Effects of forest canopy condition on the establishment of Castanopsis fargesii seedlings in a subtropical evergreen broad-leaved forest
【Abstract】Aims The establishment of seedlings is a key life-history stage during the regeneration of plant populations. This study is to investigate the effects of forest canopy condition (large-sized gap: > 150 m2, medium-sized gap: 100–150 m2, small-sized gap: 50–100 m2, and understory as control) on the establishment of Castanopsis fargesii seedlings, and to guide in situ management and restoration of subtropical evergreen broad-leaved forests. Methods We conducted a 3-year in situ seed sowing experiment in the Jinyun Mountain National Nature Reserve under different canopy conditions, and monitored the growth and survival of C. fargesii seedlings for three years (2014–2016). Important findings We found that: (1) the emergence of the seedlings lasted from July to December, and the emergence of seedlings was delayed under large canopy gaps; (2) the overall germination rate was (62.8 ± 2.0)%. The averaged survival rate during three growing seasons was (65.1 ± 2.2)%, with wither being the key type of seedling mortality; (3) there was no significant difference in the germination and survival rates under different canopy conditions in 2014, but significant difference in the survival rates in 2015 and 2016; (4) the seedling growth among canopy conditions showed no difference in 2014, but distinct differences in 2015 and 2016. The seedling growth in large-and medium-sized gaps was significantly promoted compared with those growing under closed canopies in terms of total biomass, plant height, base diameter, root length and leaf number (except for the specific leaf area) ; (5) for each of the four types of canopy conditions, the leaf mass ratio (LMR) and stem mass ratio (SMR) of seedlings growing increased within last three years, while the root mass ratio (RMR) and root shoot ratio (RSR) decreased. The LMR in large-sized gaps was significantly higher than those in closed canopies, but not for RMR and RSR. The results suggested that the initial survival and growth of C. fargesii seedlings may be supported by the nutrients stored in seeds, and thus less affected by canopy conditions. However, in late-establishment stages (i.e., the second and third years), gap size could become a key factor in affecting both the seedling survival and growth. And large- and medium-sized gaps could promote the seedling establishment success for C. fargesii.
【Keywords】 canopy condition; seed germination; seedling establishment; growth; Castanopsis fargesii;
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Vol 43, No. 01, Pages 55-64