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

Abstract

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

Potential Approaches to Developing Lichen-Based Critical Loads and Levels for Nitrogen, Sulfur and Metal-Containing Atmospheric Pollutants in North America

“…More recently, Gordon et al (2001) re-examined the impacts of nitrogen on these plots, with particular attention to the bryophyte communities. Overall bryophyte cover was unaffected by increased nitrogen supply, although this was a net result of individual species showing different responses.…”

Nutrients and biomass spatial patterns in alpine tundra ecosystem on Changbai Mountains, Northeast China

“…S is considered an essential plant macronutrient. The factors that control the rate of S reduction have not been identified with certainty in the various environments because many factors are involved, such as, oxygen and sulphate concentrations, temperature and organic matter availability [23,26]. Soil S would come from the mineralization of litter, soil organic matter and rock in alpine tundra on Changbai Mountains.…”

“…Further research should be done to elucidate the relative contribution of soil S and P during vegetation development after gigantic volcano eruption in 1702a. The ratios of C:N, C:P, C:S and C:N:P were often used as indicators of soil nutrient condition [8,26,27]. Soil N and S concentrations are lower in SA while soil P is lower in LA and higher in MA of alpine tundra on Changbai Mountains, respectively.…”

“…It is not surprising, therefore, that alpine tundra productivity is generally nutrients limited and that dominant plants are mostly species or functional groups of low nutrients requirement, or species with a conservative use of nutrients [23,24]. Most studies of alpine tundra have either addressed questions of nutrients acquisition or of decomposition and mineralization processes [24][25][26] while few studies have attempted to integrate processes in both biomass and nutrients. There is currently limited information on nutrients cycling of alpine tundra ecosystems, whereas it is important to better understand nutrients spatial pattern and potential alpine tundra response to environment change in such regions.…”

Biomass burning in eastern Europe during spring 2006 caused high deposition of ammonium in northern Fennoscandia

“…Nitrogen deposition has been shown to influence forest, heathland and bog ecosystems even on remote parts of Europe (Bobbink and Hettelingh, 2011;Dise et al, 2001;Phoenix et al, 2012). Northern ecosystems are especially vulnerable to nitrogen deposition, as bryophytes and lichens are important parts of these ecosystems and as bryophytes and lichens take the major part of their nutrition directly from the air (Cornelissen et al, 2001;Gordon et al, 2001;Bates, 2002). Furthermore, nitrogen may increase primary productivity of the ecosystems and above a certain level it is common that a few competitive species are able to exploit the available N and to dominate other species by shading and lead to changed biodiversity Stevens et al, 2011;Phoenix et al, 2012).…”