1.
Effects of nitrogen and phosphorus supply on stoichiometry of six elements in leaves of Arabidopsis thaliana.
Yan, Z, Hou, X, Han, W, Ma, S, Shen, H, Guo, Y, Fang, J
Annals of botany. 2019;(3):441-450
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Abstract
BACKGROUND AND AIMS Plant elemental composition is of fundamental importance for plant growth and metabolic functions. However, knowledge of how multi-elemental stoichiometry responds to varying nitrogen (N) and phosphorus (P) availabilities remains limited. METHODS We conducted experimental manipulations with nine repeat experiments to investigate the effects of N and P supply on the concentrations and variability of six elements, carbon (C), N, P, potassium (K), calcium (Ca) and magnesium (Mg), in leaves of Arabidopsis thaliana. KEY RESULTS N supply increased the concentrations of N, K and Mg, decreased the concentration of P, but exerted little influence on the concentrations of C and Ca in green leaves. P supply increased the concentrations of P and Ca, decreased the concentration of C, initially increased and then decreased the concentration of K, but showed little influence on the concentrations of N and Mg in green leaves. Multivariate patterns among the concentrations of these six elements in green leaves was influenced by the type of nutrient supply (i.e. N or P). Elemental variability decreased with increasing elemental concentrations in green leaves at the intraspecific level, supporting the Stability of Limiting Elements Hypothesis that was originally proposed from a meta-analysis of pooled data across species or communities. Compared with green leaves, the senesced leaves showed greater variability in C, N, P, K and Mg concentrations but lower variability in Ca concentration. CONCLUSIONS N and P supplies exerted differential influences on the concentrations of C, N, P, K, Ca and Mg in green leaves. The specific C content should be considered when assessing C cycling under global nutrient changes. Stage-dependent patterns of leaf stoichiometric homeostasis differed among elements with various chemical characteristics. These findings can help to improve our understanding of plant eco-physiological responses and acclimation under global nutrient changes from the stoichiometric perspective of multiple elements.
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Effects of nitrogen deposition on soil microbial communities in temperate and subtropical forests in China.
Tian, D, Jiang, L, Ma, S, Fang, W, Schmid, B, Xu, L, Zhu, J, Li, P, Losapio, G, Jing, X, et al
The Science of the total environment. 2017;:1367-1375
Abstract
Increasing nitrogen (N) deposition has aroused large concerns because of its potential negative effects on forest ecosystems. Although microorganisms play a vital role in ecosystem carbon (C) and nutrient cycling, the effect of N deposition on soil microbiota still remains unclear. In this study, we investigated the responses of microbial biomass C (MBC) and N (MBN) and microbial community composition to 4-5years of experimentally simulated N deposition in temperate needle-leaf forests and subtropical evergreen broadleaf forests in eastern China, using chloroform fumigation extraction and phospholipid fatty acid (PLFA) methods. We found idiosyncratic effects of N addition on microbial biomass in these two types of forest ecosystems. In the subtropical forests, N addition showed a significant negative effect on microbial biomass and community composition, while the effect of N addition was not significant in the temperate forests. The N addition decreased MBC, MBN, arbuscular mycorrhizal fungi, and the F/B ratio (ratio of fungi to bacteria biomass) in the subtropical forests, likely due to a decreased soil pH and changes in the plant community composition. These results showed that microbial biomass and community composition in subtropical forests, compared with the temperate forests, were sensitive to N deposition. Our findings suggest that N deposition may have negative influence on soil microorganisms and potentially alter carbon and nutrient cycling in subtropical forests, rather than in temperate forests.