Fire severity drives variation in post-fire recruitment and residual seed bank size of Acacia species

Abstract

Very high-severity fires are a component of many fire-prone ecosystems, yet are often viewed as detrimental to vegetation. However, species in such systems are likely to have adapted to persist under a fire regime that includes high-severity fires. We examined how fire severity affects post-fire recruitment and residual seed banks of Acacia species and whether severity may affect plant responses to fire intervals. Nine sites of either high or low burn severity were identified after a large-scale mixed-severity fire in Warrumbungle National Park, south-eastern Australia. Transects were used to sample above-ground woody plant density. Seed bank size was surveyed by soil extraction from two depths and manual searching for seeds. Residual soil seed bank and recruitment were compared across the two burn severities. Acacia seedling density was higher in areas burnt at high severity, indicating that increased severity triggers increased germination from the seed bank. Size of residual seed bank was smaller after high-severity fire, but varied between species, with few Acacia cheelii seeds remaining despite high above-ground abundance. In contrast, A. penninervis retained a small residual seed bank. There was little evidence of negative effects on populations of Acacia species after high-severity burns. However, we found that high fire severity may impact on the ability of a species to persist in response to a subsequent short fire interval. Fire management for maintaining biodiversity needs to consider other key aspects of the fire regime, including severity and season, rather than focusing solely on fire frequency.

This is a preview of subscription content, log in to check access.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5

References

  1. Abu-Hamdeh NH, Reeder RC (2000) Soil thermal conductivity effects of density, moisture, salt concentration, and organic matter. Soil Sci Soc Am J 64:1285

    CAS  Article  Google Scholar 

  2. Auld TD, Denham AJ (2005) A technique to estimate the pre-fire depth of burial of Grevillea seeds using seedlings after fire. Aust J Bot 53:401–405

    Article  Google Scholar 

  3. Auld TD, Denham AJ (2006) How much seed remains in the soil after a fire? Plant Ecol 187:15–24

    Article  Google Scholar 

  4. Auld TD, O’Connell MA (1991) Predicting patterns of post-fire germination in 35 eastern Australian Fabaceae. Aust J Ecol 16:53–70

    Article  Google Scholar 

  5. Auld TD, Keith DA, Bradstock RA (2000) Patterns in longevity of soil seedbanks in fire-prone communities of south-eastern Australia. Aust J Bot 48:539–548

    Article  Google Scholar 

  6. Auld TD, Denham AJ, Turner K (2007) Dispersal and recruitment dynamics in the fleshy-fruited Persoonia lanceolata (Proteaceae). J Veg Sci 18:903–910

    Google Scholar 

  7. Bond WJ, van Wilgen BW (1996) Fire and plants. Chapman and Hall, London

    Google Scholar 

  8. Bond WJ, Honig M, Maze KE (1999) Seed size and seedling emergence: an allometric relationship and some ecological implications. Oecologia 120:132–136

    CAS  Article  PubMed  Google Scholar 

  9. Bowman DMJS, MacDermott HJ, Nichols SC, Murphy BP (2014a) A grass-fire cycle eliminates an obligate-seeding tree in a tropical savanna. Ecol Evol 4:4185–4194

    Article  PubMed  PubMed Central  Google Scholar 

  10. Bowman DMJS, Murphy BP, Neyland DLJ, Williamson GJ, Prior LD (2014b) Abrupt fire regime change may cause landscape-wide loss of mature obligate seeder forests. Glob Change Biol 20:1008–1015

    Article  Google Scholar 

  11. Bradstock RA, Auld TD (1995) Soil temperatures during experimental bushfires in relation to fire intensity: consequences for legume germination and fire management in south-eastern Australia. J Appl Ecol 32:76–84

    Article  Google Scholar 

  12. Bradstock RA, Auld TD, Ellis MV, Cohn JS (1992) Soil temperatures during bushfires in semi-arid, mallee shrublands. Aust J Ecol 17:433–440

    Article  Google Scholar 

  13. Chafer CJ, Noonan M, Macnaught E (2004) The post-fire measurement of fire severity and intensity in the Christmas 2001 Sydney wildfires. Int J Wildland Fire 13:227–240

    Article  Google Scholar 

  14. Cohn JS, Lunt ID, Ross KA, Bradstock RA (2011) How do slow-growing, fire-sensitive conifers survive in flammable eucalypt woodlands? J Veg Sci 22:425–435

    Article  Google Scholar 

  15. DECC (2002) NSW Flora fire response database Version 1.3. NSW Department of Environment and Climate Change, Hurstville

