Different mechanisms underlying divergent responses of autotrophic and heterotrophic respiration to long-term throughfall reduction in a warm-temperate oak forest

Jinglei Zhang,Xiaojing Liu,Xinwei Guo,Shirong Liu,Junwei Luan,Hui Wang,Baoliang Niu,Cuiju Liu

doi:10.1186/s40663-021-00321-z

Abstract

BackgroundThere are many studies on disentangling the responses of autotrophic (AR) and heterotrophic (HR) respiration components of soil respiration (SR) to long-term drought, but few studies have focused on the mechanisms underlying its responses.MethodsTo explore the impact of prolonged drought on AR and HR, we conducted the 2-year measurements on soil CO2 effluxes in the 7th and 8th year of manipulated throughfall reduction (TFR) in a warm-temperate oak forest.ResultsOur results showed long-term TFR decreased HR, which was positively related to bacterial richness. More importantly, some bacterial taxa such as Novosphingobium and norank Acidimicrobiia, and fungal Leptobacillium were identified as major drivers of HR. In contrast, long-term TFR increased AR due to the increased fine root biomass and production. The increased AR accompanied by decreased HR appeared to counteract each other, and subsequently resulted in the unchanged SR under the TFR.ConclusionsOur study shows that HR and AR respond in the opposite directions to long-term TFR. Soil microorganisms and fine roots account for the respective mechanisms underlying the divergent responses of HR and AR to long-term TFR. This highlights the contrasting responses of AR and HR to prolonged drought should be taken into account when predicting soil CO2 effluxes under future droughts.

Highlights

There are many studies on disentangling the responses of autotrophic (AR) and heterotrophic (HR) respiration components of soil respiration (SR) to long-term drought, but few studies have focused on the mechanisms underlying its responses
throughfall reduction (TFR) had no significant effects on microbial biomass C (MBC) and Microbial biomass nitrogen (MBN) (Table S1), and had little effects on measured enzyme activities except for polyphenolase (P = 0.08) (Table S1)
Soil respiration and its components SR showed no significant difference between TFR and control in 2019 (2.48 ± 0.23 vs. 2.63 ± 0.19 μmol CO2∙m− 2∙s− 1) and in 2020 (2.92 ± 0.27 vs. 2.63 ± 0.24 μmol CO2∙m− 2∙s− 1) (P > 0.05; Fig. 2 and Table 1)

Summary

Introduction

There are many studies on disentangling the responses of autotrophic (AR) and heterotrophic (HR) respiration components of soil respiration (SR) to long-term drought, but few studies have focused on the mechanisms underlying its responses. A previous study in a warm-temperate oak forest suggested that drought increased SR by 26.7% at a small scale (e.g., 4 m × 4 m roof) throughfall reduction, which was mainly attributed to the increase in AR (Liu et al 2016). All of these indicate roots and soil microbes have differential sensitivities to drought, and determine the direction of SR in response to drought in different ecosystems (Luo and Zhou 2006). The mechanisms underlying different responses of AR and HR to drought are far from clear, which limits our comprehension of whether soil acts as a C sink or C source in the scenario of increased droughts

Methods

Results

Conclusion