Spatio-temporal dynamics of arbuscular mycorrhizal fungi and soil organic carbon in coastal saline soil of China

Change in glomalin-related soil protein along latitudinal gradient encompassing subtropical and temperate blue carbon zones

Glomalin-related soil protein (GRSP), an abundant and eco-friendly bioproduct associated with arbuscular mycorrhizal fungi (AMF), contributes significantly to the soil particle aggregation and carbon sequestration. Although much research has been conducted on the storage of GRSP at different spatio-temporal scales in terrestrial ecosystems. However, the deposition of GRSP in large-scale coastal environments has not been revealed, which hinders an in-depth understanding of GRSP storage patterns and environmental controls, and this knowledge gap has become one of the key uncertainties in understanding the ecological functions of GRSP as blue carbon components in coastal environments. Therefore, we conducted large-scale experiments (spanning subtropical and warm temperate climate zones, coastlines over 2500 km) to test the relative contributions of environmental drivers that shape unique GRSP storage. In salt marshes of China, we found that the abundance of GRSP ranges from 0.29 mg g-1 to 1.10 mg g-1, and its concentration decreases with increasing latitude (R2 = 0.30, p < 0.01). The GRSP-C/SOC of salt marshes ranged from 4 % to 43 % and increased with the increase in latitude (R2 = 0.13, p < 0.05). The carbon contribution of GRSP does not follow the trend of increasing abundance, but is limited by the total amount of background organic carbon. In salt marsh wetlands, precipitation, clay content and pH are the main factors influencing GRSP storage. GRSP is positively correlated with precipitation (R2 = 0.42, p < 0.01) and clay content (R2 = 0.59, p < 0.01), but negatively correlated with pH (R2 = 0.48, p < 0.01). The relative contributions of the main factors to the GRSP differed across climatic zones. Soil properties, such as clay content and pH, explained 19.8 % of the GRSP in subtropical salt marshes (20°N < 34°N), however, in warm temperate salt marshes (34°N < 40°N), precipitation explained 18.9 % of the GRSP variation. Our study provides insight into the distribution and function of GRSP in coastal environments.

Biogeographic Patterns of Arbuscular Mycorrhizal Fungal Communities Along a Land-Use Intensification Gradient in the Subtropical Atlantic Forest Biome

Information concerning arbuscular mycorrhizal (AM) fungal geographical distribution in tropical and subtropical soils from the Atlantic Forest (a global hotspot of biodiversity) are scarce and often restricted to the evaluation of richness and abundance of AM fungal species at specific ecosystems or local landscapes. In this study, we hypothesized that AM fungal diversity and community composition in subtropical soils would display fundamental differences in their geographical patterns, shaped by spatial distance and land-use change, at local and regional scales. AM fungal community composition was examined by spore-based taxonomic analysis, using soil trap cultures. Acaulospora koskei and Glomus were found as generalists, regardless of mesoregions and land uses. Other Acaulospora species were also found generalists within mesoregions. Land-use change and intensification did not influence AM fungal composition, partially rejecting our first hypothesis. We then calculated the distance-decay of similarities among pairs of AM fungal communities and the distance-decay relationship within and over mesoregions. We also performed the Mantel test and redundancy analysis to discriminate the main environmental drivers of AM fungal diversity and composition turnover. Overall, we found significant distance-decays for all land uses. We also observed a distance-decay relationship within the mesoregion scale (< 104 km) and these changes were correlated mainly to soil type (not land use), with the secondary influence of both total organic carbon and clay contents. AM fungal species distribution presented significant distance-decays, regardless of land uses, which was indicative of dispersal limitation, a stochastic neutral process. Although, we found evidence that, coupled with dispersal limitation, niche differentiation also played a role in structuring AM fungal communities, driven by long-term historical contingencies, as represented by soil type, resulting from different soil origin and mineralogy across mesoregions.