Gourmelon Véronique, Maggia Laurent, Powell Jeff R, Gigante Sarah, Hortal Sara, Gueunier Claire, Letellier Kelly, Carriconde Fabian
Institut Agronomique néo-Calédonien (IAC), Axe 2 "Diversités biologique et fonctionnelle des écosystèmes terrestres", Nouméa, New Caledonia.
CIRAD, UMR AGAP, Nouméa, New Caledonia.
PLoS One. 2016 Dec 1;11(12):e0167405. doi: 10.1371/journal.pone.0167405. eCollection 2016.
Soil microorganisms play key roles in ecosystem functioning and are known to be influenced by biotic and abiotic factors, such as plant cover or edaphic parameters. New Caledonia, a biodiversity hotspot located in the southwest Pacific, is one-third covered by ultramafic substrates. These types of soils are notably characterised by low nutrient content and high heavy metal concentrations. Ultramafic outcrops harbour diverse vegetation types and remarkable plant diversity. In this study, we aimed to assess soil bacterial and fungal diversity in New Caledonian ultramafic substrates and to determine whether floristic composition, edaphic parameters and geographical factors affect this microbial diversity. Therefore, four plant formation types at two distinct sites were studied. These formations represent different stages in a potential chronosequence. Soil cores, according to a given sampling procedure, were collected to assess microbial diversity using a metagenomic approach, and to characterise the physico-chemical parameters. A botanical inventory was also performed. Our results indicated that microbial richness, composition and abundance were linked to the plant cover type and the dominant plant species. Furthermore, a large proportion of Ascomycota phylum (fungi), mostly in non-rainforest formations, and Planctomycetes phylum (bacteria) in all formations were observed. Interestingly, such patterns could be indicators of past disturbances that occurred on different time scales. Furthermore, the bacteria and fungi were influenced by diverse edaphic parameters as well as by the interplay between these two soil communities. Another striking finding was the existence of a site effect. Differences in microbial communities between geographical locations may be explained by dispersal limitation in the context of the biogeographical island theory. In conclusion, each plant formation at each site possesses is own microbial community resulting from multiple interactions between abiotic and biotic factors.
土壤微生物在生态系统功能中发挥着关键作用，并且已知会受到生物和非生物因素的影响，例如植物覆盖或土壤参数。新喀里多尼亚是位于西南太平洋的生物多样性热点地区，三分之一的土地被超镁铁质基质覆盖。这类土壤的显著特征是养分含量低和重金属浓度高。超镁铁质露头拥有多样的植被类型和显著的植物多样性。在本研究中，我们旨在评估新喀里多尼亚超镁铁质基质中的土壤细菌和真菌多样性，并确定植物区系组成、土壤参数和地理因素是否会影响这种微生物多样性。因此，我们研究了两个不同地点的四种植物形成类型。这些形成类型代表了一个潜在时间序列中的不同阶段。按照给定的采样程序采集土壤核心样本，使用宏基因组方法评估微生物多样性，并对理化参数进行表征。还进行了植物清查。我们的结果表明，微生物的丰富度、组成和丰度与植物覆盖类型和优势植物物种有关。此外，观察到在非雨林形成类型中大部分为子囊菌门（真菌），而在所有形成类型中都有浮霉菌门（细菌）。有趣的是，这种模式可能是过去在不同时间尺度上发生的干扰的指标。此外，细菌和真菌受到多种土壤参数以及这两个土壤群落之间相互作用的影响。另一个显著发现是存在地点效应。地理位置之间微生物群落的差异可能在生物地理岛屿理论的背景下通过扩散限制来解释。总之，每个地点的每种植物形成类型都拥有由非生物和生物因素之间的多重相互作用产生的自身微生物群落。
