Abstract
Piliostigma reticulatum is a native woody shrub found in cropped fields in the Sahel and has been shown to increase crop productivity and soil quality. Frequently occurring drying and rewetting cycles (DRW) may alter the soil quality beneath these shrubs. We investigated the effect of DRW cycles on microbial community in soil beneath and outside the P. reticulatum canopy and the roles of this shrub in the adaptation of the microbial community to abiotic stress. Soils were incubated in a climate controlled chamber for 45 days, after exposure to 10 consecutive days of DRW cycles at 75% of water holding capacity (WHC). Basal respiration, β-glucosidase activity, microbial biomass carbon (MBC), and available nitrogen ( ; ) were measured at 2, 30, and 45 days after soil exposed to the DRW cycles. MBC increased significantly two days after the DRW cycles and was greater for soil beneath the shrub canopy compared with soil outside the shrub canopy. PCA analysis based on basal respiration, microbial biomass carbon, available nitrogen, and β-Glucosidase activity resulted in a tight clustering in the beneath shrub soil samples. Soils incubated for more than 30 days after DRW cycles had higher available nitrogen content than soils incubated for less than 30 days. Soil from beneath the shrub canopy significantly improved soil resilience based on β-glucosidase activity. Soil from beneath the shrub canopy also had higher nutrient levels and greater microbial activity even when subjected to DRW cycles, potentially improving the ability of crops to withstand in-season drought when they are adjacent to shrubs. The work should bring our scientific community into a more comprehensive assessment of potential effects of a crop-shrub intercropping that may allow for increased crop yields in semi-arid ecosystems under drought conditions.
Highlights
In Sub-Saharan Africa, perennial woody shrubs have been shown to significantly influence soil microbial communities in cropped fields of the semi-arid Sahel [1] [2] [3]
There was a significant effect of drying and rewetting cycles (DRW) cycles on basal respiration (Figure 2; P < 0.05)
No change was found 2 and 30 days after disturbance, 45 days after DRW cycles basal respiration was more than 3 times higher in control soils than in stressed soils (Figure 2)
Summary
In Sub-Saharan Africa, perennial woody shrubs have been shown to significantly influence soil microbial communities in cropped fields of the semi-arid Sahel [1] [2] [3]. Recent research has found that the shrub Piliostigma reticulatum, commonly found in Senegal and other parts of Sub-Saharan Africa, significantly promotes crop growth and improves soil quality [5] [6] [7] In cropped fields, these shrub species are ecologically similar to woody species in unmanaged semi-arid environments where they are known to create “islands of fertility” through increased litter inputs and root activity/turnover [8]. Interactions between native shrubs and soil biota improve plant growth and soil microbial activity through increased water and nutrient availability [9] [12] [13] These interactions are necessary for primary production of associated crops and for maintaining the long-term functioning in these semi-arid agroecosystems [14]. Soil microbial communities contribute to the stability of these important agroecosystems as key drivers in sustainable crop production [15]
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