Effects of browsing and season on defence and growth of selected woody species at the Nkuhlu exclosures

The study species represented two broad types of shoot morphology, which affected the way in which some data were collected. A. grandicornuta, A. exuvialis and D. cinerea can increase leaf area without increasing internode length. They therefore produce most of their new leaves in discrete clusters (whorls or tufts) of leaves at the nodes of old shoots or branches. The nodes are usually raised into short-shoots or spurs. Conversely, C. apiculatum, G. flavescens and E. divinorum cannot increase leaf area without extending the internodes of new long-shoots. All their new leaves are therefore arranged in either alternate or opposite positions on new shoots. The wet seasons occurring between August 2005 and July 2008 were divided into early (late November/early December), middle (late January/early February) and late (late March/early April) phases. Mature leaves above 1.5 m on randomly selected trees taller than 2 m were sampled in each phase of each wet season. The amount of canopy removed by browsing was estimated for each sampled tree. Concentrations of N, P, condensed tannins, total polyphenols, neutral detergent fibre, acid detergent fibre and acid detergent lignin ([N], [P], [CT], [TP], [NDF], [ADF] and [ADL]) were analysed. Shoot length, leaf length and photosynthesis parameters were measured each time leaves were sampled for chemical analysis in either one or two of the wet seasons. We also explored low-molecular-weight phenolics (LMWPs) in the study species in February/March 2007. Lastly, we fitted dendrometers to the study species in 2006 to measure relative growth rates of stems, which continued until 2012.