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

Abstract

AbstractQuestion: 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‐1.a‐1 for N and < 0.5 kg.ha‐1.a‐1 for P. Nutrient stores in the above‐ground biomass were 95/197 kg.ha‐1 for N and 5/13 kg.ha‐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‐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.