Spatiotemporal distribution and seed germination characteristics of Betula costata seed rain in the spruce-fir mixed forest

  Objective  The population of Betula costata in spruce-fir mixed forest in northeastern China was taken as the research object. The spatiotemporal distribution of Betula costata seed rain and seed germination characteristics were studied to provide theoretical basis for species diversity protection of the forest.

  Method  Based on the 9 sample plots, 1 ha (100 m × 100 m) each set in Wangqing Forestry Bureau, Jilin Province of northeastern China, sampling by diagonal five points, we set 5 seed traps in each sample plot, totally 45 in 9 sample plots to collect Betula costata seeds. We used 4 evaluation methods on spatial distribution types to distinguish the spatial distribution state of seed rain, including variance-mean ratio (C_x), negative binomial parameter (K), aggregation index (I), Cassie. R.M. index (C_A). In addition, 300 Betula costata seeds collected in September and October were randomly selected from each sample plot for seed germination experiment, and the 1 000-grain mass, germination potential and germination percentage were measured, respectively.

  Result  From July to November, 69 100 seeds were collected in total. The peak period of seed falling for Betula costata was October. We found that the seeds of Betula costata presented aggregation distribution at the spatial level based on 4 indexes, i.e. C_x reaching 1 116.30, K reaching 4.75, I reaching 1 115.30, C_A reaching 0.41, respectively. The average 1000-grain mass value of Betula costata seeds in September was 0.398 g, which was significantly higher than that in October (0.353 g) (P<0.01). Similarly, the average germination rate in September was (29.84 ± 11.68)%, which was significantly higher than that in October (23.52 ± 8.23)% (P < 0.05).

  Conclusion  In spruce-fir coniferous-broadleaved mixed forest, the seeds are small and fruiting for Betula costata and have obvious time distribution characteristics. Because the diffusion of Betula costata seeds is limited, as a result the seeds show an aggregated distribution pattern. In this region, the characteristics of rich provenance and poor germination ability of Betula costata will affect the distribution pattern of Betula costata, thus affect the community structure and species diversity of spruce-fir coniferous-broadleaved mixed forest in this area.