In humid areas, biocrusts cover topsoils of inland dunes and influence soil characteristics, which, in turn, may affect the hydrophobicity of soils. The hydrophobicity of topsoils typically increases with increasing organic matter content. In addition, the soil organic matter quality, for example, described by the ratio of its hydrophilic and hydrophobic functional groups, also influences hydrophobicity. Because biocrust development goes along with an increase in the organic matter content and a shift in microbial community composition, the chemical character of soil organic matter likely changes over time, which, in turn, affects the hydrophobicity of the crusts. We hypothesize that the hydrophobicity of biocrusts increases during succession because of increasing amounts and aliphatic character of organic matter. We compared organic matter contents and Fourier‐transform infrared spectra of cyanobacterial biocrusts and moss‐dominated biocrusts at two European inland dunes. The organic carbon content as well as the hydrophobicity increased during crust development at both sites. Older moss‐dominated biocrusts showed the highest hydrophobicity and the highest organic carbon content. Moreover, at one study site, the hydrophobicity of the biocrusts did increase with decreasing ratio between hydrophilic and hydrophobic (i.e., aliphatic) moieties of soil organic matter. At the second study site, this effect was only visible for the moss‐dominated biocrust. We conclude that biocrust development and organic matter accumulation go ahead with changes in the organic matter composition and induce increased hydrophobicity with a strong impact on water redistribution in inland dune ecosystems. This knowledge will help to improve nature protection strategies in rare ecosystems.

中文翻译：

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土壤有机质含量及其脂族特性决定了生物壳在不同演替阶段的疏水性

在潮湿的地区，生物结皮覆盖内陆沙丘的表层土壤并影响土壤特性，进而可能影响土壤的疏水性。表土的疏水性通常随着有机物含量的增加而增加。此外，土壤有机质的质量（例如，通过其亲水性官能团和疏水性官能团的比例来描述）也影响疏水性。由于生物地壳的发展伴随着有机质含量的增加和微生物群落组成的变化，土壤有机质的化学特性可能会随时间而变化，进而影响地壳的疏水性。我们假设生物结皮的疏水性在演替过程中会增加，因为有机物的数量和脂族特性增加。我们比较了两个欧洲内陆沙丘上的蓝细菌生物结皮和以苔藓为主的生物结皮的有机物含量和傅里叶变换红外光谱。在两个部位的结壳形成过程中，有机碳含量以及疏水性均增加。较老的以苔藓为主的生物结皮具有最高的疏水性和最高的有机碳含量。此外，在一个研究地点，生物结皮的疏水性确实随着土壤有机质的亲水性和疏水性（即脂肪族）部分之间的比率降低而增加。在第二个研究地点，这种影响仅在以苔藓为主的生物外壳中可见。我们得出的结论是，生物结壳的发展和有机物积累随着有机物组成的变化而继续进行，并导致疏水性增加，这对内陆沙丘生态系统中的水再分配具有强烈影响。这些知识将有助于改善稀有生态系统中的自然保护策略。