Differences in resprouting ability are not related to seed size or seedling growth in four riparian woody species

Abstract

1. Resprouting is a key plant attribute facilitating persistence in disturbance-prone environments. Resprouting ability in seedlings may depend on both developmental ontogeny and seed size. However, the relationships between these factors are not well explored, especially for woody species with comparatively small seeds and epigeal germination.

2. We investigated resprouting capacity in seedlings from four subtropical, riparian, Myrtaceous tree species, Melaleuca leucadendra, Asteromyrtus symphyocarpa, Eucalyptus camaldulensis var. obtusa and Tristaniopsis laurina, displaying these characteristics. We recorded resprouting in response to simulated disturbance as a function of seed mass and developmental age (5–150 days post-emergence) and examined the acquisition of resprouting ability in relation to growth and biomass allocation patterns.

3. Patterns of resprouting were distinct among species, but the acquisition of resprouting ability was not determined by seed mass. The 'small' seeded M. leucadendra and the 'intermediate' seeded E. camaldulensis showed unexpectedly high shoot resprouting vigour from cotyledon stage (70% resprouting at 5 days post-emergence), as well as greatest ongoing allocation to root mass and lateral root development. In contrast, in A. symphyocarpa (another species with 'intermediate' seed mass) and T. laurina (a 'large' seeded species) resprouting rates during early development were much lower (< 10%), although there was a trend towards increasing resprouting ability with age in A. symphyocarpa (> 150 days). Resprouting capacity was also independent of seedling size and relative growth rate.

4. Our results indicate that the size-dependency of resprouting capacity varies considerably among these species. This suggests physiological and morphological species traits other than those directly related to reserve size or relative growth rate may convey survivorship in river environments.

5. Our findings show that resprouting capacity was not related to seed size and seedling growth patterns in these four species. This is different to evidence from comparative studies undertaken in fire-prone and other temperate environments. A broader survey of seedling resprouting ability including more species is required to determine the generality of our findings in riparian species.