Plant and vegetation functional responses to cumulative high nitrogen deposition in rear-edge heathlands

Abstract

Elevated atmospheric nitrogen (N) deposition is a major driver of change, altering the structure/functioning of nutrient-poor Calluna vulgaris-heathlands over Europe. These effects amply proven for north-western/central heathlands may, however, vary across the ecosystem's distribution, especially at the range limits, as heathlands are highly vulnerable to land-use changes combined with present climate change. This is an often overlooked and greatly understudied aspect of the ecology of heathlands facing global change. We investigated the effects of five N-fertilisation treatments simulating a range of N deposition rates (0, 10, 20, and 50 kg N ha yr for 1 year; and 56 kg N ha yr for 9 years) on the Calluna-plants, the plant functional groups, species composition and richness of two life-cycle stages (building/young- and mature-phase) of Calluna-heathlands at their rear-edge limit. Our findings revealed a dose-related response of the shoot length and number of flowers of young and mature Calluna-plants to the addition of N, adhering to the findings from other heathland locations. However, cumulative high-N loading reduced the annual growth and flowering of young plants, showing early signs of N saturation. The different plant functional groups showed contrasting responses to the cumulative addition of N: annual/perennial forbs and annual graminoids increased with quite low values; perennial graminoids were rather abundant in young heathlands but only slightly augmented in mature ones; while bryophytes and lichens strongly declined at the two heathland life-cycle stages. Meanwhile there were no significant N-driven changes in plant species composition and richness. Our results demonstrated that Calluna-heathlands at their low-latitude distribution limit are moderately resistant to cumulative high-N loading. As north-western/central European heathlands under high-N inputs broadly experienced the loss of plant diversity and pronounced changes in plant species dominance, rear-edge locations may be of critical importance to unravel the mechanisms of heathland resilience to future global change.

The colors of heath flowering – quantifying spatial patterns of phenology in Calluna life‐cycle phases using high‐resolution drone imagery

“…a; Taboada et al. ). This creates a link between patterns of flowering and the distribution of functional diversity that has recently been gaining importance in ecological research, since the ecosystem conservation highly benefits from holistic biodiversity assessment that integrates functional aspects into phylogenetic and taxonomic approaches (Petchey and Gaston ; Devictor et al.…”

“…However, this phenomenon has not yet been discussed in literature for Calluna. There is evidence that functional responses such as flowering intensity of Calluna after nitrogen addition varies between different LCPs (Meyer-Gr€ unefeldt et al 2015a;Taboada et al 2018). This creates a link between patterns of flowering and the distribution of functional diversity that has recently been gaining importance in ecological research, since the ecosystem conservation highly benefits from holistic biodiversity assessment that integrates functional aspects into phylogenetic and taxonomic approaches (Petchey and Gaston 2006;Devictor et al 2010;Lausch et al 2016).…”

Transhumant Sheep Grazing Enhances Ecosystem Multifunctionality in Productive Mountain Grasslands: A Case Study in the Cantabrian Mountains

“…The normality of model residuals was inspected through q-q plots. Predicted values of the response variable in the models were computed for each level of the grazing treatment, removing the uncertainty of the random effects (Taboada et al, 2018). We obtained the significance levels of the difference between short-term and long-term grazing exclusion, and the control treatment (allowed grazing) from the model output.…”

Germination response of woody species to laboratory-simulated fire severity and airborne nitrogen deposition: a post-fire recovery strategy perspective

“…Solid granules release ammonium and nitrate slowly over the soil surface, and have been used in prior experiments assessing the ecosystem responses to airborne N deposition (e.g. Calvo-Fernández et al 2018;Taboada et al 2018).…”