Abstract

Massive gully land consolidation projects, launched in China’s Loess Plateau, aim to restore 2667 mathrm{km}^2 agricultural lands in total by consolidating 2026 highly eroded gullies. This effort represents a social engineering project where the economic development and livelihood of the farming families are closely tied to the ability of these emergent landscapes to provide agricultural services. Whether these ‘time zero’ landscapes have the resilience to provide a sustainable soil condition such as soil organic carbon (SOC) content remains unknown. By studying two watersheds, one of which is a control site, we show that the consolidated gully serves as an enhanced carbon sink, where the magnitude of SOC increase rate (1.0 mathrm{g,C}/mathrm{m}^2/mathrm{year}) is about twice that of the SOC decrease rate (− 0.5 mathrm{g,C}/mathrm{m}^2/mathrm{year}) in the surrounding natural watershed. Over a 50-year co-evolution of landscape and SOC turnover, we find that the dominant mechanisms that determine the carbon cycling are different between the consolidated gully and natural watersheds. In natural watersheds, the flux of SOC transformation is mainly driven by the flux of SOC transport; but in the consolidated gully, the transport has little impact on the transformation. Furthermore, we find that extending the surface carbon residence time has the potential to efficiently enhance carbon sequestration from the atmosphere with a rate as high as 8 mathrm{g,C}/mathrm{m}^2/mathrm{year} compared to the current 0.4 mathrm{g,C}/mathrm{m}^2/mathrm{year}. The success for the completion of all gully consolidation would lead to as high as 26.67 mathrm{Gg,C}/mathrm{year} sequestrated into soils. This work, therefore, not only provides an assessment and guidance of the long-term sustainability of the ‘time zero’ landscapes but also a solution for sequestration hbox {CO}_2 into soils.

Highlights

  • Plateau, aim to restore km agricultural lands in total by consolidating 2026 highly eroded gullies

  • Our analysis shows that the two processes that dictate the soil organic carbon (SOC) dynamics across time and space—transport and the transformation—are substantially different between engineered consolidated gullies and the natural watersheds

  • The SOC transport, which generally follows the pattern of the summer monsoon season, has little impact on the SOC transformation in consolidated gullies but has a strong influence on the SOC transformation in natural watersheds

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Summary

Introduction

Aim to restore km agricultural lands in total by consolidating 2026 highly eroded gullies This effort represents a social engineering project where the economic development and livelihood of the farming families are closely tied to the ability of these emergent landscapes to provide agricultural services. One of the recently initiated projects, gully land consolidation (GLC) (Fig. 1a), aims to restore substantial farmlands within significantly eroded large gullies—first creating 377.8 km[2] in Yan’an ­City[4,5] and up to 2667 km[2] among the whole loess p­ lateau[6]. Revegetation under the GFG project has reduced the erosion rate inside gullies along with an increased net primary production and declined surface ­runoff[13, 18], which creates favorable conditions for creating farmland inside the historically eroded gully

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