Trends in stream water concentration and export of nitrogen and phosphorus from boreal forested catchments in Finland Sakari Sarkkola 1, Harri Koivusalo 1, Ari Laurén 1, Pirkko Kortelainen 2, Tuija Mattsson 2, Sirpa Piirainen 1, Mike Starr 3 & Leena Finér 1 1 Finnish Forest Research Institute 2 Finnish Environment Institute 3 University of Helsinki, Department of Forest Ecology Metsäntutkimuslaitos Skogsforskningsintitutet Finnish Forest Research Institute www.metla.fi
Background In Finland and northern Scandinavia, 2/3 of the land area is covered by boreal forests Mostly dominated by Scots pine (Pinus sylvestris) or Norway spruce (Picea abies) About 30% of land area is covered by peatlands (histosols) In Finland, ca 80% of the forests are used for intensive forestry. Clear cutting a common method in the forest regeneration 14.5.2009 COST-FORMAN, Athens
Thinned Scots pine stand Drained peatland Timber harvesting 14.5.2009 COST-FORMAN, Athens
Aquatic habitats of lakes typically nitrogen (N) and phosphorus limited Sensitive to eutrophication N and P leachings from terrestrial ecosystems affect the water quality Water protection an important environmental question in forestry Most of the leached N and P are is dissolved organic form (DON, DOP) Sedimentation ponds are used in water protection 14.5.2009 COST-FORMAN, Athens
During the latest 10-15 years, increasing trends in dissolved organic matter concentrations have been found in the lakes and rivers across Europe and North America Climate change? Changes in atmospheric and soil chemistry? Changes in land-use management? Experimental data from boreal forested catchments and particularly from pristine areas are scarce 14.5.2009 COST-FORMAN, Athens
Objectives The aims of this study were: 1) to investigate long-term changes in TP, TON, NO 3 and NH 4 concentration and export in stream water discharged from forested headwater catchments in the boreal zone. 2) to identify the controlling factors affecting concentration and export of TP and N-fractions. climatic variables atmospheric deposition Organic matter in soil and vegetation Catchment characteristics 9.6.2008 14.5.2009 COST-FORMAN, Athens
Material Catchments 8 forested catchments in boreal zone in eastern Finland (29-494 ha) - ca 200 m a.s.l. - peatland cover 9-70% Located in same climatic area and on similar bedrock Monitored intensively (runoff daily, water samples twice a month) Time series Nurmes-catchments: 28 years Valu-catchments: 15 years Both managed and unmanaged areas are included 9.6.2008 14.5.2009 COST-FORMAN, Athens 20 km
Main stream and the gauging station in the pristine Liuhapuro catchment. Runoff and water quality have been monitored since spring 1978. 11.1.2008 14.5.2009 COST-FORMAN, Athens
Tree stands measured once during the monitoring periods (mean stand volume 26-187 m 3 ha -1 ) The thickness of organic layer has been estimated by using the sample plots and peat geological inventory data The analysis of TP, TON, NH4, NO3 concentrations in the water samples were determined using standard methods 11.1.2008 9.6.2008 14.5.2009 COST-FORMAN, Athens
Methods Seasonal concentration (mg l -1 ) and export (kg ha -1 ) of TP, TON, NH4 and NO3 were calculated for: - Spring: March-May - Summer: June-August - Autumn: September-November Annual and seasonal concentrations were calculated as averages of the measurements within given time period 11.1.2008 14.5.2009 COST-FORMAN, Athens
Weather and atmospheric deposition data were obtained from the two nearest weather stations Long-term trends were analysed using the Seasonal Kendall -test Controling factors affecting the concentration and export were identified using the mixed model -approach Climatic variables Deposition Soil and vegetation Other catchment characteristics The effect of forestry treatments were removed from the data in the time-serie analysis and modelling. 11.1.2008 14.5.2009 COST-FORMAN, Athens
Annual precipitation and mean temperature 1979-2006 Results Climate variables Mean seasonal temperatures 1979-2006 Mean temp. C Precipitation, mm 4 3 2 1 0-1 -2 800 600 400 200 0 1980 1985 1990 1995 2000 2005 Year Mean temp. Precip. mm Annual mean temperature has increased about 1.2 C during 27 years. Significant increase in summer and autumn. No trends in the annual precipitation. Mean temp. C degrees 20 15 10 5 0-5 -10-15 -20 1979 1981 1983 1985 1987 1989 1991 1993 Year 1995 1997 1999 2001 Winter Spring Summer Autumn 2003 2005 +(*) +(*) +(ns) +(ns) 11.1.2008 14.5.2009 COST-FORMAN, Athens
Runoff 700 600 Annual runoff, mm Kivipuro Liuhapuro Murtopuro Suopuro 500 Runoff, mm 400 300 200 100 1980 1985 1990 1995 2000 2005 Year -Annual runoff decreased significantly only in unmanaged Liuhapurocatchment 11.1.2008 11.12..2008 14.5.2009 COST-FORMAN, Athens
Total phosphorus Concentration TP (ug l -1 ) Export TP (g ha -1 ) 200 Total phsophorus (TP), ug l-1 150 100 50 Suopuro Välipuro Liuhapuro Kivipuro Murtopuro Total phosphorus, g ha -1 800 Suopuro Välipuro Kivipuro Liuhapuro Murtopuro 600 400 200 0 1975 1980 1985 1990 1995 2000 2005 2010 Year 0 1975 1980 1985 1990 1995 2000 2005 2010 -Treatment effect very clear in intensively managed Murtopuro catchment -The annual TP concentrations decreased in two catchments when the treatment effect was removed from the data. - Annual TP exports decreased in five catchments year 14.5.2009 COST-FORMAN, Athens
Organic nitrogen Concentrations TON ug l -1 Export TON (g ha -1 ) TON, ug l -1 1000 800 600 400 200 Suopuro Välipuro Kivipuro Liuhapuro Murtopuro Organic nitrogen, g ha -1 10000 8000 6000 4000 2000 Suopuro Välipuro Kivipuro Liuhapuro Murtopuro 0 1980 1985 1990 1995 2000 2005 year 0 1975 1980 1985 1990 1995 2000 2005 2010 Year - The TON concentrations increased or remained ungchanged - Changes occurred mostly in spring - The TON exports did not changed excluding decreasing trend in Liuhapuro 14.5.2009 COST-FORMAN, Athens
Inorganic nitrogen Ammonium (NH 4 N μg l -1 ) Nitrate (NO 3 N μg l -1 ) 120 120 NH 4, ug l -1 100 80 60 40 Suopuro Välipuro Kivipuro Liuhapuro Murtopuro NO 3, ug l -1 100 80 60 40 Suopuro Välipuro Liuhapuro Murtopuro Kivipuro 20 20 0 1980 1985 1990 1995 2000 2005 Year 0 1980 1985 1990 1995 2000 2005 Year -The concentrations have decreased since mid of 1990s. - Decreases found in every seasons - Decreasing trend found also in the exports 14.5.2009 COST-FORMAN, Athens
Atmospheric deposition, kg ha -1 yr. -1 10 8 6 4 2 Deposition SO 4 -S (-) NO 3 -N (-) NH 4 -N (-) Tot N (-) 0 1980 1985 1990 1995 2000 2005 Year Annual mean atmopheric depositions in Eastern Finland have distinctively decreased in years since beginning of 1990s. 14.5.2009 COST-FORMAN, Athens
Explanatory factors for concentrations Annual Spring Summer Autumn TP +Peatland% +Peatland% +Peatland% +Peatland% +Snow layer +Water temp. +Precipitation +Fertile sites% +Precipitation + Water temp. +Runoff TON +Peatland% +Peatland% +Peatland% +Peatland% +Snowfall +Precipitation +Water temp. NO3 +Peatland% +Peatland% +Peatland% +Tsum +N-deposition +Precipitation +Fertile sites% -Precipitation NH4 +Peatland% +Peatland% +Peatland% +Peatland% +NH4-deposition +NH4-deposition +NH4-deposit. +NH4-deposit. -Precipitation 11.12..2008 14.5.2009 COST-FORMAN, Athens
