Vertical zonation of browse quality in tree canopies exposed to a size-structured guild of African browsing ungulates.

摘要: We investigated whether the food quality of tree foliage for African savanna browsers varies across feeding height range guild. This was to address question why giraffes (Giraffa camelopardalis) generally feed at a higher level in canopy than is accessible all other browsers. defined giraffe browse unit (GBU) as length twig corresponding average "bite" taken by from two staple plants: Acacia nigrescens and Boscia albitrunca. sampled three study sites South Africa late dry season, each site clipping GBUs heights above ground: 0.5 m, 1.5 m 2.5 m; these representing levels typically browsed small, medium large-bodied browsing ungulates respectively. For GBU we measured leaf mass, total N, neutral detergent fibre condensed tannin, using near-infrared spectroscopy calibrated conventional laboratory analyses. found no differences between with regard chemistry concentrations, but biomass per significantly 1.5-m 2.5-m 0.5-m level. The larger thus gain bite-size advantage reach smaller species. A likely reason reduced low tendency small pluck individual leaves shoots, while large prune off whole shoots. contend that our findings are analogous those parallel studies on grazing guild, consistent hypothesis members ungulate guilds competitively displace ones shared when resources become restricted. prediction this guild drive succession behind maintain stratification below.