Fire increases the risk of higher soil N2O emissions from Mediterranean Macchia ecosystems

Karhu, Kristiina; Dannenmann, Michael; Kitzler, Barbara; Díaz‐Pinés, Eugenio; Tejedor, Javier; Ramírez, David A.; Parra, Antonio; Dios, Víctor Resco de; Moreno, José M.; Sánchez, Alfonso Emilio Pérez; Guimaraes-Povoas, L.; Zechmeister‐Boltenstern, Sophie; Butterbach‐Bahl, Klaus

doi:10.1016/j.soilbio.2014.12.013

Cited by 31 publications

(31 citation statements)

References 43 publications

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“…Working at the same experiment, Karhu et al () found increased gross N mineralization in the Ah horizon only 13 days after fire but not for soils sampled 3 and 35 days after fire. This could indicate that most of the mineralization may occur in the PyOM layer with subsequent incorporation and leaching of mineral N into the Ah horizon.…”

Section: Discussionmentioning

confidence: 94%

“…The postfire mineral N flush was first dominated by NH 4 + , and later at highest mineral N stocks by NO 3 − , indicating significant nitrification activity. Nitrification was likely promoted by increased postfire availability of NH 4 + , the substrate for nitrification, but also by increases in soil pH (Supporting Information Table S2), as higher pH also favours nitrification (Butterbach‐Bahl, Baggs, Dannenmann, Kiese, & Zechmeister‐Boltenstern, ; Karhu et al, ). In Mediterranean soils, nitrification is frequently inhibited by allelopathic compounds such as terpenes and phenolics (Andersson, Michelsen, Jensen, & Kjoller, ; Castaldi et al, ; Knicker, ).…”

Section: Discussionmentioning

confidence: 99%

“…Three randomly selected control plots remained unburned, while three others were burned on September 23, 2009. The detailed plot layout is illustrated in Figure of Karhu et al (). We sought to create a high‐intensity bushfire, and, consequently, we piled dead fuel material in the external perimeter of the plot to increase fire intensity.…”

Section: Methodsmentioning

confidence: 99%

“…A key process for such N loss is the transformation of NH 4 + to nitrate (NO 3 − ) through microbial nitrification, thereby opening both leaching and gaseous N loss pathways (Certini, ; Knicker, ). This could result in increased emissions of soil N 2 O (Fierro & Castaldi, ; Karhu et al, ). However, knowledge on postfire ecosystem N losses due to the microbial production of N 2 O, nitric oxide (NO) and N 2 or due to NO 3 − leaching from Mediterranean shrubland ecosystems is limited and chemical form and magnitude of postfire ecosystem N losses is unknown.…”

Section: Introductionmentioning

confidence: 99%

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Postfire nitrogen balance of Mediterranean shrublands: Direct combustion losses versus gaseous and leaching losses from the postfire soil mineral nitrogen flush

Dannenmann

Díaz‐Pinés

Kitzler

et al. 2018

Global Change Biology

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Fire is a major factor controlling global carbon (C) and nitrogen (N) cycling. While direct C and N losses caused by combustion have been comparably well established, important knowledge gaps remain on postfire N losses. Here, we quantified both direct C and N combustion losses as well as postfire gaseous losses (N O, NO and N ) and N leaching after a high-intensity experimental fire in an old shrubland in central Spain. Combustion losses of C and N were 9.4 Mg C/ha and 129 kg N/ha, respectively, representing 66% and 58% of initial aboveground vegetation and litter stocks. Moreover, fire strongly increased soil mineral N concentrations by several magnitudes to a maximum of 44 kg N/ha 2 months after the fire, with N largely originating from dead soil microbes. Postfire soil emissions increased from 5.4 to 10.1 kg N ha year for N , from 1.1 to 1.9 kg N ha year for NO and from 0.05 to 0.2 kg N ha year for N O. Maximal leaching losses occurred 2 months after peak soil mineral N concentrations, but remained with 0.1 kg N ha year of minor importance for the postfire N mass balance. N stable isotope labelling revealed that 33% of the mineral N produced by fire was incorporated in stable soil N pools, while the remainder was lost. Overall, our work reveals significant postfire N losses dominated by emissions of N that need to be considered when assessing fire effects on ecosystem N cycling and mass balance. We propose indirect N gas emissions factors for the first postfire year, equalling to 7.7% (N -N), 2.7% (NO-N) and 5.0% (N O-N) of the direct fire combustion losses of the respective N gas species.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Postfire nitrogen balance of Mediterranean shrublands: Direct combustion losses versus gaseous and leaching losses from the postfire soil mineral nitrogen flush

Dannenmann

Díaz‐Pinés

Kitzler

et al. 2018

Global Change Biology

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“…The non‐forested state may lead to lower soil fertility and higher erodibility (Karhu et al. , Vieira et al. ).…”

Section: State Transitions After Fire and Changes In Community Dominancementioning

confidence: 99%

Fire‐induced deforestation in drought‐prone Mediterranean forests: drivers and unknowns from leaves to communities

Karavani

Boer

Baudena

et al. 2018

Ecological Monographs

110

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Over the past 15 years, 3 million hectares of forests have been converted into shrublands or grasslands in the Mediterranean countries of the European Union. Fire and drought are the main drivers underlying this deforestation. Here we present a conceptual framework for the process of fire‐induced deforestation based on the interactive effects of fire and drought across three hierarchical scales: resistance in individuals, resilience in populations, and transitions to a new state. At the individual plant level, we review the traits that confer structural and physiological resistance, as well as allow for resprouting capacity: deforestation can be initiated when established individuals succumb to fire. After individuals perish, the second step toward deforestation requires a limited resilience from the population, that is, a reduced ability of that species to regenerate after fire. If individuals die after fire and the population fails to recover, then a transition to a new state will occur. We document trade‐offs between drought survival and fire survival, as embolism resistance is negatively correlated with fire tolerance in conifers and leaf shedding or drought deciduousness, a process that decreases water consumption at the peak of the dry season, temporally increases crown flammability. Propagule availability and establishment control resilience after mortality, but different hypotheses make contrasting predictions on the drivers of post‐fire establishment. Mycorrhizae play an additional role in modulating the response by favoring recovery through amelioration of the nutritional and water status of resprouts and new germinants. So far, resprouter species such as oaks have provided a buffer against deforestation in forests dominated by obligate seeder trees, when present in high enough density in the understory. While diversifying stands with resprouters is often reported as advantageous for building resilience, important knowledge gaps exist on how floristic composition interacts with stand flammability and on the “resprouter exhaustion syndrome,” a condition where pre‐fire drought stress, or short fire return intervals, seriously restrict post‐fire resprouting. Additional attention should be paid to the onset of novel fire environments in previously fire‐free environments, such as high altitude forests, and management actions need to accommodate this complexity to sustain Mediterranean forests under a changing climate.

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Forest Succession, Alternative States, and Fire-Vegetation Feedbacks

Dios

2020

Managing Forest Ecosystems

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Fire increases the risk of higher soil N2O emissions from Mediterranean Macchia ecosystems

Cited by 31 publications

References 43 publications

Postfire nitrogen balance of Mediterranean shrublands: Direct combustion losses versus gaseous and leaching losses from the postfire soil mineral nitrogen flush

Postfire nitrogen balance of Mediterranean shrublands: Direct combustion losses versus gaseous and leaching losses from the postfire soil mineral nitrogen flush

Fire‐induced deforestation in drought‐prone Mediterranean forests: drivers and unknowns from leaves to communities

Forest Succession, Alternative States, and Fire-Vegetation Feedbacks

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