Masting is a common reproductive strategy regulating seedling regeneration in many perennial plant species. The evolutionary origins and functional benefits of masting have been explained by well-supported hypotheses relating to economies of scale of seed production. Nevertheless, our understanding of the potential costs of masting for the plant seed-to-seedling transitions remains limited.

We evaluated the annual seed production of Castanopsis fargesii, a dominant species of subtropical evergreen broad-leaved forests in China from 2013 to 2018. We also tracked the seed fate for the mature seeds in the seed-to-seedling transition. Each type of killed seed (such as predated by rodents and insects, or germinated failure) were evaluated. We measured the seed mass of all intact seeds using a precision electronic balance. This dataset contains the masting data, seed fate data and seed mass data of C. fargesii for more than six years.

The study was conducted in the Jinyunshan National Nature Reserve (GNNR; 29°8′18" -29°17′29″ N, 118°2′14" -118°11′12″ E; 8107 ha in area), in Chongqing, China. The region has a subtropical monsoon climate, and the annual mean temperature is 13.6°C. Mean temperatures in January are around 3.1°C, and the mean August temperature is 24.3°C. Mean annual precipitation and relative humidity are 1611.8 mm and 87%, respectively. Vegetation on Jinyun Mountain is comprised of typical subtropical evergreen forest, dominated by Castanopsis fargesii, Machilus nanmu, Polyspora speciose, and Castanopsis carlesii var. spinulosa.

In September 2013, we established a 50 m × 100 m permanent monitoring plot that was divided into 50 subplots (10 m × 10 m). We established 86 seed traps within the study plot to sample masting patterns and seed fate in late-September 2013. Fifty seed traps were installed in the center of each 10 m × 10 m subplot, and the remaining 36 were placed at the grid intersections. The closest distance between two seed traps was 7.1 m, which was approximately equal to the average diameter of the crown of C. fargesii adult trees. Next, we established soil seed bank quadrats (1 m × 0.5 m) and seedling quadrats (1 m × 0.5 m) along the surface of the left and right sides of each seed trap, respectively. The boundaries of the soil seed bank quadrats and the seedling quadrats were marked using four pvc tubes (20 cm in height) and nylon threads. We assumed that the seed rain in the soil seed bank quadrats and seedling quadrats were similar to what was actually recorded in the seed traps.

We measured the seed rain from October to December annually from 2013 to 2018. All materials from the seed traps were collected once per week during this period. Seeds collected from the seed traps were defined as mature seeds and categorized into three groups based on careful examination of each seed: 1) intact seeds (seeds intact, without any injury); 2) vertebrate-attacked seeds (eaten by vertebrates (mostly by Callosciurus erythraeus) before seeds had fallen); and 3) insect-attacked seeds (suffered from predation by invertebrate such as Curculio sp., with obvious holes on the seed surface). We measured the seed mass of all intact seeds using a precision electronic balance.

We measured the soil seed bank in April (in the year following the seed rain) of each year from 2014 to 2019. We defined seeds from the soil seed bank quadrats as surviving seeds, which were categorized into four groups based on a careful examination of each seed: 1) viable seeds (already had an elongated radicle or healthy embryo and cotyledon); 2) fungi-infected seeds (killed by fungal infection, where the embryo and/or cotyledons were covered with hyphae and had decayed); 3) desiccated seeds (killed by desiccation, where the roots and/or cotyledons were withered and brown); and 4) rodent-attacked seed (predation by rodents; mostly by Rattus flavipectus and Rattus norvegicus).

We sampled newly germinated seedlings every two weeks from May to September each year from 2014 to 2019. Newly germinated seedlings were defined as seedlings that had grown at least one true leaf. Seedlings sampled within each seedling quadrat were censused and marked with a numbered label. In late-December of the following year (2015-2020), two growing seasons after seedling emergence, we censused the labeled seedlings that were still alive. We referred to these individuals as established seedlings.

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