Plant functional types determine how close postfire seedlings are from their parents in a species-rich shrubland

Abstract

Background and aims Fine-scale spatial patterns of the seedlings of co-occurring species reveal the relative success of reproduction and dispersal and may help interpret coexistence patterns of adult plants. To understand whether postfire community dynamics are controlled by mathematical, biological or environmental factors, we documented seedling-adult (putative parent) distances for a range of co-occurring species. We hypothesised that nearest-seedling-to-adult distances should be a function of the distance between the closest conspecific seedlings, closest inter-adult distances and seedling-to-parent ratios, and also, that these should scale up in a consistent way from all individuals, to within and between species and finally between functional types (FTs). Methods We assessed seedling–adult, seedling–seedling and adult–adult distances for 19 co-occurring shrub species ten months after fire in a species-rich shrubland in southwestern Australia. Species were categorized into 2Ó2 FTs: those that are killed by fire (non(re)sprouters) versus those that survive (resprouters) in nine taxonomically-matched pairs, and those that disperse their seeds prefire (geosporous) versus those that disperse their seeds postfire (serotinous). Key Results For the total data set and means for all species, seedling–adult distance was essentially a mathematical phenomenon, correlated positively with seedling–seedling distance and adult–adult distance, and inversely with seedlings per adult. Among the four FTs, seedling–adult distance was shortest for geosporous nonsprouters and widest for serotinous resprouters. Why adults that produce few seedlings (resprouters) should be further away from them defies a simple mathematical or biological explanation at present. Ecologically, however, it is adaptive, the closest seedling was usually under the (now incinerated) parent crown of nonsprouters whereas those of resprouters were on average four times further away. Conclusions Our study highlights the value of recognizing four reproductive syndromes within fireprone vegetation, and shows how these are characterised by marked differences in their seedling–adult spatial relations that serve to enhance biodiversity of the community.

Fire‐released seed dormancy ‐ a global synthesis

“…This is especially notable among non‐resprouting species (obligate seeders; Table 1). Postfire facultative species (Table 1) are characterized by stands of mixed ages as recruitment after each fire coexists with postfire resprouting (Lamont & Witkowski, 2021). Mixed‐age stands are even more prominent among obligate resprouters as their recruitment is independent of fire (seed production and germination occur long after the passage of fire) and is related more to environmental fluctuations.…”

Anthropogenic fire practices only ‘best’ if they promote a large seed buildup: comment on the conservation needs of a fire-killed grevillea

“…I do this by re-analysing their data, noting what population traits need to be monitored to provide informed decisions, and providing a preliminary model of the type of dynamics that can be expected to occur as a guide for future management where species conservation is the goal. The conservation requirements of targeted species, as outlined for this grevillea, highlight the challenges facing managers in terms of the need to understand their particular population demographics for effective conservation management (Enright et al 2014;Lamont and Witkowski 2021).…”