Allocation patterns of airborne nitrogen in mountainous heathlands – A 15 N tracer study in the Cantabrian Mountains (NW Spain)

Calvo-Fernández, Javier; Marcos, Elena; Calvo, Leonor

doi:10.1016/j.ecoleng.2015.07.027

Cited by 7 publications

(6 citation statements)

References 68 publications

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“…Our results support the fact that there is a reduced microbial acquisition and immobilization of nutrients that maintains the low soil fertility status of montane heathlands (Nielsen et al, 2009). Furthermore, the distinctive climatic conditions of our montane study area, characterized by low temperatures, prolonged snow cover until late-spring, and a brief summer drought (Calvo-Fernández et al, 2017), could have also influenced the low rates of soil microbial nutrient acquisition (Calvo-Fernández et al, 2015;Hagedorn et al, 2010). Moreover, previous studies indicated that longer-term (> 10-year) N inputs may be required for producing significant shifts in the nutrient content of the soil microbial biomass in heathlands due to the slow organic matter decomposition rates (Contosta et al, 2015;Rinnan et al, 2007).…”

Section: Figsupporting

confidence: 82%

Time- and age-related effects of experimentally simulated nitrogen deposition on the functioning of montane heathland ecosystems

Calvo-Fernández

Taboada

Fichtner

et al. 2018

Science of The Total Environment

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Ecosystems adapted to low nitrogen (N) conditions such as Calluna-heathlands are especially sensitive to enhanced atmospheric N deposition that affects many aspects of ecosystem functioning like nutrient cycling, soil properties and plant-microbial-enzyme relationships. We investigated the effects of five levels of experimentally-simulated N deposition rates (i.e., N fertilization treatments: 0, 10, 20 and 50kgNhayr for 3years, and 56kgNhayr for 10years) on: plant, litter, microbial biomass and soil nutrient contents, soil extracellular enzymatic activities, and plant root ericoid mycorrhizal colonization. The study was conducted in marginal montane Calluna-heathlands at different developmental stages resulting from management (young/building-phase and mature-phase). Our findings revealed that many soil properties did not show a statistically significant response to the experimental addition of N, including: total N, organic carbon (C), C:N ratio, extractable N-NO, available phosphorus (P), urease and β-glucosidase enzyme activities, and microbial biomass C and N. Our results also evidenced a considerable positive impact of chronic (10-year) high-N loading on soil extractable N-NH, acid phosphatase enzyme activity, Calluna root mycorrhizal colonization by ericoid fungi, Calluna shoot N and P contents, and litter N content and N:P ratio. The age of heathland vegetation influenced the effects of N addition on ericoid mycorrhizal colonization, resulting in higher colonized roots in young heathlands at the control, low and medium N-input rates; and in mature ones at the high and chronically high N rates. Also, young heathlands exhibited greater soil extractable N-NO, available P, microbial biomass N, Calluna shoot N and P contents, and litter N content, compared to mature ones. Our results highlighted that accounting for the N-input load and duration, as well as the developmental stage of the vegetation, is important for assessing the effects of added N, particularly at the heathlands' southern distribution limit.

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Section: Figsupporting

confidence: 82%

Time- and age-related effects of experimentally simulated nitrogen deposition on the functioning of montane heathland ecosystems

Calvo-Fernández

Taboada

Fichtner

et al. 2018

Science of The Total Environment

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“…The chemical form of N inputs is an important factor regulating plant nutrient assimilation processes in a wide variety of ecosystems (Harmens et al, 2014;Izquieta-Rojano et al, 2016;Pornon et al, 2007). So, the high NO 3 and NH 4 + concentrations in rainwater found during summer could affect the nutrient balance of N-poor ecosystems such as mountainous heathlands (Calvo-Fernández et al, 2015), since this period is the growing season and the highest amount of N is uptaken by vegetation. Previous studies have demonstrated that an increase of N depositions in heathland ecosystems could involve higher shoot N content, inducing heather defoliation by leaf beetles, such as Lochmaea suturalis (Cuesta et al, 2008;Torres, 2010), as well as a rise in soil nutrient content and higher species richness .…”

Section: Discussionmentioning

confidence: 99%

“…One of the most representative ecosystems in the mountainous areas of North-Western Spain is Calluna-vulgaris-heathland, which represents a habitat of high conservation importance at a European level (Habitats Directive 92/43/EEC). These Calluna heathlands are adapted to low-N conditions (Calvo-Fernández et al, 2015) and knowledge of N depositions rates in these sensitive-N ecosystems could be necessary to apply appropriate management strategies (Boutin et al, 2015;Calvo et al, 2005Calvo et al, , 2007Marcos et al, 2003). For this reason, modelled N deposition maps have been created in order to complement the measurement data by filling the large spatial gaps between measurement points (Vet et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Bulk deposition of atmospheric inorganic nitrogen in mountainous heathland ecosystems in North-Western Spain

