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Data from: Positive spatial and temporal density-dependence drive early reproductive economy-of-scale effects of masting in a European old-growth forest community

Cite this dataset

Pesendorfer, Mario et al. (2024). Data from: Positive spatial and temporal density-dependence drive early reproductive economy-of-scale effects of masting in a European old-growth forest community [Dataset]. Dryad. https://doi.org/10.5061/dryad.kkwh70scg

Abstract

Masting, the spatial synchronization of interannual variation in seed production, can enhance reproductive efficiency through positive density-dependent processes (DD) that result in economies of scale (EOS), such as decreased pollen limitation and predator satiation in years of high reproduction. While the general occurrence of such EOS effects has been documented for masting species, few studies simultaneously investigated how spatial and temporal variation in reproduction affects pollination and predation. Furthermore, it is unclear whether the same mechanisms apply to co-occurring species with different levels of conspecific density, pollen limitation, and seed defenses. Here, we use a long-term data set with high spatial resolution of seed production of European beech (Fagus sylvatica), Norway spruce (Picea abies), and silver fir (Abies alba) in a primeval montane forest to investigate the relationship between reproductive effort, pollination efficiency, and predispersal predation by insects. We found that, along the temporal axis, the proportion of sound (fertilized and unpredated) seeds correlated positively with annual seed production over the 14-year study period in all three species, most strongly in beech and only weakly in silver fir. Moreover, the results show that in beech, spatial seed density interacts with plot-wide annual seed rain to enhance DD effects on seed predation, suggesting additive effects of synchronous reproduction on fitness benefits.

Synthesis: For both pollination and predispersal predation in beech and spruce, the strongest DD effects occur at low levels of reproduction and quickly reach asymptotes at higher levels, suggesting the presence of thresholds in different EOS mechanisms. As variability and synchrony in mast-seeding are expected to decline with climate change, EOS effects driven by DD may remain stable until the threshold is reached, at which sudden declines would result in devastating effects on the availability of viable seeds for germination and recruitment.

README: Positive spatial and temporal density-dependence drive early reproductive economy-of-scale effects of masting in a European old-growth forest community

https://doi.org/10.5061/dryad.kkwh70scg

The data consist of the proportion of hollow (unpollinated), insect-damaged, and sound seeds in two study plots from 2008-2021, which were modeled as a function of the spatial and temporal variation in seed rain for European beech (Fagus sylvatica), Norway spruce (Picea abies), and silver fir (Abies alba).

Description of the data and file structure

For each species, there is a file containing data on annual proportions of seeds in each category, combined with the mean number of seeds of that species per m2. The second file is the cumulative number of seeds for each seed trap, and the proportions of seeds that belonged to each classification. Files are provided as ".csv" files with the variable names 

  • p.sound: proportion of seeds that are filled and show no insect damage
  • t.p.pred: total proportion of seeds with insect damage
  • t.p.duds: total proportion of hollow (unpollinated) seeds
  • mean: mean number of seeds per plot per year
  • total: total number of seeds per species accumulated for individual seed traps

Methods

Seed production was monitored since 2003 on two 1-ha study plots (Mayer-Wegelin plot “MW”, and Josef plot “JO”) each equipped with 81 seed traps of 0.24 m2 area, arranged in a geostatistical design (Gratzer et al., 2022). Starting in 2008, seeds collected in traps were sorted into “sound”, “hollow”, and “infested by insects”, as evidenced by chewing marks and exit holes. The most common predispersal seed predators are the beech moth (Cydia fagiglandana) for beech seeds, the spruce seed moth (Cydia strobilella) and Pine Knot-horn (Dioryctria abietella) for Norway spruce, and the fir seed chalcid (Megastigmus suspectus) (Nilsson & Wastljung, 1987; Skrzypczyńska, 1998; Seifert et al., 2000). Because hollow seeds are produced when ovules have been formed but not fertilized, the proportion of hollow seeds is a good proxy for pollen limitation (Nilsson & Wastljung 1987; Kormutak & Lindgren, 1996; Nygren et al., 2017). We present data for 2008 – 2021, when pollen limitation and predispersal predation data is available, but the period is representative in overall seed production patterns of the larger study (Gratzer et al., 2022).

The data constitute a) the annual means proportions of hollow, insect-damaged, and sound seeds across both study plots as shown in Fig. 2 and b) the cumulative proportion for 162 seed traps shown in Fig. 3.

Funding

FWF Austrian Science Fund, Award: P30381

Bundesministerium für Land- und Forstwirtschaft, Umwelt und Wasserwirtschaft, Award: WF 101656, Waldfonds