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首页> 外文期刊>Soil Biology & Biochemistry >Labile carbon in biological soil crusts in the Tabernas desert, SE Spain.
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Labile carbon in biological soil crusts in the Tabernas desert, SE Spain.

机译：生物土壤中的不稳定碳在塔贝纳斯沙漠，SE西班牙中结皮。

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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.
机译：分解过程在生物土壤结皮（BSC）中极为重要。尽管温度和湿度对此类过程的影响已得到广泛研究，但对易代谢底物（不稳定的C）的影响以及该底物在不同类型的BSC中的变化知之甚少。在本研究中，将由蓝细菌（CYANO）和地衣（DIPLOS和LEPRA）形成的BSC在25摄氏度（最适温度）和不同湿度下孵育，以评估地壳层中不稳定C的库。在培养期结束时，不稳定的C被估计为排放的CO 2 -C和用热水（80摄氏度）提取的C的总和。在所有地壳中，排放与水分之间的关​​系符合二次模型。对于不同的水分含量，每种结壳的排放出的CO 2 -C和热水提取的C的总和收敛为恒定值。该值被认为是地壳中不稳定的C的最大含量，在DIPLOS中极高，达到最初存在的总有机C（TOC）的40％。在所有地壳中，且与不稳定C的消耗无关，在孵育期结束时仍保留了简单的糖（蔗糖，葡萄糖），这表明这些糖可能在BSC中起保护作用。甘露醇的存在表明，在蔗糖水解过程中释放的果糖被还原为甘露醇，从而能够在强烈的呼吸压力时刻进行电子转运。 DIPLOS中的强烈呼吸部分归因于多酚的代谢，多酚的代谢可能源于在结壳孵化过程中繁殖的自由活动真菌的生长和死亡。这些结果表明，BSCs的代谢过程因形成结壳的生物类型而异，并且在暴雨事件发生后，Diploschistes BSCs有很高的C损失风险。

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