Calvo-Fernández

Marcos

Calvo

2017

Atmospheric Research

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Nitrogen (N) deposition has been identified as one of the main traits of terrestrial ecosystems, affecting their structure and functioning. Among terrestrial ecosystems, heathlands are characterised by low nutrient status and highly affected by N deposition. However, few studies have been developed under natural field conditions to evaluate the amount of N deposition in these ecosystems. Therefore, a field experiment was carried out to investigate the inorganic N inputs in mountainous heathlands of NorthWestern Spain. Two study sites (La Majúa and San Isidro) were selected on the south side of the Cantabrian Mountains, as a representative monitoring N-sensitive ecosystems. Three replicated bulk collectors and one rain gauge were installed at each study site to collect monthly rainwater samples over three years. Wet bulk N deposition was different between the study areas (2.81 kg N ha-1 year-1 in La Majúa and 4.56 kg N ha-1 year-1 in San Isidro), but showed the same temporal pattern, with the highest N deposition rate observed in April and the lowest in August-September. In general, annual wet bulk NO3-N deposition was higher than NH4+-N, reflecting the prevailing NOX emission sources. Depositions of NO3-N were mostly originated by NOX emissions from northern highly industrialized and populated areas of North Spain. The lower NH4+/NO3-ratio in rainwater observed in the study area could be due to the decline of traditional land uses (livestock grazing, heath burning and croplands) associated with NHY emissions. Despite the low rates of N deposition observed in this study, N-sensitive heathlands in NorthWestern Spain could be threatened by N depositions.

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“…As a consequence, gaseous N losses from moss carpets are considered to have significant impacts on ecosystem N budgets (Fang et al, 2015 ), and also contribute to global nitrous oxide emissions from terrestrial ecosystems (Lenhart et al, 2015 ). For example, Calvo-Fernández et al ( 2015 ) found high N losses as a result of denitrification in Cantabrian Mountain heathlands, when soils were water-saturated during winter. Fang et al ( 2015 ) concluded that the effects of denitrification losses on ecosystem N balances are often underestimated.…”

Section: Discussionmentioning

confidence: 99%

Bryophytes and Organic layers Control Uptake of Airborne Nitrogen in Low-N Environments

et al. 2017

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The effects of atmospheric nitrogen (N) deposition on ecosystem functioning largely depend on the retention of N in different ecosystem compartments, but accumulation and partitioning processes have rarely been quantified in long-term field experiments. In the present study we analysed for the first time decadal-scale flows and allocation patterns of N in a heathland ecosystem that has been subject to airborne N inputs over decades. Using a long-term 15N tracer experiment, we quantified N retention and flows to and between ecosystem compartments (above-ground/below-ground vascular biomass, moss layer, soil horizons, leachate). After 9 years, about 60% of the added 15N-tracer remained in the N cycle of the ecosystem. The moss layer proved to be a crucial link between incoming N and its allocation to different ecosystem compartments (in terms of a short-term capture, but long-term release function). However, about 50% of the 15N captured and released by the moss layer was not compensated for by a corresponding increase in recovery rates in any other compartment, probably due to denitrification losses from the moss layer in the case of water saturation after rain events. The O-horizon proved to be the most important long-term sink for added 15N, as reflected by an increase in recovery rates from 18 to 40% within 8 years. Less than 2.1% of 15N were recovered in the podzol-B-horizon, suggesting that only negligible amounts of N were withdrawn from the N cycle of the ecosystem. Moreover, 15N recovery was low in the dwarf shrub above-ground biomass (<3.9% after 9 years) and in the leachate (about 0.03% within 1 year), indicating still conservative N cycles of the ecosystem, even after decades of N inputs beyond critical load thresholds. The continuous accumulation of reactive forms of airborne N suggests that critical load-estimates need to account for cumulative effects of N additions into ecosystems.

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Allocation patterns of airborne nitrogen in mountainous heathlands – A 15 N tracer study in the Cantabrian Mountains (NW Spain)

Cited by 7 publications

References 68 publications

Time- and age-related effects of experimentally simulated nitrogen deposition on the functioning of montane heathland ecosystems

Time- and age-related effects of experimentally simulated nitrogen deposition on the functioning of montane heathland ecosystems

Bulk deposition of atmospheric inorganic nitrogen in mountainous heathland ecosystems in North-Western Spain

Bryophytes and Organic layers Control Uptake of Airborne Nitrogen in Low-N Environments

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