Diversity pattern of nitrogen fixing microbes in nodules of <i>Trifolium arvense</i> (L.) at different initial stages of ecosystem development

Abstract

Abstract. Legumes can be considered as pioneer plants during ecosystem development, as they form a symbiosis with different nitrogen fixing rhizobia species, which enable the plants to grow on soils with low available nitrogen content. In this study we compared the abundance and diversity of nitrogen fixing microbes based on the functional marker gene nifH, which codes for a subunit of the Fe-protein of the dinitrogenase reductase, in nodules of different size classes of Trifolium arvense (L.). Additionally, carbon and nitrogen contents of the bulk soil and plant material were measured. Plants were harvested from different sites, reflecting 2 (2a) and 5 (5a) yr of ecosystem development, of an opencast lignite mining area in the south of Cottbus, Lower Lusatia (Germany) where the artificial catchment "Chicken Creek" was constructed to study the development of terrestrial ecosystems. Plants from the 5a site revealed higher amounts of carbon and nitrogen, although nifH gene abundances in the nodules and carbon and nitrogen contents between the two soils did not differ significantly. Analysis of the nifH clone libraries showed a significant effect of the nodule size on the community composition of nitrogen fixing microbes. Medium sized nodules (2–5 mm) contained a uniform community composed of Rhizobium leguminosarum bv. trifolii, whereas the small nodules (<2 mm) consisted of a diverse community including clones with non-Rhizobium nifH gene sequences. Regarding the impact of the soil age on the community composition a clear distinction between the small and the medium nodules can be made. While clone libraries from the medium nodules were pretty similar at both soil ages, soil age had a significant effect on the community compositions of the small nodules, where the proportion of R. leguminosarum bv. trifolii increased with soil age.

Linkage between root systems of three pioneer plant species and soil nitrogen during early reclamation of a mine site in Lusatia, Germany

“…Thus, the Rhizobia population is hypothesized to be greatly reduced at the beginning of ecosystem development. It appears to be developing rapidly as Schulz et al (2013) found Trifolium arvense L. (rabbit foot clover) growing on 2-year-old substrate from this site hosted several Rhizobia species.…”

Editorial "Ecosystems in transition: interactions and feedbacks with an emphasis on the initial development"

“…Schulz et al (2013a) provide a general review on the role of microorganisms for initial soil development emphasizing the importance of well-established biotic-abiotic interactions for ecosystem functioning. Two other papers by Schulz et al (2013b) and Esperschütz et al (2013) present findings with regard to N-fixation and litter decomposition in early state ecosystems. Risse-Buhl et al (2013) show the importance of "old" inherited organic carbon for young ecosystems as a nutrient source for microorganisms.…”

Landscape Development From Point Zero

“…High colonization rates of specific ectomycorrhizal communities were found in red oak stands (Gebhardt et al 2007). The importance of N fixing bacteria for plant nutrition was investigated and the results indicate that the effectiveness of leguminous plants for nitrogen fixation may differ from site to site possibly due to changes in the rhizobium symbiosis (Schulz et al 2013).…”