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In macroecology, shifting from coarse- to local-scale explanatory factors is crucial for understanding how global change impacts functional diversity (FD). Plants possess diverse traits allowing them to differentially respond across a spectrum of environmental conditions. We aim to assess how macro- to microclimate, stand-scale measured soil properties, forest structure, and management type, influence forest understorey FD at the macroecological scale. Our study covers Italian forests, using thirteen predictors categorized into climate, soil, forest structure, and management. We analyzed five traits (i.e., specific leaf area, plant size, seed mass, belowground bud bank size, and clonal lateral spread) capturing independent functional dimensions to calculate the standardized effect size of functional diversity (SES-FD) for all traits (multi-trait) and for single traits. Multiple regression models were applied to assess the effect of predictors on SES-FD. We revealed that climate, soil, and forest structure significantly drive SES-FD of specific leaf area, plant size, seed mass, and bud bank. Forest management had a limited effect. However, differences emerged between herbaceous and woody growth forms of the understorey layer, with herbaceous species mainly responding to climate and soil features, while woody species were mainly affected by forest structure. Future warmer and more seasonal climate could reduce the diversity of resource economics, plant size, and persistence strategies of the forest understorey. Soil eutrophication and acidification may impact the diversity of regeneration strategies; canopy closure affects the diversity of above- and belowground traits, with a larger effect on woody species. Multifunctional approaches are vital to disentangle the effect of global changes on functional diversity since independent functional specialization axes are modulated by different drivers., Competing Interests: Declaration of competing interest We have no conflicts of interest to disclose., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Global changes, particularly rising temperatures, threaten food security in smallholder mountain communities by impacting the suitability of cultivation areas for many crops. Land-use intensification, associated with agrochemical use and tillage, threatens soil health and overall agroecosystem resilience. In the Andean region, farmers often cultivate crops at multiple elevations. Warming climates have led to a shift in cultivation upslope, but this is not feasible in many areas. Traditional soil fertility management practices together with a focus on traditional (orphan) crops offers promise to cope with rapid climate warming in the region. To understand the impacts of warming and changing nutrient management, we established two side-by-side experiments using the traditional Andean crops Oxalis tuberosa (Oca) and Lupinus mutabilis (Tarwi) at three elevations, each with two fertility treatments (organic and synthetic). Soil and climate data (i.e., temperature and precipitation) were collected throughout the growing season, and crop performance was evaluated through impacts on yield and other growth metrics (e.g., biomass, pest incidence). We used two-way ANOVA to assess the influence of site (elevation) and management type (organic vs. synthetic) on crop performance. Results indicated that warmer climates (i.e., lowest elevation) negatively impact the production and performance of O. tuberosa, but that organic fertilization (sheep manure) can help maintain crop yield and biomass production in warmer conditions relatively to synthetic nutrient inputs. In contrast, L. mutabilis showed accelerated growth in warmer conditions, but grain yield and biomass production were not significantly affected by site and showed no interaction with nutrient management. Our findings highlight that climate warming represents a serious threat to small-scale crop production in the Peruvian Andes and could cause severe declines in the production of locally important crops. Additionally, the continued reliance on traditional crops with organic inputs, instead of synthetic fertilizers, may help support agricultural productivity and resilience under climate change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)