Conclusions Increasing trends in organic nitrogen, but no large change in the exports Temperature related changes in the leaching of DON Decreasing runoff affects the exports Decreasing trends in the concentrations and exports of inorganic nitrogen fractions Decreasing deposition have a decreasing effect on leaching The ecosystem has not reached the N saturation state 11.12..2008 14.5.2009 COST-FORMAN, Athens
The peatland cover important factor explaining particularly the leaching of organic N. - Weather conditions control significantly the exports The identified trends in the concentrations and exports were smaller than the annual and seasonal variation and the variation between the catchments, however. 14.5.2009 COST-FORMAN, Athens
Thank you!! 11.1.2008 9.6.2008 14.5.2009 COST-FORMAN, Athens
TOC, mg l -1 yr -1 TOC, mg l -1 yr -1 11.1.2008 9.6.2008 50 40 30 20 10 50 40 30 20 10 Annual mean TOC concentrations Cutting 69.0 1975 1980 1985 1990 1995 2000 2005 2010 Porkkasalo (unmanaged) Kangaslampi (unmanaged) Korsukorpi (Unmanaged) Iso-Kauhea (managed) Kangasvaara (managed) Year Year Kivipuro (cutting 1983) Murtopuro (cutting 1983) Liuhapuro (unmanaged) Välipuro (Unmanaged) +(***) +(**) +(**) -(NS) +(*) +(**) +(***) +(**) +(ns) 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 TOC, kg ha -1 yr -1 250 200 150 100 50 TOC, kg ha -1 yr -1 Annual mean TOC export cutting 361 0 1975 1980 1985 1990 1995 2000 2005 2010 250 200 150 100 Porkkasalo Kangasvaara Kangaslampi Korsukorpi Iso-Kauhea Kangasvaara year Year Kivipuro Murtopuro Liuhapuro Välipuro +(*) -(NS) +(NS) -(NS) -(NS) +(NS) 50 -(NS) +(NS) 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 - Significant annual trends in TOC concentrations found particularly in pristine catchments - The largest increase in concentrations occurred after the middle of 1990s - Clear effect of intensive clearcuttings (57%of the area) and drainage (40%) in Murtopuro area - TOC export is largely controlled by runoff
Seasonal TOC-trends Significant (p<=0.05) seasonal trends in TOC concentration and export Catchment TOC, concentration TOC, export Winter Spring Summer Autumn Winter Spring Summer Autumn Suopuro Managed (+) (+) Kivipuro Managed (+) (+) (-) Koivupuro Managed (+) (+) Murtopuro Managed (-) (-) (+) (-) Isokauhea Managed (+) (+) Kangasvaara Managed (+) Välipuro Unmanaged (+) (+) (+) Liuhapuro Unmanaged (+) (+) Korsukorpi Unmanaged (+) Porkkavaara Unmanaged (+) (+) Kangaslampi Unmanaged (+) (+) 9.6.2008 14.5.2009 COST-FORMAN, Athens
In the mixed models, percentage of peatland, amount of biologically active peat, and mean water temperature mostly explained the change in the concentrations (The direction of the effects have been presented). Concentration Winter Spring Summer Autumn (mg l -1 ) +Peatland% +Peatland% +Act.peat (kg/ha) +Act.peat (kg/ha) +Water temp. +Water temp. +Water temp. +Ditch/Area + Mean air temp. Export Winter Spring Summer Autumn (kg ha -1 ) + Runoff + Runoff + Runoff + Runoff +Peatland% +Peatland% +Act.peat (kg/ha) +Act.peat (kg/ha) +Precipitation +Precipitation -Precip. snow -Precip. snow +Temp. sum +Temp. sum Tree stand volume or biomass did not affect the concentrations or export 9.6.2008 14.5.2009 COST-FORMAN, Athens
Mound Furrow 25 years old planted Scots pine stand in heavily managed Murtopuro catchment. The furrows of the site preparation measures are still visible, but the soil is already in stable state. 11.1.2008 14.5.2009 COST-FORMAN, Athens