Ecological Indicators (Jun 2021)
Nitrogen and phosphorus resorption of desert plants with various degree of propensity to salt in response to drought and saline stress
Abstract
Nutrient resorption efficiency (NuRE), an important plant functional trait, is closely related to plant nutrient utilization and biogeochemical cycling. Under severe aridity and salinity stress, plants developed various strategies to adapt to these adverse conditions after long-term structural and functional evolution in desert ecosystems. However, the impact of arid environment on plant nutrient resorption remains uncertain for desert halophytes. Here we compared the nitrogen and phosphorus resorption efficiency (NRE and PRE) among four desert plant groups (i.e., euhalophytes, secretohalophytes, pseudohalophytes and glycophytes) and analyzed the responses of NuRE to drought and saline indicators within and across the four plant groups. Our results demonstrated that the NRE and PRE of all desert plants were averagely 52.8% and 57.1%, respectively. Pseudohalophytes had significantly higher NRE (59.9%) and glycophytes had significantly lower PRE (53.2%) than the other groups. Besides, the relative resorption efficiencies (NRE − PRE) were significantly lower than zero for euhalophytes, secretohalophytes, and overall plants, but non-significantly different from zero for pseudohalophytes and glycophytes, suggesting that euhalophytes and secretohalophytes were generally P-limited: they tend to resorb more P than N from senescing leaves; but pseudohalophytes and glycophytes were both N- and P-limited: they resorb N and P in a balanced way (the relative resorption hypothesis). NuRE of the three halophytic groups responded to drought and saline stress in a generally consistent way: both NRE and PRE significantly increased with increasing water-stress (lower soil water stress coefficient (Ksoil) and aridity index (AI)) and salinity-stress (higher soil pH and electrical conductivity (EC)), although the relationships between PRE of euhalophytes and these four indicators, and between PRE of the three halophytic groups and soil EC, were non-significant. By contrary, NRE of the glycophytes showed a non-significant relation with water stress indicators (Ksoil) and soil EC. Overall, the patterns of NuRE in desert plants with different salt propensity suggest the evolutionary divergence (halophytes vs glycophytes) and convergence (euhalophytes, secretohalophytes, and pseudohalophytes) strategies in response to salinity and water stress. These findings provide a new perspective for understanding the nutrient resorption strategies of desert plants, and may also help better predict the nutrients biogeochemical cycling in desert ecosystem under global climate changes.
