Soil microbes develop plastic nutrient acquisition strategies under changing plant litter inputs

Resource allocation theory posits that nutrient acquisition by soil microbes must optimize extracellular enzyme production and microbial growth, yet their specific strategies under changing resource conditions remain uncertain. Litter, the dominant nutrient source for soil microbes, is undergoing sustained shifts globally due to press and pulse disturbances. Understanding microbial responses to these changes, especially over longer timescales, is critical for predicting global nutrient cycling. We synthesize global litter manipulation experiments to assess how litter addition and removal influence microbial nutrient acquisition strategies, based on nitrogen (N)- and phosphorus (P)-related soil enzyme activities and their temporal dynamics. We identify two consistent types of microbial responses. First, litter addition stimulates N- and P-acquiring enzyme activities, with stronger investment in the most limiting nutrient (N at N-limited sites, P at P-limited sites), but this effect weakens over time. Second, litter removal initially suppresses enzyme activities and favors P acquisition, but shifts toward N acquisition and microbial growth over time. Our findings illustrate the plasticity of microbial nutrient acquisition strategies, providing new insights into microbial resource allocation theory and a mechanistic understanding of how changing plant litter inputs alter soil nutrient availability via microbial nutrient acquisition processes.