Alexandra Sandhage-Hofmann

INRES - Allgemeine Bodenkunde und Bodenökologie

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Dr. Alexandra Sandhage-Hofmann

+49 228 732967

+49 228 732782


Nußallee 13

53115 Bonn

+49 228 732967

Research Interest

Understanding processes in soil under different land uses, climates, and parent substrates, with particular emphasis on soil organic carbon. This involves studies on :

carbon pools, carbon sequestration, soil fertility combined with biomarker analyses and isotopes.

The studies are mainly conducted in the context of social-ecological projects to understand the coupling and linkage within different land uses such as cropland, rangeland or wildlife conservation. 

Regional focus is on Sub Saharan Africa.


Future rural Africa“ is an interdisciplinary collaborative research center funded by the German Research Council (DFG) involving geographers, anthropologists, political scientists, agroeconomists, soil scientists and ecologists from the Universities of Bonn and Cologne as well as external partners to address large-scale land use change and related social-ecological transformations along growth corridors in Eastern and Southern Africa. Future-making, the CRC´s key concept, means that ideas of the future as envisioned today are translated into plans, policies, and spatial transformations. The CRC is funded by German Research Foundation (DFG, runtime of 2st phase: 01/2022 – 12/2025).

Future Carbon Storage 

This interdisciplinary project views the future-making in rural Africa through a carbon lens, focusing on two conflicting visions: wildlife conservation and agricultural intensification. Together with vegetation ecologists, we as soil scientists determine carbon storage in soil under varying land-uses. Along two major pathways of land-use change (conservation and agricultural intensification), we evaluate carbon storage dynamics and carbon losses through disturbances. Along the conflicting pathways, we furthermore assess synergies and trade-offs between carbon storage and other ecosystem services which are important to local livelihoods.

Based on previous findings in the first project phase,  we will address in Phase II three hypotheses, keeping carbon as the common currency within our project.  We aim to understand how (1) historical settlement processes have co-determined current land-access and land-use patterns, as well as related rural wealth dynamics and variations in soil and vegetation quality. At the farm scale, we plan to study how (2) farmers actively shape their future by spatially modulating land management to improve soil and vegetation quality in the vicinity of their farms. At the regional scale and beyond, we will finally analyse (3) to what extent external shocks (e.g. COVID-19 pandemic) and spatio-temporal variations in policy regimes affect biophysical and socio-economic outcomes.

To test these hypotheses, we are working with farmers in Namibia and Zambia based on a household survey that were conducted in 2019. We are assessing soil fertility and quality in combination with ecosystem services and economic outcomes.

In the past years, more and more examples of tipping points in ecosystems have raised concern among scientists, environmental managers and policy makers. Changing environmental conditions in combination with increasing land use pressure can cause ecosystems to suddenly collapse or tip over. Due to the close interaction between nature and society, these tipping points are not yet well understood. They often come as an unpleasant surprise and can have serious environmental and socio-economic impacts, which at worst are irreversible.

Tipping points play an important role in dryland ecosystems. When pastures are heavily overgrazed and droughts occur in addition, they can "tip" into a desert-like state. Perennial forage grasses are then often permanently lost, leaving behind barren soils. Desertification is a pressing problem in Namibia, where drought and overghrazing may act as driving forces. . The project is part of the "bioTip" funding line and  funded by the Federal Ministry of Education and Research (BMBF, duration 02/2019 - 02/2023)

Soils are underrepresented in studies of tipping points, but are very important as a slow-response ecosystem compartment to disturbance, also to assess the resilience of ecosystems to stress. In our sub-project, we specifically ask how different grazing pressure and/or drought affect different soil parameters (fertility, water, respiration) and whether we can isolate early warning indicators in soil to avoid tipping points.

To adress these question, we work on grazing gradients in different tenure systems, but focus also on tipping point behaviour under simulated stress (TipEx).


