A research team led by Prof. WU Jinshui from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences reported that enzyme activities are more sensitive to C addition than to temperature in paddy soil and soil organic matter (SOM) decomposition is accelerated by both C input and warming, especially at low temperatures.
Scientists believe that elevated temperatures can increase the decomposition of organic matter in paddy soil for two reasons. One is that the increase in temperature can directly increase the activity of microorganisms, and the second is that higher temperatures increase C addition into soil through the input of plant litter, root biomass, and rhizodeposits as labile C sources for soil microorganisms.
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 were more sensitive to organic C addition than to warming. Enzyme activity was limited by interactions of environmental and biochemical factors: at low temperature - the enzyme activity was limited by the temperature and substrates are sufficiently available.
With increasing temperature, the substrates will be consumed fast, even become exhausted. Then the limited substrate, especially at high temperature suppress for enzyme activities. 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, published in Soil Biology and Biochemistry, 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 (Image by ISA)
A research team led by Prof. WU Jinshui from the Institute of Subtropical Agriculture found that the regulation of "regulating valve" mechanism on organic carbon mineralization in paddy soil is determined by oxygen conditions.
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