submerged, heated, and agitated in neutral detergent fiber solution removing soluble cell
contents and leaving non-detergent fiber (% NDF). In the second step, the bagged
samples were treated with acid-detergent solution, which removed hemicellulose and left
acid-detergent fiber (% ADF) consisting of cellulose, lignin, cutin and insoluble ash. In
the third step, samples were treated with 70% sulfuric acid, which removed cellulose and
left lignin, cutin and insoluble ash inside the bags. Between steps, sample bags were dried
at 1000C overnight to determine the dry mass, and each fiber fraction was calculated by
subtraction. Afterwards, the remaining sample was combusted at 5000C to determine
percent insoluble ash. Mass of labile cell contents + hemicellulose + cellulose + lignin +
insoluble ash add up to 100% of the original dry mass.
Percent critical height
Percent critical height (% Her) measures the relationship between stem height and
how tall it could be before it buckles under its own weight (Holbrook & Putz 1989).
Percent critical height was calculated for each seedling stem according to the formula
given by Greenhill (1881):
Her = 1.26(E/w)" (db) 23 (1-2)
where E = Young's modulus of elasticity (Pa), w = fresh weight/unit volume (Nm-3), and
db = diameter at base (m). The ratio of Her to the actual stem height multiplied by 100 is
% Her, which is an indication of mechanical risk-taking. In other words, the higher the
% Her the lower the margin of safety for the stem to remain free-standing.
Flexural stiffness
Flexural Stiffness (El) describes the ability of a structure to withstand mechanical
loads, taking into account the size and shape of the structure as well as the material
properties of its tissues (Gartner 1991). It is the product of E, which describes the