Land-use induced soil carbon stabilization at the expense of rock derived nutrients: insights from pristine Andean soils

Abstract

Soils contain significantly more carbon than the atmosphere, hence we should understand how best to stabilize it. Unfortunately, the role of human interventions on soil organic carbon (SOC) persistence in the Anthropocene remains vague, lacking adequate sites that allow unbiased direct comparisons of pristine and human influenced soils. Here we present data from a unique study system in the High Andes that guarantees pristineness of the reference sites by physical inaccessibility through vertical cliffs. By comparing the isotopic signatures of SOC, mineral related carbon stabilization, and soil nutrient status across grazed versus pristine soils, we provide counterintuitive evidence that thousands of years of pastoralism increased soil C persistence. Mineral associated organic carbon (MAOC) was significantly higher in pastures. Land use increased poorly crystalline minerals (PCM’s), of which aluminum correlated best with MAOC. On the other hand, human’s acceleration of weathering led to acidification and higher losses of cations. This highlights a dilemma of lower soil quality but higher persistence of SOC due to millennia of pastoralism. The dynamics of soil genesis in the Anthropocene needs better understanding, but if human-induced weathering proves generally to promote soil carbon persistence it will need to be included in climate—soil feedback projections.

Comparative analysis of soil organic matter fractions, lability, stability ratios, and carbon management index in various land use types within bharatpur catchment, Chitwan District, Nepal

“…This increased structural stability of pasture soil could be attributed to its higher stable fraction of soil organic matter content [ 105 ]. In addition to the great biodiversity and root exudates in pastures, the reduced soil disturbance allows the stable SOM to be less exposed to conditions that could accelerate its decomposition, allowing it to accumulate over time [ 106 ]. The presence of grazing animals in pastures also influences the cycling of organic matter and nutrients, promoting a more balanced decomposition process and further contributing to SOM carbon stabilization [ 107 ].…”

Anthropogenic modifications: impacts and conservation strategies

“…The authors compared two island systems, Jersey (Channel Islands) and St Mary's (Isles of Scilly), to assess how different sewage infrastructure affects nitrogen loading and demonstrated that upgrading sewer systems in the islands is necessary to reduce environmental problems. Two studies focused their attention instead on the soil 9 , 10 . Jungkunst et al highlight how the relationship between human actions and the presence of organic carbon (SOC) in soil in the Anthropocene is vague, mainly due to the lack of comparison between pristine sites and sites where human activities are present 9 .…”

“…Two studies focused their attention instead on the soil 9 , 10 . Jungkunst et al highlight how the relationship between human actions and the presence of organic carbon (SOC) in soil in the Anthropocene is vague, mainly due to the lack of comparison between pristine sites and sites where human activities are present 9 . Thanks to their study, conducted on an intact site in the high Andes, they provide evidence that thousands of years of pastoralism have increased the persistence of carbon in the soil.…”