Critical N:P values: predicting nutrient deficiencies in desert shrublands

• Published in: Plant and soil Vol. 259; no. 1-2; pp. 59 - 69
• Main Authors: Drenovsky, R.E, Richards, J.H
• Format: Journal Article
• Language: English
• Published: Dordrecht Kluwer Academic Publishers 01.02.2004; Springer; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Chrysothamnus nauseosus; Desert soils; Deserts; fertilizer application; Flowers & plants; Fundamental and applied biological sciences. Psychology; Growing season; Irrigation; Leaves; mycorrhizae; Nitrogen; nitrogen fertilizers; Nutrient availability; Nutrient requirements; Nutritional deficiencies; phosphorus; phosphorus fertilizers; Plant growth; Plant nutrition; plant response; Plants; Sarcobatus vermiculatus; Shrubs; Soil nutrients; Stem elongation; Synecology; Terrestrial ecosystems; Wetlands; xerophytes; California; United States; North America; America; Xerophyte; Chrysothamnus nauseosus; Compositae; Inorganic element; Dicotyledones; Ecosystem; Limitation; Angiospermae; Chemical concentration; Shrubbery; Terrestrial environment; ARID SOILS; Sarcobatus vermiculatus; Fertilization; Arid environment; Deficiency; Prediction; Phosphorus; Plant leaf; Woody plant; Nitrogen; Chenopodiaceae; Desert soil; Spermatophyta; Desert; Soil plant relation
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/B:PLSO.0000020945.09809.3d

Many terrestrial ecosystems are nutrient limited. Koerselman and Meuleman (1996) proposed critical foliar N:P values that could predict wetland nutrient deficiencies (N:P < 14, N limitation; N:P > 16, P limitation). Although critical N:P values have potential as ecological and diagnostic tools, species differences in N and P requirements must be tested. The objectives of our experiments were 1) to determine if two desert species share critical N:P values, and 2) to assess the N:P tool's applicability in a non-wetland system. We studied two common, co-occurring North American desert shrubs, Chrysothamnus nauseosus spp. consimilis and Sarcobatus vermiculatus. Based on leaf N and P concentrations, effective mycorrhizal status, and leaf N:P, we predicted Chrysothamnus would be N limited and Sarcobatus would be P limited. During the 2000 and 2001 growing seasons, juvenile shrubs received N, P, N+P, or control treatments. To assess interaction with water limitation, other shrubs were irrigated and fertilized in 2001 (N+IR, P+IR, N+P+IR, control IR). Contrary to the predicted N limitation in Chrysothamnus, stem growth was 1.7-fold greater in P+IR plants relative to IR controls, although without irrigation Chrysothamnus did not respond to P addition. Also, contrary to the predicted P limitation in Sarcobatus, stem growth was 2.7-fold and 1.5-fold greater in N and N+IR plants, respectively, relative to their controls. Leaf N was significantly higher in N-treated Sarcobatus, both with and without irrigation. Our study suggests species-specific critical N:P values and that the N:P tool does not effectively predict desert shrub nutrient limitations. Species adapted to low nutrient conditions may not respond to increased nutrient availability due to water and nutrient co-limitation, lack of plasticity, or lower tissue nutrient requirements.