Keywords: Soil organic carbon, Soil nitrogen, Illumina sequencing, Soil bacterial diversity, Climatic regions
Soil microbial community in forest ecosystems plays a significant role in carbon and nutrient cycling. Very little is known about the effect of vegetation cover on soil bacterial community composition and diversity across different climatic regions of India. Soil was sampled from the plant cover dominated by seasonal herbs and grasses (PAS), Pinus roxburghii Sarg (PIN), Abies pindrow L. (FIR), Quercus incana Roxb (OKF), Mitragyna parvifolia Roxb (MIK); Acacia nilotica L. and Salvadora spp. (MIA) in three different climatic regions (humid, moist sub-humid and semi-arid) of India. The soil physical, chemical and biological properties such as sand (SAN), silt (SIL), clay (CLY), bulk density (SBD), wilting point (SWP), field capacity (SFC), saturated hydraulic conductivity (SHC), pH (SpH), organic carbon (SOC), nitrogen (SN), C:N ratio, available phosphorous (SAP) and total microbial activity (SMA) were determined. Illumina sequencing of specific 16S rRNA gene was applied to identify bacterial community composition in the soils under different vegetation cover. Results showed that the soil properties varied under different vegetation cover across the different climatic regions. SOC, SN, SMA were highest in the moist sub-humid region sites (PAS, PIN) followed by humid region (OKF, FIR) and semi-arid region (MIK, MIA) sites. However, the Chao 1 (species richness), Shannon and Simpson index (diversity) were highest in OKF, followed by MIK, FIR, MIA, PIN and PAS. The predominant bacterial phyla and genera in the soils under different vegetation cover were Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Planctomycetes, Verrucomicrobia, Thermotogae and Geobacter, Methylocapsa, Sphingomonas, Pseudomonas, Erysipelotrichaceae_incertae_sedis, Sporotomaculum, Amorphus, Helicobacter, Paenibacillus, Bauldia, Skermanella, Methylosinus, Singulisphaera, Marinobacter and Lamprocystis. We also found the exclusive OTUs abundance of some bacterial phyla and genera in the soils, which were not correlated with any one of the studied soil variables. In our analysis, we found only the Firmicutes, Verrucomicrobia and Bacteroidetes are linearly correlated (P < 0.05) with CLY, SWP and SpH. Likewise, bacterial genera Methylocapsa, Methylosinus and Amorphus were linearly correlated (P < 0.05) with SIL, SpH, C:N ratio and SAP. Our results suggested that the type of vegetation cover has a significant impact on changes in soil properties, controlling the soil bacterial community composition and diversity across different climatic regions of India. The soil bacterial community composition and diversity may serve as a potential ecological indicator with respect to land use and land cover change on biogeochemical cycling processes across different climatic regions of India.
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This work was financially supported by DST (DST-IS-STAC/CO2-SR-148/12(G), UGC-DSK-PDF (BSR/BL/16-17/0146) New Delhi and University of Delhi under strengthening R&D programs of Faculty at University of Delhi. Authors are thankful to Dr. R.K. Maikhuri, for his support during the selection of the study site in central Himalaya. Also authors are thankful to the forest department’s officials in Rajouri (J&K) and Bharatpur (Rajasthan) during the collection of soil samples. We thankful to Prof. Manu Agarwal for his help in illumina sequencing and bioinformatics analysis.