Abundance and composition of free and aggregate-occluded carbohydrates and lignin in two forest soils as affected by wildfires of different severity
Abundance and composition of free and aggregate-occluded carbohydrates and lignin in two forest soils as affected by wildfires of different severity
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DOI：
10.1016/j.geoderma.2015.01.006
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发表时间：
2015-05
期刊：
影响因子：
6.1
通讯作者：
G. Mastrolonardo;C. Rumpel;C. Forte;S. Doerr;G. Certini
中科院分区：
文献类型：
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作者：
G. Mastrolonardo;C. Rumpel;C. Forte;S. Doerr;G. Certini
有机质是受野火影响最大的土壤成分，无论是在丰度还是成分方面。火引起的土壤有机质变化取决于加热强度和持续时间、氧气供应以及与地形、气候、土壤和植被特征相关的其他因素。特别是受火灾的影响是凋落物层，但从最上层的矿质土壤的有机质也可以经历一些重大的变化。在这项研究中，我们调查了火灾对分子SOM参数的直接影响，在两个森林，最近经历了不同严重程度的野火从顶部2.5厘米的矿物质土壤中分离的密度组分。其中一个位于意大利中部的托斯卡纳，是一个绒毛橡树和海洋松的混合林，在桑迪湖相沉积物上形成的Acrisol上发育，受到中度严重火灾的影响。另一个位于澳大利亚东南部的维多利亚，是一个混合物种的桉树林，在泥盆纪桑迪沉积物上形成的形成层上发育，受到极其严重的火灾（臭名昭著的“黑色星期六”火灾）的影响。本研究的目的是评估火灾引起的变化的数量和组成的散装SOM和SOM与土壤组分具有不同的密度。我们使用1.8 Mg m− 3作为密度截止值，并区分自由和聚集体封闭的SOM。特别是，分析集中在丰度和组成的两个主要的SOM组件，提出作为火灾严重程度的分子指标：非纤维素中性糖，消化三氟乙酸（TFA），和木质素衍生的酚类单体，释放氧化铜（CuO）氧化。散装SOM和SOM馏分的化学结构进行了分析，通过固态13 C核磁共振spectroscopy.In对比的中度严重的火灾影响意大利网站，在澳大利亚网站的极其严重的火灾造成的SOM从顶部矿物土壤的大量损失。这两次火灾对有机质组成有重大影响。尽管它们经历了明显的影响，但无论是可水解糖还是木质素酚都不能成为火灾严重程度的可靠指标。此外，这两次火灾显然打破了土壤团聚体，从而促进了一些封闭的有机物质的释放。观测到的森林火灾引起的有机质变化对碳循环有影响，因此突出了野火发生和严重程度在气候变化中的关键作用。
Organic matter is the soil component most affected by wildfires, both in terms of abundance and composition. Fire-induced alteration of soil organic matter (SOM) depends on heating intensity and duration, oxygen availability and other factors related to topography, climate, soil and vegetation features. Particularly affected by fire is the litter layer, but SOM from the uppermost mineral soil can also experience some major changes. In this study, we investigated the direct impact of fire on molecular SOM parameters in density fractions isolated from the top 2.5 cm of mineral soil in two forests that recently experienced wildfires of different severity. One, located in Tuscany, Central Italy, is a mixed forest of Downy oak and Maritime pine, developed on Acrisols formed on sandy lacustrine deposits, affected by a moderately severe fire. The other, located in Victoria, South-East Australia, is a mixed-species eucalypt forest, developed on a Cambisol formed on sandy Devonian sediments, affected by an extremely severe fire (the infamous ‘Black Saturday’ fire). The purpose of this study was the assessment of fire-induced changes on amount and composition of the bulk SOM and SOM associated to soil fractions having different densities. We used 1.8 Mg m− 3as density cut-off and distinguished between free and aggregate-occluded SOM. In particular, the analyses focused on abundance and composition of two major SOM components, proposed as molecular indicators of fire severity: the non-cellulosic neutral sugars, digested by trifluoroacetic acid (TFA), and the lignin-derived phenolic monomers, released by cupric oxide (CuO) oxidation. The chemical structure of both bulk SOM and SOM fractions were analysed by solid-state13C nuclear magnetic resonance spectroscopy.In contrast to the moderately severe fire affecting the Italian site, the extremely severe fire at the Australian site caused substantial loss of SOM from the top mineral soil. Both fires had major effects on SOM composition. In spite of the evident impact they experienced, neither hydrolysable sugars nor lignin phenols resulted to be reliable indicators of fire severity. Moreover, both fires apparently broke up soil aggregates, hence promoting the release of some occluded organic matter. The fire-induced changes of SOM observed have implications for the C cycle, so highlighting the critical role of wildfire occurrence and severity in climate change.