Functional diversity of culturable bacterial communities in the rhizosphere in relation to fine-root and soil parameters in alder stands on forest, abandoned agricultural, and oil-shale mining areas.

摘要

Grey alder (Alnus incana) and black alder (Alnus glutinosa) stands on forest land, abandoned agricultural, and reclaimed oil-shale mining areas were investigated with the aim of analysing the functional diversity and activity of microbial communities in the soil-root interface and in the bulk soil in relation to fine-root parameters, alder species, and soil type. Biolog Ecoplates were used to determine community-level physiological profiles (CLPP) of culturable bacteria in soil-root interface and bulk soil samples. CLPP were summarized as AWCD (average well colour development, OD 48 h-1) and by Shannon diversity index, which varied between 4.3 and 4.6 for soil-root interface. The soil-root interface/bulk soil ratio of AWCD was estimated. Substrate-induced respiration (SIR) and basal respiration (BAS) of bulk soil samples were measured and metabolic quotient (Q=BAS/SIR) was calculated. SIR and Q varied from 0.24 to 2.89 mg C g-1 and from 0.12 to 0.51, respectively. Short-root morphological studies were carried out by WinRHIZOTM Pro 2003b; mean specific root area (SRA) varied for grey alder and black alder from 69 to 103 and from 54 to 155 m2 kg-1, respectively. The greatest differences between AWCD values of culturable bacterial communities in soil-root interface and bulk soil were found for the young alder stands on oil-shale mining spoil and on abandoned agricultural land. Soil-root interface/bulk soil AWCD ratio, ratio for Shannon diversity indices, and SRA were positively correlated. Foliar assimilation efficiency (FOE) was negatively correlated with soil-root interface/bulk soil AWCD ratio. The impact of soil and alder species on short-root morphology was significant; short-root tip volume and mass were greater for black alder than grey alder. For the investigated microbiological characteristics, no alder-species-related differences were revealed..