Soil bacterial community composition and diversity respond to cultivation in Karst ecosystems

Abstract

Soil microorganisms play vital roles in recovering and maintaining the health of ecosystems, particularly in fragile Karst ecosystems that are easily degraded after cultivation. We investigated the composition and diversity of soil bacterial communities, based on RFLP and 16S rDNA sequencing, in a cropland, a naturally revegetated land with former cultivation disturbance and a primeval forest in the subtropical Karst of southwest China. Our results illustrated that Proteobacteria accounted for 44.8% of the 600 tested clones, making it the most dominant phylum observed. This phylum was followed by Acidobacteria and Planctomycetes for the three Karst soils analyzed. Compared with the primeval forest soil, the proportions of Proteobacteria were decreased by 30.2 and 37.9%, while Acidobacteria increased by 93.9 and 87.9%, and the Shannon-Wiener diversity indices and the physicochemical parameters declined in the cropland and the revegetated land, respectively. Among the three soils, the proportion of dominant bacterial phyla and the diversity indices in the revegetated land were similar to the cropland, implying the bacterial community in the cropland was relatively stable, and the after-effects of cultivation were difficult to eliminate. However, similar distributions of the four Proteobacteria subphyla were observed between the revegetated land and the primeval forest soil. Furthermore, the proportion of Rhizobiales belonging to α-Proteobacteria was sharply decreased with cultivation compared to the primeval forest soil, while a small cluster of Rhizobiales recurred with vegetation recovery. These results indicated that although the subphyla of the dominant bacterial phylum had some positive responses to 20 years of vegetation recovery, it is a slow process. Our results suggest that priority should be given to conserve the primeval forest and inoculation of functional microorganisms on the basis of vegetation recovery may be more effective for the restoration of Karst ecosystems after cultivation.

Effect of vegetation types on soil arbuscular mycorrhizal fungi and nitrogen-fixing bacterial communities in a karst region

“…A previous study by our team indicates that soil fertility improves from naturally revegetated land to primary forests in the karst region of southwest China (Chen et al 2012). Strong interaction exist between plant diversity and bacterial and fungal diversity during restoration of karst vegetation (He et al 2008).…”

“…Microbial DNA was extracted, in triplicate, from 500 mg of freeze-dried soil using the sodium dodecyl sulfate-guanidine isothiocyanate-polyethylene glycol (SDS-GITC-PEG) method described by Chen et al (2012). The DNA extracted was dissolved in 50 μL water, quantified by spectrophotometry, and stored at −20°C until further use.…”

Slow restoration of soil microbial functions in an Acacia plantation established on degraded land in Thailand

“…Based on the ribosomal DNA sequences, the closest matching relatives were chosen from other soils ( Table 3). The closest relative to the bacterium represented by the DGGE band as an indicator of the rehabilitation/conservation was an unidentified bacterium from a Ferralsol in Madagascar, and the second closest was an uncultured bacterium from the soil of a plot of 20-yearold grassland, which is part of a restoration ecosystem from a crop rotation agricultural land in subtropical China (Chen et al 2012). The land degradation was described by the relatively high occurrence of the bacteria close to those found in disturbed soils under a coniferous monoculture in Taiwan (Lin et al 2011), a Korean ginseng field (Baek et al 2011), a pasture land (Jangid et al 2008), pyreneexposed soil, or volcanic deposits.…”

Culture dependent diversity and phylogeny of thermophilic bacilli from a natural hot spring reservoir in the Gir Forest, Gujarat (India)

“…A low value of the Shannon index indicates uneven species distribution in a particular habitat. Reportedly, the Shannon index was used to explain the microbial diversity of the Arabian Sea (Kapley et al, 2007) and the Southern West of the China (Chen et al, 2012). More recently, Yousuf et al (2012) used the Simpson and the Shannon indices, together with Chao and ACE richness estimators to explore microbial diversity and richness.…”