Researchers Demenstrate How Importance of Microbial Charcateristics in Soil Organic Matter Formation
Reactive nitrogen (N) that enters forest ecosystems through atmospheric deposition can effectively alleviate nitrogen limitation to plant growth, and thus can increase plant biomass. However, excessive N input may result in soil acidification and soil nutrient imbalance, and damaging the stability of ecosystem. Recent researches have been focused on effects of N deposition on plant growth, plant diversity and plant community structure, but how the increasing N input affects microbial diversity and nutrient use efficiency is still poorly understood.
In August 2019, Associate Prof. Wang Chao together with master student Li Jing from the Biogeochemistry Group of the Institute of Applied Ecology (IAE), Chinese Academy of Sciences (CAS), collected soil samples from a N addition experiment, which was established in 2014 in a natural Korean pine and broadleaf mixed forest in Changbai Mountain.
The researchers estimated microbial carbon use efficiency (CUE) and nitrogen use efficiency (NUE) by 18O-labelled H2O incubation method and found that N addition (low, ambient and high N addition) and soil horizon (organic vs. mineral layer) affected microbial CUE and NUE, however no obvious change regulation was observed. In addition, researchers also found a polynomial correlation between microbial CUE and NUE, with the inflection point at CUE=0.4. Regression analysis showed that the variation in microbial community structure and the phosphorus stoichiometry imbalance were two main factors that affected microbial nutrient use efficiency.
The results indicated that phosphorus (P) deficiency caused by N deposition may alter functions of microorganisms in order to maintain the stability of microbial communities. So far, little is known about how does P stoichiometry imbalance caused by N addition changes microbial community structure.
In view of this, assistant Prof. Xia Zongwei and his colleagues from Wang’s group conducted a N and P addition experiment, which was established in 2015 in a natural Korean pine and broadleaf mixed forest in Changbai Mountain. Researchers measured soil microbial community structure with high-throughput sequencing technology and found that N addition reduced microbial diversity in organic soil, while P addition could lessen this effect to a large extent. Specifically, N addition reduced C sequestration in organic soil through affecting metabolic potential of bacteria and fungi, while P addition alleviated or change these effects.
The results clarified the mechanisms by which N and P regulate the structure and function of soil microbial communities in the temperate forest.
The results were published in Soil Biology & Biochemistry entitled "Stoichiometric imbalance and microbial community regulate microbial elements use efficiencies under nitrogen addition", and in the journal Microorganisms entitled "Phosphorus reduces negative effects of nitrogen addition on soil microbial communities and functions".
The studies were supported by the National Natural Science Foundation of China and the the Youth Promotion Association of CAS.