Underestimated Life on the Surface
Biocrusts at the Frontline of Climate Change
21.01.2025
In drylands, where water is scarce and vegetation sparse, biological soil crusts—communities of microorganisms, lichens, and mosses—play an essential role in maintaining ecosystem health. These fragile crusts, which cover the soil's surface, are critical for regulating carbon and nitrogen cycles in these arid regions. But as the planet warms and drought conditions intensify, the ability of biocrusts to sustain these vital functions is increasingly under threat. To better understand how global change is impacting these ecosystems, TUM researchers and their partners conducted an innovative study at the TUMmesa facility.
The researchers made use of the advanced climate simulation capabilities of the TUM Model EcoSystem Analyser (TUMmesa) and recreated the environmental challenges of a warming planet. Soil samples from the semi-arid Santa Gracia region in Chile, complete with their biocrust layers, were subjected to increased temperatures and reduced water availability, mimicking the effects of climate change. Using state-of-the-art stable isotope labeling techniques, this controlled environment allowed the researchers to closely monitor how these stressors affected the ability of biocrusts to capture carbon and nitrogen and integrate them into the soil.
The success of this study relied on the unique technical features of TUMmesa, which made it possible to simulate and monitor environmental conditions with high precision. Autoclaving water directly on-site before irrigation ensured that microbial contamination was avoided, a critical step for the microbial analyses conducted during the study. Continuous soil temperature monitoring and precise control of air temperature at different points within the chamber provided the stability required for accurate results. The facility also enabled real-time, on-site gas measurements, allowing researchers to obtain quick and reliable results while ensuring sample integrity. Off-site monitoring of the chamber’s status added an additional layer of control, enabling researchers to resolve issues or deviations from the experimental program immediately.
The experiments revealed both the resilience and vulnerability of biocrusts. Under optimal conditions, these living crusts significantly enhanced the storage of carbon and nitrogen in the soil, supporting critical nutrient cycles. However, drought conditions drastically limited their ability to absorb carbon dioxide, while warming accelerated soil respiration—leading to a net loss of carbon from the system. Moreover, the intricate fungal networks that transport nutrients from the crusts into deeper soil layers were disrupted when exposed to the combined stresses of heat and drought.
The findings highlight a delicate balance: while biocrusts are invaluable for the health of dryland ecosystems, their ability to function is deeply connected to stable environmental conditions. As climate change continues to alter these landscapes, the long-term implications for soil health, carbon storage, and overall ecosystem stability are profound.
This research underscores the urgent need to protect and conserve these natural systems. By shedding light on the invisible yet vital processes that sustain drylands, it highlights the complex connections between climate, soil, and microbial life—and the pressing need to act before those connections are irrevocably altered.
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Witzgall, K., Hesse, B. D., Pacay-Barrientos, N. L., Jansa, J., Seguel, O., Oses, R., Buegger, F., Guigue, J., Rojas, C., Rousk, K., Grams., T. E. E., Pietrasniak, N., Mueller, C. W. (2024): Soil carbon and nitrogen cycling at the atmosphere–soil interface: Quantifying the responses of biocrust–soil interactions to global change. Global Change Biology, 30:e17519.
Kristina Witzgall
Soil Science
TUM School of Life Sciences
Technical University of Munich
Prof. Dr. Carsten Müller
Soil Science
Institute of Ecology
Technical University of Berlin
Funding information
Deutsche Forschungsgemeinschaft (DFG) National Science Foundation (NSF)
Grant/Award Number: MU3021/6-2 Grant/ Award Number: EAR-2012475