Assessing the role of forests in mitigating eutrophication downstream of pasture during spring snowmelt

Abstract

Abstract:Little research has examined whether forests reduce stream water eutrophication in agricultural areas during spring snowmelt periods. This study evaluated the role of forests in ameliorating deteriorated stream water quality in agricultural areas, including pasture, during snowmelt periods. Temporal variation in stream water quality at a mixed land-use basin (565 ha: pasture 13%, forestry 87%), northern Japan, was monitored for 7 years. Synoptic stream water sampling was also conducted at 16 sites across a wide range of forest and agricultural areas in a basin (18.3 km 2 ) in spring, summer and fall. Atmospheric nitrogen (N) and phosphorus (P) deposition were measured for 4 years. The results showed that concentration pulses of nitrate, organic N and total P in stream water were observed when discharge increased during spring snowmelt. Their concentrations were high when silicate concentrations were low, suggesting surface water exported from pasture largely contributed to stream water pollution during snowmelt. Atmospheric N and P deposition (4.1 kg N ha À1 y À1 ; 0.09 kg P ha À1 y À1, respectively) was too low to affect the background concentrations of N and P in streams from forested areas. Reduction of eutrophication caused by nutrients from pasture was mainly due to dilution by water containing low concentrations of N and P exported from forested areas, whereas instream reduction was not a dominant process. Results indicate that forests have a limited capacity to reduce the concentration pulses of N and P in stream water during snowmelt in this study basin.

Nitrogen inputs drive nitrogen concentrations in U.S. streams and rivers during summer low flow conditions

“…This finding supports other reports that instream retention and removal is most efficient when concentrations are lowest, but has a muted effect on high concentrations. As a result, when terrestrial inputs vary widely, they largely control spatial variability in concentrations (Chiwa et al, 2015;Lin et al, 2015;Scanlon et al, 2010).…”

Soil microbial community responding to moderately elevated nitrogen deposition in a Japanese cool temperate forest surrounded by fertilized grasslands

“…In the present study, we focused on the relationship between spatially varied nitrogen deposition and soil microbial properties within a cool temperate forest in the eastern area of Hokkaido, Japan. Eastern Hokkaido, including the investigated forest, receives relatively low nitrogen deposition from the atmosphere (2-5 kg N ha −1 yr −1 as a typical value) (Chiwa et al 2015; Network Center for EANET 2021), while nitrogen deposition in the boundary area of the forest (i.e., forest edge) is possibly more than that in the interior area of the forest (forest interior) owing to advection of nitrogen fertilizer, which was supplied to surrounding pasture grasslands ( Fig. 1) (Reinmann and Hutyra 2017;Remy et al 2016Remy et al , 2017Remy et al , 2018aRemy et al , 2018b.…”

Soil microbial community responding to moderately elevated nitrogen deposition in a Japanese cool temperate forest surrounded by fertilized grasslands

“…In the present study, we focused on the relationship between spatially varied nitrogen deposition and soil microbial properties within a cool temperate forest in the eastern area of Hokkaido, Japan. Eastern Hokkaido, including the investigated forest, receives relatively low nitrogen deposition from the atmosphere (2-5 kg N ha −1 yr −1 as a typical value) (Chiwa et al 2015; Network Center for EANET 2021), while nitrogen deposition in the boundary area of the forest (i.e., forest edge) is possibly more than that in the interior area of the forest (forest interior) owing to advection of nitrogen fertilizer, which was supplied to surrounding pasture grasslands (Fig. 1) (Reinmann and Hutyra 2017;Remy et al 2016Remy et al , 2017Remy et al , 2018aRemy et al , 2018b.…”