Nitrogen-mineralizing community in the rice rhizosphere exhibits greater resilience than that of maize and wheat in response to elevated CO2 and temperature

Abstract

Climate change, characterized by rising CO2 concentrations and warming, impacts soil microbial processes regulating nitrogen (N) availability for crops. This study aimed to elucidate the responses to elevated CO2 and warming of rhizosphere microbial communities involved in N mineralization under major cereal crops. A controlled pot experiment was conducted in open-top chambers with four treatments: ambient conditions (Control), elevated CO2 (700 ppm), warming (2°C above ambient), and their combination. Maize, wheat, and rice were grown in a Mollisol for 92 days. Functional microbial communities were characterized by sequencing of the chiA and pepA genes, which encode key enzymes involved in chitin and peptide degradation, respectively. Principal coordinate and network analyses revealed distinct, crop-specific microbial assemblages and responses to climate factors. Rice rhizosphere communities exhibited significantly greater functional resilience under elevated CO2 and warming compared with those of maize and wheat. This resilience may be attributed to anaerobic conditions of flooded rice paddies, which buffer temperature and moisture fluctuations and promote microbial functional redundancy, enabling species replacement as a primary adaptive response. In contrast, dryland systems (maize and wheat) showed higher sensitivity, with disrupted microbial networks, lower abundance of key taxa, and greater variability in predicted N mineralization potential. These findings highlight that crop-specific rhizosphere environments shape the resilience of N-cycling microbiomes under climate change. The study provides practical implications for N-fertilizer management and the design of climate-resilient cropping systems that maintain soil N supply in a warming and CO2-enriched climate.