A Nitrogen-Saturated Plantation of Cryptomeria japonica and Chamaecyparis obtusa in Japan Is a Large Nonpoint Nitrogen Source

Abstract

Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) plantations account for approximately 30% of the total forested area in Japan. Both are arbuscular mycorrhizal trees that leach more NO 3 -in response to nitrogen (N) deposition than do forests of ectomycorrhizal trees. However, little information is available about the size of N exports from these plantations. The aim of this study was to evaluate nonpoint source N exports from a N-saturated plantation. We collected stream water samples in base-flow (25 samples) and storm-flow conditions (20 events) in a watershed (2.98 ha) where Japanese cypress and Japanese cedar were planted in 1969 (41 yr old). The annual NO 3 -export was calculated from load-discharge relationships. Atmospheric N deposition was also determined. The stream water contained high ) could explain the N saturation. There were only small variations in NO 3 -concentrations in stream water in response to discharge volume, because of the N saturation of the forest ecosystem. Consequently, there were only small errors in estimating annual NO 3 -exports from the studied watershed. The annual NO 3 -export was high (36.1 kg N ha -1 yr -1 ), comparable to values reported for agricultural and urbanized areas. These results suggest that N-saturated forest plantations can become important nonpoint N sources. Our results also suggest that N exports from forest plantations across Japan should be quantified to evaluate nonpoint source N accurately.

Nutrients exported from upland stream water enlarge perennial biomass crops

“…S3) could increase the NO 3 − , SRP, and mineral concentrations of stream water in the Rawan and Moashoro Rivers. Stream water NO 3 − concentrations in the Rawan and Moashoro Rivers were more than 100 μmol L −1 , which was much higher than the average concentration of NO 3 − (25 μmol L −1 ) 8 in the water of 34 streams in forests in Japan and comparable with that reported in streams in urban/suburban forests [9][10][11] . Higher NO 3 concentrations in stream water are generally caused by agricultural activity 12 .…”

Differences in seasonality and temperature dependency of stand transpiration and canopy conductance between Japanese cypress (Hinoki) and Japanese cedar (Sugi) in a plantation

“…These correspond to 0.88 and 0.87 of the yield index, indicating similar levels of maturity. Chiwa et al () reported that stream water in the basin contained high NO 3 − concentrations and that the site experienced a high bulk atmospheric N deposition rate, suggesting N saturation in the YEC.…”

Contrasting nitrate leaching from an abandoned Moso bamboo forest and a Japanese cedar plantation: role of vegetation in mitigating nitrate leaching

“…(2004) reported that NO 3 − levels in soil were higher in sugar maple stands than in stands of other tree species in eastern America. Chiwa et al (2015) also found that Japanese cedar (Cryptomeria japonica) plantations in areas under high atmospheric N deposition leach a large amount of NO 3 − into stream water in Japan. It has been reported that the NO 3 − concentration in a soil solution from a Japanese cedar stand was much higher than that in a nearby Japanese oak (Quercus acuta) stand in western Japan (Yang and Chiwa 2021).…”