Süß C, Kemmann B, Helfrich M, Well R, Flessa H (2024) Nitrogen transformation as affected by decomposition of ¹⁵N-labeled cover crop shoots and roots. J Plant Nutr Soil Sci 187(6):748-765, DOI:10.1002/jpln.202200437

https://literatur.thuenen.de/digbib_extern/dn068734.pdf

Helfrich M, Dechow R, Merl S, Fuß R, Räbiger T, Kühling I, Schlathölter M, Kage H, Flessa H (2024) Winter cover crops decreased soil mineral N contents and increased soil organic C stocks and N₂O emission. Agric Ecosyst Environ 367:108985, DOI:10.1016/j.agee.2024.108985

https://literatur.thuenen.de/digbib_extern/dn068251.pdf

Kühling I, Mikuszies P, Helfrich M, Flessa H, Schlathölter M, Sieling K, Kage H (2023) Effects of winter cover crops from different functional groups on soil-plant nitrogen dynamics and silage maize yield. Eur J Agron 148:126878, DOI:10.1016/j.eja.2023.126878

Kalks F, Noren G, Mueller CW, Helfrich M, Rethemeyer J, Don A (2021) Geogenic organic carbon in terrestrial sediments and its contribution to total soil carbon. Soil 7(2):347-362, DOI:10.5194/soil-7-347-2021

https://literatur.thuenen.de/digbib_extern/dn064229.pdf

Schroeder J, Kammann L, Helfrich M, Tebbe CC, Poeplau C (2021) Impact of common sample pre-treatments on key soil microbial properties. Soil Biol Biochem 160:108321, DOI:10.1016/j.soilbio.2021.108321

https://literatur.thuenen.de/digbib_extern/dn063708.pdf

Helfrich M, Nicolay G, Well R, Buchen-Tschiskale C, Dechow R, Fuß R, Gensior A, Paulsen HM, Berendonk C, Flessa H (2020) Effect of chemical and mechanical grassland conversion to cropland on soil mineral N dynamics and N₂O emission. Agric Ecosyst Environ 298:106975, DOI:10.1016/j.agee.2020.106975

https://literatur.thuenen.de/digbib_extern/dn062805.pdf

Kalks F, Liebmann P, Wordell-Dietrich P, Guggenberger G, Kalbitz K, Mikutta R, Helfrich M, Don A (2020) Fate and stability of dissolved organic carbon in topsoils and subsoils under beech forests. Biogeochemistry 148:111-128, DOI:10.1007/s10533-020-00649-8

https://literatur.thuenen.de/digbib_extern/dn062308.pdf

Poeplau C, Helfrich M, Dechow R, Szoboszlay M, Tebbe CC, Don A, Greiner B, Zopf D, Thumm U, Korevaar H, Geerts R (2019) Increased microbial anabolism contributes to soil carbon sequestration by mineral fertilization in temperate grasslands. Soil Biol Biochem 130:167-176, DOI:10.1016/j.soilbio.2018.12.019

Gronwald M, Helfrich M, Don A, Fuß R, Well R, Flessa H (2018) Application of hydrochar and pyrochar to manure is not effective for mitigation of ammonia emissions from cattle slurry and poultry manure. Biol Fertil Soils 54:451-465, DOI:10.1007/s00374-018-1273-x)

Linsler D, Nüsse A, Buchen C, Helfrich M, Piepho HP, Ludwig B (2018) Effects of chemical and physical grassland renovation on the temporal dynamics of organic carbon stocks and water-stable aggregate distribution in a sandy temperate grassland soil. Soil Use Manag 34(4):490-499, DOI:10.1111/sum.12451

Wordell-Dietrich P, Don A, Helfrich M (2017) Controlling factors for the stability of subsoil carbon in a dystric cambisol. Geoderma 304:40-48, DOI:10.1016/j.geoderma.2016.08.023

Heinze S, Ludwig B, Piepho HP, Mikutta R, Don A, Wordell-Dietrich P, Helfrich M, Hertel D, Leuschner C, Kirfel K, Kandeler E, Preusser S, Guggenberger G, Leinemann T, Marschner B (2017) Factors controlling the variability of organic matter in the top- and subsoil of a sandy Dystric Cambisol under beech forest. Geoderma 311:37-44, DOI:10.1016/j.geoderma.2017.09.028

Buchen C, Well R, Helfrich M, Fuß R, Kayser M, Gensior A, Benke M, Flessa H (2017) Soil mineral N dynamics and N₂O emissions following grassland renewal. Agric Ecosyst Environ 246:325-342, DOI:10.1016/j.agee.2017.06.013.

