Group of Soil and Vegetation in the Mediterranean (SOLIPLANT), Plant Physiology Unit, Department of Environmental Sciences, University of Girona, Campus Montilivi, 17003 Girona, Spain.
Group of Soil and Vegetation in the Mediterranean (SOLIPLANT), Plant Physiology Unit, Department of Environmental Sciences, University of Girona, Campus Montilivi, 17003 Girona, Spain.
Sci Total Environ. 2022 Sep 10;838(Pt 1):155743. doi: 10.1016/j.scitotenv.2022.155743. Epub 2022 May 6.
Studies of litter decomposition in salt marshes have been mainly focused on the measurement of decomposition rates, being litter quality, the type of microbial decomposers and their extracellular enzyme activity, rarely considered. Moreover, most of these studies have been conducted in Poaceae and Cyperaceae species, being scarce the literature on Chenopodiaceae species, which are abundant in Mediterranean salt marshes. Here we analyse the litter decomposition process of two Chenopodiaceae (Sarcocornia fruticosa and Halimione portulacoides) and one Poaceae (Elytrigia atherica) species, belonging S. fruticosa to a halophilous scrub habitat and the other two to a salt meadow habitat of a Mediterranean salt marsh. For each species, we analysed litter decomposition rates, litter quality, fungal and bacterial biomass and potential extracellular enzymes activities. In order to embrace the spatial heterogeneity, two zones were considered within each habitat. Litter of E. atherica decomposed 7- and 13-fold slower than those of S. fruticosa and H. portulacoides, respectively, suggesting that this species is the one that would favour most the carbon sequestration into the soil. The different decomposition rates would be explained by the higher initial lignin and cellulose content of E. atherica rather than by the initial carbon and nitrogen content and C/N ratio. Moreover, enzyme efficiency, compared to enzyme activity, better contributes to explain the different decomposition rates observed. Bacteria dominated throughout the litter decomposition process regardless the species, but fungi increased their relevance in the later stages, when the relative lignin litter content increased. Litter decomposition was affected by microhabitat spatial differences, although the responses depended on the species. Hence, flooding (in the habitat of S. fruticosa) or soil texture (in the habitat of E. atherica and H. portulacoides) might have modulated the decomposition process, being H. portulacoides the most sensitive species to the spatial differences of the salt meadow habitat.
盐沼凋落物分解的研究主要集中在分解速率的测量上，而凋落物质量、微生物分解者的类型及其胞外酶活性很少被考虑。此外，这些研究大多集中在禾本科和莎草科物种上，而对于在富含地中海盐沼的藜科物种的相关文献则很少。在这里，我们分析了两种藜科（盐角草和海蓬子）和一种禾本科（节节麦）物种的凋落物分解过程，其中盐角草属于盐生灌丛生境，后两种属于地中海盐沼盐草甸生境。对于每个物种，我们分析了凋落物分解速率、凋落物质量、真菌和细菌生物量以及潜在的胞外酶活性。为了涵盖空间异质性，在每个生境中考虑了两个区域。节节麦的凋落物分解速度比盐角草和海蓬子分别慢 7 倍和 13 倍，这表明该物种最有利于将碳固定在土壤中。不同的分解速率可以通过节节麦较高的初始木质素和纤维素含量来解释，而不是通过初始碳和氮含量以及 C/N 比。此外，与酶活性相比，酶效率更好地解释了观察到的不同分解速率。无论物种如何，细菌在整个凋落物分解过程中都占主导地位，但真菌在相对木质素凋落物含量增加的后期阶段增加了其相关性。凋落物分解受到微生境空间差异的影响，尽管反应取决于物种。因此，淹没（在盐角草生境中）或土壤质地（在节节麦和海蓬子生境中）可能调节了分解过程，而海蓬子对盐草甸生境的空间差异最敏感。
