11:15 AM - 11:30 AM
[MIS11-09] Chloride cycling in forested watersheds in the Shimanto River Basin
Keywords:Chloride, Forest, Sea salt
The main sources of chloride input to forest ecosystems are sea salt and anthropogenic sources such as coal combustion. A long-term monitoring in forest watersheds in the Shimanto River Basin has shown that runoff of Cl- is much larger than the input of Cl- in bulk precipitation. In addition, Cl- concentration in bulk precipitation and stream water was decreasing for 20 years. The information about Cl- input by throughfall is required when we discuss the factors affecting Cl- cycling in the forest watersheds. Objective of the study is that Cl- input by throughfall in fir, Japanese cedar and hinoki cypress forests were quantified and that Cl budget of fir and planation forest watersheds were calculated to understand the possible role of dry deposition of Cl-.
The input of Cl- by throughfall in the fir, Japanese cedar, and hinoki cypress forests was, 1.75 kmolc ha-1,0.95 kmolc ha-1, and 0.82 kmolc ha-1, respectively, which is 2.9-fold, 1.6-fold and 1.4-fold larger than that in bulk precipitation, respectively (0.60 kmolc ha-1). The percentage of non- sea salt Cl- in bulk precipitation and throughfall in fir, Japanese cedar and hinoki cypress was 1%, 17%, 11% and 11%, respectively. There are two main sources of non- sea salt Cl-; canopy exchange and anthropogenic sources. In the fir forest, leaching of K+ is greater than other two forests (1.35 kmolc ha-1) and Cl- was moved following K+. Non-sea salt Cl- input in early spring without K+ leaching suggests the anthropogenic sources.
Input and output of Cl were determined for20 years from 2000 to 2019. The average of Cl- input by bulk precipitation was 0.65 kmolc ha-1, and Cl- runoff in the fir and plantation forest watersheds were 1.54 kmolc ha-1 and 1.17 kmolc ha-1, respectively. The ratio of Cl- runoff to the Cl- input was 2.4 and 1.8, respectively. When input of Cl- is calculated based on the results of throughfall, Cl- input was larger than Cl- runoff in the fir forest whereas Cl- input was smaller than Cl- runoff in the plantation. The Cl- input in the fir forest was overestimated due to counting the canopy exchange of Cl-. Input and output of Cl- were determined from 2000 to 2009 and from 2010-2019. The ratio Cl- input by bulk precipitation in the latter period to that in the former period was 0.76. The ratio in the Cl- runoff in fir and plantation forests was 0.86, and 0.85, respectively. When we assume that input and output of Cl- is equal, the result suggest that the contribution of Cl- input by dry deposition was greater in the latter period.
The input of Cl- by throughfall in the fir, Japanese cedar, and hinoki cypress forests was, 1.75 kmolc ha-1,0.95 kmolc ha-1, and 0.82 kmolc ha-1, respectively, which is 2.9-fold, 1.6-fold and 1.4-fold larger than that in bulk precipitation, respectively (0.60 kmolc ha-1). The percentage of non- sea salt Cl- in bulk precipitation and throughfall in fir, Japanese cedar and hinoki cypress was 1%, 17%, 11% and 11%, respectively. There are two main sources of non- sea salt Cl-; canopy exchange and anthropogenic sources. In the fir forest, leaching of K+ is greater than other two forests (1.35 kmolc ha-1) and Cl- was moved following K+. Non-sea salt Cl- input in early spring without K+ leaching suggests the anthropogenic sources.
Input and output of Cl were determined for20 years from 2000 to 2019. The average of Cl- input by bulk precipitation was 0.65 kmolc ha-1, and Cl- runoff in the fir and plantation forest watersheds were 1.54 kmolc ha-1 and 1.17 kmolc ha-1, respectively. The ratio of Cl- runoff to the Cl- input was 2.4 and 1.8, respectively. When input of Cl- is calculated based on the results of throughfall, Cl- input was larger than Cl- runoff in the fir forest whereas Cl- input was smaller than Cl- runoff in the plantation. The Cl- input in the fir forest was overestimated due to counting the canopy exchange of Cl-. Input and output of Cl- were determined from 2000 to 2009 and from 2010-2019. The ratio Cl- input by bulk precipitation in the latter period to that in the former period was 0.76. The ratio in the Cl- runoff in fir and plantation forests was 0.86, and 0.85, respectively. When we assume that input and output of Cl- is equal, the result suggest that the contribution of Cl- input by dry deposition was greater in the latter period.