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The presence of multiple global change factors affects most ecosystems, especially urban soils, which face stressors like heat, drought, road salt, nitrogen deposition, surfactants, microplastics, and heavy metals. These factors are often studied in isolation or in pairs, leaving their combined effects poorly understood. Importantly, understanding how removing a single factor impacts an ecosystem amidst multiple stressors is crucial for effective restoration.
We explored this through a subtractive design, comparing single-factor treatments (addition) to treatments where a specific factor was removed (subtraction). The results varied: salinity had predominantly negative effects, warming had positive effects, and drought had mixed effects as single factors. However, removing these factors from a multi-factor context generally improved soil properties and biological processes. Microplastics and surfactants enhanced microbial activity individually but showed no such benefit in multi-factor scenarios.
Our findings highlight that the combined effects of factors often differ from their individual impacts. In restoration, priority should be given to mitigating factors with the strongest negative influence in multi-stressor contexts, rather than targeting those with significant isolated effects. This approach can better address the complexities of global change in ecosystems.