CONICET | Buscador de Institutos y Recursos Humanos

The planting of seedlings is the most effective measure for vegetation restoration. However, this practice is challenging in desert ecosystems where water and nutrients are scarce. Calligonum mongolicum is a sand‐fixing pioneer shrub species, and its adaptive strategy for nitrogen (N) deposition and drought is poorly understood.Thus, in a pot experiment, we studied the impacts of four N levels (0, 3, 6, 9 gN·m‐2·yr‐1) under drought or a well‐watered regime on multiple eco‐physiological responses of 1‐year‐old C. mongolicum seedlings.Compared to well‐watered conditions, drought considerably influenced seedling growth by impairing photosynthesis, osmolyte accumulation, and the activities of superoxide dismutase and enzymes related to N metabolism. N addition improved the productivity of drought‐stressed seedlings, as revealed by increased water use efficiency, enhanced superoxide dismutase and nitrite reductase activities, and elevated N and phosphorus (P) levels in seedlings. Nevertheless, the addition of moderate to high levels of N (6?9 gN·m‐2·yr‐1) impaired the net photosynthetic rate, osmolyte accumulation, and nitrate reductase activity. As a coping strategy, N addition and water regimes did not markedly change the N:P ratios of aboveground parts; meanwhile, more biomass and nutrients were allocated to fine roots to assimilate insufficient resources. Soluble protein in assimilating shoots might play a vital role in adaptation to the desert environment.The response of C. mongolicum seedlings to N deposition and drought involved an interdependency between soluble protein and morphological, physiological, and biochemical processes. These findings provide an important reference for vegetation restoration in arid land under global change.