Nitrogen storage dynamics are affected by masting events in Fagus crenata

Abstract

It is generally assumed that the production of a large crop of seeds depletes stores of resources and that these take more than 1 year to replenish; this is accepted, theoretically, as the proximate mechanism of mast seeding (resource budget model). However, direct evidence of resource depletion in masting trees is very rare. Here, we trace seasonal and inter-annual variations in nitrogen (N) concentration and estimate the N storage pool of individuals after full masting of Fagus crenata in two stands. In 2005, a full masting year, the amount of N in fruit litter represented half of the N present in mature leaves in an old stand (age 190-260 years), and was about equivalent to the amount of N in mature leaves in a younger stand (age 83-84 years). Due to this additional burden, both tissue N concentration and individual N storage decreased in 2006; this was followed by significant replenishment in 2007, although a substantial N store remained even after full masting. These results indicate that internal storage may be important and that N may be the limiting factor for fruiting. In the 4 years following full masting, the old stand experienced two moderate masting events separated by 2 years, whilst trees in the younger stand did not fruit. This different fruiting behavior may be related to different "costs of reproduction" in the full masting year 2005, thus providing more evidence that N may limit fruiting. Compared to the non-fruiting stand, individuals in the fruiting stand exhibited an additional increase in N concentrations in roots early in the 2007 growing season, suggesting additional N uptake from the soil to supply resource demand. The enhanced uptake may alleviate the N storage depletion observed in the full masting year. This study suggests that masting affects N cycle dynamics in mature Fagus crenata and N may be one factor limiting fruiting.

Effects of climate on reproductive investment in a masting species: assessment of climatic predictors and underlying mechanisms

“…; Han et al . ). Accordingly, Kelly () proposed that individual variation in seed output in masting species might largely depend on how heavily each plant invests resources during masting events, the so‐called depletion coefficient.…”

Parameterisation and validation of a resource budget model for masting using spatiotemporal flowering data of individual trees

“…This finding adds an additional evidence for the importance of nitrogen dynamics on masting as previously demonstrated by significant depletion of nitrogen in leaves and branches after seed production (Han et al . , ), modification of climatic effect on masting by nitrogen availability (Smaill et al . ; Tanentzap et al .…”

Elevation‐dependent responses of tree mast seeding to climate change over 45 years

“…; Han et al. , ) or by enhancing photosynthesis and the supply of fixed carbohydrates for growth (e.g., Waring and Schlesinger ). The demands of seeding events can subsequently deplete stored nutrients in trees (e.g., Sala et al.…”