    Google Scholar 

  16. DellaSala DA, Lindenmayer DB, Hanson CT, Furnish J (2015) In the aftermath of fire: logging and related actions degrade mixed- and high-severity burn areas. In: DellaSala DA, Hanson CT (eds) The ecological importance of mixed-severity fires. Elsevier, Amsterdam, pp 313–347

    Google Scholar 

  17. Denham AJ, Vincent BE, Clarke PJ, Auld TD (2016) Responses of tree species to a severe fire indicate major structural change to Eucalyptus-Callitris forests. Plant Ecol 217:617–629

    Article  Google Scholar 

  18. Enright NJ, Fontaine JB, Bowman DMJS, Bradstock RA, Williams RJ (2015) Interval squeeze: altered fire regimes and demographic responses interact to threaten woody species persistence as climate changes. Front Ecol Environ 13:265–272

    Article  Google Scholar 

  19. Fairman TA, Nitschke CR, Bennett LT (2016) Too much, too soon? A review of the effects of increasing wildfire frequency on tree mortality and regeneration in temperate eucalypt forests. Int J Wildland Fire 25:831–848

    Article  Google Scholar 

  20. Fenner M, Thompson K (2005) The ecology of seeds. CAB International, Wallingford

    Google Scholar 

  21. Gibson MR, Richardson DM, Marchante E et al (2011) Reproductive biology of Australian acacias: important mediator of invasiveness? Divers Distrib 17:911–933

    Article  Google Scholar 

  22. Gordon CE, Price OF, Tasker EM, Denham AJ (2017) Acacia shrubs respond positively to high severity wildfire: implications for conservation and fuel hazard management. Sci Total Environ 575:858–868

    CAS  Article  PubMed  Google Scholar 

  23. Hanley ME, Unna JE, Darvill B (2003) Seed size and germination response: a relationship for fire-following plant species exposed to thermal shock. Oecologia 134:18–22

    CAS  Article  PubMed  Google Scholar 

  24. Herranz JM, Ferrandis P, Martinez-Sanchez JJ (1998) Influence of heat on seed germination of seven Mediterranean Leguminosae species. Plant Ecol 136:95–103

    Article  Google Scholar 

  25. Hunter JT (2008) Vegetation and floristics of Warrumbungle National Park. Report to NSW National Parks and Wildlife Service, Coonabarabran

    Google Scholar 

  26. Jeffery DJ, Holmes PM, Rebelo AG (1988) Effects of dry heat on seed germination in selected indigenous and alien legume species in South Africa. S Afr J Bot 54:28–34

    Article  Google Scholar 

  27. Keeley JE (2009) Fire intensity, fire severity and burn severity: a brief review and suggested usage. Int J Wildland Fire 18:116–126

    Article  Google Scholar 

  28. Keeley JE, Meyers A (1985) Effect of heat on seed germination of southwestern Yucca species. Southwestern Nat 30:303–304

    Article  Google Scholar 

  29. Keith DA (1996) Fire-driven extinction of plant populations: a synthesis of theory and review of evidence from Australian vegetation. P Linn Soc NSW 116:37–78

    Google Scholar 

  30. Keith DA (2004) Ocean shores to desert dunes: the native vegetation of New South Wales. Department of Environment and Conservation (NSW), Hurstville

    Google Scholar 

  31. Knox KJE, Morrison DA (2005) Effects of inter-fire intervals on the reproductive output of resprouters and obligate seeders in the Proteaceae. Austral Ecol 30:407–413

    Article  Google Scholar 

  32. Liyanage GS, Ooi MKJ (2015) Intra-population level variation in thresholds for physical dormancy-breaking temperature. Ann Bot Lond 116:123–131

    CAS  Article  Google Scholar 

  33. Liyanage GS, Ooi MKJ (2018) Seed size-mediated dormancy thresholds: a case for the selective pressure of fire on physically dormant species. Biol J Linn Soc 123:135–143

    Article  Google Scholar 

  34. Mackenzie BDE, Auld TD, Keith DA, Hui FKC, Ooi MKJ (2016) The effect of seasonal ambient temperatures on fire-stimulated germination of species with physiological dormancy: a case study using Boronia (Rutaceae). PLoS ONE 11:e0156142

    Article  PubMed  PubMed Central  Google Scholar 

  35. Merritt DJ, Turner SR, Clarke S, Dixon KW (2007) Seed dormancy and germination stimulation syndromes for Australian temperate species. Aust J Bot 55:336–344

    Article  Google Scholar 

  36. Mondal NS, Sukumar R (2014) Fire and soil temperatures during controlled burns in seasonally dry tropical forests of southern India. Curr Sci India 107:1590–1594

