Salinization causes abrupt reduction in soil nematode abundance in the Caatinga area of the Submedio San Francisco Valley, Brazilian semiarid region

Abstract

Soil salinization is a global problem, mainly affecting arid and semi-arid regions, which are susceptible to salinity due to high evaporation and low rainfall. Salinization in soils causes negative effects on edaphic organisms and, consequently, on plants. Understanding the effects of salinization in soils is important for future intervention in these salinized areas in order to make them productive again. Although there are many tools for soil quality assessment, the quantification of soil nematodes has been highlighted because of the high sensitivity of these organisms to soil conditions. The present study evaluated the nematofauna in a salinized Caatinga area in the Brazilian semiarid region. This area is located next to a stream that flooded the area in 2004, did not recover from the flood, and has been suggested as a desertification area. Sample collection for this study was carried out in the salinized Caatinga and the adjacent natural Caatinga (control) during two seasons (dry and rainy). In each area and period, 20 samples were collected and nematodes were extracted and quantified according to their trophic group. The abundance of bacterivorous, fungivorous, omnivores, and phytonematoids was much lower in the salinized Caatinga (on average 1/100 mL of soil) compared to control area (on average 25/100 mL of soil) soil. The electrical conductivity reached 106.20 dS/m in the salinized Caatinga during the rainy season. Our results show that salinization negatively affects the nematodes of the Caatinga soil in the Brazilian semiarid region, highlighting the damage of salinity to soil nematodes, since the abundance was greatly reduced in the salinized Caatinga within all trophic groups, compromising the functionality of the ecosystem.