In a study published in Functional Ecology on June 1, research team led by Pro. LI Dejun from the Institute of Subtropical Agriculture, Chinese Academy of Sciences, first revealed that land use type is the dominant factor regulating the climate responsiveness of soil organic nitrogen (SON) transformation. These findings provide critical insights into the mechanisms underlying land-type-specific nitrogen management strategies and global change modeling.

As a key component of global nutrient cycling and ecosystem productivity, SON transformation encompasses interrelated processes such as gross protein degradation (GPD), microbial nitrogen growth (N_growth), gross nitrogen mineralization (GNM), and microbial nitrogen use efficiency (NUE). Climate change (warming and changes in precipitation) may alter these processes by affecting enzyme kinetics, microbial metabolism, and substrate diffusion. The direction and magnitude of these changes are regulated by ecosystem type, soil properties, and nutrient status.

Dr. DUAN Pengpeng, one of the corresponding author emphasised that their stuy was systematically comparing SON transformation processes in natural forests and intensively farmed fields across different climatic gradients, and trying to predict how land use regulates the response of the nitrogen cycle to climate change.

In this study, 30 forest-farmland paired plots along the subtropical climatic gradient in southwest China were selected. Soil physicochemical properties, SON transformation rates (using ¹⁵N and ¹⁸O isotope tracing methods), functional gene abundance, and enzyme activity were measured. Linear mixed models, hierarchical partitioning, and structural equation modeling were used to analyze the driving factors.

The results show that land use type is the dominant factor regulating the response of soil organic nitrogen transformation to climate change. Natural forests are highly sensitive to warming and increased precipitation due to mineral-enzyme interactions and phosphorus limitations, resulting in an increased risk of nitrogen loss. Whereas, intensive croplands buffer climate impacts through fertilization and tillage but experience a decoupling of nitrogen cycling processes.

Furthmore, compared to intensively farmed fields that benefit from the buffering effects of fertilization and tillage, natural forest soils are more sensitive and vulnerable to climate-driven changes in the nitrogen cycle.

“Our findings provide a mechanistic basis for soil nitrogen management under different land-use scenarios as a response to climate change.” Dr. YANG Xinyi, the first author said “Under future climate warming and changes in precipitation, forest soils face a greater risk of nitrogen loss, necessitating a focus on phosphorus-limiting management; while farmland possesses buffering capacity, nutrient management still needs to be optimized to maintain nitrogen use efficiency.”

Contacted: LI Dejun

Email: dejunli@isa.ac.cn

Mechanistic pathways linking multiple factors to soil organic nitrogen transformation processes（Imaged by YANG Xinyi）