Effects of seed size and emergence time on tree seedling establishment: importance of developmental constraints

Abstract

To evaluate the importance of developmental constraints in the determination of the relative importance of seed size and emergence time, early seedling performance of two woody species with contrasting growth phenology were observed under competitive conditions with tall herbs in an early successional habitat. The oak, Quercus mongolica var. grosseserrata, with determinate shoot development (a single leaf flush), showed a marked influence of seed size on subsequent seedling height growth and survival. Because of determinate growth, emergence time had negligible effects. The walnut, Juglans ailanthifolia, which continued to produce new leaves throughout the growing season (indeterminate development), showed a marked influence of time of emergence on seedling performance, because it affected the amount of growth that could be achieved; seed size, however, had negligible effects as the seedlings grew. These results suggest that relative importance of seed size and emergence time for early seedling performance is closely associated with developmental constraints (growth phenology).

The relevance of seed size in modulating leaf physiology and early plant performance in two tree species

“…The benefits of seed size for growth were not mediated by a better access of seedlings to water or a higher concentration of leaf nitrogen. Rather, the direct link between seed size and plant growth found by path analysis suggests a translocation of seed carbohydrates to plant organs, in support of previous works that found that early seedling growth was strongly determined by seed cotyledonary reserves (Kennedy et al 2004;Seiwa 2000;Urbieta et al 2008). Since both species have an episodic flush-type pattern of shoot growth and most seedlings did not produce a second shoot flush after emergence, leaf WUE was irrelevant for plant growth, at least for vertical plant growth.…”

“…Alternatively, assuming that first-year leaf 5 C resulted from the seed-toleaf mobilization of C-enriched components, the increasing probability of survival of Q. pyrenaica as leaf 5 C decreased could be mostly reflecting a positive effect of first-year photosynthetic carbon gain on subsequent survival. A large part of the carbon gained by photosynthesis in the first year was stored-as suggests the single flush of shoot growth-so that the more carbohydrates were stored the higher were tolerance of stress, recovery from damage and, eventually, survival in the following year (McDowell et al 2008;Ramel et al 2009;Seiwa 2000). The different contribution of 5 C to survival for each species might reside on their distinct phenology.…”

“…On one hand, seed size has generally a favourable effect on seedling survival and growth (Bonfil 1998;Castro et al 2008;Quero et al 2007) that may persist for various years (Seiwa 2000;Tripathi and Khan 1990). On the other hand, microsites of high overstory canopy closure provide poor conditions for numerous tree species, and seedlings tend to recruit in gaps or areas of sparse canopy cover (Asbjornsen et al 2004;Gómez-Aparicio et al 2008;Rodríguez-Calcerrada et al 2010).…”

“…Emergence time is an important component of fitness (Castro 2006;Seiwa 2000;Urbieta et al 2008;Verdu and Traveset 2005) that is partly related to seed size (Du and Huang 2008;Tripathi and Khan 1990) and canopy closure (Augspurger et al 2005;Jones et al 1997;Seiwa 1998). Early emergence gives plants a performance advantage during recruitment due in part to the pre-emption of aboveand below-ground resources to competitors (Geber and Griffen 2003).…”

Interference of Pteridium arachnoideum (Kaulf.) Maxon. (Dennstaedtiaceae) on the establishment of rainforest trees

“…However, both height ( Figure 1c) and stem diameter of three pioneer species (Schinus terebinthifolia, Cordia superba and Guarea kunthiana) were slightly greater in the control area whereas the height of the two secondary species (Tabebuia heptaphylla and Cedrela fissilis) was greater in the P. arachnoideum stand. Hutchings, 1997;Seiwa, 2000), any inhibitory impact on these processes could decrease the chances of plant establishment. In general, early germinating seedlings have a greater competitive ability because, amongst other factors, they occupy the available space quickly, and pre-empt any resource limitation (Stanton, 1984;Zhang and Maun, 1990;Seiwa, 2000), while later-germinating seedlings can suffer increased mortality and/or reduced growth (Zimmerman and Weis, 1983).…”