Arbuscular mycorrhizal colonization of Tamarix ramosissima along a salinity gradient in the southwestern United States

Tamarix ramosissima is a highly salt- and drought-resistant arbuscular mycorrhizal tree species. Arbuscular mycorrhizal fungi (AMF) colonization of T. ramosissima roots is reportedly low, but the effect of salt on AMF colonization remains unclear. Here we examined soil and roots of T. ramosissima at five locations with different soil salinity levels to determine the effect of soil salinity levels on AMF colonization. The AMF colonization rate of T. ramosissima was determined as well as the water content, pH, electrical conductivity (EC), water-soluble cations, total nitrogen, and available phosphorus of the collected soil. AMF colonization was low at each site (2.4–12.3 %), and a low level of colonization (2.4 %) was even observed in high-salinity areas with a surface soil EC of 14.4 ds m⁻¹. AMF colonization increased with soil EC at low to medium soil salinity levels (0.4–4.3 dS m⁻¹), but it decreased at high salinity levels (>7 dS m⁻¹). Our results showed that the AMF colonization rate of T. ramosissima was affected by soil salinity levels, although colonization was even observed at high salinity levels.