The research team led by Prof. WU Jinshui from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences  recently reported that enzyme activities are more sensitive to C addition than to temperature in paddy soil and SOM decomposition is accelerated by both C input and warming, especially at low temperatures.

Warming of the atmosphere around the global 30-degree latitude, which includes the tropics and subtropics, is faster than that at other latitudes. The subtropical region is one of the main rice producing areas.

Scientists believe that elevated temperatures can increase the decomposition of organic matter in paddy soil for two reasons: one is the increase in temperature can directly increase the activity of microorganisms then accelerate the decomposition of soil organic matter and the second has increased C addition into soil through the input of plant litter, root biomass, and rhizodeposits as labile C sources for soil microorganisms.

The temperature and substrate availability also affect soil extracellular enzyme activity (Vmax). For example, temperature increase can significantly increase soil enzyme activity; enzyme activity is insensitive to temperature in the case of lower substrate availability. However, the effects of labile C availability (biochemical factor) and temperature (environmental factor) on enzyme activities remain poorly understood.

In this research, scientists found that extracellular enzyme activities are more sensitive to organic C addition than to warming. Enzyme activity is limited by interactions of environmental and biochemical factors: at low temperature – the enzyme activity is limited by the temperature and substrates are sufficiently available.

With increasing temperature, the substrates will be consumed fast, become exhausted and get the limiting factor for enzyme activities at high temperature. This shift of the enzyme activity limitation from environmental to biochemical factors partly explains the acclimation of various processes with increasing temperature.

This study can provide theoretical basis and data support for the understanding of organic matter decomposition of paddy soil and sustainable management under anaerobic conditions in rice fields.

The study entitled “Labile carbon matters more than temperature for enzyme activity in paddy soil” was published in Soil Biology and Biochemistry, details can be found at https://www.sciencedirect.com/science/article/abs/pii/S0038071719301300. The study was supported by the National Natural Science Foundation of China and the Youth Innovation Team Project of ISA, CAS.

Generalized responses of enzyme catalytic properties to temperature and substrate concentration

Contact: GE Tida

E-mail: gtd@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences