Patch structure and ramet demography of the clonal tree, Asimina triloba, under gap and closed-canopy

Abstract

Clonal understory trees develop into patches of interconnected and genetically identical ramets that have the potential to persist for decades or centuries. These patches develop beneath forest canopies that are structurally heterogeneous in space and time. Canopy heterogeneity, in turn, is responsible for the highly variable understory light environment that is typically associated with deciduous forests. We investigated what aspects of patch structure (density, size structure, and reproductive frequency of ramets) of the clonal understory tree, Asimina triloba, were correlated with forest canopy conditions. Specifically, we compared A. triloba patches located beneath closed canopies and canopy gaps. We also conducted a three-year demographic study of individual ramets within patches distributed across a light gradient. The closed canopy-gap comparison demonstrated that the patches of A. triloba had a higher frequency of large and flowering ramets in gaps compared to closed-canopy stands, but total ramet density was lower in gaps than in closed canopy stands. In the demographic study, individual ramet growth was positively correlated with light availability, although the pattern was not consistent for all years. Neither ramet recruitment nor mortality was correlated with light conditions. Our results indicate that the structure of A. triloba patches was influenced by canopy condition, but does not necessarily depend on the responses of ramets to current light conditions. The lack of differences in ramet recruitment and mortality under varying canopy conditions is likely to be a primary reason for the long-term expansion and persistence of the patches. The primary benefit of a positive growth response to increasing light is the transition of relatively small ramets into flowering ramets within a short period of time.

Effects of male fecundity, interindividual distance and anisotropic pollen dispersal on mating success in a Scots pine (Pinus sylvestris) seed orchard

“…Anisotropic patterns of pollen dispersal have been reported in some studies (Burczyk et al, 1996;Burczyk and Prat, 1997;Lian et al, 2001;Bacles et al, 2005;Austerlitz et al, 2007), but other studies have failed to detect such effects in natural populations of wind-pollinated tree species (Dow and Ashley, 1996;Streiff et al, 1999;Hanaoka et al, 2007;Pluess et al, 2009). As the spatial arrangements of individuals with varying degrees of fecundity (for example, flower numbers per individual) are evidently nonrandom in natural populations (Itoh et al, 2003;Kanno and Seiwa, 2004;Hosaka et al, 2008), anisotropic pollen dispersal will be masked if trees that produce small quantities of pollen can transfer pollen grains to other trees effectively with the aid of directional air movement. Strong anisotropic pollen dispersal patterns are expected to violate the assumption of random mating in plant populations, resulting in more restricted local breeding neighborhoods than expected.…”

Intensity and mode of Lindera melissifolia reproduction are affected by flooding and light availability

“…plants having more reproductive stem length in that environment (Lockhart et al, 2013) Light availability exerts strong influence on sexual reproduction for many clonal, woody plants in temperate understories (Hosaka et al, 2008;Kanno & Seiwa, 2004;Roper et al, 1995). V. myrtillus L. produced a greater number of flower buds, flowers, and fruit in the relatively high light environment of forest gaps compared to closed-canopy locations in southern Germany (Eckerter et al, 2019).…”

“…Most of these clonal plants can generate new ramets across a wide range of light environments, but ramet development often peaks in high-light environments more supportive of plant vigor (Kawamura & Takeda, 2002, 2008Kowarik, 1995). However, Hosaka et al (2008), who studied A. triloba in temperate broadleaf forests in Maryland, USA, reported that ramet recruitment did not correlate with light availability beneath closed canopy versus canopy gap locations. Also, clonal plants that rely on other forms of asexual reproduction, such as layering or fragmentation, may show higher rates of ramet development in relatively low-light environments where genet persistence is critical (Kanno & Seiwa, 2004).…”

“…Investigations in temperate forests demonstrate that plasticity in expression of reproductive mode by clonal woody plants is driven by changes in components of the forest environment across space and time (Bunnell, 1990 ; Hewitt, 2020 ; Hosaka et al., 2008 ; Kanno & Seiwa, 2004 ; Moola & Vasseur, 2009 ; Salter et al., 2010 ). Variations in the availability of light, soil moisture, and other biotic and abiotic resources can affect resource acquisition, which then influences resource allocation patterns of a plant.…”

Immediate and Delayed Effects of Severe Winds on an Old-Growth Forest in Kentucky: A Forty-Year Retrospective

“…Spicebush and pawpaw are clonal species and shade tolerant. Both species, however, are also responsive to openings in the canopy that may enhance their productivity, growth and reproduction [43][44][45]. Hosaka et al [46] suggested that the growth habit of pawpaw may take advantage of temporal variations in light.…”