Impact of Simulated Drought Stress on Soil Microbiology, and Nematofauna in a Native Shrub + Millet Intercropping System in Senegal

Drought stress strongly affects soil biota and impairs crop production, which under climate change will be exacerbated in semi-arid cropping regions such as the Sahel. Hence soil management systems are needed that can buffer against drought. In West Africa, field studies have found intercropping of millet with the native shrub Piliostigma reticulatum improves soil-plant-water relations, microbial activity and diversity, and suppress parasitic nematodes, which can significantly increase crop yield. However, little information is available on its beneficial or negative effects on soils or crops during water stress. Therefore, the objective was to investigate the impact of P. reticulatum in moderating water stress effects on soil properties and pearl millet (Pennisetum glaucum [L.] R. Br.) productivity. In the greenhouse, soil chemical and microbial properties and millet growth were investigated with a factorial experiment of varying levels of soil moisture (favorable, moderately stressed, or severely stressed water conditions) that was imposed for 55 days on soils containing sole P. reticulatum or millet, or millet + P. reticulatum. The results showed that the presence of P. reticulatum did not buffer soils against water stress in relation to soil chemical and microbial properties measured at the end of the experiment. Severe water stress did significantly decrease the height, number of leaves, and aboveground biomass of millet plants. Additionally, respiration, nematofauna trophic structure and abundance decreased as water stress increased. Lastly, bacterial feeders and plant parasitic nematodes were the most sensitive to severe water stress while fungal feeding nematodes remained unaffected. The results suggested that the intensity of water stress had more negative effects on soil basal respiration rather than soil microbial biomass.

Invasibility and recoverability of a plant community following invasion depend on its successional stages

Exotic species invasion represent important causes of harming the structure,function,and ecological environment in ecosystems.Yet,knowledge remains limited on the invasibility(invasion advantage of exotic species)and recoverability(recovery ability of native species)of a plant community following invasion depend on its successional stages.We selected three grasses of Setaria viridis,Artemisia gmelinii,and Bothriochloa ischemum representing early(E),middle(M),and late(L)successional species,respectively.Meanwhile,the grasses of Panicum virgatum was selected to represent exotic species(invasion species).Three types of soil were collected to treat the three E,M,and L successional species,and one type of soil was collected to treat the exotic species.We compared the performance of the three native plant species and one exotic species grown in their“own”and“other”soils in a 2-year greenhouse experiment.Our study showed that exotic species performed better in soils of E and M successional species than in the soil of L successional species.After exotic species removed,E and M successional species exhibited poor growth in the soil of exotic species,while that of L successional species performed poor in field exotic species soils,but performed better in soils disturbed by exotic species.Our study demonstrated that the invasibility and recoverability of native plant communities changed with vegetation succession.