Lithology controlled soil organic carbon stabilization in an alpine grassland of the Peruvian Andes

Songyu Yang,Rutger L Van Hall,Erik L H Cammeraat,Karsten Kalbitz,Fresia O Chunga Castro,Boris Jansen

doi:10.1007/s12665-019-8796-9

Songyu Yang, Rutger L Van Hall + Show 4 more

Open Access

https://doi.org/10.1007/s12665-019-8796-9

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Journal: Environmental Geology	Publication Date: Jan 1, 2020
Citations: 19	License type: open-access

Affiliation: University of Amsterdam, TU Dresden

Abstract

Alpine grasslands of the Neotropical Andes have high soil organic carbon (SOC) stocks and provide crucial ecosystem services. However, stability of the SOC in these grasslands is not well-studied. Having insights into SOC stability contributes to a better understanding of ecosystem vulnerability and maintaining of ecosystem services. The objectives were to get a first insight into organic matter (OM) stabilization in soils from different bedrocks of Andean alpine grasslands near Cajamarca, Peru (7° 11″ S, 78° 35″ W) and how this controls SOC stocks. Samples were collected from soils formed on limestone and acid igneous rocks. Stabilization mechanisms of OM were investigated using selective extraction methods separating active Fe, Al and Ca fractions and determined SOC stocks. In both soil types, the results showed important contributions of complexation with and/or adsorption on Fe and Al (oxides) to OM stabilization. Exclusively in the limestone soils, Ca induced OM stabilization by promoting the formation of Ca2+ bridges between OM and mineral surfaces. Furthermore, no evidence showed that OM stabilization was controlled by crystalline Fe oxides, clay contents, allophones, Al toxicity or aggregate stability. Limestone soils had significantly higher SOC stocks (405 ± 42 Mg ha−1) compared to the acid igneous rock soils (226 ± 6 Mg ha−1), which is likely explained by OM stabilization related to Ca2+ bridges in addition to the stabilization related to Fe and Al (oxides) in the limestone soils. Our results suggest a shift from OM stabilization dominated by Fe and Al (oxides) to that with the presence of Ca-related cation bridges, with increasing pH values driven by lithology.

Highlights

The soil acts as the largest terrestrial carbon (C) pool and plays an important role in global C dynamics (Lal 2004; Luo et al 2016)
Our present study aimed to explore the differences in soil organic carbon (SOC) stocks between well-developed limestone soils (LSs) and acid igneous rock soils (ASs) in the Peruvian Andes, and to elucidate potential differences in organic matter (OM) stabilization mechanisms operating in these different lithologies
The results indicate that lithology is the key factor controlling soil OM stabilization mechanisms in the studied soils of the Northern Peruvian Andes

Summary

Introduction

The soil acts as the largest terrestrial carbon (C) pool and plays an important role in global C dynamics (Lal 2004; Luo et al 2016). Andes are characterized by their high soil organic carbon (SOC) stocks and play an important role as the water source for the coastal regions with an arid climate (Tonneijck et al 2010; Buytaert et al 2011; Rolando et al 2017b). These grasslands suffer high risks of degradation due to ongoing and future climate change (Gang et al 2014). Soils formed on substrates other than volcanic ash, such as soils that occur in the central and southern Peruvian highland,

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