title: Separate estimation of N export into baseline N leakage without disturbance and N loss due to insect defoliation in a pine forest watershed in central Japan.
abstract: Pine wilt disease (PWD) is caused by a non-native pest that has spread extensively throughout Japan. Previous research has indicated that most infected trees have died and the litter deposited has resulted in changes to stream-water chemistry, particularly increased nitrate (NO(3)(-)) concentrations. In this study, we divided stream nitrogen (N) export into N loss due to PWD and baseline N leakage without disturbance based on long-term monitoring. The annual N export was 110.0 mol N ha(-1) year(-1) in 1990 and 749.8 mol N ha(-1) year(-1) in 1997, and had decreased to 37.0 mol N ha(-1) year(-1) in 2005. N export under PWD influence was estimated to be 3697 mol N ha(-1), and N loss due to PWD was 2810 mol N ha(-1). N loss due to PWD was three times larger than baseline N leakage for the disturbed period. These changes in plant-herbivore relationships could affect N status in a forest ecosystem. So-called "semi-natural" disturbances related to non-native species invasion and increases of atmospheric N deposition caused by human activity will increase. Long-term monitoring studies of various aspects are necessary to offer insight into this ecosystem.
authors.affiliation: Field Science Education and Research Center, Kyoto University, Kitashirakawa Kyoto, 606-8502 Kyoto, Japan,.tokuchi@kais.kyoto-u.ac.jp
authors.forename: Tokuchi
authors.initials: T
authors.lastname: Naoko
authors.forename: Ohte
authors.initials: O
authors.lastname: Nobuhito
authors.forename: Osaka
authors.initials: O
authors.lastname: Ken'ichi
authors.forename: Katsuyama
authors.initials: K
authors.lastname: Masanori
mesh_terms: D000818:Animals; D017753:Ecosystem; D004784:Environmental Monitoring; D007313:Insecta / Q000502:physiology*; D009584:Nitrogen / Q000032:analysis*; D058458:Nitrogen Cycle; D045483:Rivers / Q000737:chemistry; D014197:Trees; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D009584:Nitrogen