TY - JOUR

T1 - Time- and age-related effects of experimentally simulated nitrogen deposition on the functioning of montane heathland ecosystems

AU - Calvo-Fernández, Javier

AU - Taboada, Angela

AU - Fichtner, Andreas

AU - Härdtle, Werner

AU - Calvo, Leonor

AU - Marcos, Elena

PY - 2018/2/1

Y1 - 2018/2/1

N2 - 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 50 kg N ha − 1 yr − 1 for 3 years, and 56 kg N ha − 1 yr − 1 for 10 years) 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 3 −, 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 4 +, 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 3 −, 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.

AB - 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 50 kg N ha − 1 yr − 1 for 3 years, and 56 kg N ha − 1 yr − 1 for 10 years) 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 3 −, 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 4 +, 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 3 −, 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.

KW - Ecosystems Research

KW - Air pollution

KW - Calluna vulgaris heathland

KW - Plant-litter-soil nutrient relationship

KW - Extracellular enzymatic activity

KW - Soil microbial biomass

KW - Ericoid mycorrhizal colonization

KW - Air Pollution

KW - Calluna vulgaris heathland

KW - Ericoid mycorrhizal colonization

KW - Extracellular enzymatic activity

KW - Plant-litter-soil nutrient relationship

KW - Soil microbial biomass

UR - http://www.scopus.com/inward/record.url?scp=85029086352&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2017.08.307

DO - 10.1016/j.scitotenv.2017.08.307

M3 - Journal articles

C2 - 28910717

VL - 613-614

SP - 149

EP - 159

JO - The Science of The Total Environment

JF - The Science of The Total Environment

SN - 0048-9697

ER -