Groundwater and its nutrients sustain the establishment of deep-rooted phreatophytes. Rapid root elongation immediately after seed germination is the key for desert plants to obtain deep water and nutrients. However, we have a poor understanding of the response strategies of phreatophyte seedlings to water and nutrients in topsoil before the roots of desert deep-rooted plants reach groundwater. Also, nitrogen (N) enrichment has a fertilization effect in desert ecosystems, while drought can limit the movement of soil nutrients. There is little attention paid to the effects of their interactions on desert deep-rooted plants.
Focusing on the above problem, researchers from the State Key Laboratory of Desert-Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, systematically studied the two phreatophyte species, Alhagi sparsifolia, and Calligonum mongolicum seedlings, dominating in the southern margin of the Taklimakan desert, through simulating N deposition and water stress.
It was found that N and water independently or interactively influenced photosynthesis, drought tolerance, morphological characteristics, and the distribution pattern of biomass and nutrients among organs of the two plants. The increased N input improved the uptake of N and P by increasing root biomass of A. sparsifolia, thus adapting to drought. For C. mongolicum seedlings, the proper addition of N enhanced the resistance to water stress by improving the water use efficiency, superoxide dismutase, and nitrite reductase activities, in which soluble protein played an important role.
In general, an appropriate amount of N addition can alleviate the drought stress of desert plant seedlings. The response of desert deep-rooted plant seedlings to N enrichment and drought involves the interdependence of aboveground- and underground-part functional traits, and more biomass and nutrients are allocated to thin roots to absorb scarce resources. These findings are helpful to further understand the water use pathways and nutrient response strategies of desert deep-rooted plant seedlings and provide an important scientific basis for the study of vegetation degradation mechanism and restoration technology in arid areas and the optimal management of desert ecosystems under the scenario of global change.
These findings have been published in Plant Physiology and Biochemistry and Plant Biology, entitled "Nitrogen application mitigates drought-induced metabolic changes in Alhagi sparsifolia seedlings by regulating nutrient and biomass allocation patterns" and "Involvement of soluble proteins in growth and metabolic adjustments of drought-stressed Calligonum mongolicum seedlings under nitrogen addition", respectively.
Article link: https://www.sciencedirect.com/science/article/pii/S0981942820304186
FIG. Effects of N addition and moisture status on nutrient distribution in A. sparsifolia (left panel), and C. mongolicum (right panel) seedlings