07 Mar 2022
07 Mar 2022
Status: this preprint is currently under review for the journal SOIL.

Biocrust-linked changes in soil aggregate stability along a climatic gradient in the Chilean Coastal Range

Nicolás Riveras-Muñoz1, Steffen Seitz1, Kristina Witzgall2, Victoria Rodríguez3, Peter Kühn1, Carsten W. Mueller4, Rómulo Oses5, Oscar Seguel6, Dirk Wagner3,7, and Thomas Scholten1 Nicolás Riveras-Muñoz et al.
  • 1University of Tübingen, Department of Geosciences, Soil Science and Geomorphology, Rümelinstr. 19–23, 72070 Tübingen, Germany
  • 2Technical University of Munich, Soil Science, Emil-Ramann-Str. 2, 85354 Freising, Germany
  • 3GFZ German Research Centre for Geosciences, Section 5.3 Geomicrobiology, Telegrafenberg, 14473 Potsdam, Germany
  • 4Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark
  • 5Universidad de Atacama, Centro Regional de Investigación y Desarrollo Sustentable de Atacama (CRIDESAT), Copayapu 485, Copiapó, Chile
  • 6Universidad de Chile, Facultad de Ciencias Agronómicas, Av. Santa Rosa #11315, La Pintana, 8820808 Santiago, Chile
  • 7University of Potsdam, Institute of Geosciences, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany

Abstract. Biological soil crusts (biocrusts) composed of cyanobacteria, bacteria, algae, fungi, lichens, and bryophytes stabilize the soil surface. This effect has mainly been studied in arid climates, where biocrusts constitute the main biological agent to stabilize and connect soil aggregates. Besides, biocrusts are an integral part of the soil surface under mediterranean and humid climate conditions, mainly covering open spaces in forests and on denudated lands. They often develop after vegetation disturbances, when their ability to compete with vascular plants increases, acting as pioneer communities and affecting the stability of soil aggregates. To better understand how biocrusts mediate changes in soil aggregate stability under different climate conditions, we analyzed soil aggregate samples taken under biocrust communities from four national parks in Chile along a large climatic gradient ranging from (north to south) arid (Pan de Azúcar), semi-arid (Santa Gracia), mediterranean (La Campana) to humid (Nahuelbuta). Biocrust communities showed a stabilizing effect on the soil aggregates in dry fractions for the three northern and the wet aggregates for the southernmost sites. Here, permanent vascular plants and higher contents of organic carbon and nitrogen in the soil control aggregate stability more than biocrusts, which are in intense competition to higher plant communities. Moreover, we found an increase in stability for edge aggregate size classes (< 2.0 mm and 9.5–30.0 mm). The geometric mean diameter of the soil aggregates showed a clear effect due to the climatic gradient, indicating that the aggregate stability presents a log-normal instead of a normal distribution, with a trend of low change between aggregate size fractions. Based on our results, we assume that biocrusts affect the soil structure in all climates. Their role for aggregate stability is masked under humid conditions by higher vegetation and organic matter contents in the topsoil.

Nicolás Riveras-Muñoz et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on soil-2021-141', Anonymous Referee #1, 11 Mar 2022
    • AC1: 'Reply on RC1', Nicolás Riveras Muñoz, 16 Mar 2022
  • AC2: 'Comment on soil-2021-141', Nicolás Riveras Muñoz, 05 Apr 2022
  • RC2: 'Comment on soil-2021-141', Anonymous Referee #2, 17 May 2022
    • AC3: 'Reply on RC2', Nicolás Riveras Muñoz, 17 Jun 2022

Nicolás Riveras-Muñoz et al.

Nicolás Riveras-Muñoz et al.


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Short summary
Biorusts stabilize the soil surface mainly in arid regions but are also present in mediterranean and humid climates. We studied this stabilizing effect through wet and dry sieving along a large climatic gradient in Chile and found that the stabilization of soil aggregates persists in all climates, but their role is masked and reserved for a limited number of size fractions under humid conditions by higher vegetation and organic matter contents in the topsoil.