Variation of nutrient fluxes by rainfall redistribution processes in the forest canopy of an urban larch plantation in northeast China

Abstract

Atmospheric deposition (dry and wet deposition) is one of the primary sources of chemical inputs to terrestrial ecosystems and replenishes the nutrient pool in forest ecosystems. Precipitation often acts as a primary transporting agent and solvent; thus, nutrient cycles in forests are closely linked to hydrological processes. We collected precipitation data during a growing season to explore variations in nutrient cycling and nutrient balances in the rainfall redistribution process (wet deposition) in a larch plantation in northeast China. We measured nutrient (${\mathrm{NO}}_{3}^{-}$, ${\mathrm{PO}}_{4}^{3-}$, Cl⁻, K, Ca, Na, and Mg) inputs via bulk precipitation, throughfall and stemflow, and used a canopy budget model to estimate nutrient fluxes via canopy exchange. Our results suggest that the average concentrations of the base cation (K, Ca, Na, and Mg) showed the following order: stemflow > throughfall > bulk precipitation. Throughfall and stemflow chemistry dramatically fluctuated over the growing season when net fluxes (throughfall + stemflow—bulk precipitation) of ${\mathrm{NO}}_{3}^{-}$, ${\mathrm{PO}}_{4}^{3-}$, ${\mathrm{SO}}_{4}^{2-}$, Cl⁻, K, Ca, Na, and Mg were − 6.676 kg·ha⁻¹, − 1.094 kg·ha⁻¹, − 2.371 kg·ha⁻¹, 1.975 kg·ha⁻¹, 0.470 kg·ha⁻¹, − 5.202 kg·ha⁻¹, − 0.336 kg·ha⁻¹, and 1.397 kg·ha⁻¹, respectively. These results suggest that ${\mathrm{NO}}_{3}^{-}$, ${\mathrm{PO}}_{4}^{3-}$, ${\mathrm{SO}}_{4}^{2-}$, Ca, and Na were retained, while Cl⁻, K, and Mg were washed off by throughfall and stemflow.