Abstract:
Nitrogen (N) deposition has emerged as a significant environmental issue affecting ecosystems worldwide, particularly temperate forests. This study aims to investigate the effects of N deposition on the nutrient status of litter in temperate forest communities, exploring the underlying mechanisms and potential ecological implications.
Methods:
1. Site Selection: We established research plots in four temperate forests representing a gradient of N deposition levels (low, intermediate, and high).
2. Litter Collection: Litter samples were collected from each plot during the autumn season, including leaves, twigs, and reproductive parts.
3. Nutrient Analysis: Litter samples were analyzed for essential nutrients, including carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg).
4. Statistical Analysis: We employed linear mixed-effects models to examine the effects of N deposition on litter nutrient concentrations and stoichiometric ratios. Structural equation modeling (SEM) was used to investigate the potential mechanisms linking N deposition to litter nutrient status.
Results:
1. Nutrient Concentrations: N deposition significantly affected litter nutrient concentrations. High N deposition led to increased N and decreased P concentrations, while K, Ca, and Mg remained relatively stable.
2. Stoichiometric Ratios: N deposition altered the stoichiometric ratios of litter nutrients. C:N ratios decreased, indicating a relative increase in N concentration compared to C. Conversely, N:P ratios increased, suggesting a decline in P relative to N.
3. Structural Equation Modeling: SEM revealed that N deposition directly influenced litter nutrient concentrations, with indirect effects mediated through changes in soil pH, microbial biomass, and litter decomposition rates.
Conclusion:
Our study demonstrates that N deposition alters the nutrient status of litter in temperate forest communities. Elevated N inputs result in increased N concentration and decreased C:N ratios, indicating a shift toward nutrient-rich litter. These changes are mediated by various mechanisms, including soil acidification, microbial responses, and altered decomposition dynamics. Understanding the impacts of N deposition on litter nutrient status is crucial for predicting ecosystem responses to global change and developing strategies for sustainable forest management.
