Abstract
ABSTRACT Growth and survival of understory seedlings are influenced by their interactions with the environmental variables. The understanding of the relationships between stand density, canopy structure, and understory seedlings’ growth help forest managers conduct successful establishment through natural regeneration. In this study, the influence of stand basal area (BA) (m2.ha-1), photosynthetically active radiation transmitted through canopy (PART), leaf area index (LAI), height-to-crown base (HCB) and aspect on the root-collar diameter (RCD) (mm) growth, height growth (cm) and belowground/aboveground biomass (g) of seedlings is observed in uneven-aged Trojan fir stands. Seedling growth and belowground/aboveground biomass models were developed for five growing seasons after germination. PART, aspect and HCB were found to be the most strongly related to RCD and height growth of Trojan fir seedlings. PART and aspect explained the most variance in belowground/aboveground biomass of the seedlings. The data also showed that the light transmitted through the canopy was the most significant predictor of understory seedlings growth; thus, PART reaching understory can accelerate the development of sub-canopy layers in uneven-aged Trojan fir stands. Although survival of Trojan fir seedlings is usually high under canopy, results suggest that complete canopy closure should be avoided even in stands of shade-tolerant species such as Trojan fir to increase a seedling’s vigor for its successful recruitment into middle and overstory. The findings of this study will be helpful for forest managers to enhance the establishment and recruitment of Trojan fir seedlings in uneven-aged stands.
Highlights
Successful regeneration of forest stands is usually associated with seedling growth and survival
This study considers the variables of stand basal area (BA) (m2.ha-1), photosynthetically active radiation transmitted through canopy (PART), leaf area index (LAI), height-to-crown base (HCB), and aspect
100-m2 plots, while PART, LAI and HCB were measured above each seedling selected
Summary
Successful regeneration of forest stands is usually associated with seedling growth and survival. Growth and mortality of understory seedlings are affected by their interactions with the environmental variables including light, moisture, wind, and temperature (Mason et al, 2004). These variables in a stand could be influenced by stand canopy structure (Aussenac, 2000). Belowground root biomass is as important as aboveground seedling growth for the successful development of a stand. The interactions among environmental factors and stand canopy structure could impact seedling growth aboveground as well as root biomass belowground (Waring and Powers, 2017)
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