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

火是最重要的地貌因素之一--这是一种极端事件，导致元素形态的巨大变化，并在很短的时间内导致生态系统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发生的火灾导致微生物动员的所有元素和腐泥岩中的植被发生了戏剧性的重新分配。在第一阶段-微生物(主要是真菌)中，研究了根对元素的动员，碳输入到土壤中，以及植物从土壤和腐殖质中吸收养分。在第二阶段，将同时调查这些元素在火灾中和火灾后的损失以及对微生物群落和功能的影响。根据土壤中有效养分和压载元素的含量(1)人工焚烧后和(2)自然火灾后生态系统恢复的时间序列，我们将得出元素在短期和中期内的损失。根据N、K、Ca和Si示踪剂的实验，这些损失将被分配给淋溶和侵蚀。火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生真菌门和重氮化菌的丰富程度、酶活性和PLFA组成来追踪。火灾后恢复过程中的微生物演替研究将重点放在耐压和矿物风化真菌上。通过qPCR分析与高通量测序数据的比较，将支持真菌和细菌的功能作用。将特别关注真菌，因为在岩石表面和根/土壤界面上的好氧条件下，真菌特别重要：(I)受压力保护的真菌细胞(I)与矿物形成广泛接触，并加强矿物中营养物质的化学释放，(Ii)加速火灾后土壤的再繁殖。微生物群落在短期和中期的演替将与表层土壤酶活性、PLFA组成、养分活化和积累的增加有关。从Pande 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。第一阶段的结果将被用来概括稳态下的养分循环和风化输入--在依赖于气候的稳定生态系统中。第二阶段的结果将使人们能够概括极端事件--火灾--在微生物和植被演替期间恢复生态系统中元素的损失及其随后因风化而积累的戏剧性影响。考虑到世界范围内日益多样化以及由此导致的火灾频率，对生态系统养分和压载元素损失以及随后的风化的预期预测具有全球相关性。

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.