Growth strategies of a shade‐tolerant tropical tree: the interactive effects of canopy gaps and simulated herbivory

Abstract

Summary 1We hypothesized that the survival of shade-tolerant juvenile trees in the understorey depends on allocation strategies that slow their growth but enhance recovery from herbivore damage. In contrast, allocation patterns should maximize height growth in gaps where competitors grow rapidly. We tested the interactive effects of canopy gaps and simulated herbivory (by removing the apical meristem, or 10%, 50% or 90% of tissue from all leaves) on juvenile (< 1 cm diameter at breast height) Shorea quadrinervis Sloot (Dipterocarpaceae), a dominant canopy tree in Borneo. 2 Damage did not diminish survival over 8 months, except for 90% foliage removal from understorey plants.Height growth in the understorey was negligible in both control and damaged plants. In gaps, height growth was stimulated by removal of either the apical meristem or 10% of leaf tissue; growth was reduced only after 90% foliage removal. 3 Higher damage levels increased subsequent net leaf loss. Leaf production was much greater, but leaf retention much lower, in gaps than in the understorey. Ninety per cent foliage removal drastically reduced production in gaps and retention in the understorey. After 10% defoliation, height growth was enhanced in gaps despite approximately 30% net leaf loss. 4 In a separate experiment, juveniles were moved from a shade house to gaps. After 8 months, gap plants had more leaves and more total biomass, but only half the root : shoot ratio of plants left in the shade. 5 Allocation patterns, together with the survival of understorey plants after all but the highest levels of damage, indicate that root : shoot allocation there tends to reduce the risk of mortality following herbivore or mechanical damage at the expense of growth. In contrast, in gaps, where interference competition for light is high, resource allocation apparently maximizes height growth.The interaction between resource availability and herbivore damage provides the basis for a more synthetic theory of resource allocation and growth strategies than one based on resource availability alone.

Environmental context determines within- and potential between-generation consequences of herbivory

“…Deer-browsed plants were over 4 times more likely to die in light gaps than in the understory. In contrast, tree seedlings have been shown to have lower survival in response to clipping or mammalian browsing in understory habitats in many species (Blundell and Peart 2001;Milbrath 2008;Norghauer et al 2008) but not all (Husheer et al 2006). The diVerence in survival found here was caused by disparities in the extent of deer-inXicted damage to lightgap and understory plants.…”

Fire survival of lowland tropical rain forest trees in relation to stem diameter and topographic position

“…Apparently climax trees are able to survive under a canopy existing mainly of pioneers. This is perhaps not really surprising giving the fact that most climax trees are shade tolerant and are also able to survive prolonged periods of shade in the understorey of unburned forest (Turner 1990;Clark and Clark 1992;Lewis and Tanner 2000;Blundell and Peart 2001).…”

Variability in Compensatory Ability and Relative Invasive Potential in Ornamental Cleomes

“…Reallocation of resources to growth or reproduction after herbivory can be advantageous for species colonizing new areas (Blundell & Peart, 2001;Erneberg, 1999;Rogers & Siemann, 2004;Sun et al, 2009). However, establishing the connection between response to herbivory and invasive potential is extremely difficult.…”