Relation of ramet size to acorn production in five oak species of xeric upland habitats in south‐central Florida

Abstract

This study examined variation in two components of acorn production. Percentage of bearing ramets (stems) and number of acorns per bearing ramet were examined in five clonal oaks in three xeric habitats of south-central peninsular Florida in relation to ramet size within and between species and vegetative associations. Counts of acorns on two white oaks (Quercus chapmanii and Q. geminata) and three red oaks (Q. inopina, Q. laevis, and Q. myrtifolia) were conducted annually from 1969 to 1996 (except in 1991) on permanent grids in southern ridge sandhill, sand pine scrub, and scrubby flatwoods associations at the Archbold Biological Station, Florida, USA. Percentage of bearing individuals and mean number of acorns per bearing individual increased with increasing ramet size for all species across all vegetation associations. However, in Q. geminata and Q. myrtifolia, acorn production declined in the largest size class (>3.2 m), implying that larger individuals of these clonal species may become senescent. All oak species in sand pine scrub, which had a nearly closed overstory, had lower frequencies of bearing oaks and mean numbers of acorns compared with similar-sized individuals of the same species in the more open-canopied southern ridge sandhill and scrubby flatwoods associations, suggesting light limitation. The annual production of acorns by a given oak species was correlated across vegetative associations and annual acorn production of oak species was correlated for species within the same section. Intermediate-size class oaks contributed the most acorns per unit area, suggesting that stands managed with short fire-return times will provide fewer acorns to wildlife than stands managed to produce more variable distributions of oak size classes. However, our study suggests that long-unburned stands, such as those studied here, will maintain relatively constant levels of acorn production as a consequence of ramet replacement within the clones of these shrubby oaks to create a variable distribution of size classes. Of the oak species studied, Q. myrtifolia had the highest acorn production and the smallest acorns, while Q. laevis had the lowest acorn production and the largest acorns, suggesting an allocation trade-off between acorn numbers and size.

Long‐term trends in annual reproductive output of the scrub hickory: factors influencing variation in size of nut crop

“…A similar trend was exhibited by the five oak species that co-occur with scrub hickory (Abrahamson and Layne, 2002a), as well as in other oak species (e.g., Moody, 1953;Greenberg, 2000). A high correlation (r ϭ 0.84, P Ͻ 0.001) between ramet height and crown width in a random sample (N ϭ 269) of stems ranging from sprouts to mature scrub hickories from all associations suggests that the increase in nut production with size is due to increased canopy coverage rather than an increased number of nuts per unit area of canopy.…”

“…Canopy coverage is nearly complete in scrub as a consequence of the dense sand pine overstory, which translates into scrub having the lowest available PAR of the associations studied (Abrahamson and Rubinstein, 1976;Abrahamson, 1999). This pattern of production across associations was parallel to that of acorn production by the oaks of these three associations (Abrahamson and Layne, 2002a). Coblentz (1980) also reported a similar trend of lower acorn production by Quercus garryana in closed canopy vs. open savannah.…”

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

“…Acorn production on four branches per tree was recorded each September, i.e. at the peak of seed production in holm oaks before acorns were ripe enough to fall or to be harvested in appreciable number by birds (see Abrahamson and Layne 2002). The total number of acorns produced per tree was estimated by multiplying the mean acorn production per branch by the number of branches per tree (see Espelta et al 2008 for further details).…”

Narrow genetic base in forest restoration with holm oak (Quercus ilex L.) in Sicily

“…Since fecundity and acorn production are positively correlated with plant or crown 332 size [1,15], individuals are expected to differ greatly in their contribution to the next 333 generation in both male and female fertility. Additionally, the overlapping of crowns 334 of some old individuals (m3, m4, m5) among them and with an equal-size maple 335 (Acer monspessulanum), may restrict flower and fruit development due to space 336 competition or light limitation [1,22].…”

“…Additionally, the overlapping of crowns 334 of some old individuals (m3, m4, m5) among them and with an equal-size maple 335 (Acer monspessulanum), may restrict flower and fruit development due to space 336 competition or light limitation [1,22]. In fact, it is remarkable that the large tree m5, 337 the closer to the maple (Figure 1 seed origin stand and the plantation is about 700 m).…”