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Quantifying the incipient development of soil structure and functions within a glacial forefield chronosequence

Andrianaki Maria, Bernasconi, Stéphane, Nikolaidis Nikolaos

Πλήρης Εγγραφή

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Περίληψη

In this study, we used the newly developed mathematical model CAST (carbon, aggregation, and structure turnover) to simulate the accumulation of soil organic carbon and the development of soil structure along the 150 years soil chronosequence of the Damma glacier Critical Zone Observatory (CZO). As first step in the modeling procedure, an adaptation of the widely used multipool Rothamsted carbon model RothC was tested. The calibration of the model is based on the extensive dataset available for the Damma glacier CZO and a published reconstruction of climate back to 1867. The adapted RothC model simulates effectively the dynamics of total organic carbon (TOC), microbial biomass (BIO), and humified organic matter (HUM) pools, while decomposable plant material (DPM) and resistant plant material (RPM) pools which are calculated by the model are slightly overestimated compared to measured values. In a second set of simulations, the CAST model was applied and captured effectively the carbon content of the three aggregate classes which are considered by the model (macroaggregates: > 250 μm (AC3), microaggregates: 53–250 μm (AC2), silt–clay-sized aggregates: < 53 μm (AC1)). The major percentage of aggregates belongs to the AC3 class, which consists of the particulate organic matter primarily loosely bound with the mineral particles. The amount of aggregates within the AC1 aggregate class is low, while the formation of the AC2 aggregates has not been initiated at this stage of soil development. One of the most important finding of this study is that the CAST model realistically calculates the processes during the initial stages of soil structure development, even though the soils of the Damma glacier CZO soil chronosequence are characterized by very poor soil structure and low clay content. The main process for soil development at this early stage is identified to be the macroaggregation through the addition of particulate organic matter. Microaggregation of smaller-sized particles and aggregates is not found to be a major contribution to soil structure development at this stage and it is only observed at the end of the chronosequence. Finally, despite the extreme climatic conditions of the alpine environment, the young nature of the soils and the short growing season, both models performed very well after calibration of the carbon turnover rates.

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