Soil Organic Matter Changes Under Experimental Pedoclimatic Modifications in Mountain Grasslands of the French Alps

45 Pages Posted: 16 Feb 2022

See all articles by Norine Khedim

Norine Khedim

affiliation not provided to SSRN

Jérôme Poulenard

affiliation not provided to SSRN

Lauric Cécillon

affiliation not provided to SSRN

François Baudin

Université Paris Est Créteil - Sorbonne Université

Pierre Barré

affiliation not provided to SSRN

Amélie Saillard

affiliation not provided to SSRN

Billur Bektaş

affiliation not provided to SSRN

Karl Grigulis

affiliation not provided to SSRN

Sandra Lavorel

affiliation not provided to SSRN

Tamara Münkemüller

affiliation not provided to SSRN

Philippe Choler

affiliation not provided to SSRN

Abstract

Mountain grasslands contain large stocks of soil organic carbon (SOC), of which a good part is in labile particulate form. This labile SOC may be protected by cold climate that limits microbial activity. Strong climate change in mountain regions threatens to destabilize these SOC stocks. However, so far the climate response of SOC stocks in mountain grasslands remains highly uncertain, under either warming or cooling conditions. To overcome this knowledge gap, we studied the effect of pedoclimatic regime changes on topsoil (0–10 cm) SOC in two complementary experiments:  3 °C of warming or cooling by reciprocal transplanting to an alpine (2450 m a.s.l.) and a subalpine (1950 m a.s.l.) grassland and 1 °C of warming by open-top chambers in the same grasslands.Topsoil SOC stocks were higher at the alpine site than at the subalpine site, and the biogeochemical signature of the soil organic matter (SOM) also differed between the two study sites. SOM was O-enriched, H-depleted, and more thermally stable at the warmer subalpine site. After three years, abrupt warming by transplanting tended to decrease topsoil SOC content. The remaining SOC was characterized by a more thermostable signature. This result suggests the preferential depletion of labile SOC upon experimental topsoil warming. Cooling did not modify overall SOC content but uphill transplanted topsoils showed a more thermolabile biogeochemical signature. In contrast, open-top chamber warming of alpine and subalpine topsoils caused limited changes to SOC stocks and SOM biogeochemical signature, possibly because the induced pedoclimatic change was more limited and more gradual compared to the warming by transplantating which reduced the annual snow cover period by around 60 days and increased cumulative degree days by a factor of ten as compared to the OTC-induced warming. Gradual temperature changes may take longer to become effective than a shock transplant treatment. We conclude that SOC in mountain grassland topsoils can be highly reactive to climate shocks.

Keywords: Soil organic carbon, Thermal analysis, mountain soils, cooling experiment, warming experiment

Suggested Citation

Khedim, Norine and Poulenard, Jérôme and Cécillon, Lauric and Baudin, François and Barré, Pierre and Saillard, Amélie and Bektaş, Billur and Grigulis, Karl and Lavorel, Sandra and Münkemüller, Tamara and Choler, Philippe, Soil Organic Matter Changes Under Experimental Pedoclimatic Modifications in Mountain Grasslands of the French Alps. Available at SSRN: https://ssrn.com/abstract=4036357 or http://dx.doi.org/10.2139/ssrn.4036357

Norine Khedim (Contact Author)

affiliation not provided to SSRN ( email )

No Address Available

Jérôme Poulenard

affiliation not provided to SSRN ( email )

No Address Available

Lauric Cécillon

affiliation not provided to SSRN ( email )

No Address Available

François Baudin

Université Paris Est Créteil - Sorbonne Université ( email )

Pierre Barré

affiliation not provided to SSRN ( email )

No Address Available

Amélie Saillard

affiliation not provided to SSRN ( email )

No Address Available

Billur Bektaş

affiliation not provided to SSRN ( email )

No Address Available

Karl Grigulis

affiliation not provided to SSRN ( email )

No Address Available

Sandra Lavorel

affiliation not provided to SSRN ( email )

No Address Available

Tamara Münkemüller

affiliation not provided to SSRN ( email )

No Address Available

Philippe Choler

affiliation not provided to SSRN ( email )

No Address Available

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