Deposition pattern and throughfall fluxes in secondary cool temperate forest, South Korea

Publication date: July 2017
Source:Atmospheric Environment, Volume 161
Author(s): Mukesh Kumar Gautam, Kwang-Sik Lee, Byeong -Yeol Song
Chemistry and deposition fluxes in the rainfall and throughfall of red pine (Pinus densiflora), black locust (Robinia pseudoacacia), and chestnut (Castanea crenata) monocultures, and mixed red pine–black locust–chestnut stands were examined in a nutrient-limited cool temperate forest of central South Korea. Throughfall was enriched in both basic and acidic constituents relative to rainfall, suggesting that both dry deposition and canopy leaching are important sources of throughfall constituents. Net throughfall fluxes (NTFs) of cations and anions significantly differed among four different stands as well as seasonally. Red pine exhibited highest fluxes (TF and NTF) for Ca²⁺, black locust for K⁺, mixed stands for Mg²⁺, and chestnut for Na⁺. In contrast, NTF of SO4^2-, NO3⁻, and NH4⁺was highest in the red pine, intermediate in the chestnut and mixed stands, and lowest in the black locust. In general, canopy uptake of H⁺ and NH4⁺ for all stands was higher in summer than in winter. Dry deposition appears to play a major role in atmospheric deposition to this cool temperate forest, especially in summer. Dry deposition for both cations and anions displayed high spatial variability, even though stands were adjacent to one another and experienced identical atmospheric deposition loads. Canopy leaching of K⁺ (95–78% of NTF), Mg²⁺ (92–23% of NTF), and Ca²⁺ (91–12% of NTF) was highest for the black locust, lowest for chestnut, and intermediate for the red pine and mixed stands. The present study documented significant changes in throughfall chemistry and NTF among different forest stands, which presumably be related with the differences in the canopy characteristics and differences in their scavenging capacity for dry deposition and canopy exchange. Difference in the canopy retention of H⁺ and base cation leaching suggests that canopy exchange was mainly driven by weak acid excretion and lesser by H⁺ exchange reaction. Our results indicate that despite a high base cation deposition, a combination of higher input of acidifying constituents, low soil pH, and total acidic deposition approaching South Korean critical loads make regional forest vulnerable to acidification.

Graphical abstract

http://ift.tt/2oWmmrz