Comparison of the impacts of acid and nitrogen additions on carbon fluxes in European conifer and broadleaf forests

Oulehle, Filip; Tahovská, Karolina; Chuman, Tomáš; Evans, Chris; Hruška, Jakub; Růžek, Michal; Bárta, Jiří

doi:10.1016/j.envpol.2018.03.081

Cited by 33 publications

(9 citation statements)

References 65 publications

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“…Our results highlight the importance of forest type on net ecosystem N retention, consistent with previous studies that demonstrated species‐specific effects on N cycling (Booth et al, 2005; Oulehle et al, 2018; Templer et al, 2005). The ∼45% greater biomass N increment (Table 3) in West Bear hardwood compared to East Bear hardwood stands suggests N additions reduced N limitations resulting in accelerated biomass and N annual increment in the treated watershed.…”

Section: Discussionsupporting

confidence: 92%

Forest N Dynamics after 25 years of Whole Watershed N Enrichment: The Bear Brook Watershed in Maine

Patel

Fernandez

Nelson

et al. 2019

Soil Science Soc of Amer J

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Core Ideas Chronic N enrichment increased N exports, although ecosystem N retention was still high. Soil was the largest ecosystem N pool, but it was not significantly altered by chronic N enrichment. Chronic N enrichment increased biomass N accumulation in hardwood but not in softwood stands. We examine the temporal trend of input–output N fluxes and net ecosystem N retention, and estimate a mass balance for ecosystem soil and vegetation pools, after 25 yr of chemical manipulation at the Bear Brook Watershed in Maine (BBWM). The BBWM is a paired whole watershed manipulation experiment designed to study the effects of elevated N and S deposition on forest ecosystem function. Starting in 1989, 25.2 kg N ha−1 was added annually to the West Bear (treated) watershed. The N additions in West Bear stimulated N loss through stream exports, and West Bear retained 81% of the annual N inputs, compared to 94% retention in the reference, East Bear. After 25 yr of N additions, the West Bear watershed had accumulated ∼700 kg ha−1 more N than East Bear in soils and vegetation, with ∼10% of the accumulated N stored in forest biomass. The treatment increased recent biomass N accumulation rates in the hardwood stands, but not in the softwoods. Soils did not show detectable differences in total N content between watersheds, although the organic soils had greater N in West Bear. This paper presents a unique set of findings from one of the few long‐term whole forest ecosystem N enrichment studies in the world. While N dynamics were clearly altered in West Bear, with evidence of accelerated N cycling, the treated watershed did not attain an advanced stage of N saturation during the study period, based on the evidence from forest growth and stream N exports.

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Section: Discussionsupporting

confidence: 92%

Forest N Dynamics after 25 years of Whole Watershed N Enrichment: The Bear Brook Watershed in Maine

Patel

Fernandez

Nelson

et al. 2019

Soil Science Soc of Amer J

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“…Organic functional groups associated with the much higher organic matter concentration and content in North Buck than South Buck also provided a greater capacity in North Buck to buffer against decreased acidity of soil solutions (Ross et al, ) as acidic deposition rates decreased. This interpretation is supported by a recent experiment that showed a more stressed microbial community in acidic soil of a Norway spruce stand than in soil of a less acidic beech stand at the start of the experiment, an effect that was intensified with the addition of sulfuric acid (Oulehle et al, ).…”

Section: Discussionmentioning

confidence: 61%

Recovery of Soils From Acidic Deposition May Exacerbate Nitrogen Export From Forested Watersheds

2020

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Effects of ambient decreases in N deposition on forest N cycling remain unclear as soils recover from acidic deposition. To investigate, repeated soil sampling data were related to deposition, vegetation, and stream data, for 2000-2015 in North and South Buck Creek watersheds, in the Adirondack region of New York, USA. In 63 other Adirondack streams, NO 3 − concentrations were also compared between 2004-2005 and 2014-2015, and a link between soil calcium and stream NO 3 − was investigated using data from 387 Adirondack streams that were sampled in either 2003-2005 or 2010-2011. No trends in N export or NO 3 − concentrations were observed in either Buck watershed despite a 45% decrease in N deposition,although South Buck N export was 2 to 3 times higher than in North Buck, where 48% of deposited N was accounted for by accumulation in the upper soil. In marked contrast, the upper profile in South Buck showed a net loss of N. Increased decomposition appeared likely in South Buck as those soils are adjusted to lower levels of acidifying S deposition, whereas decomposition increases in North Buck were likely suppressed by high levels of natural organic acidity. Stream NO 3 − concentrations in Buck watersheds bracketed regional results and were consistent with the regional streams that showed no overall change in NO 3 − concentrations between 2004 and 2014. A negative correlation observed between NO 3 − concentration and watershed buffering capacity expressed as the ratio of Ca 2+ to SO 4 2− also suggested that stream NO 3 − concentrations were elevated where soil Ca depletion had occurred.

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“…Second, the nutrient limitation of microbial growth due to soil base cation loss (e.g. Mg 2+ , Ca 2+ ) (Bowman et al 2008, Oulehle et al 2018) and other ion (e.g. H + , Al 3+ ) toxicity (Tian and Niu 2015) tend to reduce soil heterotrophic respiration.…”

Section: Discussionmentioning

confidence: 99%

Global soil acidification impacts on belowground processes

Meng

Tian

Zeng

et al. 2019

Environ. Res. Lett.

151

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With continuous nitrogen (N) enrichment and sulfur (S) deposition, soil acidification has accelerated and become a global environmental issue. However, a full understanding of the general pattern of ecosystem belowground processes in response to soil acidification due to the impacting factors remains elusive. We conducted a meta-analysis of soil acidification impacts on belowground functions using 304 observations from 49 independent studies, mainly including soil cations, soil nutrient, respiration, root and microbial biomass. Our results show that acid addition significantly reduced soil pH by 0.24 on average, with less pH decrease in forest than non-forest ecosystems. The response ratio of soil pH was positively correlated with site precipitation and temperature, but negatively with initial soil pH. Soil base cations (Ca 2+ , Mg 2+ , Na + ) decreased while non-base cations (Al 3+ , Fe 3+ ) increased with soil acidification. Soil respiration, fine root biomass, microbial biomass carbon and nitrogen were significantly reduced by 14.7%, 19.1%, 9.6% and 12.1%, respectively, under acid addition. These indicate that soil carbon processes are sensitive to soil acidification. Overall, our meta-analysis suggests a strong negative impact of soil acidification on belowground functions, with the potential to suppress soil carbon emission. It also arouses our attention to the toxic effects of soil ions on terrestrial ecosystems.

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Comparison of the impacts of acid and nitrogen additions on carbon fluxes in European conifer and broadleaf forests

Cited by 33 publications

References 65 publications

Forest N Dynamics after 25 years of Whole Watershed N Enrichment: The Bear Brook Watershed in Maine

Forest N Dynamics after 25 years of Whole Watershed N Enrichment: The Bear Brook Watershed in Maine

Recovery of Soils From Acidic Deposition May Exacerbate Nitrogen Export From Forested Watersheds

Global soil acidification impacts on belowground processes

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