Afforestation neutralizes soil pH

Songbai Hong,Anping Chen,Shushi Peng,Lingli Liu,Jordi Sardans,Shilong Piao,Hui Zeng,Yongwen Liu,Yan Sun,Josep Peñuelas

doi:10.1038/s41467-018-02970-1

Abstract

Soil pH regulates soil biogeochemical processes and has cascading effects on terrestrial ecosystem structure and functions. Afforestation has been widely adopted to increase terrestrial carbon sequestration and enhance water and soil preservation. However, the effect of afforestation on soil pH is still poorly understood and inconclusive. Here we investigate the afforestation-caused soil pH changes with pairwise samplings from 549 afforested and 148 control plots in northern China. We find significant soil pH neutralization by afforestation—afforestation lowers pH in relatively alkaline soil but raises pH in relatively acid soil. The soil pH thresholds (TpH), the point when afforestation changes from increasing to decreasing soil pH, are species-specific, ranging from 5.5 (Pinus koraiensis) to 7.3 (Populus spp.) with a mean of 6.3. These findings indicate that afforestation can modify soil pH if tree species and initial pH are properly matched, which may potentially improve soil fertility and promote ecosystem productivity.

Highlights

Soil pH regulates soil biogeochemical processes and has cascading effects on terrestrial ecosystem structure and functions
In 2012−2013, we sampled across 148 sites within the Three-North Shelterbelt Development Program (TNSDP) area to conduct pairwise comparisons on soil pH between planted forests and nonafforested control plots
These findings provide improved understandings on how afforestation impacts soil pH across a broad range of soil types and afforestation tree species, which is critical for developing climate change mitigation strategies and ecological sustainability plans

Summary

Introduction

Soil pH regulates soil biogeochemical processes and has cascading effects on terrestrial ecosystem structure and functions. The TNSDP program has generated important environmental and socioeconomic benefits, including reduced soil erosion and sand storms, and increased carbon sequestration[27,28] This large-scale afforestation project provides a rare opportunity to investigate the effects of afforestation on soil properties. Our results show significant soil pH neutralization by afforestation—afforestation decreases soil pH in alkaline soils but increases soil pH in acidic soils These findings provide improved understandings on how afforestation impacts soil pH across a broad range of soil types and afforestation tree species, which is critical for developing climate change mitigation strategies and ecological sustainability plans

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Conclusion