Humboldt-Universität zu Berlin - Ecology

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The field experiment

The experimental agricultural field site is located near Göttingen, with known site history of cropping system. Management practice was changed from C3 to C4 crop in 2009. The following treatment variants are established:

Table maize

 Macro Wheat

Sampling for soil fauna at the wheat plots

(maize plot in background)

Aboveground plant tissues predominantly consist of complex, recalcitrant carbon compounds (e.g. cellulose, lignin), whereas belowground plant carbon mainly derives from rhizodeposition, i.e. labile sources (e.g. sugars, carboxylic acids, amino acids). Corn maize adds both litter and rhizodeposits to the soil, whereas fodder maize, where entire plants are removed at harvest, mainly supplies belowground carbon sources. Wheat serves as control to compare 13C/12C ratios between C3 and C4 cropping systems. At the plots “wheat + maize litter” fresh maize litter in amounts comparable to the input by corn maize is applied by hand to introduce the isotopic signal of aboveground maize resources into the food web of the C3 soil.

Maize bus

Corn maize – harvested by hand!

The microbial and faunal community at the field site is studied at three sampling occasions per year: (1) June – highest exudation, (2) September – maize harvest and plant residues input, and (3) December – high migration of DOM and MOM. To relate food web complexity to resources, the project does not just explore the Ap horizon but also deeper soil layers. Within this depth transect resource quality and availability, and in turn trophic diversity, declines. The investigations comprise the soil compartments: (1) top soil within the plough horizon, (2) rooted zone below ploughshare, and (3) root free soil in deeper horizons.

Sampling depth transects

Sampling a depth transect for microorganisms and microfauna

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