Quality of fresh organic matter affects priming of soil organic matter and substrate utilization patterns of microbes.

Hui Wang,Edith Bai,Thomas W Boutton,Ping Jiang,Guoqing Hu,Wenhua Xu

doi:10.1038/srep10102

Abstract

Changes in biogeochemical cycles and the climate system due to human activities are expected to change the quantity and quality of plant litter inputs to soils. How changing quality of fresh organic matter (FOM) might influence the priming effect (PE) on soil organic matter (SOM) mineralization is still under debate. Here we determined the PE induced by two 13C-labeled FOMs with contrasting nutritional quality (leaf vs. stalk of Zea mays L.). Soils from two different forest types yielded consistent results: soils amended with leaf tissue switched faster from negative PE to positive PE due to greater microbial growth compared to soils amended with stalks. However, after 16 d of incubation, soils amended with stalks had a higher PE than those amended with leaf. Phospholipid fatty acid (PLFA) results suggested that microbial demand for carbon and other nutrients was one of the major determinants of the PE observed. Therefore, consideration of both microbial demands for nutrients and FOM supply simultaneously is essential to understand the underlying mechanisms of PE. Our study provided evidence that changes in FOM quality could affect microbial utilization of substrate and PE on SOM mineralization, which may exacerbate global warming problems under future climate change.

Highlights

Limitation, increasing the mineralization of soil organic matter (SOM) which contains higher amount of N and other nutrients than fresh organic matter (FOM), i.e. the “N-mining” theory[9,16]
During 9 ~ 30 d of the incubation, total CO2 respiration and FOM-derived CO2 were higher under stalk treatment than under leaf treatment, but SOM-derived CO2 was similar under both FOM treatments
Negative priming effect (PE) has often been explained as the result of “preferential substrate utilization”, meaning that the preference of microorganisms for substrates switched from relatively recalcitrant SOM to amended FOM24,25

Summary

Introduction

Limitation, increasing the mineralization of SOM which contains higher amount of N and other nutrients than FOM, i.e. the “N-mining” theory[9,16]. On the contrary, based on the second theory, FOM with higher C:N ratio would lead to higher N limitation and greater PE on SOM mineralization. These two mechanisms do not necessarily have to be alternative, but may happen simultaneously. Those contradictory findings of PE induced by FOM with different quality may be because one mechanism dominates over the other in different cases[17] Both theories highlight the potentially important role of soil microbial community in regulating PE on SOM mineralization. We hypothesized that stalk (i.e. lower quality FOM) would induce higher positive PE based on the “N-mining” theory because its high C:N ratio means it would lead to more severe N limitation. Two forest soils (Larch Plantation soil and Secondary Forest soil) with different resource history and soil properties were used to test the generality of our findings

Objectives

Methods

Results

Conclusion