  • Sandhage-Hofmann, A., Angombe, S., Kindermann, L., Linstädter, A., Mörchen, R.2022. Conservation with elephants and agricultural intensification: effects on lignin and n-alkanes in soils of sub-Saharan Africa, Geoderma, Volume 425, 2022, 116009, ISSN 0016-7061,
  • Kiesel, C, Dannenberg, P., Hulke, C., Kairu, J., Revilla Diez., J, Sandhage-Hofmann, A., 2022. An argument for place-based policies: The importance of local agro-economic, political and environmental conditions for agricultural policies exemplified by the Zambezi region, Namibia, Environmental Science & Policy, vol. 129, pp. 137-149 
  • Sandhage-Hofmann, A., Linstädter, A., Angombe, S., Kindermann, L., Amelung, W., 2021. Conservation with elevated elephant densities sequesters carbon in soils despite losses of woody biomass. Global Change Biology 27, 4601-4614.
  • Vergara Sosa, M. Lehndorff, E., Rodionov, A.,  Gocke, M.,  Sandhage-Hofmann, A., Amelung, W., 2020. Micro-scale resolution of carbon turnover in soil - Insights from laser ablation isotope ratio mass spectrometry on water-glass embedded aggregates. Soil Biology and Biochemistry 159, 108279. 
  • Sandhage-Hofmann, A., Löffler,J.,Kotzé, E.,Weijers, S., Wingate, V., Wundram, D., Weihermüller, L., Pape, R., du Preez, C.C., Amelung, W. 2020. Woody encroachment and related soil properties in different tenure-based management systems of semiarid rangelands. Geoderma 372, 114399
  • Braun, M., Kappenberg, A., Sandhage-Hofmann, A., Lendorff, E. 2020. Leachable soil black carbon after biochar application. Organic Geochemistry 143. 103996 
  • Bauke, S.L., v Sperber, C, Tamburini, F., Honermeier, B., Schweitzer, K., Baumecker, M, Don, A., Sandhage-Hofmann, A., Amelung, W.  2018 Subsoil phosphorus is affected by fertilization regime in long-term agricultural experimental trials.
  • Sandhage-Hofmann, A.; Löffler, J., Kotze, E.; Pape, R.; Weihermuller, L.; Wundram, D.; du Preez, CC.; Amelung, W. 2017. Bush encroachment and soil properties in rotational and continuous grazing systems of semiarid rangelands, South Africa. submitted Land Degradation and Development
  • Kotze, E., Sandhage-Hofmann, A., Amelung, W., du Preez, CC. 2017. Soil microbial communities in different rangeland management systems of a sandy savanna and clayey grassland ecosystem, South Africa. Nutrient Cycling in Agroecosystems, Nutr Cycl Agroecosyst. DOI 10.1007/s10705-017-9832-3
  • Sandhage-Hofmann, A., 2016. Rangeland Management – A review. Reference Module in Earth Systems and Environment. 
  • Linstädter, A.,  Kuhn, A. , Naumann, C. , Rasch, S., Sandhage-Hofmann, A., Amelung, W., Jordaan, J., Du Preez, C.C.,  Bollig, M. 2016. Assessing the resilience of a real-world social-ecological system: lessons from a multidisciplinary evaluation of a South African pastoral system.
  • Sandhage-Hofmann, A. Kotze, E. van Delden, L., Dominiak,M.  Fouche, H.J.,  van der Westhuizen, H.C., Oomen, R.J., du Preez, CC. Amelung, W., 2015. Rangeland management effects on soil properties in the savanna biome, South Africa: A case study along grazing gradients incommunal and commercial farms. J. Arid Environ 120, 40-125.
    v. Glisczynski, F., Pude, R., Amelung, W., Sandhage-Hofmann, A. 2016. Biochar-compost substrates in short-rotation coppice: Effects on soil and trees in a three-year field experiment. J. Plant Nutr. Soil Sci. 2016, 000, 1–10 DOI: 10.1002/jpln.201500545. 
  • v. Glisczynski, F., A. Sandhage-Hofmann, W. Amelung R. Pude. 2016. Biochar-compost substrates do not promote growth and fruit quality of a replanted German apple orchard with fertile Haplic Luvisol soils.Scienta Horticulturae 2013: 110-114. 
  • Sandhage-Hofmann, A. Kotze, E. van Delden, L., Dominiak,M.  Fouche, H.J.,  van der Westhuizen, H.C., Oomen, R.J., du Preez, CC. Amelung, W., 2015. Rangeland management effects on soil properties in the savanna biome, South Africa: A case study along grazing gradients in communal and commercial farms. J. Arid Environ 120, 40-125.
    Rehbein, K., Sandhage-Hofmann, A., Amelung, W., 2015. Soil carbon accrual in particle-size fractions under Miscanthus x. giganteus cultivation. Biomass and Bioenergy 78, 80-91.
  • Anne Ostermann, A., Gao, J., Welp, G., Siemens, J., Roelcke, M., Heimann, L., Nieder, R., Xue, Q., Lin, X., Sandhage-Hofmann, A., Amelung, W. 2014. Identification of soil contamination hotspots with veterinary antibiotics using heavy metal concentrations and leaching data—a field study in China. Environ Monit Assess (2014) 186:7693–7707. DOI 10.1007/s10661-014-3960-x
  • Sandhage-Hofmann, A. 2013. Kohlenstoffverluiste im Boden Ursachen und Maßnahmen zur Vermeidung Geographische Rundschau 22.
    Kotze, E., Sandhage-Hofmann, A., Meinel, J.-A., du Preez, C.C., Amelung, W., 2013. Rangeland management impacts on the properties of clayey soils along grazing gradients in the semi-arid grassland biome of South Africa. J. Arid Environ. 97,220-229.
  • Lobe, I., Sandhage-Hofmann, A., Brodowski, S., Amelung, W., 2011: Aggregate dynamics and associated soil organic matter contents as influenced by prolonged arable cropping in the South African Highveld. Geoderma 162, 251-261.
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