Impact of sheep grazing on nutrient budgets of dry heathlands

Abstract

Abstract Questions: What effect does sheep grazing have on the nutrient budgets of heathlands? Can grazing compensate for atmospheric nutrient loads in heathland ecosystems? What are the conclusions for heathland management? Location: Lüneburg Heath, NW Germany. Methods: During a one‐year grazing experiment (stocking rate 1.1 sheep/ha) nutrient balances for N, Ca, K, Mg and P were calculated by quantifying input rates (atmospheric deposition, sheep excrement) and output rates (biomass removal, leaching). Results: Atmospheric nutrient deposition amounted to 22.8 kg.ha −1 .a −1 for N and < 0.2 kg.ha −1 .a −1 for P. Sheep excrement increased the inputs for N and P by ca. 3.5 and 0.2 kg.ha −1 .a −1 , respectively. Grazing reduced N‐ and P‐stores in the above‐ground biomass by 25.6 and 1.9 kg.ha −1 .a −1 , respectively. N‐and P‐losses via leaching amounted to 2.2 and < 0.2 kg.ha −1 .a −1 . Output:input ratios for P were high, indicating that grazing severely affected P‐budgets of heaths. Conclusions: Our results suggest that sheep grazing has the potential to compensate for atmospheric nutrient loads (particularly for current N deposition rates). However, in the long term the combination of elevated N‐deposition and P‐loss due to grazing may cause a shift from N‐(co‐) limited to more P‐(co‐) limited plant growth. To counteract an aggravation of P‐deficiency in the long term, grazing may be combined with management measures that affect P‐budgets to a lesser extent (e.g. prescribed burning).