Linkages of C: N: P stoichiometry between soil and leaf and their response to climatic factors along altitudinal gradients

Abstract

Altitudinal gradients have been recognized as a natural experiment to assess the structure and functions of above - and below-ground ecosystem under global climate change. Nutrient stoichiometry is tightly linked both the above-and below-ground functioning, but how the altitudinal gradients affect nutrient stoichiometry among plant and soil systems remains unclear. Soil samples were collected at 17 sites along an altitudinal gradient from 1362 to 3320 m in the North Slope of Taibai Mountain. These samples represent three different climate zones, including a warm temperate zone, a cold temperate zone, and an alpine cold zone. Soil moisture (SM), soil temperature (ST), and the concentrations of carbon (C), nitrogen (N), and phosphorus (P) in soil and leaves were determined. The C and N in soil and leaves were higher at medium altitudes than that at low or high altitudes, while P concentrations increased significantly as altitude increased. The C: N ratio in soil and leaves was not significantly affected by altitudinal gradients, but the C: P and N: P ratios were lower at high altitudes. In particular, the leaf N:P ratio at high altitudes was less than 12, suggesting an increase in N limitation along altitudinal gradients. Moreover, except the C: N ratio, soil C: N: P stoichiometry was significantly related to leaf C: N: P stoichiometry, and both showed closed relationships with ST and SM. These results suggest that stoichiometric characteristics appear to be closely linked with climatic factors, and improved knowledge of C: N: P stoichiometry patterns along altitudinal gradients will be indispensable to a comprehensive understanding of the influences of climate change on ecosystems.