Browsing by Person "Brandt, Luise"

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    Formation of mineral‐associated organic matter in temperate soils is primarily controlled by mineral type and modified by land use and management intensity
    (2023) Bramble, De Shorn E.; Ulrich, Susanne; Schöning, Ingo; Mikutta, Robert; Brandt, Luise; Poll, Christian; Kandeler, Ellen; Mikutta, Christian; Konrad, Alexander; Siemens, Jan; Yang, Yang; Polle, Andrea; Schall, Peter; Ammer, Christian; Kaiser, Klaus; Schrumpf, Marion
    Formation of mineral-associated organic matter (MAOM) supports the accumulation and stabilization of carbon (C) in soil, and thus, is a key factor in the global C cycle. Little is known about the interplay of mineral type, land use and management intensity in MAOM formation, especially on subdecadal time scales. We exposed mineral containers with goethite or illite, the most abundant iron oxide and phyllosilicate clay in temperate soils, for 5 years in topsoils of 150 forest and 150 grassland sites in three regions across Germany. Results show that irrespective of land use and management intensity, more C accumulated on goethite than illite (on average 0.23 ± 0.10 and 0.06 ± 0.03 mg m−2 mineral surface respectively). Carbon accumulation across regions was consistently higher in coniferous forests than in deciduous forests and grasslands. Structural equation models further showed that thinning and harvesting reduced MAOM formation in forests. Formation of MAOM in grasslands was not affected by grazing. Fertilization had opposite effects on MAOM formation, with the positive effect being mediated by enhanced plant productivity and the negative effect by reduced plant species richness. This highlights the caveat of applying fertilizers as a strategy to increase soil C stocks in temperate grasslands. Overall, we demonstrate that the rate and amount of MAOM formation in soil is primarily driven by mineral type, and can be modulated by land use and management intensity even on subdecadal time scales. Our results suggest that temperate soils dominated by oxides have a higher capacity to accumulate and store C than those dominated by phyllosilicate clays, even under circumneutral pH conditions. Therefore, adopting land use and management practices that increase C inputs into oxide-rich soils that are under their capacity to store C may offer great potential to enhance near-term soil C sequestration.
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    Release of glucose from dissolved and mineral‐bound organic matter by enzymatic hydrolysis
    (2023) Lenhardt, Katharina R.; Brandt, Luise; Poll, Christian; Rennert, Thilo; Kandeler, Ellen
    Sorption of dissolved organic matter (DOM) by poorly crystalline minerals during their formation may protect large amounts of carbon in soils from mineralization. We investigated the bioavailability of carbohydrates in DOM and after co-precipitation with short-range ordered aluminosilicates. Carbohydrates originated from soil solutions collected in situ at two depths of a Dystric Cambisol, and from litter extracts. Quantification of substrate-specific degradability was achieved by the addition of β-glucosidase at an optimal concentration and subsequent determination of glucose release. Depending on DOM composition, 0.6–41.4 mg g−1 C−1 of glucose was enzymatically released from dissolved carbohydrates. Co-precipitated carbohydrates were partially accessible, resulting in a glucose release of 0.7–5.2 mg g−1 C−1. Restricted enzymatic depolymerization due to co-precipitation may contribute to accumulation of easily degradable substrates in soils.
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    Soil water status shapes nutrient cycling in agroecosystems from micrometer to landscape scales
    (2022) Bauke, Sara L.; Amelung, Wulf; Bol, Roland; Brandt, Luise; Brüggemann, Nicolas; Kandeler, Ellen; Meyer, Nele; Or, Dani; Schnepf, Andrea; Schloter, Michael; Schulz, Stefanie; Siebers, Nina; von Sperber, Christian; Vereecken, Harry
    Soil water status, which refers to the wetness or dryness of soils, is crucial for the productivity of agroecosystems, as it determines nutrient cycling and uptake physically via transport, biologically via the moisture‐dependent activity of soil flora, fauna, and plants, and chemically via specific hydrolyses and redox reactions. Here, we focus on the dynamics of nitrogen (N), phosphorus (P), and sulfur (S) and review how soil water is coupled to the cycling of these elements and related stoichiometric controls across different scales within agroecosystems. These scales span processes at the molecular level, where nutrients and water are consumed, to processes in the soil pore system, within a soil profile and across the landscape. We highlight that with increasing mobility of the nutrients in water, water‐based nutrient flux may alleviate or even exacerbate imbalances in nutrient supply within soils, for example, by transport of mobile nutrients towards previously depleted microsites (alleviating imbalances), or by selective loss of mobile nutrients from microsites (increasing imbalances). These imbalances can be modulated by biological activity, especially by fungal hyphae and roots, which contribute to nutrient redistribution within soils, and which are themselves dependent on specific, optimal water availability. At larger scales, such small‐scale effects converge with nutrient inputs from atmospheric (wet deposition) or nonlocal sources and with nutrient losses from the soil system towards aquifers. Hence, water acts as a major control in nutrient cycling across scales in agroecosystems and may either exacerbate or remove spatial disparities in the availability of the individual nutrients (N, P, S) required for biological activity.