DOI: 10.5061/dryad.ffbg79czs
title: Dataset for: Variations in the reproductive cycle of Bornean montane tree species along elevational gradients on ultrabasic and non-ultrabasic soils

description: Although lowland tree species in the ever-wet regions of Southeast Asia
 are characterised by the supra-annual cycle of reproduction, the
 reproductive phenology of montane tree species remains poorly understood.
 In this study, we investigated the reproductive phenology of montane tree
 species using litter samples that were collected every two weeks from six
 rainforest sites, consisting of three elevations (1700, 2700, and 3100 m),
 on Mount Kinabalu, Borneo. At each elevation, one site was on infertile
 ultrabasic soil and one was on relatively fertile non-ultrabasic soil. We
 used a composite sample from 10 or 20 litter traps per site and sorted it
 by species. Therefore, the obtained data captured reproductive phenology
 in the population of each species rather than in an individual tree.
 Ten-year time series of flower and fruit litterfall were obtained for 30
 and 39 tree species, respectively. Fourier analysis was used to identify
 the dominant cycle of each time series. The most abundant cycle across
 species was supra-annual, followed by sub-annual, and annual cycles. Many
 species at higher elevations showed supra-annual cycles of flower
 litterfall, whereas species in the 1700 m sites often showed annual or
 sub-annual cycles regardless of soil type. No systematic differences were
 found among sites for fruit litterfall. Mechanisms underlying these
 elevational patterns in the reproductive cycle remain unclear but may
 include more severe El Niño droughts, lower primary productivity, lower
 soil fertility, and the absence of some sub-annually or annually
 reproducing families at higher elevations.
description: Litter samples were collected every two weeks between February
 1996 and March 2006 by earlier studies (Kitayama et al., 2015, 2021).
 Twenty, ten, and ten litter traps (0.5 m<sup>2</sup> area)
 were placed at 10 m intervals at 1700, 2700, and 3100 m sites,
 respectively. After drying at 70°C, these samples were combined per
 sampling date. Therefore, only a single composite sample was obtained per
 site at each sampling date. Reproductive litter sample was sorted by
 species and weighed after being grouped into two categories: flower and
 fruit. Flowers included inflorescences with flower buds, petals, stigmas,
 and stamens. The remaining reproductive organs, with immature and mature
 fruit, were categorised as fruit. Regarding conifers, male cones always
 had pollen scales, whereas the developmental stages of seed cones were not
 easily identifiable. Male-cone and seed-cone litter were grouped with
 flower and fruit litter, respectively. In the dataset, these groups will
 be referred to as ‘flower/male-cone’ and ‘fruit/seed-cone’ litters,
 respectively. Exceptionally, the flowers of
 <em>Lithocarpus</em> and <em>Quercus </em>at 1700
 m non-ultrabasic site and the flowers and fruits of Syzygium at 1700 m
 sites were sorted by genus. In the dataset, the unit of litterfall data is
 dry mass (g) per trap. The area of each trap was 0.5
 m<sup>2</sup>. Dates in the first row correspond to sampling
 dates.