Stiftelsen Oscar och Lili Lamms Minne
Du är här: Hem // 2019 
TitelThe microbial control of carbon sequestration and fertility in drought-affected soils
NoFO2019-0038
UniversitetLund University
InstitutionDepartment of Biology
HuvudsökandeLettice Hicks
Beviljat belopp 391 500
Sammanfattning
Climate change will expose terrestrial ecosystems to more extreme drought and rainfall events. Indeed, recently in Sweden, drought events of an unprecedented severity have occurred. This will have a profound effect on soil functioning and biogeochemical cycling. Fungi and bacteria – the two principal decomposer groups in soil – break down organic matter, thus releasing inorganic nutrients for plant uptake and CO2 to the atmosphere. As such, soil microorganisms are key to maintaining soil fertility, and determine the carbon (C) sequestration potential of soils through their carbon use efficiency (CUE; the proportion of C used for growth relative to C respired). Water availability is a dominant controller of microbial activity. Under dry conditions, microbial activity is severely reduced. However, upon rewetting, there is a pulse of CO2 release to the atmosphere, accompanied by pronounced microbial growth responses. Poor understanding of the mechanisms which determine microbial CUE, as well as nitrogen (N) and phosphorus (P) mineralization responses to drying-rewetting (D/RW) events hinders the development of effective land management strategies to conserve soil C storage and fertility in the face of future climate change. To investigate the determinants and dynamics of bacterial and fungal growth, and resulting biogeochemistry, during the perturbation event induced in soil by D/RW, I will: (1) Resolve bacterial and fungal contributions to C-, N- and P-mineralization in knock-out experiments, by using bacterial- and fungal-specific antibiotics to experimentally inhibit either bacteria or fungi following D/RW (2) Identify limiting-factors for microbial growth following D/RW – using soils from natural fertility gradients – to assess microbial nutrient limitation during perturbation events and whether C:N:P mineralization ratios reflect microbial demand for N and P (3) Determine microbial CUE in response to D/RW across a gradient of bacterially-dominated (i.e. grassland) to fungal-dominated (i.e. forest) soils, to evaluate how differences in the initial dominance of the two major decomposer groups affect growth and mineralization responses to D/RW and the resulting CUE (4) Synthesise findings from 1-3 in order to elucidate how soil nutrient availability, microbial nutrient demand and the dominance of fungal and bacterial decomposers drive soil biogeochemistry in response to D/RW. I will employ a powerful methodological approach, combining experimental microcosm systems with ecosystem-level evaluations of soils from natural fertility gradients and soils reflecting different land-uses across Sweden, in four parallel work-packages. This will inform two central aspects of nature conservation, namely the preservation of C sequestration and fertility, which are essential functions that soils and soil microorganisms provide (see Relevance further detailed elsewhere). This ambitious project is feasible within the proposed time-frame due to the infrastructure available at the Rousk Laboratory, LU and the practical-framework already established by the applicant (see CV and publication list). Moreover, as the applicant’s salary is already covered, funds are only requested for experiment running-costs, offering excellent cost-efficiency to the foundation.