Response in root growth of Tamarix ramosissima seedlings to different water treatments in the arid lower Tarim River

Deficient water resources in the arid lower Tarim River impose constraints to the growth and survival of planted seedlings of Tamarix ramosissima which is very needed in the rehabilitation of degraded desert riparian forest. The objective of this study was to compare root morphology, biomass production of the seedlings treated by two irrigation methods, i.e. side deep-ditch irrigation (SDDI) and above-ground irrigation (AGI), and three water levels, i.e. high water level (W1, 50L plant^-1 once^-1), medium water level (W2, 25L plant^-1 once^-1) and low water level (W3, 12.5L plant^-1 once^-1), to identify SDDI had a significant effect on promoting root growth. The results showed that SDDI significantly increased fine root (0.5 mm <; d <; 2 mm) length, fine root surface area, coarse root (d >; 2 mm) biomass, below and above-ground biomasses compared with AGI. The vertical growth rate under SDDI and W1 was significantly higher than that in other treatments. SDDI caused an increase in specific root length (SRL) of the fine root at high and medium water levels. Our results suggest that SDDI caused rapid and great root elongation and root biomass production of Tamarix ramosissima seedlings, which benefited the seedlings survival in the early growing stage.