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Project 6 (phase I):

Root carbon shapes nutrient mobilization and recycling in the weathering zone


Investigator Names and Contact Info:

  • Yakov Kuzyakov (Soil Science, Biogeochemistry). Soil Science of Temperate Ecosystems, Georg-August-University Goettingen, Germany
  • Anna Gorbushina (Geomicrobiology). Freie Universität Berlin & Bundesanstalt für Materialforschung und -prüfing (BAM), Germany


Chilean Collaborators Involved:

  • Francisco J. Matus B. (Biogeochemistry / Nutrient cycles). Ciencias de Recursos Naturales, Universidad de la Frontera, Temuco, Chile
  • Roberto Godoy (Biology, Chemistry). Instituto de Ciencias Ambientales & Evolutivas, Universidad Austral de Chile, Valdivia, Chile
  • Carolina Merino (Biogeochemistry, Microbiology, Enzymology). Universidad de la Frontera, Temuco, Chile


Quantification of bacterial and fungal populations in soil.


  • Khaled Abdallah. Bundesanstalt für Materialforschung und -prüfung (BAM), Germany

Supervisor: Prof. Anna Gorbushina, Co-supervisor: Prof. Yakov Kuzyakov



Effect of drying, rewetting and thawing on soil gas fluxes: understanding the response and underlying mechanisms.



Supervisor: Prof. Francisco Matus, Co-supervisor: Prof. Yakov Kuziakov



Analysis of root carbon contribution to nutrient mobilization and recycling in the weathering zone of soil in Chile.



Supervisor: Prof. Yakov Kuzyakov, Co-supervisor: Prof. Anna Gorbushina



Changes in the soil CO2 efflux due to different soil moisture and nitrogen content.


visiting PhD-Student (until end of July 2017):

Supervisor: Prof. Yakov Kuzyakov, Co-supervisor: Prof. Anna Gorbushina


Project Summary:

Interacting plant- and microbial-communities weather and weaken rocks, thereby shaping the earth surface, by mobilizing, capturing and recycling nutrients. Energy is fixed by photosynthesis of plants and phototrophic microorganisms and made available via exudates to functional microbial groups contributing to mineral weathering. Elevated carbon (C) supply enables microorganisms to acquire more nutrients – including such derived from rocks (K, Ca, P) and to fix atmospheric nitrogen (N). Quantitative estimates of photosynthesis-derived C inputs into the weathering zone are scarce. We hypothesize that the plant C input belowground is regulated on four spatial scales: i) the continental scale - mainly via climatic conditions ii) the landscape scale - by redistribution of water and nutrients; iii) within the soil profile - by roots distribution; and iv) at the micro-scale - via microbial distribution and activity along rock fissures. To localize C inputs down to the weathering zone, plants will be labeled with 13CO2 on site. Dominant photoautotrophic organisms in the three primary focus areas will be labeled on North (dry) and South (wet) catchment slopes. 13C allocation and distribution in roots, soil and microorganisms will be traced down to the weathering zone. We will use 13C-PLFA (phospholipid fatty acids) to analyze the initial utilization of photosynthesis-derived C by fungi and bacteria. N uptake from various depths will be localized by 15N application into soil down to saprolite and compared to the activity of bacterial N2 fixation analyzed by expression of the nifH gene. The δ13C and δ15N incorporation into amino sugars will allow conclusions about the medium term contribution of bacteria and fungi to C and N stabilization. Rock-weathering microbial communities will be identified in hotspots of rock fissures by qPCR. To estimate the importance of fissures for saprolite weathering, the gradients of microbial community composition and enzyme activities will be analyzed from the fissure surface to the un-weathered rock at the microscale. Spatial distribution of enzyme activity will be assessed by field zymography. N recycling within the ecosystems will be assessed based on 15N natural abundance measurements along soil profiles. The analysis of C and N fluxes at four spatial scales: Continental scale, landscape scale, soil profile and micro-scale, will deepen our understanding about the contribution of plant-microbial interactions to mineral weathering.