TY - JOUR
T1 - Reactive Nitrogen Hotspots Related to Microscale Heterogeneity in Biological Soil Crusts
AU - Kratz, Alexandra Maria
AU - Maier, Stefanie
AU - Weber, Jens
AU - Kim, Minsu
AU - Mele, Giacomo
AU - Gargiulo, Laura
AU - Leifke, Anna Lena
AU - Prass, Maria
AU - Abed, Raeid M.M.
AU - Cheng, Yafang
AU - Su, Hang
AU - Pöschl, Ulrich
AU - Weber, Bettina
N1 - Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/8/5
Y1 - 2022/8/5
N2 - Biocrusts covering drylands account for major fractions of terrestrial biological nitrogen fixation and release large amounts of gaseous reactive nitrogen (Nr) as nitrous acid (HONO) and nitric oxide (NO). Recent investigations suggested that aerobic and anaerobic microbial nitrogen transformations occur simultaneously upon desiccation of biocrusts, but the spatio-temporal distribution of seemingly contradictory processes remained unclear. Here, we explore small-scale gradients in chemical concentrations related to structural characteristics and organism distribution. X-ray microtomography and fluorescence microscopy revealed mixed pore size structures, where photoautotrophs and cyanobacterial polysaccharides clustered irregularly in the uppermost millimeter. Microsensor measurements showed strong gradients of pH, oxygen, and nitrite, nitrate, and ammonium ion concentrations at micrometer scales in both vertical and lateral directions. Initial oxygen saturation was mostly low (∼30%) at full water holding capacity, suggesting widely anoxic conditions, and increased rapidly upon desiccation. Nitrite concentrations (∼6 to 800 μM) and pH values (∼6.5 to 9.5) were highest around 70% WHC. During further desiccation they decreased, while emissions of HONO and NO increased, reaching maximum values around 20% WHC. Our results illustrate simultaneous, spatially separated aerobic and anaerobic nitrogen transformations, which are critical for Nremissions, but might be impacted by future global change and land management.
AB - Biocrusts covering drylands account for major fractions of terrestrial biological nitrogen fixation and release large amounts of gaseous reactive nitrogen (Nr) as nitrous acid (HONO) and nitric oxide (NO). Recent investigations suggested that aerobic and anaerobic microbial nitrogen transformations occur simultaneously upon desiccation of biocrusts, but the spatio-temporal distribution of seemingly contradictory processes remained unclear. Here, we explore small-scale gradients in chemical concentrations related to structural characteristics and organism distribution. X-ray microtomography and fluorescence microscopy revealed mixed pore size structures, where photoautotrophs and cyanobacterial polysaccharides clustered irregularly in the uppermost millimeter. Microsensor measurements showed strong gradients of pH, oxygen, and nitrite, nitrate, and ammonium ion concentrations at micrometer scales in both vertical and lateral directions. Initial oxygen saturation was mostly low (∼30%) at full water holding capacity, suggesting widely anoxic conditions, and increased rapidly upon desiccation. Nitrite concentrations (∼6 to 800 μM) and pH values (∼6.5 to 9.5) were highest around 70% WHC. During further desiccation they decreased, while emissions of HONO and NO increased, reaching maximum values around 20% WHC. Our results illustrate simultaneous, spatially separated aerobic and anaerobic nitrogen transformations, which are critical for Nremissions, but might be impacted by future global change and land management.
KW - X-ray microtomography
KW - biological soil crusts
KW - fluorescence microscopy
KW - microsensors
KW - nitric oxide (NO)
KW - nitrous acid (HONO)
KW - reactive nitrogen
KW - Soil/chemistry
KW - Nitrites
KW - Nitrous Oxide/analysis
KW - Nitrous Acid/chemistry
KW - Nitrogen/analysis
KW - Nitric Oxide
KW - Cyanobacteria
UR - http://www.scopus.com/inward/record.url?scp=85136103279&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85136103279&partnerID=8YFLogxK
UR - https://www.mendeley.com/catalogue/1151cee9-fd6e-34d1-8d1b-b01920146f73/
U2 - 10.1021/acs.est.2c02207
DO - 10.1021/acs.est.2c02207
M3 - Article
C2 - 35929951
AN - SCOPUS:85136103279
SN - 0013-936X
VL - 56
SP - 11865
EP - 11877
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 16
ER -