Abstract
This study evaluated whether nitrogen (N) saturated upland forests can degrade downstream water quality in the Tatara River Basin, northern Kyushu, western Japan. Our hypothesis is that elevated atmospheric N deposition degrades downstream water quality in a watershed containing N-saturated forests because a considerable amount of atmospherically deposited N passes into the streams without being retained. Synoptic stream water samplings were conducted at 23 sites across a wide range of land-use categories in the basin over 1 year. A long-term temporal analysis of downstream water quality over the last 30 years (1977-2007) was conducted and compared with long-term trends in related factors such as urban/agricultural activity, sewage wastewater treatment, atmospheric N deposition, and forest condition. The results showed that atmospherically deposited N to N-saturated forests can be a large enough non-point source of N leaving the watershed to impact downstream water quality. This was highlighted by the reduction in pollutant exports derived from urban/agricultural activities, an increase in atmospheric N deposition, and the maturation of coniferous plantation forests in the past 30 years. These have led to reductions in total phosphorus and organic nitrogen concentrations in downstream water, whereas downstream nitrate (NO 3 -) concentrations increased over the last 30 years. The consequent increase in the downstream N:P ratio indicated P limitation. Reducing the NO 3 - exports from N-saturated upland forests is suggested as a strategy to improve regional downstream NO 3 - pollution, but involves intercontinental-scale action in reducing atmospheric N emissions.
| Original language | English |
|---|---|
| Pages (from-to) | 230-241 |
| Number of pages | 12 |
| Journal | Ecosystems |
| Volume | 15 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Mar 1 2012 |
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All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Environmental Chemistry
- Ecology
Cite this
Impact of N-Saturated Upland Forests on Downstream N Pollution in the Tatara River Basin, Japan. / Chiwa, Masaaki; Onikura, Norio; Ide, Junichiro; Kume, Atsushi.
In: Ecosystems, Vol. 15, No. 2, 01.03.2012, p. 230-241.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Impact of N-Saturated Upland Forests on Downstream N Pollution in the Tatara River Basin, Japan
AU - Chiwa, Masaaki
AU - Onikura, Norio
AU - Ide, Junichiro
AU - Kume, Atsushi
PY - 2012/3/1
Y1 - 2012/3/1
N2 - This study evaluated whether nitrogen (N) saturated upland forests can degrade downstream water quality in the Tatara River Basin, northern Kyushu, western Japan. Our hypothesis is that elevated atmospheric N deposition degrades downstream water quality in a watershed containing N-saturated forests because a considerable amount of atmospherically deposited N passes into the streams without being retained. Synoptic stream water samplings were conducted at 23 sites across a wide range of land-use categories in the basin over 1 year. A long-term temporal analysis of downstream water quality over the last 30 years (1977-2007) was conducted and compared with long-term trends in related factors such as urban/agricultural activity, sewage wastewater treatment, atmospheric N deposition, and forest condition. The results showed that atmospherically deposited N to N-saturated forests can be a large enough non-point source of N leaving the watershed to impact downstream water quality. This was highlighted by the reduction in pollutant exports derived from urban/agricultural activities, an increase in atmospheric N deposition, and the maturation of coniferous plantation forests in the past 30 years. These have led to reductions in total phosphorus and organic nitrogen concentrations in downstream water, whereas downstream nitrate (NO 3 -) concentrations increased over the last 30 years. The consequent increase in the downstream N:P ratio indicated P limitation. Reducing the NO 3 - exports from N-saturated upland forests is suggested as a strategy to improve regional downstream NO 3 - pollution, but involves intercontinental-scale action in reducing atmospheric N emissions.
AB - This study evaluated whether nitrogen (N) saturated upland forests can degrade downstream water quality in the Tatara River Basin, northern Kyushu, western Japan. Our hypothesis is that elevated atmospheric N deposition degrades downstream water quality in a watershed containing N-saturated forests because a considerable amount of atmospherically deposited N passes into the streams without being retained. Synoptic stream water samplings were conducted at 23 sites across a wide range of land-use categories in the basin over 1 year. A long-term temporal analysis of downstream water quality over the last 30 years (1977-2007) was conducted and compared with long-term trends in related factors such as urban/agricultural activity, sewage wastewater treatment, atmospheric N deposition, and forest condition. The results showed that atmospherically deposited N to N-saturated forests can be a large enough non-point source of N leaving the watershed to impact downstream water quality. This was highlighted by the reduction in pollutant exports derived from urban/agricultural activities, an increase in atmospheric N deposition, and the maturation of coniferous plantation forests in the past 30 years. These have led to reductions in total phosphorus and organic nitrogen concentrations in downstream water, whereas downstream nitrate (NO 3 -) concentrations increased over the last 30 years. The consequent increase in the downstream N:P ratio indicated P limitation. Reducing the NO 3 - exports from N-saturated upland forests is suggested as a strategy to improve regional downstream NO 3 - pollution, but involves intercontinental-scale action in reducing atmospheric N emissions.
UR - http://www.scopus.com/inward/record.url?scp=84857786427&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84857786427&partnerID=8YFLogxK
U2 - 10.1007/s10021-011-9505-z
DO - 10.1007/s10021-011-9505-z
M3 - Article
AN - SCOPUS:84857786427
VL - 15
SP - 230
EP - 241
JO - Ecosystems
JF - Ecosystems
SN - 1432-9840
IS - 2
ER -