Abstract
Plant C:N:P stoichiometric relations drive powerful constraints on ecological interactions and processes. However, information about plant stoichiometric responses to N and P availability in desert grassland is limited. We conducted two field experiments with 7 levels of N (from 0.5 g to 24 g N ∙ m−2 yr−1) and P (from 0.05 g to 3.2 g P ∙ m−2 yr−1) additions in a desert grassland of Kunlun Mountain in the northwest of China to investigate the effects of these addition rates on the N and P stoichiometry of the dominant grass species Seriphidium korovinii. Nitrogen and P additions both affected plant stoichiometry. N addition suppressed P concentrations, whereas P addition had no effect on plant N concentrations. The N:P ratios of green aboveground biomass (AGB) were positively correlated with N addition ranging from 14.73 to 29.08, whereas those for P additions decreased ranging from 14.73 to 8.29. N concentrations were positively correlated with soil available N:P ratios, whereas, P concentrations were negatively correlated with soil availably N:P. Our results suggest that chemistry and stoichiometry of S. korovinii was directly affected by soil nutrient availability. Soil N availability affects S. korovinii stoichiometry to a greater extent that does soil P availability in this ecosystem. These findings suggest that N-deposition could affect the stoichiometry of this desert grassland ecosystem, and thereby potentially alter litter decomposition, plant community composition, nutrient cycling, and food-web dynamics of these desert ecosystems.
Highlights
Plant C:N:P stoichiometric relations drive powerful constraints on ecological interactions and processes
C, N, P concentrations of both green and senesced aboveground biomass (AGB) were affected by short-term N and P additions (Figs. 1 and 2)
The P concentration of green AGB were positively correlated with P addition rates (P = 0.001, R2 = 0.39), whereas those of senesced tissues had no significant changes (P = 0.183) (Fig. 4)
Summary
Plant C:N:P stoichiometric relations drive powerful constraints on ecological interactions and processes. Given the conflicting results of these studies, extra evidence from various ecosystem types are needed to distinguish general patterns in plant ecological stoichiometry responses to nutrient addition. Nutrient additions such as N and P are a common strategy to improve grassland productivity and restore the degraded grasslands[26]. Besides the artificial additions by human activities, the natural processes such as N deposition and sand storm can have significant effect on soil nutrient availability This is especially true for the desert grassland on the northern slope of Kunlun Mountain in northwest China. A better understanding of plant ecological stoichiometric responses to concurrent alterations in N and P availability is critical for projection of nutrient cycling dynamics under future global change
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