Effects of Anion Adsorption Characteristics of a Volcanic Ash Soil on Long-term NO3- Leaching from a Partial Clear-cut Cedar and Cypress Watershed.

Abstract

Effects of Anion Adsorption Characteristics of a Volcanic Ash Soil on Long-term NO 3 Leaching from a Partial Clear-cut Cedar and Cypress Watershed. J. Jpn. For. Soc. 91: 184 191. Long-term changes in the water quality of soil water and streamwater were monitored before and after cutting at the lower slope position in a small forested watershed composed of artificial stands of old aged Japanese cedar and cypress in the northern Kanto region in Japan. The NO 3 concentration in soil water directly reflected the N dynamics, i.e., the reduced nutrient uptake and accelerated nitrogen mineralization in the surface soil layer immediately after the cutting, and the increased nutrient uptake induced by regenerated trees several years after the practice. In contrast, the NO 3 concentration in streamwater maintained higher level than before cutting in the sixth year after the practice. The NO 3 concentrations in high and low discharge, which is dominated by direct flow and base flow, respectively, were calculated from the relationships between discharge rates and the NO 3 concentration in streamwater. The results suggested that the NO 3 distribution in soil affects the NO 3 concentration in streamwater. Changes in the NO 3 concentration in the subsoil were calculated using the HYDRUS-1D model, and these changes were consistent with previously measured seasonal and long-term changes in the NO 3 concentration in streamwater. This finding implies that NO 3 adsorption characteristics of the volcanic ash subsoil affects NO 3 leaching into streamwater. In order to clarify the effects of the aging of artificial forests, the method of cutting, and environmental changes on N dynamics in soil and streamwater, it is necessary to consider the NO 3 adsorption characteristics of volcanic ash soil.

Implications of seasonal variation in nitrate export from forested ecosystems: a review from the hydrological perspective of ecosystem dynamics

“…Coordinated comparisons among geographically varied catchments allow discussion not only of the climatological and hydrological influences considered in this review but also of other environmental variations such as geological setting and soil properties. For example, Urakawa et al (2009) pointed out that the NO 3 À adsorption characteristics of volcanic ash subsoil containing allophane clay affect NO 3 À leaching into streamwater of a Japanese coniferous forest. Such differences may lead to contrasting levels of NO 3 À export from forest catchments between regions with volcanic geology, such as the Japanese mountainous region, and regions lying on old continental geology, such as North America and Europe.…”

Causal Relationships between Stream NO₃⁻ Concentrations at Baseflow Conditions and Key Regulating Factors in the Kinki Region of Japan, Including the Japan-sea Side Area and Encompassing a Climatic Gradient

“…However, the stream NO 3 − concentrations in JSK were lower than the entire KIN [13,14]. Though all possible factors which can affect NO 3 − leaching such as topography [15,16], climate [8,[17][18][19][20][21], vegetation [9,22,23], soil chemistry [9,22,23], soil type [24,25], geology [26][27][28], and historical land-use and disturbance [8,9,[29][30][31] were examined, Makino et al [14] demonstrated that both the amount of N deposition and several climatic factors such as precipitation and temperature were important for regulating stream NO 3 − concentrations at baseflow conditions. Along the JSK, snow depth was also important.…”