EFFECTS OF ANTHROPOGENIC STRESSORS ON WATER QUALITY IN NORWEGIAN FORESTS

Transcription

1 EFFECTS OF ANTHROPOGENIC STRESSORS ON WATER QUALITY IN NORWEGIAN FORESTS Nicholas Clarke Norwegian Institute of Bioeconomy Research Photo: Kjersti Holt Hanssen Photo: Nicholas Clarke

2 Background About 37% of Norway is covered by forest. The main area for forestry is eastern Norway

3 Source: National Atlas for Norway: Vegetation Solid geology Areas rich in mineral nutrients

4 Mean annual temperature (left, C) and precipitation (right, mm) for Source: Norwegian Meteorological Institute

5 What are the prognoses for climate change in Norway? Mean annual temperature increase by C Highest temperature increase in inland and northern Norway Milder winters Increased precipitation by 5-% Greatest increase in precipitation along the southwest coast and in the extreme north Longer growing season Increased summer drought risk Increased risk for pathogen and pest attacks? More extreme weather events (storms etc.) Depends on scenario

6 More total organic carbon (TOC) in winter runoff when winter temperatures increase above C (Wright and Jenkins 1) Possible increase in N fluxes in runoff; ecosystem changes from N sink to source (Wright 1998), related to increased N mineralisation (Verburg 1998)

7 Changes in average total ground vegetation species number per plot (yaxis) in nine boreal Norway spruce forest monitoring areas, 1988 to present Granneset, Nordland Gutulia, Hedmark Bringen, Buskerud Grytdalen, Telemark Urdvatnet, Sør-Trøndelag Otterstadstølen, Hordaland Østmarka, Akershus Solhomfjell, Aust-Agder Paulen, Vest-Agder

8 Deposition of acidifying components Total S (mgs/m 2 ) 2-6 Inorganic N (mgn/m 2 ) 2-6 Source: Aas et al. (11)

9 The Norwegian Monitoring Programme for Forest Damage (OPS), part of ICP Forests Source: Andreassen et al. (12)

10 Non-marine sulphate in bulk precipitation (meq/m 2 ) Source: Andreassen et al. (12)

11 Inorganic nitrogen in bulk precipitation (meq/m 2 ) Source: Andreassen et al. (12)

12 ph in soil water at 15 cm depth Source: Andreassen et al. (12)

13 18 SO 2-4 in soil solution SO 2-4 in soil solution Ca 2+ in soil solution 199: : Ca 2+ in soil solution Prognoses: MAGIC modelling for soil at Birkenes 18 BC/Al ratio in soil solution BC/Al ratio in soil solution % 3 Base saturation % 3 Base saturation Source: Larssen et al. (2) Observed annual values Hindcast Maximum Feasible Reduction Current Legislation Oslo protocol

14 18 SO 2-4 in stream SO 2-4 in stream Ca 2+ in stream ANC in stream Ca 2+ in stream ANC in stream Prognoses: MAGIC modelling for stream water at Birkenes % Base saturation % Base saturation Source: Larssen et al. (2) Observed annual values - Hindcast Maximum Feasible Reduction Current Legislation Oslo protocol

15 Effects of intensified forest harvesting There has been political interest in Norway in increasing production of bioenergy If harvesting residues such as branches and tops are to be used as a source of bioenergy, this will require more intensive use of the forests For this to be sustainable, we need to know what the consequences might be for the forest ecosystem There may be conflict between different political goals: on the one hand, increased use of forest biomass for energy and on the other, sustainable use of forest resources, carbon sequestration, and preservation of biological diversity

16 Side 16 We established two integrated field experiments in semi-natural Norway spruce forests at sites on moraine but with contrasting climate and topography, to compare the effects of stem-only (SOH) and whole-tree (WTH) harvesting on soils, ground vegetation and regeneration WTH: Two sub-treatments, piles and removal The same measurements were made at both sites Vindberg Gaupen Mean annual precipitation (mm) Mean annual temperature ( C) Slope ( ) 23 9 Harvesting Jan 11 Mar 9 Slash removal Oct 11 Sept 9 Number of replicates 5(x2) 6(x2)

17 SOH WTH pile WTH removal Changes in mean concentrations (mg N/l) of NO 3 -N in soil water at 3 cm depth with time at Gaupen (above) and Vindberg (below). Note the different scales SOH WTH pile WTH removal Side 17

18 SOH WTH pile WTH removal Changes in mean concentrations (mg/l) of Mg in soil water at 3 cm depth with time at Gaupen (above) and Vindberg (below) SOH WTH pile WTH removal

19 SOH WTH pile WTH removal Changes in mean concentrations (mg/l) of K in soil water at 3 cm depth with time at Gaupen (above) and Vindberg (below) SOH WTH pile WTH removal

20 Mg (mg l -1 ) Field experiment: Effects of fertilisation with wood ash and nitrogen on dissolved Mg concentrations at 4 cm depth Ctrl Ash N Ash+N

21 Conclusions The climate is likely to become warmer, wetter and wilder: more storms Effects on C and N runoff Possible effects on plant biodiversity Acidifying deposition has declined in Norway (as elsewhere in Europe) In the most impacted areas, recovery to pre-industrial levels is unlikely to be reached soon Removal of branches and tops for bioenergy has shortterm effects on soil solution chemistry, with increasing concentrations of nutrients in soil solution. Effects are site-specific N fertiliser but not wood ash has short-term effects on soil solution chemistry

22 Thank you for your attention Photo: Jørn Frode Nordbakken