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

Abstract

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.

Sustainable Conservation Tillage Improves Soil Nutrients and Reduces Nitrogen and Phosphorous Losses in Maize Farmland in Southern China

“…Exchangeable K was determined using flame photometry [14]. Soil total N (TN) was determined by the macro-Kjeldahl wet oxidation method [15]. Soil Alkaline N (AN) content was determined using alkaline hydrolysis diffusion method [16].…”

Effect of exogenous phosphate on the lability and phytoavailability of arsenic in soils

“…Total organic matter content was estimated using the potassium dichromate volumetric method (He et al 2017). Soil total N content was determined using semi-micro Macro Kjeldahl method (Calvo-Fernández et al 2018). Soil total P content was determined using UV spectrophotometry following alkali fusion (Meena et al 2018).…”

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

“…The study was conducted in three Calluna heathland sites (San Isidro, Riopinos I, and Riopinos II) located in the Cantabrian Mountains (NW Spain; 43°02-03′N, 5°21-26′W; 1560-1660 m a.s.l. ; 18-35 ha in size) [see Calvo-Fernández et al, 2018 for additional information] included as priority habitat type in Annex I of the Habitats Directive (92/43/ECC; habitat code 4060: alpine and boreal heaths). The climate is Eurosiberian (total precipitation of 1308 mm and mean temperature of 7.0 ± 4.9°C during the study year 2014) with a brief and moderate drought period in July-August, and a snow cover duration from late-autumn until the end of May.…”

“…Moreover, a few long-term researches demonstrated the lasting nature of the majority of these N-driven impacts on the heathland ecosystem (Carroll et al, 1999;Field et al, 2017;Power et al, 2006;Southon et al, 2012) that are expected to continue over coming decades (Payne et al, 2017;Stevens et al, 2016). These studies, however, have principally been accomplished in north-western and central European Calluna-heathlands; very little is known about the responses of southern heathlands at the rear-edge of the ecosystem's distribution to elevated N availability (Calvo et al, 2005(Calvo et al, , 2007Cuesta et al, 2008;Marcos et al, 2003), especially over the long-term (Calvo-Fernández et al, 2018;Taboada et al, 2016). This lack of knowledge impedes the implementation of proper on-site management to counterbalance the potentially detrimental impacts of N loading in rear-edge heathland locations that are also vulnerable to present climate change (Fagúndez, 2013).…”