Abstract
To reveal the effect of the interactions between soil depth and different land use types on soil nutrients and soil bacterial communities in a karst area, fifty soil samples from five different karst land use types in Huajiang town, Guizhou province, Southwest China were collected, and the soil bacteria were analyzed using high-throughput absolute quantification sequencing. Our results showed that land use types (LUT) and soil depth (SD) significantly influenced the content of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NN), ammonium nitrogen (AN) and available soil phosphorus (AP), and pH; further, the interaction of LUT and SD also significantly influenced SOC, NN, NA, AP, and pH. In addition, LUT clearly impacted the Chao1 and Shannon indexes, but, SD and LUT * SD markedly affect Chao1 and Shannon index, respectively. All the soil bacterial communities were significantly different in the five different five land use types according to PERMANOVA. Importantly, Acidobacteria and Proteobacteria were the predominant phyla at soil depths of 0–20 cm and 20–40 cm among all the LUTs. At 0–20 cm, TN, AN, and SOC exerted a strong positive influence on Acidobacteria, but NN exerted a strong negative influence on Acidobacteria; at 20–40 cm soil, TN and AN exerted a strong positive influence on Acidobacteria; TP exerted no marked influence on any of the phyla at these two soil depths. At 0–20 cm of soil depth, we also found that Chao1 index changes were closely related to the TN, SOC, AN, and NN; similarly, Shannon index changes were significantly correlated to the AN, TN, and SOC; the PCoA was clearly related to the TN, SOC, and AN. Interestingly, at soil depth of 20–40 cm, Chao 1 was markedly related to the TN and pH; Shannon was markedly correlated with the SOC, TP, AN, and AP; and the PCoA was significantly correlated with the TN and pH. Our findings imply that soil nutrients and soil bacteria communities are strongly influenced by land use types and soil depth in karst areas.
Highlights
Karst topography is widely distributed globally and accounts for about 15% of the global land surface [1]
We found that the interaction of land use types (LUT) × soil depth (SD) influenced soil organic carbon (SOC) (p < 0.001, Table 1), NN (p < 0.001, Table 1), ammonium nitrogen (AN) (p < 0.001, Table 1), available soil phosphorus (AP) (p < 0.001, Table 1), and pH (p < 0.001, Table 1)
The NN content at the 0–20 cm depth increased by 1640.0%, 409.4%, and 300.0% compared to 20–40 cm depth under Zanthoxylum planispinum land, Hylocereus spp
Summary
Karst topography is widely distributed globally and accounts for about 15% of the global land surface [1]. The karst topography of Southwest China covers a range of about 540,000 km, making it one of the three largest karst regions on a global scale, the available land area in karst areas is limited [2,3,4]. The land available for cultivation is limited by the sufficient depth of soil distribution between rock outcrops in karst regions. The rational use of land and soil depths in karst areas is critical. Recent reports highlight that land use type, revegetation process, and rocky karst desertification influence the structure and diversity of microbial communities [7,8,9,10]. The coupled influence of land use and soil depth on the composition and structure of soil microbial communities remains unknown
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