Response of Wheat Root Distribution to Warming Depends upon the Tillage System.

The ecological impact of global warming on wheat roots is poorly understood, especially under different tillage systems. We conducted a field warming experiment on winter wheat in the North China Plain to study the response of root biomass and distribution in different long-term tillage systems warmed in situ by infrared heaters. Soil temperature was increased by nearly 2¡ãC at 5 cm depth since 2010. Soil monoliths were collected across two rows of wheat and dissected to determine root biomass from three soil depths (0-10, 10-20 and 20-30 cm) in 2011 and 2013. Warming significantly increased wheat root biomass under both till and no-till systems (12.1 and 12.9% respectively for 2011; 9.9 and 14.5% respectively for 2013) in the 0-30 cm soil profile. However, these increases were located in the deeper soil layers (i.e. 10-20 and 20-30 cm) for till, while the increase for no-till was focused in the surface (0-10 cm) depth. We hypothesized that the relatively small increase in soil and air temperatures enhanced photosynthesis as indicated by the increase of wheat root and shoot biomass. Differences in the root and shoot response to tillage and no-tillage was ascribed to differences in nitrogen fertilizer application and soil bulk density between the two tillage systems. Our findings help design nutrient and tillage management systems for warmer conditions by better projecting the wheat growth and nutrient uptake, and soil C and N cycling under climate change.