Decadal changes in fire frequencies shift tree communities and functional traits

Pellegrini, Adam F. A.; Refsland, Tyler; Averill, Colin; Terrer, César; Staver, A. Carla; Brockway, Dale G.; Caprio, Anthony C.; Clatterbuck, Wayne K.; Coetsee, Corli; Haywood, James D.; Hobbie, Sarah E.; Hoffmann, William A.; Kush, John S.; Lewis, Tom; Moser, W. Keith; Overby, Steven T.; Patterson, William A.; Peay, Kabir G.; Reich, Peter B.; Ryan, Casey M.; Sayer, Mary Anne Sword; Scharenbroch, Bryant C.; Schoennagel, Tania; Smith, Gabriel Reuben; Stephan, Kirsten; Swanston, Chris; Turner, Monica G.; Varner, J. Morgan; Jackson, Robert B.

doi:10.1038/s41559-021-01401-7

Cited by 55 publications

(44 citation statements)

References 92 publications

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“…Severe fires can have legacy impacts on ecosystem function even after carbon stocks have been largely regenerated. Severe fires in Eucalyptus forests have been shown to include persistent changes to canopy structure (Karna et al, 2019), increase tree mortality (Bennett et al, 2016;Etchells et al, 2020) and cause changes in understory composition and structure (D. M. J. S. Bowman et al, 2014;Fairman et al, 2016;Fletcher et al, 2014;Pellegrini et al, 2021). In particular, fire-induced tree mortalities are generally higher in smaller-younger cohorts (Bennett et al, 2016;Bowd et al, 2021).…”

Section: Implications For Southeast Australiamentioning

confidence: 99%

The Carbon Cycle of Southeast Australia During 2019–2020: Drought, Fires, and Subsequent Recovery

et al. 2021

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Extreme drought and heat events can result in single-year carbon losses equal to many years of carbon sequestration (Bastos et al., 2014;Ciais et al., 2005). Hot-dry conditions can directly suppress both gross primary productivity (GPP) and ecosystem respiration (TER), with greater suppression of GPP leading to carbon loss (Reichstein et al., 2007;Sippel et al., 2018). These conditions also dry fuels, increase litterfall, and elevate levels of tree mortality, all of which may trigger additional carbon losses by means of wildfire (Abram et al., 2020; D. M. J. S. Bowman et al., 2009). Impacted ecosystems often experience legacy effects that can impact the carbon cycling for years after the extreme events have passed (Batllori et al., 2020;Frank et al., 2015;Lindenmayer et al., 2021). Southeast Australia (Figure 1) has a highly variable climate (Harris & Lucas, 2019;King et al., 2020), and frequently experiences both drought and fire. In fact, this susceptibility to fire has been a key factor in the evolution of the regional flora and fauna, acting as a process of disturbance and also regeneration (Bowman, 2000;

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Section: Implications For Southeast Australiamentioning

confidence: 99%

The Carbon Cycle of Southeast Australia During 2019–2020: Drought, Fires, and Subsequent Recovery

et al. 2021

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“…Furthermore, some disturbances D r a f t may only impact trees in particular regions. For instance, fire is an important disturbance agent in western North America, and plays an important role in structuring tree communities throughout the globe (Pellegrini et al 2021). Effects of fire on population-level genetic diversity may differ among species and whether, e.g., species regenerate clonally or through the seed bank.…”

Section: R a F T Discussionmentioning

confidence: 99%

Geographic patterns of genetic diversity in North American trees: a continent-wide analysis

Gougherty

2022

Can. J. For. Res.

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In the northern hemisphere, many species have been reported to have greater genetic diversity in southern populations than northern populations - ostensibly due to migration northward following the last glacial maximum (LGM). The generality of this pattern, while well-established for some taxa, remains unclear for North American trees. To address this issue, I collected published population genetics data for 73 North American tree species, and tested whether genetic diversity was associated with latitude or longitude and whether geographic trends were associated with dispersal traits, range or study characteristics. I found there were no general geographic patterns in genetic diversity, and the strength of the geographic gradients were not associated with any species or study characteristics. Species in the northern and western regions of North America tended to have more species with genetic diversity that declined with latitude, but most species had no significant trend. This work shows that North American trees have complex, individualistic, patterns of genetic diversity that may negate explanation by any particular dispersal trait or range characteristic.

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“…Fourth, nutrient losses could limit microbial biomass and activity (Hartman & Richardson, 2013), which may explain the positive correlation between IN and both respiration and extracellular enzyme activity. Finally, changes in plant communities with different symbiotic strategies such as N‐fixing shrubs or trees with different mycorrhizal strategies may also contribute to changes in soil C and nutrient turnover (Pellegrini et al, 2021). These are just a few of the potential processes that may contribute to fire‐driven changes in organic matter decomposition, but all deserve future study.…”

Section: Discussionmentioning

confidence: 99%

Low‐intensity frequent fires in coniferous forests transform soil organic matter in ways that may offset ecosystem carbon losses

Pellegrini

Caprio

Georgiou

et al. 2021

Global Change Biology

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The impact of shifting disturbance regimes on soil carbon (C) storage is a key uncertainty in global change research. Wildfires in coniferous forests are becoming more frequent in many regions, potentially causing large C emissions. Repeated low‐intensity prescribed fires can mitigate wildfire severity, but repeated combustion may decrease soil C unless compensatory responses stabilize soil organic matter. Here, we tested how 30 years of decadal prescribed burning affected C and nitrogen (N) in plants, detritus, and soils in coniferous forests in the Sierra Nevada mountains, USA. Tree basal area and litter stocks were resilient to fire, but fire reduced forest floor C by 77% (−36.4 Mg C/ha). In mineral soils, fire reduced C that was free from minerals by 41% (−4.4 Mg C/ha) but not C associated with minerals, and only in depths ≤ 5 cm. Fire also transformed the properties of remaining mineral soil organic matter by increasing the proportion of C in a pyrogenic form (from 3.2% to 7.5%) and associated with minerals (from 46% to 58%), suggesting the remaining soil C is more resistant to decomposition. Laboratory assays illustrated that fire reduced microbial CO2 respiration rates by 55% and the activity of eight extracellular enzymes that degrade cellulosic and aromatic compounds by 40–66%. Lower decomposition was correlated with lower inorganic N (−49%), especially ammonium, suggesting N availability is coupled with decomposition. The relative increase in forms of soil organic matter that are resistant to decay or stabilized onto mineral surfaces, and the associated decline in decomposition suggest that low‐intensity fires may promote mineral soil C storage in pools with long mean residence times in coniferous forests.

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Decadal changes in fire frequencies shift tree communities and functional traits

Cited by 55 publications

References 92 publications

The Carbon Cycle of Southeast Australia During 2019–2020: Drought, Fires, and Subsequent Recovery

The Carbon Cycle of Southeast Australia During 2019–2020: Drought, Fires, and Subsequent Recovery

Geographic patterns of genetic diversity in North American trees: a continent-wide analysis

Low‐intensity frequent fires in coniferous forests transform soil organic matter in ways that may offset ecosystem carbon losses

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