Dynamics of soil organic carbon in the steppes of Russia and Kazakhstan under past and future climate and land use

Susanne Rolinski,Norbert Bischoff,Georg Guggenberger,Florian Schierhorn,Irina Kurganova,Daniel Müller,Christoph Müller,Alexander V Prishchepov

doi:10.1007/s10113-021-01799-7

Abstract

Changes in land use and climate are the main drivers of change in soil organic matter contents. We investigated the impact of the largest policy-induced land conversion to arable land, the Virgin Lands Campaign (VLC), from 1954 to 1963, of the massive cropland abandonment after 1990 and of climate change on soil organic carbon (SOC) stocks in steppes of Russia and Kazakhstan. We simulated carbon budgets from the pre-VLC period (1900) until 2100 using a dynamic vegetation model to assess the impacts of observed land-use change as well as future climate and land-use change scenarios. The simulations suggest for the entire VLC region (266 million hectares) that the historic cropland expansion resulted in emissions of 1.6⋅ 1015 g (= 1.6 Pg) carbon between 1950 and 1965 compared to 0.6 Pg in a scenario without the expansion. From 1990 to 2100, climate change alone is projected to cause emissions of about 1.8 (± 1.1) Pg carbon. Hypothetical recultivation of the cropland that has been abandoned after the fall of the Soviet Union until 2050 may cause emissions of 3.5 (± 0.9) Pg carbon until 2100, whereas the abandonment of all cropland until 2050 would lead to sequestration of 1.8 (± 1.2) Pg carbon. For the climate scenarios based on SRES (Special Report on Emission Scenarios) emission pathways, SOC declined only moderately for constant land use but substantially with further cropland expansion. The variation of SOC in response to the climate scenarios was smaller than that in response to the land-use scenarios. This suggests that the effects of land-use change on SOC dynamics may become as relevant as those of future climate change in the Eurasian steppes.

Highlights

Soil organic carbon (SOC) stocks received increasing attention in the context of climate change, food security and degradation of soils (FAO 2017)
We examined the central area that was subject to the Virgin Lands Campaign (VLC), 226 million hectares (Mha) in total
We examined the effects of changes in land use and climate for soil organic carbon content in the entire area that was exposed to the Virgin Lands Campaign

Summary

Introduction

Soil organic carbon (SOC) stocks received increasing attention in the context of climate change, food security and degradation of soils (FAO 2017). The anthropogenic influence on SOC stocks affects the capacity of soils to be a carbon sink or could. Under stable climatic conditions without anthropogenic interference, an equilibrium establishes between the SOC stocks and the carbon fluxes between atmosphere, biosphere and the soil. SOC losses caused, for example, by cropland expansion can be determined by estimating three carbon fluxes: the net annual emissions from land-use change, the residual terrestrial carbon sink and the lost additional sink capacity (Houghton 2018). Previous analyses have suggested that global estimates for historical losses of SOC due to agricultural activities and soil degradation range between 42–78 PgC (Lal 2004) and 133 PgC (Lal 2020).

Objectives

Methods

Results

Discussion

Conclusion