Project: Fire-Induced Redistribution and Losses of Elements in the Weathering Zone (FIRE)
EarthShape (Phase II): The project is an
affiliated project to the DFG priority program EarthShape (SPP 1803)
Summary
Fire is one of the most important geomorphological factors – an extreme event leading to huge changes of the element speciation and subsequent losses of nutrients and ballast elements from ecosystems during a very short period. Frequent fires in (semi)arid, Mediterranean and even in forest ecosystems induce dramatic reallocation of all elements that microorganisms mobilized and vegetation uplifted from the saprolite. In the 1st phase – microbial (mainly fungal) mobilization of elements by root carbon input into the soil and uptake of nutrients by plants from the soil and saprolite were investigated. In the 2nd phase, the losses of these elements by and after fires will be investigated in parallel with the effects on microbial communities and functions. Based on available nutrient and ballast element contents in soils i) after artificial burning and ii) chronosequences of ecosystems recoveries after natural fires, we will conclude about the element losses over short- and medium-term. These losses will be partitioned for leaching and erosion based on the experiments with tracers for N, K, Ca and Si. The fatal effects of fire on microbial communities and functions will be traced through the abundance of symbiotic and saprotrophic fungal phyla and diazotrophic organisms, enzyme activities and PLFA composition in the topsoil. Microbial succession during after-fire-recovery will be studied with a special accent on stress-tolerant and mineral-weathering fungi. The functional role of fungi and bacteria will be supported by comparisons of qPCR analysis to high throughput sequencing data. Special focus will be given to fungi as under aerobic conditions on rock surfaces and at the root/soil interfaces, fungi are of particular importance: Stress-protected fungal cells (i) form extensive contacts with minerals and enhance chemical release of nutrients from minerals and (ii) accelerate the recolonization of soils after the fire. The succession of microbial communities over short- and medium-term will be related to the increase of enzyme activities, PLFA composition, nutrient mobilization and accumulation in the topsoil. The aridity gradient from Pan de Azucar to Nahuelbuta will elucidate the effects of precipitation on absolute and relative losses of nutrients and ballast elements after fire as well as on ecosystem recovery.
Results of the 1st phase will be used to generalize the nutrient cycling and input by weathering under steady-state – in the stable ecosystems depending on climate. The results of the 2nd phase will allow generalization of the dramatic effects of the extreme event – fire – on the losses of the elements and their subsequent accumulation by weathering in recovering ecosystems during microbial and vegetation succession. Considering the worldwide increasing aridization and consequently the fire frequencies, the expected prediction of losses of nutrients and ballast elements from ecosystems and subsequent weathering possess a global relevance.
Keywords
Nutrient losses, Fire consequences, Weathering by microorganisms, Microbial succession, Pyrogenic residues
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