Abstract
ABSTRACT Liaodong oak (Quercus liaotungensis) is an ecologically important tree species on the Loess Plateau in China that experiences strong intraspecific competition. Therefore, here, we aimed to clarify the strategies of Liaodong oak under intraspecific competition by examining the growth, architecture, and biomass allocation, and analyzed their relationships with the competition intensity. We found that intraspecific competition severely limited the accumulation of biomass in Liaodong oak and this competition was asymmetric among individuals. Intense competition among these trees resulted in a greater allocation of biomass to the belowground parts, allowing them to compete for moisture, which is a limited resource. Aboveground, the trees tended to allocate more resources to their trunks to ensure that tree height growth was not affected, resulting in a decreased diameter at breast height (DBH)/tree height ratio and tapering of the tree, thereby improving stem quality. By contrast, the amount of biomass that was allocated to the branches was greatly reduced through a reduction in the diameter and length of the branches rather than the number of branches.
Highlights
Competition occurs between individuals of the same or different species when the required environmental resources or energy are insufficient or a particular environmental factor is limited (Seifert et al 2014)
Plot No 16 was selected as the study plot because of its representativeness (DBH, competition situation and canopy closure close to average) and operability (Flat and close to the road); Liaodong oak surrounded only by Liaodong oak was selected as subject tree since we focus on the main competition mode
The results of competition analysis of Liaodong oak showed that the total competition index of Liaodong oak in 20 plots is 1719.69 (Table 4), among them, the intraspecific competition was 1392.288, accounting for 82.6%, and the interspecific competition was 327.959, accounting for 17.4%
Summary
Competition occurs between individuals of the same or different species when the required environmental resources or energy are insufficient or a particular environmental factor is limited (Seifert et al 2014). Competition mainly occurs between neighboring individuals and usually involves the competition between crowns for light resources or between belowground root systems for soil water and nutrients (Cahill 1999; Song et al 2012). This neighborhood competition has been shown to affect the growth, stem shape, crown shape, and biomass allocation of trees (Wu and Wang 2000; Liu et al 2010; Cao et al 2014). The intensity of competition has been found to be significantly negatively correlated with radial growth in Larix chinensis (Weiner 1990; Schwinning and Weiner 1998; Duan and Wang 2005) and biomass growth in stinky fir (Abies nephrolepis), Wang et al (2012) indicating that strong neighborhood competition reduces the available resources and decreases the growth and biomass accumulation of trees
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