Trade-offs among restored ecosystem functions are context-dependent in Mediterranean-type regions

Global biodiversity hotspots, including Mediterranean-type ecosystems worldwide, are highly threatened by global change that alters biodiversity, ecosystem functions, and services. Some restoration activities enhance ecosystem functions by reintroducing plant species based on known relationships between plant traits and ecosystem processes. Achieving multiple functions across different site conditions, however, requires understanding how abiotic factors like climate and soil, along with plant assemblages, influence ecosystem functions, including their trade-offs and synergies. We used the ModEST ecosystem simulation model, which integrates carbon, water, and nutrient processes with plant traits, to assess the relationships between restored plant assemblages and ecosystem functions in Mediterranean-type climates and soils. We investigated whether maximised carbon increment, water use efficiency, and nitrogen use efficiency, along with their trade-offs and synergies, varied across different abiotic contexts. Further, we asked whether assemblages that maximised functions varied across environments and among these functions. We found that maximised ecosystem carbon increment and nitrogen use efficiency occurred under moist, warm conditions, while water use efficiency peaked under drier conditions. Generally, the assemblage that maximised one function differed from those for other maximised functions. Synergies were rare, except between water and nitrogen use efficiencies in loam soils across most climates. Trade-offs among maximised functions were common, varying in strength with abiotic context and plant assemblages, and were more pronounced in sandy loam soils compared to clay-rich soils. Our findings suggest that due to variation in abiotic conditions within and across Mediterranean-type regions at the global scale, site-specific plant assemblages are required to maximise ecosystem functions. Thus, lessons from a single site cannot be transferred to another site, eve. Authors: Fiedler, Sebastian [Freie Univ., Berlin (Germany); Univ. of Bayreuth (Germany); Univ. of Goettingen (Germany); Technische Univ. Berlin (Germany)] (ORCID:0000000156206989); Perring, Michael P. [UK Centre for Ecology and Hydrology (UKCEH ), Bangor (United Kingdom); Univ. of Western Australia, Perth, WA (Australia)] (ORCID:0000000185534893); Monteiro, José A. [Freie Univ., Berlin (Germany); Statistical Office Basel-Stadt, Basel (Switzerland)] (ORCID:0000000235209918); Branquinho, Cristina [Universidade de Lisboa (Portugal)] (ORCID:0000000182947924); Buzhdygan, Oksana [Freie Univ., Berlin (Germany)]. DOE Contract: AC02-05CH11231; SC0021023. Subjects: 54 ENVIRONMENTAL SCIENCES; Mediterranean-type ecosystems (MTEs); biotic and abiotic context; ecosystem functioning; ecosystem restoration; process-based simulation modelling; trade-offs and synergies