Hydro-chemical Characteristics of Rainfall and Redistribution Process in Rainy Season of Birch Forest in XiaoWuTaiShan Area

Water samples from five processes—rainfall, throughfall, stemflow, litter leachate, and slope runoff—were collected in the birch forest of the Xiaowutaishan Mountain, Shanjiankou Basin, to measure pH, HCO₃⁻, and the concentrations of Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, and Fe²⁺. The results showed: (1) Compared to rainfall, Mg²⁺ concentrations decreased during redistribution processes, while Fe²⁺, Ca²⁺, and Mn²⁺ concentrations increased. Zn²⁺ concentrations showed an overall upward trend except for decreases observed in stemflow and slope runoff. (2) Compared to throughfall, Mn²⁺ and Fe²⁺ concentrations increased in stemflow, indicating leaching processes, while Zn²⁺, Ca²⁺, and Mg²⁺ concentrations decreased, suggesting adsorption. Furthermore, slope runoff, compared to litter leachate, exhibited decreases in Zn²⁺, Ca²⁺, and Mg²⁺ concentrations due to interception and increases in Mn²⁺ and Fe²⁺ concentrations due to leaching. (3) Birch forests intercepted over 94% of the rainfall, demonstrating their significant role in water conservation. (4) Mg²⁺ and Fe²⁺ were found to be in a state of net loss in the soil, while Ca²⁺, Mn²⁺, and Zn²⁺ remained in a state of accumulation.