Buchen C, Lewicka-Szczebak D, Fuß R, Helfrich M, Flessa H, Well R (2016) Fluxes of N₂ and N₂O and contributing processes in summer after grassland renewal and grassland conversion to maize cropping on a Plaggic Anthrosol and a Histic Gleysol. Soil Biol Biochem 101:6-19, DOI:10.1016/j.soilbio.2016.06.028

Gronwald M, Vos C, Helfrich M, Don A (2016) Stability of pyrochar and hydrochar in agricultural soil - a new field incubation method. Geoderma 284:85-92, DOI:10.1016/j.geoderma.2016.08.019

Eibisch N, Durner W, Bechtold M, Fuß R, Mikutta R, Woche SK, Helfrich M (2015) Does water repellency of pyrochars and hydrochars counter their positive effects on soil hydraulic properties? Geoderma 245-246:31-39, DOI:10.1016/j.geoderma.2015.01.009

Gronwald M, Don A, Tiemeyer B, Helfrich M (2015) Effects of fresh and aged chars from pyrolysis and hydrothermal carbonization on nutrient sorption in agricultural soils. Soil(1):475-489, DOI:10.5194/soil-1-475-2015

https://literatur.thuenen.de/digbib_extern/dn055272.pdf

Basler A, Dippold M, Helfrich M, Dyckmans J (2015) Microbial carbon recycling - an underestimated process controlling soil carbon dynamics - Part 1: A long term laboratory incubation experiment. Biogeosciences 12(20):5929-5940, DOI:10.5194/bg-12-5929-2015

https://literatur.thuenen.de/digbib_extern/dn055847.pdf

Basler A, Dippold M, Helfrich M, Dyckmans J (2015) Microbial carbon recycling: an underestimated process controlling soil carbon dynamics - Part 2: C₃-C₄ vegetation change field labelling experiment. Biogeosciences 12(21):6291-6299, DOI:10.5184/bf-12-6291-2015

https://literatur.thuenen.de/digbib_extern/dn055897.pdf

Eibisch N, Schroll R, Fuß R, Mikutta R, Helfrich M, Flessa H (2015) Pyrochars and hydrochars differently alter the sorption of the herbicide isoprotyron in an agricultural soil. Chemosphere 119:155-162, DOI:10.1016/j.chemospere.2014.05.059

Helfrich M, Ludwig B, Thoms W, Gleixner G, Flessa H (2015) The role of soil fungi and bacteria in plant litter decomposition and macroaggregate formation determined using phospholipid fatty acids. Appl Soil Ecol 96:261-264

Steffens C, Helfrich M, Joergensen RG, Eissfeller V, Flessa H (2015) Translocation of ¹³C-babeled leaf or root litter carbon of beech (Fagus sylvatica L.) and ash (Fraxinus excelsior L) during decomposision a laboratory incubation experiment. Soil Biol Biochem 83:125-137, DOI:10.1016/j.soilbio.2015.01.015

Langenbruch C, Helfrich M, Joergensen RG, Gordon J, Flessa H (2014) Partitioning of carbon and nitrogen during decomposition of ¹³C¹⁵N-labeled beech and ash leaf litter. J Plant Nutr Soil Sci 177:178-188, DOI:10.1002/jpln.201200643

Eibisch N, Helfrich M, Don A, Mikutta R, Kruse A, Ellerbrock RH, Flessa H (2013) Properties and degradability of hydrothermal carbonization products. J Environ Quality 42(5):1565-1573, doi:10.2134/jeq2013.02.0045

Langenbruch C, Helfrich M, Flessa H (2012) Effects of beech (Fagus sylvatica), ash (Fraxinus excelsior) and lime (Tilia spec.) on soil chemical properties in a mixed deciduous forest. Plant Soil 352(1-2):389-403, DOI:10.1007/s11104-011-1004-7

Jacobs A, Helfrich M, Dyckmans J, Rauber R, Ludwig B (2011) Effects of residue location on soil organic matter turnover: results from an incubation experiment with ¹⁵N-maize. J Plant Nutr Soil Sci 174(4):634-643, DOI:10.1002/jpln.201000208

Jacobs A, Helfrich M, Hanisch S, Quendt U, Rauber R, Ludwig B (2010) Effect of conventional and minimum tillage on physical and biochemical stabilization of soil organic matter. Biol Fertil Soils 46(7):671-680, DOI:10.1007/s00374-010-0472-x

Helfrich M, Flessa H, Dreves A, Ludwig B (2010) Is thermal oxidation at different temperatures suitable to isolate soil organic carbon fractions with different turnover? J Plant Nutr Soil Sci 173(1):61-66, DOI:10.1002/jpln.200700280

Helfrich M, Flessa H, Ludwig B (2010) Modeling carbon dynamics in subsoils using simple models. J Plant Nutr Soil Sci 173(5):671-677, DOI:10.1002/jpln.200900050