Review of Literature on the Function and Allometric Relationships of Tree Stems and Branches

Abstract

The goal of maintenance pruning is the development of a tree canopy that meets a defined objective while minimizing the risk of failure. An indepth understanding of the primary functions of branches and how they influence canopy form is needed in order to assess the impacts of cultural practices such as pruning or plant spacing on canopy development. Allometric modeling describes the relationship between size and shape of organisms. This paper explores three allometric methods of modeling branch form (pipe model theory, fractal dimensioning, and power laws) and their potential in guiding pruning research. Additionally, two principal functions of plants—hydraulic and mechanical—are discussed in light of their impact of stem and branch form.

Tensile properties of six desert shrub species in Hobq Desert, China

“…There is a "hardening" stage before failure, e.g., the curves of T. ramosissima and H. rhamnoides. The orientation changes of cellulose microfibrils, the strengths of lignin and microfibrils, and internal micro-structures all could influence the macro-mechanics of plant tissues (Spatz et al 1999;Dahle and Grabosky 2009). As a first approximation and for the convenience of comparing different shrub species, all viscoelastic and plastic effects are neglected.…”

“…The change of mechanical parameters with stem diameter is an interesting phenomenon (Spatz and Bruechert 2000;Dahle and Grabosky 2009). From the viewpoint of material mechanics, an interpretation is as follows.…”

“…For the stems less than 3.0 mm in diameter of Caragana korshinskii, Hippophae rhamnoides, Medicago sativa, Astragalus adsurgens Pall, Melilotus officinalis, the mean tensile strengths are 50.13, 37.27, 30.25, 22.74, 22.22 MPa (Ge et al 2013). It was proposed that tensile strength and Young's modulus should vary with stem diameter (Spatz and Bruechert 2000;Dahle and Grabosky 2009), because the mechanical properties of biological materials usually depend on their spatial scales (Weinkamer and Fratzl 2011). Tensile strength might be a decreasing function of diameter, whereas the changes of Young's modulus with diameter behaved greatly differently among different shrub specials (Xue et al 2012;Zuo et al 2015).…”

Can Mechanical Strain and Aspect Ratio Be Used to Determine Codominant Unions in Red Maple without Included Bark

“…Reasons why separation angle was smaller as branches were longer and larger in diameter can be better explained by looking more closely at what happens as branches get longer and increase in diameter. As a branch becomes longer and thicker (diameter), it becomes less flexible [46,47]. This makes intuitive sense and can be seen in nature regularly.…”

“…Branches become less flexible as the cross-sectional area and moment of inertia increases [24], while at the same time the modulus of rupture and modulus of elasticity of the new wood increases as it transitions from juvenile to mature wood [48][49][50]. Branches become more rigid as they grow, and their primary function shifts away from sun branches with photosynthetic tissue to structural branches that hold smaller sun branches [47,[51][52][53][54]. As branch diameter increases, strain induced during bending should also increase, as strain increases with the distance from the pith [5,26,55,56].…”