Impact of prescribed burning on the nutrient balance of heathlands with particular reference to nitrogen and phosphorus

Question: Can prescribed winter burning compensate atmospheric nutrient loads for dry heathlands? What effects does prescribed burning have on nutrient balances, particularly as regards the limiting nutrients N and P?Location: Lueneburg Heath, NW Germany.Methods: In two burning experiments (in 10/15 year old Calluna-stands) nutrient balances (for N, Ca, K, Mg, P) were calculated by analysing nutrient inputs (atmospheric deposition, ash deposition), nutrient stores (above-ground biomass, organic horizon) and nutrient outputs (biomass combustion, leaching).Results: Atmospheric nutrient deposition amounted to 22.8 kg.ha super(-1).a super(-1) for N and < 0.5 kg.ha super(-1).a super(-1) for P. Nutrient stores in the above-ground biomass were 95/197 kg.ha super(-1) for N and 5/13 kg.ha super(-1) for P (first/second experiment, respectively). From these stores 90/53% (for N) and 25/14% (for P) were removed by burning. Effects of leaching on nutrient balances were low. In the first two years after burning, leaching rates of N increased by about 4/6 kg.ha super(-1), whereas leaching rates of P did not change significantly. Input/output-ratios showed that prescribed burning leads to positive nutrient balances for N, Ca and Mg in the long term. For example, the amounts of N removed by prescribed burning are equivalent to ca. five years of atmospheric inputs. Applied in ten-year cycles, this measure alone cannot prevent N accumulation in the long term.Conclusion: Regarding 10/15 year old Calluna-heaths, we assume that prescribed burning cannot compensate for atmospheric N inputs, thus making long-term changes in the nutritional state inevitable. Therefore, prescribed burning should be applied in combination with high-intensity management measures.Abbreviation: TEP = Theoretical Effective Period.