Long‐term hydrochemical monitoring in an Oyasan Experimental Forest Watershed comprised of two small forested watersheds of Japanese cedar and Japanese cypress

Abstract

Forest ecosystems are self‐fertilizing systems, and development of forest stands depends on nutrient supply via biogeochemical cycling within the ecosystem. Therefore, it is important to clarify the nutrient cycle mediating growth and development. In addition, long‐term hydrochemical monitoring is needed to understand the influence of environmental changes on biogeochemical cycling in forest ecosystems. The Oyasan Experimental Forest Watershed (OEFW) is located in the Field Museum Oyasan, the university forest of Tokyo University of Agriculture and Technology, in Gunma prefecture, Japan. OEFW comprises two small adjacent forested watersheds—A‐watershed and B‐watershed—with respective areas of 1.3 and 1.8 ha. A‐watershed is a reestablished forest planted with sugi (Japanese cedar; Cryptomeria japonica) and hinoki (Japanese cypress; Chamaecyparis obtusa) in 1976, and has been managed intensively with fertilizer application. By contrast, B‐watershed is an established forest planted with sugi and hinoki in 1907. No forest practices have been carried out except for thinning of suppressed trees in 1983. However, the sugi plantation on the lowest slope (18% of the watershed area) was cut in 2000, and sugi was replanted the following year. In this data paper, we present data on the daily precipitation, discharge, pH, and concentrations of major nutrients (Ca2+, Mg2+, K+, Na+, NH4+, Cl−, NO3−, and SO42−) in rainwater and stream water since November 1978. The arithmetical mean pH of precipitation, stream water in A‐ and B‐watershed from the beginning of the monitoring to the present were 4.77 ± 0.67, 6.85 ± 0.41 and 6.88 ± 0.36 (average ± SD), respectively. The arithmetical mean concentrations in precipitation in mmolc L−1 were 0.030 ± 0.030 for Ca2+, 0.010 ± 0.011 for Mg2+, 0.009 ± 0.013 for K+, 0.020 ± 0.024 for Na+, 0.035 ± 0.041 for NH4+, 0.026 ± 0.029 for Cl−, 0.033 ± 0.038 for NO3−, and 0.046 ± 0.043 for SO42−. The mean concentrations in stream water in A‐watershed were 0.180 ± 0.032 for Ca2+, 0.073 ± 0.013 for Mg2+, 0.018 ± 0.009 for K+, 0.182 ± 0.024 for Na+, 0.010 ± 0.010 for NH4+, 0.060 ± 0.008 for Cl−, 0.111 ± 0.038 for NO3−, and 0.074 ± 0.012 for SO42−; whereas for B‐watershed the mean concentrations were 0.169 ± 0.025 for Ca2+, 0.079 ± 0.016 for Mg2+, 0.018 ± 0.005 for K+, 0.192 ± 0.026 for Na+, 0.010 ± 0.010 for NH4+, 0.065 ± 0.010 for Cl−, 0.093 ± 0.025 for NO3−, and 0.087 ± 0.011 for SO42−.

Stream Runoff and Nitrate Recovery Times After Forest Disturbance in the USA and Japan

“…Since this intensity of disturbance and the effects may be differ from overstory‐only clearcutting, we separated Cut+ from Cut. The catchments included in the analysis are described elsewhere (Adams et al, ; Fukuzawa et al, ; Likens & Buso, ; Oda et al, ; Ohte et al, ; Riscassi & Scanlon, ; Sebestyen et al, ; Urakawa et al, ).…”

Effects of climate and acidic deposition on inter-annual variations of stream water chemistry in forested watersheds in the Shimanto River Basin, southern Japan

“…The stream water NO 3 concentrations decreased at annual rates of 2.55% and 0.95% in Yusuhara and Taisho, respectively. Previous studies reported similar decreasing trends (Urakawa et al, 2012;Lucas et al, 2016;Grofmann et al, 2018;Chiwa, 2021) but others found no clear trends (Stoddard et al, 1999;Chiwa, 2021;Sase et al, 2021). Mechanisms by which the stream NO 3 concentration declines with reducing nitrogen deposition have been proposed.…”

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research

“…Modeling and analysis coupled with long-term monitoring and field experiments provide powerful research tools to help understand the dynamic features of the N cycle driven by multiple environmental factors, and to address new parameters to be monitored or examined (e.g., Aber et al 2002;Driscoll et al 2003). There are clearly regional research gaps in the context of long-term site-based research on N biogeochemistry: East Asia, South America, and Africa (e.g., Anderson et al 2012;Urakawa et al 2012), where increased Nr pollution has been predicted for the coming decades (Galloway et al 2004). Also, longterm research sites in agricultural and urban ecosystems are currently limited despite their large importance in global N cycles.…”