    Google Scholar 

  37. Moreno JM, Oechel WC (1991) Fire intensity effects on germination of shrubs and herbs in southern California chaparral. Ecology 72:1993–2004

    Article  Google Scholar 

  38. Morrison DA, Auld TD, Rish S, Porter C, McClay K (1992) Patterns of testa-imposed seed dormancy in native Australian legumes. Ann Bot Lond 70:157–163

    Article  Google Scholar 

  39. Odion DC, Davis FW (2000) Fire, soil heating, and the formation of vegetation patterns in chaparral. Ecol Monogr 70:149–169

    Article  Google Scholar 

  40. Ooi MJK (2007) Dormancy classification and potential dormancy-breaking cues for shrub species from fire-prone south-eastern Australia. In: Adkins SA, Ashmore SE, Navie SC (eds) Seeds: biology, development and ecology. CAB International, New York, pp 205–216

    Google Scholar 

  41. Ooi MKJ (2010) Delayed emergence and post-fire recruitment success: effects of seasonal germination, fire season and dormancy type. Aust J Bot 58:248–256

    Google Scholar 

  42. Ooi MKJ, Auld TD, Whelan RJ (2007) Distinguishing between persistence and dormancy in soil seed banks of three shrub species from fire-prone southeastern Australia. J Veg Sci 18:405–412

    Article  Google Scholar 

  43. Ooi MKJ, Denham AJ, Santana VM, Auld TD (2014) Temperature thresholds of physically dormant seeds and plant functional response to fire: variation among species and relative impact of climate change. Ecol Evol 4:656–671

    Article  PubMed  PubMed Central  Google Scholar 

  44. Penman TD, Towerton AL (2008) Soil temperatures during autumn prescribed burning: implications for the germination of fire responsive species? Int J Wildland Fire 17:572–578

    Article  Google Scholar 

  45. Stoof CR, De Kort A, Bishop TFA, Moore D, Wesseling JG, Ritsema CJ (2011) How rock fragments and moisture affect soil temperatures during fire. Soil Sci Soc Am J 75:1133–1143

    CAS  Article  Google Scholar 

  46. Storey M, Price O, Tasker E (2016) The role of weather, past fire and topography in crown fire occurrence in eastern Australia. Int J Wildland Fire 25:1048–1060

    Article  Google Scholar 

  47. Thaxton JM, Platt WJ (2006) Small-scale fuel variation alters fire intensity and shrub abundance in a pine savanna. Ecology 87:1331–1337

    Article  PubMed  Google Scholar 

  48. Tozer MG (1998) Distribution of the soil seedbank and influence of fire on seedling emergence in Acacia saligna growing on the central coast of New South Wales. Aust J Bot 46:743–755

    Article  Google Scholar 

  49. Van Wijk WR (1963) Physics of plant environment. North-Holland Publishing Company, Amsterdam

    Google Scholar 

  50. Vivian LM, Cary GJ, Bradstock RA, Gill AM (2008) Influence of fire severity on the regeneration, recruitment and distribution of eucalypts in the Cotter River Catchment, Australian Capital Territory. Austral Ecol 33:55–67

    Article  Google Scholar 

  51. Whelan RJ (1995) The ecology of fire. Cambridge University Press, Cambridge

    Google Scholar 

  52. Wright BR, Latz PK, Zuur AF (2016) Fire severity mediates seedling recruitment patterns in slender mulga (Acacia aptaneura), a fire-sensitive Australian desert shrub with heat-stimulated germination. Plant Ecol 217:789–800

    Article  Google Scholar 

Download references

Acknowledgements

We thank Martin Henery and Justin Collette for field assistance, Lisa Metcalfe for laboratory assistance, Craig Wall and the National Parks and Wildlife Service Coonabarabran office for permission to work in Warrumbungle NP and Jessica Meade for assistance with drafting figures. The project was supported by funding from the NSW Office of Environment and Heritage, and as part of the Australian Government’s National Environmental Science Programme (NESP), Threatened Species Recovery Hub (1.3).

Author information

Affiliations

Authors

Corresponding author

Correspondence to Harrison D. Palmer.

Additional information

Communicated by Stephen Brewer.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Palmer, H.D., Denham, A.J. & Ooi, M.K.J. Fire severity drives variation in post-fire recruitment and residual seed bank size of Acacia species. Plant Ecol 219, 527–537 (2018). https://doi.org/10.1007/s11258-018-0815-5

Download citation

Keywords

  • Physical dormancy
  • Fire severity
  • Heat shock
  • Acacia
  • Recruitment
  • Residual seed bank
  • Obligate seeder
  • Land management