Relationships between atmospheric nitrogen inputs and the vertical nitrogen and phosphorus concentration gradients in the lichen Cladonia portentosa

Abstract

The relationship between precipitation chemistry and the concentrations of nitrogen ([N]) and phosphorus ([P]) in the cushion-forming lichen Cladonia portentosa (Dufour) Coem. (l C. impexa (Harm)) was investigated. Samples of C. portentosa were collected from heathlands and upland moorlands close to 31 rural sampling stations in the UK Acid Deposition Monitoring Network, which provides data on wet deposition and NO # concentrations in air. The [N] and [P] were measured in the top 5 mm of lichen thalli (thallus apices) and also in a horizontal stratum between 40-50 mm from the apices (thallus base). The [N] (per unit dry mass) was 0n08-1n82 % and [P] was 0n04-0n17 %, depending on collection site and lichen fraction analysed. Concentrations of both elements were c. 2-5 times greater in the apices than in the basal strata, and [N] and [P] values in each stratum were strongly positively correlated. Lichen [N] was positively correlated with N deposition : this relationship was stronger when using [N] values for thallus bases than for the apices. By contrast, thallus [N] was poorly correlated with [N] values in precipitation. When [NO # ] in air was included together with NO $ − deposition in a linear regression model explaining thallus base N, the model fit was significantly improved, whereas modelled values of NH $ deposition rate for the heathland sites did not correlate with lichen [N]. It is suggested that the proportionately greater enrichment of [N] in the thallus base might reflect a perturbation of internal recycling of thallus N at polluted sites. Thallus [P] was generally weakly linked to wet N deposition but positively correlated with [NO # ] in air. It is not known whether the trend for increasing thallus [P] values indicates decreasing lichen growth rate and reduced growth dilution of P in polluted areas, or is due to regional variation in P deposition rate.

External nutrient inputs into terrestrial ecosystems of the Falkland Islands and the Maritime Antarctic region

“…However, at Signy Island, most lichens had a significantly lower signature than that of the wind blown material, indicating that they are unlikely to rely on this source of nitrogen. Their signature was more similar to that of precipitation, from which many lichens are known to obtain nutrients (Greenfield 1992b;Crittenden 1998;Hyvarinen and Crittenden 1998), rather than soil (Ellis et al 2004).…”

Bio-monitoring in Western North America: What Can Lichens Tell Us About Ecological Disturbances?

“…For example, even small increases in N deposition can alter ecosystem processes in Nlimited environments, and previous studies suggest that current levels of N deposition are predicted to adversely affect a range of sensitive ecosystems in the western North America (Fenn et al 2008;McMurray et al 2013;Geiser et al 2010;Glavich and Geiser 2008;Hyvärinen and Crittenden 1998;Jovan and Carlberg 2007). The primary nitrogen-containing atmospheric pollutants are nitrogen oxides and ammonia, but may also include further oxidized forms including, ammonium, nitrates, and nitric acid vapor (McCune and Geiser 2009).…”

“…To varying degrees, these land-use practices have had a substantial ecological impact, including habitat and community alteration, increased levels of pollutants, and the introduction and spread of non-native species (Fleischner 1994;Miller et al 1989). Additionally, air pollution, altered fire regimes, and other broadscale disturbances have been shown to impact ecological health throughout the intermountain region (Smith et al 2000;Miller et al 1989 (Dillman 1996;Hyvärinen and Crittenden 1998).…”

Nitrogen fixation by associative cyanobacteria in the Canadian Arctic.

“…For example, cyanolichens that lack a rooting system are limited to nutrient acquisition from atmospheric sources and nutrients concentrated at the surface of the substrate (Hyvarinen & Critteneden 1998;Weiss et al, 2005). Mat-forming lichens also tend to form large quantities of basal necromass that can isolate the living thalli from chemical influences of the soil beneath (Crittenden, 1991;Hyvarinen & Crittenden, 1998).…”

“…Fixed N may also be maintained within the lichen due to tight N recycling within the thalli of mat forming lichens. There is evidence of translocation of N from the degenerating lower thallus to the apices where there is an N sink for new growth (Crittenden, 1991;Hyvarinen & Crittenden, 1998;Ellis et al, 2004).…”