Masting in Fagus crenata and its influence on the nitrogen content and dry mass of winter buds

Abstract

In Fagus, full-mast seeding years are invariably followed by at least one non-mast year. Both flower and leaf primordia develop during the summer within the same winter buds. Flower bud initiation occurs when the N content of developing seeds is increasing rapidly. We hypothesized that competition for nitrogen (N) between developing seeds and buds limits flower primordium formation in mast years and, hence, limits seed production in years following mast years. We tested this hypothesis in three Fagus crenata Blume forests at elevations of 550, 900 and 1500 m. Bud N concentration (N con), amount of N per bud (N bud) and dry mass per bud (DM) were compared between a mast year (2005) and the following non-mast year (2006), and between winter buds containing both leaf and flower primoridia (BF), which were formed during the non-mast year, and winter buds containing leaf primordia only (BL), which were formed in both mast and non-mast years. In addition, leaf numbers per shoot corresponding to the analyzed buds were counted, and the effect of masting on litter production was analyzed by quantifying the amounts of litter that fell in the years 2004 to 2007. The dry mass and N content of BF formed in 2006 by trees at both 550 and 1500 m were 2.1-3.4-fold higher than the corresponding amounts in BL, although the numbers of leaves per current-year shoot in 2007 that developed from the two bud types in the same individuals did not differ significantly. These results indicate that more N and carbohydrate are expended in producing BF than in producing BL. The amount of litter from reproductive organs produced in the mast year was similar to the amount of leaf litter at 900 and 1500 m, but three times as much at 550 m. Leaf numbers per shoot were significantly lower at all elevations in the mast year than in the non-mast years (and the amount of leaf litter at 550 and 1500 m tended to be lower in the mast year than in the non-mast years. In conclusion, preferential allocation of resources to seeds in the mast year reduced the availability of resources for flower primordium formation, and this may have accounted for the poor seed production in the following non-mast year.

An increase in canopy cover leads to masting in Quercus ilex

“…Current-year leaves increased to the highest fraction of leaf dry mass 3 years after the masting. Singh et al (1990) and Han et al (2008) showed how masting influenced negatively the production of leaf primordia and growth in the following years. Leaf shedding is enhanced after the masting event.…”

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

“…For example, a drastic reduction in crown cover was detected in two birch species (Betula alleghaniensis and B. papyrifera) during a mast year (Gross 1972), and Fagus sp. has also shown drastic reductions in crown conditions due to large seed harvests (Innes 1992;Ferretti et al 1998;Han et al 2008;Vicca et al 2014). In these kinds of forests, masting could be detected after substantial decreases in the EVI not explained by weather conditions .…”

Soil nutrient supply modulates temperature‐induction cues in mast‐seeding grasses

“…For example, competition for nitrogen (N) and carbohydrates between floral and leaf buds may drive variation in flowering in some species (Han et al 2008), and these competitive interactions may be relaxed through increasing soil nutrients (e.g., Neilsen et al 1990). High-fertility soils are thus predicted to increase reproductive output (i.e., seeds per m 2 ) and lower interannual variation, increasing the number of years with medium-or low-intensity flowering at the expense of those with negligible flowering (Kelly and Sork 2002).…”