Data from: Humus forms and organic matter decomposition in the Swiss Alps
Abstract
Organic matter decomposition is influenced by abiotic factors (i.e., climate) and biotic factors (i.e., plants and soil decomposers). To qualitatively assess the rate at which organic matter is degraded and integrated into the topsoil layers, a classification of humus forms has been developed. Yet, whether different humus forms could be experimentally linked to litter decomposition has still to be fully assessed.
To determine the relative influence of humus systems on organic matter decomposition, we worked in two regions of the Swiss Alps (Valais and Ticino) along elevational gradients by following a north/south exposure design. First, we quantified humus forms macrorests proportion types by the Ponge small-volume method (Ponge, 1984). Second, we measured the decomposition of green tea and rooibos teabags within the Parasystems and Terrosystems.
We found that Parasystems and Terrosystems differed in teabags decomposition rates, with a slower decomposition in Parasystems and a faster decomposition in Terrosystems. We also observed that elevation, and hence, vegetation type (i.e., forest versus grassland), drives humus forms distribution with Parasystem at the alpine and subalpine levels in Ticino. In contrast, in Valais, Parasystem were found only at the alpine level and Terrosystems at the subalpine level.
Our results thus indicate that organic matter decomposition is influenced by climate but also by different soil biota, for instance, highlighting more fungal activity in the subalpine level with wooden debris and the presence of earthworms in the less woody litters.
Further analyses are however needed to identify other variables that best correlate with variation in decomposition processes within humus systems, such as soil decomposer’s community composition.
https://doi.org/10.5061/dryad.xd2547dnp
Description of the data and file structure
This data set comprises the following data files:
- my_data22.csv: Results of the decomposition of two tea types (green tea and rooibos tea)
- ponge_ok2.csv: Results of top layer’s soil physico-chemical properties of 24 sites in the Swiss Alps
Files and variables
File: my_data22.csv
Description: Site description
Variables
- plot_id: Unique identifier for each sampling plot (alphanumeric code)
- region: Geographic region where the plot is located (categorical)
- expo: Slope exposure or aspect (e.g., N, S, E, W; categorical)
- alti: Altitude of the plot in meters above sea level [m]
- soil_class_wrb: Soil classification based on the World Reference Base for Soil Resources (WRB) system (categorical)
- soil_class: Local or national soil classification (categorical)
- level: Humus form level(e.g., Parasystem categorical)
- syst_humus: System of humus classification (e.g., Mull, Moder, Mor; categorical)
- form_humus: Specific humus form (e.g., Rhizomull, Dysmoder; categorical)
- roiboos: Mass loss of rooibos tea after decomposition [%]
- green_tea: Mass loss of green tea after decomposition [%]
- aggregates: Proportion of soil aggregates [%]
- wMonocot: Weighted average proportion of monocotyledonous plant material [%]
- wDicot: Weighted average proportion of dicotyledonous plant material [%]
- wNeedleCOnes: Weighted average proportion of needle and cone material [%]
- wRoots: Weighted average proportion of root material [%]
- wWood: Weighted average proportion of woody material [%]
- wBryophyte: Weighted average proportion of bryophyte (moss) material [%]
- wHolorganic: Weighted average proportion of holorganic material [%]
- wOrganomin: Weighted average proportion of organo-mineral material [%]
- wMineral: Weighted average proportion of mineral material [%]
- wMycelium: Weighted average proportion of fungal mycelium [%]
- wOther: Weighted average proportion of other materials not classified above [%]
- clay: Proportion of clay in the soil [%]
- sand: Proportion of sand in the soil [%]
- CN: Carbon to nitrogen ratio in the soil [unitless]
- LOI: Loss on ignition – a proxy for organic matter content [%]
- Rhizomoder: Presence or classification of Rhizomoder humus form (binary or categorical)
File: ponge_ok2.csv
Description: Same as my_data22.csv but with two additional columns
Variables
- Horizon: Soil horizon label (e.g., L, F, H, A; categorical)
- ID: Unique identifier for each sample or horizon (alphanumeric)
- alti: Altitude of the sampling location in meters above sea level [m]
- expo: Slope exposure or aspect (e.g., N, S, E, W; categorical)
- region: Geographic region of the sampling site (categorical)
- level: Humus form level(e.g., Parasystem categorical)
- syst_humus: System of humus classification (e.g., Mull, Moder, Mor; categorical)
- form_humus: Specific humus form (e.g., Dysmoder, Rhizomull; categorical)
- top: Upper depth boundary of the horizon [cm]
- bottom: Lower depth boundary of the horizon [cm]
- Monocot: Proportion of monocotyledonous plant material [%]
- Dicot: Proportion of dicotyledonous plant material [%]
- NeedleCones: Proportion of needle and cone material [%]
- Roots: Proportion of root material [%]
- Wood: Proportion of woody material [%]
- Bryophyte: Proportion of bryophyte (moss) material [%]
- Holorganic: Proportion of holorganic (pure organic) material [%]
- Organomin: Proportion of organo-mineral material [%]
- Mineral: Proportion of mineral material [%]
- Mycelium: Proportion of fungal mycelium [%]
- Other: Proportion of other or unclassified materials [%]
Additional Files: Description and Structure
The remaining files (e.g., TNH1 to 3.csv, TNM1 to 3.csv, TSH1 to 3.csv, TSM1 to 3.csv, VNH1 to 3.csv, VNM1 to 3.csv, VSH1 to 3.csv, VSM1 to 3.csv) contain detailed data on small-volume macrorest proportions collected from various sites in the Swiss Alps. The file names correspond to specific site codes, which match the plot_id or ID columns in the main datasets (my_data22.csv and ponge_ok2.csv). The number in the file name (e.g., 1 to 3) refers to the replicate or horizon number within each site. Each file includes the following columns:
- Horizon: Soil horizon label (e.g., L, F, H)
- ID: Unique identifier for the sample or horizon
- alti: Altitude of the sampling location [m]
- expo: Slope exposure (e.g., N, S, E, W)
- region: Geographic region of the site
- level: Humus form level(e.g., Parasystem categorical)
- syst_humus: Humus system classification (e.g., Mull, Moder)
- form_humus: Specific humus form (e.g., Dysmoder, Rhizomull)
- top and bottom: Depth boundaries of the horizon [cm]
- Monocot, Dicot, NeedleCones, Roots, Wood, Bryophyte, Holorganic, Organomin, Mineral, Mycelium, Other: Proportions of different macrorest types [% of total material]
These files provide a more granular view of the organic matter composition across soil horizons and replicate samples, complementing the broader site-level data in the main datasets.
Code/software
Microsoft Excel and R Studio
Access information
Other publicly accessible locations of the data:
- UniNe, Laboratory of Functional Ecology, Sergio Rasmann's Lab
These data were collected during the summer of 2020.
- Semeraro, Sarah; Fazzari, Maud; Kipf, Pascal et al. (2023). Humus Forms and Organic Matter Decomposition in the Swiss Alps. International Journal of Plant Biology. https://doi.org/10.3390/ijpb14030054