Abteilung Forstbotanik und Baumphysiologie, Büsgen-Institut, Georg-August Universität Göttingen, Büsgenweg 2, 37077 Göttingen, Germany.
Appl Environ Microbiol. 2010 Mar;76(6):1831-41. doi: 10.1128/AEM.01703-09. Epub 2010 Jan 22.
The relationships between plant carbon resources, soil carbon and nitrogen content, and ectomycorrhizal fungal (EMF) diversity in a monospecific, old-growth beech (Fagus sylvatica) forest were investigated by manipulating carbon flux by girdling. We hypothesized that disruption of the carbon supply would not affect diversity and EMF species numbers if EM fungi can be supplied by plant internal carbohydrate resources or would result in selective disappearance of EMF taxa because of differences in carbon demand of different fungi. Tree carbohydrate status, root demography, EMF colonization, and EMF taxon abundance were measured repeatedly during 1 year after girdling. Girdling did not affect root colonization but decreased EMF species richness of an estimated 79 to 90 taxa to about 40 taxa. Cenococcum geophilum, Lactarius blennius, and Tomentella lapida were dominant, colonizing about 70% of the root tips, and remained unaffected by girdling. Mainly cryptic EMF species disappeared. Therefore, the Shannon-Wiener index (H') decreased but evenness was unaffected. H' was positively correlated with glucose, fructose, and starch concentrations of fine roots and also with the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC/DON), suggesting that both H' and DOC/DON were governed by changes in belowground carbon allocation. Our results suggest that beech maintains numerous rare EMF species by recent photosynthate. These EM fungi may constitute biological insurance for adaptation to changing environmental conditions. The preservation of taxa previously not known to colonize beech may, thus, form an important reservoir for future forest development.
我们通过环割来操纵碳通量，研究了单一种群、老龄山毛榉（Fagus sylvatica）森林中植物碳资源、土壤碳和氮含量以及外生菌根真菌（EMF）多样性之间的关系。我们假设，如果 EM 真菌可以从植物内部碳水化合物资源中获得供应，那么碳供应的中断不会影响多样性和 EMF 物种数量；或者由于不同真菌对碳需求的差异，会导致 EMF 分类群的选择性消失。在环割后 1 年内，我们多次测量了树木碳水化合物状况、根系动态、EMF 定殖和 EMF 分类群丰度。环割没有影响根定殖，但使估计的 79 到 90 个 EMF 种的丰富度减少到约 40 个。 Cenococcum geophilum、Lactarius blennius 和 Tomentella lapida 是优势种，定殖了约 70%的根尖，并且不受环割的影响。主要是隐蔽的 EMF 物种消失了。因此，香农-威纳指数（H'）下降，但均匀度不受影响。H'与细根的葡萄糖、果糖和淀粉浓度呈正相关，也与溶解有机碳与溶解有机氮（DOC/DON）的比值呈正相关，表明 H'和 DOC/DON 都受到地下碳分配变化的控制。我们的结果表明，山毛榉通过最近的光合作用产物维持了许多罕见的 EMF 物种。这些 EM 真菌可能为适应不断变化的环境条件提供生物保险。以前不知道定殖山毛榉的分类群的保存，因此可能成为未来森林发展的重要储备库。
