Ergebnisse aus 10 Jahren Humusmonitoring auf Ackerflächen in Nordrhein-Westfalen

Seit 2009 wird vom Landesamt für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen (LANUV NRW) in Zusammenarbeit mit dem Geologischen Dienst NRW, der Landwirtschaftskammer NRW sowie der Universität Bonn ein Humusmonitoringprogramm in Nordrhein-Westfalen durchgeführt. Ziele sind die Bestimmung der Gehalte und Vorräte an organischem Kohlenstoff (Corg) von Ackerböden in Nordrhein-Westfalen sowie die Abschätzung von Veränderungen der Corg-Gehalte und Vorräte. Zusätzlich sollen die Einflussfaktoren, wie z.B. Klimawandel und die landwirtschaftliche Nutzung, auf Gehalte und Vorräte ermittelt werden. Die Ergebnisse sollen auch eine wissen-schaftlich fundierte Basis schaffen, um die Landwirte bei allen Fragen der Humuspflege optimal zu beraten. Die Corg-Gehalte der Beprobung von 197 Flächen in 2009 liegen in einer Spanne von 0,7 bis 3,4 % mit deutlichen Unterschieden zwischen den untersuchten naturräumlichen Regionen. Rund 75 % der Flächen weisen Gehalte zwischen 1 und 2 % Corg auf. Die bisherigen Ergebnisse im Intensivmonitoring (2009 – 2018) von 45 ausgewählten Ackerflächen zeigen bisher keine NRW-weit gerichtete Entwicklung bei den Corg-Gehalten. Es sind jedoch regionale Trends zu beobachten. Multivariate Auswertungen haben gezeigt, dass insgesamt die organische Düngung, der Corg-Gehalt zu Beginn der Messreihe sowie die Temperaturzunahme den größten Einfluss auf die Veränderung der Corg-Gehalte aller 45 Flächen haben. Hervorzuheben sind dabei das Niederrheinische Tiefland und die Rheinische Bucht, in denen in den letzten zehn Jahren im Oberboden eine signifikante Zunahme der Corg-Gehalte zu beobachten ist und dies vermutlich vor allem auf die Zufuhr organischer Dünger zurückzuführen ist

An incubation study on the stability and biological effects of pyrogenic and hydrothermal biochar in two soils

The success and feasibility of CO2-sequestration through incorporation of biochar into soils depends strongly on the long-term biochar stability and on the improvements of physical and microbial soil properties. In this study, the stability of two maize-derived biochars (from pyrolysis and hydrothermal carbonization) and of a compost-biochar mixture and their effects on microbial biomass and enzyme activity were determined in two soils during a 57-day incubation. Soil samples amended with biochar increased soil organic carbon (SOC) content by 20 or 40%. Samples amended with hydrothermal biochar showed the largest respiration rates and the largest increase in microbial and enzymatic activity compared with the untreated controls. Carbon and 13C mass balances showed that between 13 and 16% of the added hydrochar was mineralized within 8 weeks. In the arable soil, hydrochar additions greatly stimulated the degradation of SOC, thus inducing positive priming effects. The mineralization of pyrogenic biochar (pyrochar and a pyrochar-compost mixture) was significantly less (1.4–3%) and comparable to the SOC mineralization in the control soils

Temperature response of soil respiration largely unaltered with experimental warming

© 2016, National Academy of Sciences. All rights reserved. The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling \u3e 3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving our mechanistic understanding of how soil carbon dynamics change with climatic warming

Temperature response of soil respiration largely unaltered with experimental warming

The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving our mechanistic understanding of how soil carbon dynamics change with climatic warming