Resprouting grasses are associated with less frequent fire than seeders

Abstract

 Plant populations persist under recurrent fire via resprouting from surviving tissues (resprouters) or seedling recruitment (seeders). Woody species are inherently slow-maturing, meaning that seeders are confined to infrequent fire regimes. However, for grasses, which mature faster, the relationships between persistence strategy and fire regime remains unknown.  Globally, we analysed associations between fire regimes experienced by hundreds of grass species and their persistence strategy, within a phylogenetic context. We also tested whether persistence strategies are associated with morphological and physiological traits.  Resprouters were associated with less frequent fire than seeders. Whilst modal fire frequencies were similar (fire return interval of 4-6 years), seeders were restricted to regions with more frequent fire than resprouters, suggesting that greater competition with long-lived resprouters restricts seeder recruitment and survival when fire is rare. Resprouting was associated with lower leaf N, higher C/N ratios and the presence of below-ground buds, but was unrelated to photosynthetic pathway.  Differences between the life histories of grasses and woody species lead to a contrasting prevalence of seeders and resprouters in relation to fire frequency. Rapid sexual maturation in grasses means that seeder distributions, relative to fire regime, are determined by competitive ability and recruitment, rather than time to reproductive maturity.

Traits explain sorting of C4 grasses along a global precipitation gradient

“…Grasslands in high precipitation environments are associated with a predictable dry season and frequent fires, whereas the dry season in arid grasslands is less predictable and fires are less frequent (Govender et al., 2006). The ability to resprout from meristematic tissue is an important trait in seasonally drought‐prone systems which are controlled by fire (Pausas et al., 2016; Simpson et al., 2020). We hypothesize that drought‐avoiding grass species will grow quickly under wet conditions, senesce rapidly under drought “creating fuel for grassland fires” but will have the ability to resprout rapidly from drought‐tolerant meristems following drought and fire.…”

When do grasses resprout after fire?

“…Although fire activity is correlated with drought, Simpson et al . (2021) showed that grass seeders were abundant in drought‐prone areas regardless of fire. Seeders may be abundant in drought‐prone areas with infrequent fire as an adaptation to drought because of their ability to escape.…”

“…Current understanding of post-fire persistence strategies is largely based on woody species or are regional in context (Bellingham & Sparrow, 2000;Clarke et al, 2013;Moore et al, 2019). In this issue of New Phytologist, Simpson et al (2021;pp. 832-844) make an impressive contribution to further our understanding of how regeneration strategies in grasses (Poaceae) are related to fire regimes.…”

“…The study by Simpson et al (2021) is timely because fire has played a major role in the success of grasses in many parts of the globe and their persistence strategies are understudied (Moore et al, 2019;Pausas & Paula, 2020). Simpson et al (2021) derived spatially-explicit datasets on the distribution of 763 grass species and modelled their association with fire regimes, climate, phylogeny, and plant traits to assess the relative importance of different drivers for persistence strategies of seeders and resprouters. Using georeferenced occurrence records from the Global Biodiversity Information Facility (GBIF), Simpson et al (2021) obtained measures of fire frequency and fire intensity using satellite-derived data (moderate resolution imaging spectroradiometer, MODIS).…”

“…Simpson et al (2021) derived spatially-explicit datasets on the distribution of 763 grass species and modelled their association with fire regimes, climate, phylogeny, and plant traits to assess the relative importance of different drivers for persistence strategies of seeders and resprouters. Using georeferenced occurrence records from the Global Biodiversity Information Facility (GBIF), Simpson et al (2021) obtained measures of fire frequency and fire intensity using satellite-derived data (moderate resolution imaging spectroradiometer, MODIS). They derived a drought index and collated a database of plant traits.…”