IMPACT OF AGRICULTURAL PRACTICES ON BIODIVERSITY OF SOIL INVERTEBRATES, ASSESSMENT THROUGH DNA METABARCODING APPROACH

Abstract

In spite of the increase of the organically farmed areas worldwide, it has been always doubted if the organic farming really enhances the soil biodiversity, as the main component in the agroecosystems. This doubt was a target of many studies, trying to reveal the true impact of the applied agricultural practices in the adopted farming strategies, targeting the soil invertebrates as bioindicators of the impact. Unfortunately, the doubt is still, due to the limitations in the sampling and taxonomy of the soil’s invertebrates communities. In the last years, the molecular approaches represent promising methods to overcome these limitations. Thus, the DNA metabarcoding was applied targeting the COI gene in the DNA extracted from soil samples collected in different farming strategies (organic vs non organic), with a different cropping systems (stable meadow vs barley) and different levels in the field from the margin to center, this sampling was performed in three seasons (May, July and October). In addition, the soil properties (pH, texture, N%, C% and C/N ratio) were determined for the selected samples. The illumine MiSeq run was performed and the obtained reads were processed bioinformatically to get the OTU table (Operational Taxonomic Unite). This OTU table was used for the statistical and ecological analysis. Finally, the QBS, a soil quality index depends on the soil inhibiting microarthropods, was calculated by its classic method and estimated based on the obtained molecular data, to check the correlation between the resulted values. Results showed that the DNA metabarcoding approach represents a promising method for the assessment of soil biodiversity in the agroecosystem, but this approach is not able to detect the seasonal changes of the soil invertebrates’ communities. Regarding the farming strategies, the farming management as organic or non organic (conventional) did not affect significantly the community structure of soil invertebrates and the biodiversity indices Shannon and Pielou’s evenness, while the species richness was significantly lower in the conventional farm. Soil invertebrates’ communities were significantly affected by the crop and the position of the field (as margin or field), and the C/N ratio. For Rotifera and Tardigrada communities’ structure were affected by the farming strategy, while insects’ communities were affected by the pH of the soil. The role of the margin of the field as a reservoir is increased in the cultivated fields (barley), while in the stable meadows the interactions between the margin and the center of the field are lower. Finally, the soil biological quality is decreased from the margin to the center of the field (of the same field), also decreased in the barley field comparing to the stable meadows. The obtained molecular index mQBS that is developed based on the QBS-ar is a promising approach for the soil biological quality estimation.