Responses of plant distributions in drainage ditch banks to soil salinity in an arid agricultural irrigation region of Northwest China

In arid agricultural irrigation regions, drainage ditches are important ecotones subjected to both soil salinity and artificial drainage. To explore plant community structures under varying levels of salt stress and the long-term distribution patterns of salt-tolerant species in arid open-ditch banks, a comprehensive study of soil-plant interrelationships was conducted in 39 drainage ditches of a Yellow River irrigation area of Northwest China. The results showed that larger drainage ditches exhibited higher NaCl-induced salt levels (mean >4.8 dS/m) but lower plant coverage and diversity in banks. In all, 21 families, 47 genera, and 62 plant species were detected; Phragmites australis presented the highest frequency and coverage. The high-salinity environment of >6.0 dS/m inhibited the appearance of nearly half of all species, and halophytes preferred K+-rich soils. Canonical correspondence analysis showed that mineral ions including K+, Ca2+, Mg2+, HCO3- and SO42- rather than macronutrients significantly affected the distributive heterogeneity of glycophytes under salt stress. This research revealed that smaller-sized drainage ditch habitats provided more abundant halophyte resources than larger ones and that high-diversity drainage ditches deserve more positive protection in ecologically fragile arid regions. The results of this study can aid the optimisation of plant diversity conservation strategies in agroecosystem management.