Excessive Accumulation of Chinese Fir Litter Inhibits Its Own Seedling Emergence and Early Growth—A Greenhouse Perspective

Abstract

Litter accumulation can strongly influence plants' natural regeneration via both physical and chemical mechanisms, but the relative influence of each mechanism on seedling establishment remains to be elucidated. Chinese fir (Cunninghamia lanceolata) is one of the most important commercial plantations in southern China, but its natural regeneration is poor, possibly due to its thick leaf litter accumulation. We used natural and plastic litter to study the effects of Chinese fir litter on its own seedling emergence and early growth, as well as to assess whether the effect is physical or chemical in nature. Results showed that high litter amount (800 g·m −2 ) significantly reduced seedling emergence and the survival rate for both natural and plastic litter. Low litter amount (200 g·m −2 ) exerted a slightly positive effect on root mass, leaf mass, and total mass, while high litter amount significantly inhibited root mass, leaf mass, and total mass for both natural and plastic litter. Root-mass ratio was significantly lower, and leaf-mass ratio was significantly greater under high litter cover than under control for both natural and plastic litter. Although the root/shoot ratio decreased with increasing litter amount, such effect was only significant for high litter treatment for both natural and plastic litter. Seedling robustness (aboveground biomass divided by seedling height) decreased with increasing litter amount, with high litter treatment generating the least robust seedlings. Because plastic and natural litter did not differ in their effects on seedling emergence and growth, the litter layer's short-term influence is primarily physical. These data indicated that as litter cover increased, the initial slightly positive effects on seedling emergence and early growth could shift to inhibitory effects. Furthermore, to penetrate the thick litter layer, Chinese fir seedlings allocated more resources towards stems and aboveground growth at the expense of their roots. This study provided experimental evidence of litter amount as a key ecological factor affecting seedling development and subsequent natural regeneration of Chinese fir.

Appropriate Removal of Forest Litter is Beneficial to Pinus tabuliformis Carr. Regeneration in a Pine and Oak Mixed Forest in the Qinling Mountains, China

“…This indicated that the inhibition effect of litter on P. tabuliformis seed might be related to allelopathy and biofiltration. The physical and chemical effects of litter on seedling emergence have been studied using natural and plastic litter, concluding that the short-term effects of Chinese fir litter on seedlings are mainly physical [42]. Similarly, many previous studies have shown that the influence of litter on seed and seedling growth exerts physical hindrance as well as allelopathic effects [43][44][45].…”

Effects of Sucrose, Boric Acid, pH, and Incubation Time on in Vitro Germination of Pollen and Tube Growth of Chinese fir (Cunnighamial lanceolata L.)

“…Since the 1980s, decreasing production of Chinese fir plantations has been reported, primarily due to soil degradation [7,8]. Currently, the sustainability of Chinese fir plantations is threatened by biodiversity reduction, production loss, soil degradation, and a lack of self-regeneration [4,9]. Therefore, understanding the factors that control regeneration, systematic breeding and selection of the best potential trees for future breeding programs are a major research priority for this tree.…”

Seedling emergence and early growth of Chinese fir under different light levels and seed positions: implications for natural regeneration

“…Unfortunately, the sustainability of these Chinese fir plantations is threatened by biodiversity reduction, production loss, soil degradation, and a lack of self-regeneration (Yang et al 2004;Bi et al 2007;Ma et al 2007;Chen et al 2014;Luo et al 2014;Zhang et al 2018). The lack of natural regeneration is of particular concern as forest management shifts focus from timber production to sustainability (i.e., maintaining ecological functions), and sustainable forestry relies on the ability of plant species to self-regenerate (Robert 2014;Bertacchi et al 2016;Chazdon et al 2016;Pirard et al 2016;Liu et al 2017). While understanding the factors that control tree regeneration is a major research priority for forest managers worldwide (Carnevale et al 2002;Dupuy et al 2008), surprisingly only a few studies have addressed the ecological factors that influence tree regeneration in Chinese fir plantations (e.g., Liu et al 2017).…”

“…Seedling emergence and early growth are more sensitive than other developmental stages to environmental fluctuation, thus representing a major bottleneck to tree regeneration (Zhu et al 2003;Walck et al 2011). Environmental factors such as light, soil moisture, temperature, soil conditions, pH, and litter cover are known to 4 influence these two bottleneck developmental processes (Liu et al 2011;Liu et al 2017;Liu t al. 2018;Wu et al 2017), although the degree of influence varies from region to region.…”

“…Evidence from field observations suggests that Chinese fir can regenerate naturally along the edges of Chinese fir stands and in gaps of natural broad-leaved forests, but not in dense pure Chinese fir stands (Chen et al 2000;Zhu et al 2011). Therefore, low light penetration and thick litter layer are major limiting factors that influence seedling emergence and early growth of many coniferous species (Cornett et al, 1998;Day et al, 2005;Wang et al, 2006), including Chinese fir (Chen et al 2014;Liu et al 2017;Liu et al 2018).…”