Temporal and spatial variation of arbuscular mycorrhizal fungi under the canopy of Hedysarum scoparium in the northern desert, China

Abstract

Despite the evident importance of arbuscular mycorrhizal fungi (AMF) associated with the root system of plants inhabiting desert regions, limit is known about the distribution and activity of AMF in desert ecosystems. Accordingly, AMF diversity, community composition and glomalin were investigated in the northern desert of China. Soil samples from 0 to 30 cm in depth over seven plots were collected under the canopy of Hedysarum scoparium in July of 2015 and 2016. A total of 51 molecular operational taxonomic units (OTUs) were identified by MiSeq sequencing based on small subunit (SSU) ribosomal RNA genes, and Diversispora celata and Diversispora trimurales were discovered for the first time in a desert ecosystem in China. The abundant genera included Glomus (56.4%), Diversispora (25.1%), Claroideoglomus (6.0%), Funneliformis (6.1%) and Paraglomus (5.5%). Archaeospora and Scutellospora sequences represented <1.0% of total sequences. AMF community composition and diversity and two Bradford-reactive soil protein (BRSP) assays were significantly different among the seven studied plots and sampling times. Moreover, AMF diversity and richness tended to increase first and then decrease as the precipitation decreased in the barren sandy grey desert and aeolian sandy soil. Correlation coefficient analysis demonstrated that the Shannon-Wiener index was significantly and positively correlated with acid phosphatase (P < 0.05) and precipitation (P < 0.01) and was significantly and negatively correlated with soil pH (P < 0.01). The richness of AMF was significantly and positively correlated with precipitation (P < 0.01) and negatively correlated with soil organic carbon (SOC) (P < 0.05) and soil pH (P < 0.01). The BRSP fractions were also significantly and positively correlated with edaphic factors (e.g., soil moisture, soil organic carbon) and soil enzymes (e.g., soil acid and alkaline phosphatase). The means of total BRSP and easily extractable BRSP were 5.86 mg·g−1 and 1.90 mg·g−1, respectively. The levels of BRSP in the desert soil were slightly lower than those in native and arable soils, but the ratios of BRSP to SOC were much higher than in farmland soils. Our findings provide insights into important factors affecting the native AMF community and glomalin in the northern desert of China and suggest that AMF diversity and glomalin might be useful for monitoring desertification and soil degradation.