Effect of elevation gradient to ecological stoichiometric ratio of plant leaves during dry season and rainy season

To explore the response of soil-plant system stoichiometry to elevational gradients during the dry and rainy seasons and to identify key factors influencing nutrient content variations, this study aimed to reveal nutrient cycling mechanisms and provide a scientific basis for the sustainable development of protected areas.

In Dry season and Rainy season of 2022, samples were collected from four elevation gradients (1 800, 2 100, 2 400, and 2 700 m) within the Liziping National Nature Reserve, followed by laboratory analysis.

The study investigated the stoichiometric characteristics of leaf carbon (C), nitrogen (N), and phosphorus (P) and their driving factors. The results showed that elevation, season, and their interaction significantly influenced the stoichiometric composition of plant leaves. Leaf C content exhibited a relatively narrow range of variation (366.61-445.16 g/kg in the dry season and 339.80-442.55 g/kg in the rainy season), remaining relatively stable between seasons, but showing a trend of initially increasing and then decreasing with elevation. Leaf N content increased at first and then declined with elevation during the dry season, while the opposite pattern occurred during the rainy season, with significant seasonal differences across elevations. Nitrogen limitation on plant growth was more pronounced, particularly at low elevations (1 800 m), where seasonal differences were minimal. Leaf P content was 2.56 g/kg in the dry season and 1.71 g/kg in the rainy season, both exceeding the global average for plant P content (1.49 g/kg). At mid-to-high altitudes (2 100 m, 2 400 m), the nitrogen (N) element levels are classified as weakly sensitive and weakly stable, respectively. For other altitudes, the stability of plant leaf indicators shows absolute stability. Across all elevations and seasons, leaf N: P ratios were below 14, suggesting that most plants were co-limited by N and P, with P limitation being more pronounced. Seasonal changes led to stabilization in plant growth and metabolic rates across elevations, reflecting strong adaptability. Correlation and redundancy analyses revealed that soil factors, including C, N, P, available phosphorus (AP), available nitrogen (AN), and the C: N ratio, were the primary drivers of leaf nutrient content, with nitrogen and soil water content (SWC) identified as the most critical factors.

Plant growth was predominantly limited by nitrogen availability, particularly in mid- to high-elevation regions, while phosphorus limitation was more evident at higher elevations. Under P-limited conditions, plants demonstrated strong homeostasis during growth. Variations in soil nutrient supply caused by seasonal and elevation regulated plant leaf nutrient content and stoichiometric characteristics.