Growth Responses of Agropyron Mongolicum Keng to Nitrogen Addition Is Linked to Root Morphological Traits and Nitrogen-Use Efficiency.

Background: and aims Nitrogen (N) is the primary limiting factors for plant growth and development, and increasingly N deposition alters plant composition, consequently affecting ecosystem function have been widely acknowledged. However, the effects of N fertilization on native species in desert grassland ecosystem and underlying mechanisms of these effects are still poorly understood. This study was conducted to examine the growth response of Agropyron mongolicum keng to N addition and potential mechanisms underlying this effect. Methods: A.mongolicum Keng was subjected to five N addition levels (0, 0.8,1.6, 2.4, and 4.0g N m −2 yr −1 ) for six months under greenhouse conditions. A combination of linear and structural equation modelling was used to examine growth response of A.mongolicum Keng to N addition and test whether its response related to root morphological traits and N-use efficiency. Results: Growth responses of A. mongolicum Keng to increasing N addition appeared a unimodal-shaped with a N saturation threshold at 3.2g N m -1 yr -1 . Its response closely related to the root surface area, volume, length, and forks number, N uptake and utilization efficiency. Besides, N-induced changes in soil available nutrient have an indirect impaction biomass of A. mongolicum Keng via regulation of root morphological traits and N-use efficiency. Conclusions: These findings highlight the sensibility of A. mongolicum Keng to N addition and the importance of root morphological traits and N-use efficiency in affecting biomass. Therefore, these can provide important insights into potential changes of native species survival and development in nutrient-limited desert grassland caused by N deposition.