Biocrusts beneath replanted shrubs account for the enrichment of macro and micronutrients in semi-arid sandy land

• Moss-dominated crust (MDC) formed under 30-year-old Caragana microphylla shrubs.
• MDC enhanced the enrichment of available P, Fe, Mn, Cu, Zn in topsoil under shrubs.
• The effects of MDC on nutrient availability were slight at the end of wet season.
• P and micronutrient availability increased significantly at the end of dry season.
• Spatiotemporal heterogeneity of exchangeable K, Ca, Mg was mostly negligible.

After 30 years of rehabilitation, moss-dominated crusts (biocrusts) formed under the canopies of Caragana microphylla shrubs on shifting sand dunes in the Horqin Sandy Land, China. Their impact on the spatiotemporal distribution of macro/micronutrients beneath the shrubs was determined. Soils were collected from 0 to 1 and 1–5 cm layers at three locations: two beneath shrubs (with/without biocrusts), the third at between-shrub interspaces, at end August 2013 (end wet season) and early June 2014 (end dry season). The biocrusts beneath shrubs enhanced macro/micronutrient enrichment (except extractable Ca), particularly in the 0–1 cm layer. Such positive effects exhibited seasonal dependence, i.e., the availability of phosphorus and micronutrients (iron, manganese, copper, zinc) in the 0–1 cm layer under biocrusts was significantly higher than at the other two sampling sites at end of dry season; no similar trend was observed at end of wet season. Significant increases in phosphorus and micronutrient availability were observed at end of dry season compared to wet season in both sampling layers at all sites, except topsoil beneath C. microphylla without biocrusts. This means that the colonization of moss-dominated crusts beneath C. microphylla can accumulate essential macro/micronutrients and partly compensate for the deficiency of essential nutrients in Horqin Sandy Land.