Land use and climate change are primary causes of changes in the supply of ecosystem services (ESs). Although the consequences of climate change on ecosystem properties and associated services are well documented, the cascading impacts of climate change on ESs through changes in land use are largely overlooked. We present a trait-based framework based on an empirical model to elucidate how climate change affects tradeoffs among ESs. Using alternative scenarios for mountain grasslands, we predicted how direct effects of climate change on ecosystems and indirect effects through farmers' adaptations are likely to affect ES bundles through changes in plant functional properties. ES supply was overall more sensitive to climate than to induced management change, and ES bundles remained stable across scenarios. These responses largely reflected the restricted extent of management change in this constrained system, which was incorporated when scaling up plot level climate and management effects on ecosystem properties to the entire landscape. The trait-based approach revealed how the combination of common driving traits and common responses to changed fertility determined interactions and tradeoffs among ESs.plant functional traits | trade-offs | global change | mountain agriculture E cosystem services (ESs) are increasingly used to assess and make land and natural resource use decisions that typically involve tradeoffs between conflicting goals and, in particular, between the different bundles of services that a given ecosystem could provide. These decisions are, however, rarely grounded in a mechanistic understanding of the ecosystem properties or processes that enable provision of multiple ESs. At the same time, mechanisms leading to tradeoffs among ESs are still poorly understood (1). Effective ES-based management decisions, especially in a climate-change context, require that we go beyond the description of spatial co-occurrences of targeted ESs under current climates (e.g., refs. 2 and 3) to understand direct interactions between ESs, and the effects of common drivers of change in ESs (4).A mechanistic approach to ES supply will be grounded in the relevant characteristics of the ecosystem components that contribute to it. Functional traits of ES providers are novel and powerful proxies (5, 6) that make it possible to scale wellunderstood functional tradeoffs from the organism level to ecosystem functioning and to ESs (7,8). Their relevance to ES modeling rests on the discovery that response functional traits that determine community response (e.g., fertilization favors plants with nitrogenrich leaves) overlap with effect functional traits that determine effects on ecosystem functioning (e.g., a majority of nitrogen-rich leaves promotes high primary productivity) (9).Scenario-based studies have compared bundles of ESs, and associated positive and negative relationships, across scenarios (10), but few published studies have sought to tease out the respective effects of different scenario drivers. Large-scale studies...