Impacts of increased nitrogen supply on high Arctic heath: the importance of bryophytes and phosphorus availability.

摘要: Summary • This study investigates effects of nitrogen and phosphorus on high Arctic heath vegetation, particularly bryophytes. • Heath communities received factorial combinations (0, 10 50 kg ha−1 yr−1) (0 5 kg ha−1 yr−1) in five applications per growing season, for 8 yr. • Nitrogen decreased lichen cover but did not affect any other functional type. However, just 10 kg ha−1 yr−1 increased the proportion physiologically active bryophte shoots, their nitrate assimilation capacity. Phosphorus had greater effects, combination both nutrients altered species composition. Individual bryophyte displayed contrasting responses to fertilization, suggesting that they should be grouped as a single type. • The ‘critical load’ lies below 10 kg ha−1 yr−1. Nitrogen are colimiting this sytem, so critical load will lower where availability is greater. Responses vegetation increase net mineralisation due soil warming depend ratio which availabilities increase. The nutrient enhancement very persistent.