dispersal were lower than the expected additive effect. This highlights the need to account for the joint operation of multiple stressors to accurately predict the impacts of global change on the link between biodiversity and ecosystem functioning.

中文翻译：

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毁损，树木死亡率增加和密度补偿对种子扩散的相互影响

当代的毁灭具有深远的生态后果，从相互作用物种的本地乃至全球灭绝到对人类至关重要的生态系统功能和服务的丧失。全球变化的其他组成部分（气候变化，引入的有害生物，土地利用变化）也正在通过增加全世界树木的死亡率来损害生态系统的功能。在许多人为改变的生态系统中，毁损和树木死亡率增加经常同时发生，但是它们是否相互作用，从而导致对生态系统功能的非累加影响，仍然是未知的。但是，在某些生态环境中，由于毁灭而导致的一种物种的减少或灭绝可以通过增加某些功能相似的物种的丰度来抵消（即“密度补偿”）。我们将长期的田间数据与基于个体的建模相结合，以研究种子分散剂损失，树木死亡率增加和密度补偿对异质景观种子扩散的潜在交互作用。我们的模拟实验表明，两种应激源不仅显着限制了种子散播的数量，而且显着限制了种子的质量，因为对种子散播的影响在生境类型之间的差异很大，而生境类型对于树的适宜性差异很大。密度补偿对种子传播具有显着的积极影响，然而，在树木死亡率增加的情况下，密度补偿受到很大限制。消沉和增加树木死亡率对种子扩散的综合负面影响低于预期的累加效应。