Labile carbon in biological soil crusts in the Tabernas desert, SE Spain
Labile carbon in biological soil crusts in the Tabernas desert, SE Spain
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DOI：
10.1016/j.soilbio.2012.11.010
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发表时间：
2013-03-01
影响因子：
9.7
通讯作者：
Gil-Sotres, Fernando
中科院分区：
文献类型：
--
作者：
Miralles, Isabel;Trasar-Cepeda, Carmen;Gil-Sotres, Fernando
在生物土壤结皮中，分解过程是极其重要的。虽然温度和水分对这些过程的影响已经被广泛研究，但关于易代谢底物(不稳定C)的影响以及这种底物在不同类型的BSCs中的变化还知之甚少。在本研究中，蓝藻(氰藻)和地衣(双壳和LEPRA)形成的BSCs在25℃(最适温度)和不同的水分水平下孵育，以评估结皮层中活性C的库。不稳定碳是指孵化期结束时排放的二氧化碳碳和用热水(80摄氏度)提取的碳的总和。在所有结皮中，排放与水分的关系符合二次模型。对于不同的水分含量，每种结皮类型的CO2-C排放和热水提取的C的总和收敛到一个恒定值。这一数值被认为是地壳中活性碳的最大含量，在双线生物中非常高，高达最初存在的总有机碳(TOC)的40%。在所有的结皮中，与不稳定C的消耗无关，单糖(蔗糖、葡萄糖)在孵化期结束时仍然存在，这表明这些糖可能对BSCs起到保护作用。甘露醇的存在表明，蔗糖在水解过程中释放的果糖被还原为甘露醇，从而在强烈的呼吸应激时刻能够进行电子传递。双胞体强烈的呼吸作用部分是由于多酚的代谢，多酚可能来自于结壳孵化过程中繁殖的自由生活真菌的生长和死亡。这些结果表明，形成结壳的生物类型不同，生物干细胞中的代谢过程也不同，强降雨事件后，结壳生物干细胞有很高的碳损失风险。(C)2012爱思唯尔有限公司。保留所有权利。
Decomposition processes are extremely important in biological soil crusts (BSCs). Although the effects of temperature and moisture on such processes have been widely studied, little is known about the influence of the readily metabolizable substrate (labile C) and how this substrate varies in different types of BSCs. In the present study, BSCs formed by cyanobacteria (CYANO) and by lichens (DIPLOS and LEPRA) were incubated at 25 degrees C (optimum temperature) and different moisture levels, for evaluation of the pool of labile C in the crust layers. Labile C was estimated as the sum of CO2-C emitted and the C extracted with hot water (80 degrees C) at the end of the incubation period. In all crusts, the relationship between emission and moisture fitted a quadratic model. For the different moisture contents, the sum of CO2-C emitted and C extracted with hot water converged to a constant value for each type of crust. This value, considered as the maximum content of labile C in the crust, was extremely high in DIPLOS, reaching up to 40% of the total organic C (TOC) initially present. In all crusts, and independently of the consumption of labile C, simple sugars (sucrose, glucose) remained at the end of the incubation period, which suggests that these sugars may play a protective role in BSCs. The presence of mannitol suggests that the fructose released during hydrolysis of sucrose was reduced to mannitol, thus enabling electron transport during moments of intense respiratory stress. The intense respiration in DIPLOS is partly due to the metabolism of polyphenols, which are possibly derived from the growth and death of free-living fungi that proliferate during incubation of the crusts. These results demonstrate that the metabolic processes in BSCs differ depending on the type of organisms that form the crusts and that there is a high risk of C loss from Diploschistes BSCs after heavy rainfall events. (C) 2012 Elsevier Ltd. All rights reserved.