Light transmittance and understory junipers influence the survival and growth of seedlings and litter decomposition in black pine forests

Abstract

Previous studies examining the influence of understory shrubs and light transmittance through the canopy (LT) (%) on seedling establishment of desired species and litter decomposition have reported inconsistent findings. Uncertainty still also remains about the effects of understory junipers (Juniperus oxycedrus L. subsp. oxycedrus) and LT on survival and growth of black pine (Pinus nigra Arnold.) seedlings as well as on litter decomposition across species' geographical range. Thus, this study aimed to examine the influence of understory junipers and LT on the growth and survival of black pine seedlings. Moreover, how junipers and LT affect litter decomposition was also monitored for eighteen months. Survival and growth of seedlings were most significantly affected by LT and understory junipers. LT and junipers negatively affected the survival of black pine seedlings. LT increased root-collar diameter (RCD) growth of the seedlings, while the RCD growth rate decreased with the presence of understory junipers. Moreover, the influences of LT and junipers on litter mass loss were mainly statistically significant; the presence of junipers and increasing LT in understory retarded litter decomposition. The findings may help our knowledge of ecological processes such as litter decomposition and seedling establishment in black pine forests. The results would also provide important guidance for evaluating the effects of overstory thinning (i.e., providing light to understory) and removing junipers on the ecological processes associated with litter decomposition and seedling recruitment in a black pine stand.