Abstract
Seedling recruitment following a masting event, where more fruits are produced in synchrony and intermittently compared with other species, plays a crucial role in determining species diversity and community structure. Such seedling recruitment can be superabundant, but followed by high mortality shortly thereafter. Differences in biotic factors such as seedling characteristics, competition, and herbivory, and microsite‐specific abiotic factors could determine seedling fate in space and time.In a subtropical forest in south China, for 2 years using censuses conducted every 1–2 months, we monitored 40 seed traps and 120, 1 m2 quadrats in five 1‐ha plots located from 1,400 to 1,850 m asl for the masting maple species, Acer campbellii subsp. sinense (Pax) P.C.DeJong. We measured biotic—conspecific and heterospecific seedling density, species richness, herbivory, seedling height, and leaf number—and abiotic—canopy openness, slope, and aspect—factors to assess drivers of seedling survival and evaluated A. campbellii subsp. sinense presence in the soil seed bank (SSB).The masting seed dispersal peak and seedling emergence peak occurred between October 2017 and January 2018, and May 2018, respectively. Of 688 selected seedlings, mortality was 92.7% within one year. No seeds were observed in the SSB. Seedling height and leaf number positively affected seedling survival, while seed placement as measured by aspect also showed effects on survival. Conspecific and heterospecific density and herbivory did not show any clear effect. Higher probabilities of seedling survival were found in areas with larger canopy openness (≥12% canopy gap size) and in steeper microsites (≥35°). Synthesis. Masting is mainly studied as a population‐level phenomenon from the fruiting tree perspective. Our study of individual seedling fate revealed that intrinsic biotic factors and seed placement were key drivers of survival. Although biotic determinants such as competition from conspecifics or heterospecifics or herbivory did not determine survival, their ubiquitous presence may be an underlying equalizer in community dynamics where seedlings that overcome biotic pressures, if placed at the right microsite, are at better odds at being recruited to the next life history stages.
Highlights
The seedling stage represents a crucial bottleneck in plant establishment, where most individuals do not survive to the ontogenetic stage (Harms, Wright, Calderón, Hernández, & Herre, 2000; Queenborough, Burslem, Garwood, & Valencia, 2007)
We found 5,820 seeds from 97 morpho-species that emerged in the soil seed bank (SSB) assessment, but we did not find any seeds of A. campbellii subsp. sinense
Seedlings emerging in more open areas, as measured by canopy openness, had greater survival probability compared with smaller gaps (p = .0014; Figure 4b)
Summary
The seedling stage represents a crucial bottleneck in plant establishment, where most individuals do not survive to the ontogenetic stage (Harms, Wright, Calderón, Hernández, & Herre, 2000; Queenborough, Burslem, Garwood, & Valencia, 2007). Seedlings can be superabundant following an interannual and synchronous reproductive episode of high seed production (masting) (Kelly & Sork, 2002). This evolutionary strategy influences forest regeneration and affects animal populations (Curran & Leighton, 2000; Zwolak, Witczuk, Bogdziewicz, Rychlik, & Pagacz, 2018) with cascading effect on species diversity and composition. Studies that investigated the drivers of seedling survival following a masting event coupled with the assessment of advanced regeneration and persistence in the SSB are limited (Cleavitt, Battles, Fahey, & Blum, 2014; Oshima, Tokumoto, & Nakagawa, 2015)
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