d.f. = 7, P <0.001; Figure 2-2D). Only 4.1% of the seedlings were affected by litterfall,

with no interspecific differences in damage agent distribution over time (log-rank X2

13.7, d.f. = 7, P >0.05).

Types of Mechanical Damage

 Four types of mechanical damage were recorded during 1 yr: damaged leaves, bent

stems, broken stems, and uprooted seedlings, caused by vertebrates, litterfall, or

invertebrate herbivores (in the case of leaf damage). At the end of the study, 77% of

seedlings showed some form of damage, of which leaf damage was the most frequent.

After 1 yr, 30.6% exhibited leaf damage, 28.7% of the seedlings had broken stems,

23.9% had bent stems, and 25.6% had been uprooted (Table 2-2). These categories were

not mutually exclusive. In fact, 45% of the damaged seedlings had two or more types of

damage.

 Species differed in their likelihood to die after suffering leaf damage or bent stems,

but not after being uprooted or having their stem broken. Percent damage fatality (as

defined by Formula 2-1) differed among species for leaf damage or bent stem (leaf

damage: 2 = 78.6, d.f. = 7, P <0.001; stem bent: 2 = 57.3, d.f. = 7, P <0.001). In

contrast, there was no interspecific difference in damage fatality for uprooted seedlings or

those with broken stems (uprooted: 2 = 14.0, d.f. = 7, P = 0.052; stem broken: 2 = 9.4,

d.f. = 7, P = 0.226). It should be pointed out that because of the low number of uprooted

and broken seedlings in some species (cell N< 5), results should be interpreted with

caution. From all the biomechanical and ecological measurements tested (Table 1-4 in

Chapter 1), only stem toughness, stem tissue density, and second moment of area were

correlated with damage fatality (Table 2-3). Tougher, denser stems died less when their