Contribution Analysis Of Permanent And Sporadic Controls Of Co2 Efflux From Chernozems Over Four Seasons

Dmitry V Karelin,Olga E Sukhoveeva

doi:10.24057/2071-9388-2021-042

Abstract

We analyzed four years field observations (2017–2020) of soil CO2 efflux from Chernozems of arable and foreststeppe ecosystems of Kursk region (Russia), which correspond to the period of the maximal current warming. Three wellknown simulation models of different structure and variable sets (DNDC, RothC, T&P) and nonparametric regression analysis were used to estimate annual CO2 emission from soil and contributions of constant and sporadic controls. The applied models satisfactorily predict both the rate of annual soil CO2 emission and its seasonal dynamics on arable Chernozems. However, while RothC is suitable for the whole set of crops considered, DNDC is most suitable for cereals and T&R for bare soils only. A comparison of the contributions of permanent and sporadic factors to soil respiration showed that on an inter-annual scale soil temperature and moisture are less important than yearly crop rotation in Chernozem plowlands, making the latter the most important predictor apart from general land-use type. Although the combination of significant permanent and sporadic factors is able to explain 41% of the soil CO2 emission variance, the leading involvement of spatial controls prevents the construction of quantitative regression models that are able to make forecasts, requiring the use of more sophisticated simulation models (i.e. RothC) in this case. However, the use of the latter does not yet solve the problem of predicting soil CO2 emission and its net balance in forest-covered or steppe areas of Chernozem forest-steppe landscape.

Highlights

The problem of identifying and quantifying permanent factors of CO2 emission from various types of soils has been elaborated in sufficient detail (Zavarzin and Kudeyarov 2006; Kuzyakov 2006; Luo and Zhou 2006; Kudeyarov et al 2007; Naumov 2009; Stepanov 2011; Chen et al 2014; Karelin et al 2014, 2020 a,b; Kurganova et al 2020) and might be considered close to final solution
Our study focuses on the analysis of permanent and sporadic controls of soil carbon dioxide emission in the agronomically well-developed foreststeppe zone of the European territory of Russia, where arable Chernozems are widely distributed
On the day of its fallout, compared with the previous day, the flux of CO2 from the soil increases sharply, and the respiration rate can rise 2.5 times for winter wheat and barley crops, almost 3-fold for soybeans and more than 5-fold for sunflowers. This is due to the coefficient introduced into do not differ significantly from the field (DNDC), according to which the rate of mineralization of soil organic carbon (SOC) increases in proportion to the square of the soil moisture content

Summary

INTRODUCTION

The problem of identifying and quantifying permanent factors of CO2 emission from various types of soils has been elaborated in sufficient detail (Zavarzin and Kudeyarov 2006; Kuzyakov 2006; Luo and Zhou 2006; Kudeyarov et al 2007; Naumov 2009; Stepanov 2011; Chen et al 2014; Karelin et al 2014, 2020 a,b; Kurganova et al 2020) and might be considered close to final solution. The goal of the study is to compare estimates of annual soil CO2 emissions obtained from field observations and by various methods of modelling and statistical analysis, and use them to identify relative contributions of permanent and sporadic carbon dioxide emission drivers in the Chernozem landscape under different land-use variants. Simulation using RothC was evaluated for each crop over Based on Selyaninov’s hydro-termal coefficients, wetting during the entire observation period, as the time step of the model is active growing seasons was sufficient: 1.00 in 2017, 0.99 in 2018 one month, which significantly reduces the size of the data series and 1.03 in 2020, (except 2019: 0.80), with a norm value of 1.1 ±.

Method

16. PRECDAY

Findings

CONCLUSIONS