Soil microbial community successional patterns during forest ecosystem restoration

Abstract

Soil microbial community characterization is increasingly being used to determine the responses of soils to stress and disturbances and to assess ecosystem sustainability. However, there is little experimental evidence to indicate that predictable patterns in microbial community structure or composition occur during secondary succession or ecosystem restoration. This study utilized a chronosequence of developing jarrah (Eucalyptus marginata) forest ecosystems, rehabilitated after bauxite mining (up to 18 years old), to examine changes in soil bacterial and fungal community structures (by automated ribosomal intergenic spacer analysis [ARISA]) and changes in specific soil bacterial phyla by 16S rRNA gene microarray analysis. This study demonstrated that mining in these ecosystems significantly altered soil bacterial and fungal community structures. The hypothesis that the soil microbial community structures would become more similar to those of the surrounding nonmined forest with rehabilitation age was broadly supported by shifts in the bacterial but not the fungal community. Microarray analysis enabled the identification of clear successional trends in the bacterial community at the phylum level and supported the finding of an increase in similarity to nonmined forest soil with rehabilitation age. Changes in soil microbial community structure were significantly related to the size of the microbial biomass as well as numerous edaphic variables (including pH and C, N, and P nutrient concentrations). These findings suggest that soil bacterial community dynamics follow a pattern in developing ecosystems that may be predictable and can be conceptualized as providing an integrated assessment of numerous edaphic variables.

Fig. 1.

Principal coordinate (PCO) analysis of bacterial community structure by ARISA (a) and fungal community structure by ARISA (b) of a jarrah forest rehabilitation chronosequence and nonmined reference soils, and bacterial community structure by microarray analysis of a sample subset (rehabilitation soils from furrows and nonmined S-type forest only) (c). Labels for a and b are as follows: M, mound soils; F, furrow soils; NM, nonmined soils of S and TS forest site vegetation types. Vectors show Pearson correlations with six selected soil characteristics. Abbreviations are as follows: C_tot, total C; N_tot, total N; C_mic, microbial biomass C; P, available (Colwell) P.

Fig. 2.

Changes in mean relative abundance of individual soil bacterial phyla exhibiting a decreasing trend (a), increasing trend (b), or no change or trend (c) with rehabilitation age and of classes of Proteobacteria (d) in a jarrah forest rehabilitation chronosequence, determined by microarray analysis of 16S rRNA genes using the PhyloChip. Data have been normalized to the mean relative abundance of each phylum or class found within nonmined reference soil, represented by the dotted line at y = 1.