Fire-Induced Redistribution and Losses of Elements in the Weathering Zone (FIRE)

火灾是最重要的地貌因素之一，它是一种极端事件，会在很短的时间内导致生态系统中元素形态的巨大变化和随后的营养物质和压载元素的损失。在（半）干旱、地中海甚至森林生态系统中，频繁的火灾导致微生物调动的所有元素和从腐腐岩中升起的植被的急剧重新分配。在第一阶段，研究了微生物（主要是真菌）通过根系向土壤输入碳来调动元素，以及植物从土壤和腐腐岩中吸收养分。在第二阶段，将研究火灾前后这些元素的损失以及对微生物群落和功能的影响。根据i)人工燃烧后土壤中有效养分和压载元素含量以及ii)自然火灾后生态系统恢复的时间序列，我们将得出短期和中期元素损失的结论。根据对N、K、Ca和Si示踪剂的实验，这些损失将被划分为淋溶和侵蚀。火灾对微生物群落和功能的致命影响将通过表层土壤中共生和腐养真菌门和重氮营养生物的丰度，酶活性和PLFA组成来追踪。火灾恢复后的微生物演替将特别着重于耐应力和矿物风化真菌。真菌和细菌的功能作用将通过qPCR分析与高通量测序数据的比较得到支持。将特别关注真菌，因为在岩石表面和根/土壤界面的有氧条件下，真菌特别重要：应力保护真菌细胞(i)与矿物质形成广泛的接触，增强矿物质中的营养物质的化学释放；（ii）加速火灾后土壤的再定植。短期和中期微生物群落的演替将与表层土壤中酶活性、PLFA组成、养分动员和积累的增加有关。从Pan de Azucar到Nahuelbuta的干旱梯度将阐明降水对火灾后营养物质和压载元素的绝对和相对损失以及对生态系统恢复的影响。第一阶段的结果将用于推广稳定状态下的营养循环和风化输入-在稳定的生态系统中，取决于气候。第二阶段的结果将有助于概括极端事件（火灾）对微生物和植被演替过程中恢复生态系统中元素损失及其随后的风化积累的巨大影响。考虑到世界范围内日益增加的干旱化和随之而来的火灾频率，对生态系统中营养物质和压载元素损失的预期预测以及随后的风化具有全球相关性。

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 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 fire. 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.