Are stored carbohydrates necessary for seed production in temperate deciduous trees?

Abstract

Summary1. Many tree species undergo large fluctuations from year to year in seed production, a phenomenon known as masting. The resource budget model, based on the assumption that abundant seeding in a masting year depends on the abundance of resources stored over several years, is a key hypothesis in explaining the mechanism of masting. But do masting species really need such long-term storage to produce a large seed crop? 2. To test this hypothesis, we studied the relationship between the carbon accumulation period for seed production, as estimated by radiocarbon ( 14 C) analyses, and the coefficient of variation of annual seed production in 10 canopy tree species in a temperate deciduous forest. These species differ widely in their reproductive intervals. 3. In all the species studied, the accumulation period was < 1.4 years before seed maturation. Moreover, without taking species or reproductive intervals into account, there was no significant correlation between the carbon accumulation period and the fluctuation of annual seed production; both remained at an even level. 4. Synthesis. Our results suggest that temperate canopy trees used photosynthates produced in the current and/or the previous year for seed production, regardless of reproductive intervals. It might therefore be necessary to reconsider the importance of stored carbohydrate resources for masting.

Temporal trends in the enhanced vegetation index and spring weather predict seed production in Mediterranean oaks

“…This initial EVI threshold may suggest the need of a minimum amount of previously stored resources to produce buds before a mast seeding event, while the importance of the seasonal increase in the EVI and the favourable weather conditions in spring supports the relevance of the immediate availability of resources for triggering the masting episode. Our results thus fully agree with those recently found for deciduous trees in studies that applied isotopic analyses to show that the main photosynthates spent in the production of seed crops were those accumulated during the last growing seasons (within 17 months) (Ichie et al 2013;Hoch et al 2013). …”

“…1, 2). These recently synthesised carbohydrates could be those identified in isotopic studies (Ichie et al 2013;Hoch et al 2013). However, since only deciduous species were used in these studies, caution should be taken when extrapolating these conclusions for the evergreen Q. ilex.…”

“…Recent studies based on carbon isotopes suggest that seed production in several tree species in temperate forests depends only on the carbohydrates photosynthesised during the months prior to seeding (Ichie et al 2013;Hoch et al 2013). Unfortunately, the measurement of resource availability at a plant level is time-consuming and expensive and so is difficult to perform at broad spatial and temporal scales.…”

Nonstructural Carbon in Woody Plants

“…New leaves, sapwood, and fine roots are predominantly made from current-year assimilates, though almost half can originate from NSC that is several years old (32,54,84). Trees utilize recent NSC (current and previous year) for reproductive masting-years of large, synchronized seed production among conspecific individuals-regardless of the interval between mast years (52). New roots, leaf buds, and flowers grow from stored NSC up to two years old (52,139), and stored NSC up to three or four years old has been incorporated into tree ring cellulose growth (54,65).…”

Ecología evolutiva de la reproducción en dos pinos mediterráneos: Pinus pinaster Ait. y Pinus halepensis Mill.

“…As before, treatment 165 was defined as fixed but we used no covariate. Population was included as a random factor as 166 well as an observation-level random factor in order to account for overdisperssion in our data 167 Sala et al, 2012) and carbohydrates (Ichie et al, 2013) . Such an example is also provided by our data at the phenotypic 228 level.…”