Induced chemical defences in <i>Colophospermum mopane</i> trees

Wessels, Dirk; Waal, C. van der; Boer, Willem F. de

doi:10.2989/ajrfs.2007.24.3.4.297

Cited by 31 publications

(28 citation statements)

References 26 publications

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“…On the x-axis, the eight sample periods from the beginning of February (end of the wet summer period) until the end of May (mid dry winter period) are displayed: 1 means the first 2 weeks of the month and 2 the last 2 weeks although digestion of especially hindgut fermenters is assumed to be negatively affected under high concentrations of condensed tannins (Duncan and Poppi 2008). It has been suggested that elephant can tolerate condensed tannins (Lagendijk et al 2005;Wessels et al 2007). Styles and Skinner (2000) and Rooke et al (2004) suggested that browsers can produce salivary tannin-binding proteins as an adaptation to tannin-rich forage.…”

Section: Month % Monocots In Faecesmentioning

confidence: 99%

“…However, mopane contains high levels of condensed tannins and other secondary compounds compared to other plant species. This condensed tannin concentration fluctuates between seasons (Ferwerda et al 2005;Codron et al 2006;Wessels et al 2007). Mopane maintains its foliage well into the dry season, providing an important food source for browsers and intermediate feeders both in the wet season (summer) and dry season (winter).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal diet changes in elephant and impala in mopane woodland

et al. 2011

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Elephant and impala as intermediate feeders, having a mixed diet of grass and browse, respond to seasonal fluctuations of forage quality by changing their diet composition. We tested the hypotheses that (1) the decrease in forage quality is accompanied by a change in diet from more monocots in the wet season to more dicots in the dry season and that that change is more pronounced and faster in impala than in elephant; (2) mopane (Colophospermum mopane), the most abundant dicot species, is the most important species in the elephant diet in mopane woodland, whereas impala feed relatively less on mopane due to the high condensed tannin concentration; and (3) impala on nutrient-rich soils have a diet consisting of more grass and change later to diet of more browse than impala on nutrient-poor soils. The phosphorus content and in vitro digestibility of monocots decreased and the NDF content increased significantly towards the end of the wet season, whereas in dicots no significant trend could be detected. We argue that this decreasing monocot quality caused elephant and impala to consume more dicots in the dry season. Elephant changed their diet gradually over a 16-week period from 70% to 25% monocots, whereas impala changed diets rapidly (2-4 weeks) from 95% to 70% monocots. For both elephants and impala, there was a positive correlation between percentage of monocots and dicots in the diet and the in vitro digestibility of these forage items. Mopane was the most important dicot species in the elephant diet and its contribution to the diet increased significantly in the dry season, whereas impala selected other dicot species. On nutrient-rich gabbroic soils, impala ate significantly more monocots than impala from nutrient-poor granitic soils, which was related to the higher in vitro digestibility of the monocots on gabbroic soil. Digestibility of food items appears to be an important determinant of diet change from the wet to the dry season in impala and elephants.

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Section: Month % Monocots In Faecesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seasonal diet changes in elephant and impala in mopane woodland

et al. 2011

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“…However, very few studies have quantified the relationship between browsing by elephants (or simulation thereof) and either growth rate or nutritional value of individual trees, and the results are inconsistent. Increasing the severity of simulated elephant browsing of Colophospermum mopane trees once in the growth season led to increased investment in CBSMs, which remained elevated for 2 years (Wessels et al 2007). In contrast, severe browsing (including branch breakage) by elephants had no effect on either N or CBSMs in C. mopane and led to increased shoot growth compared with no browsing (Hrabar et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Inter- and intra-plant variations in nitrogen, tannins and shoot growth of Sclerocarya birrea browsed by elephants

2011

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Impacts of elephants (Loxodonta africana africana) on woody vegetation has attracted substantial attention for decades, but plant-level responses remain a gap in the understanding of savanna ecology. Marula (Sclerocarya birrea caffra) forms an important part of elephant diets. We investigated the relationships between browsing intensity and shoot/leaf size, nitrogen (N) and condensed tannin (CT) concentrations in upper and lower canopies of male and female marula individuals in Hluhluwe-iMfolozi Park, South Africa. Browsing intensity (54%) did not differ between sexes, suggesting no preference by elephants for either sex. Females had higher [CT] than males and tannin decreased with increasing browsing intensity in both sexes. In lightly or moderately browsed trees, [CT] was controlled by unmeasured factors such that within-tree impacts of browsing were more variable in lightly/moderately browsed than heavily browsed trees. There was little change in [N] up to *60% browsing intensity, but [N] increased dramatically at higher intensity. Shoots and leaves on broken branches in the lower canopy were larger (2.5 and 1.2 times, respectively) than those on unbroken branches in either upper or lower canopies. Chemical responses were systemic and potentially influence browsing among trees, while growth responses were strongly localised and potentially influence browsing within trees. Although marula trees are able to compensate vigorously for browsing at the scale of individual organs, trees may become progressively carbon-deficient and have their lives shortened if total plant growth is negatively affected by chronic browsing, e.g. near permanent water.

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“…While defoliation may induce defences in woody plants (Ward and Young 2002;Wessels et al 2007), severe browsing has been reported to have the opposite effect, by causing either increased N concentrations or reduced tannin concentrations in individual plants (du Toit et al 1990;Danell et al 2003;Persson et al 2005). Therefore, heavily browsed plants may switch to a vegetative state characterised by N-rich/Cpoor tissues.…”

Section: Introductionmentioning

confidence: 99%

“…Increases in CBSM concentrations, sometimes associated with decreases in [N] and [P], have been detected in the same season of browsing/clipping or in the growing season after browsing/ clipping (e.g. Bryant et al 1991;Wessels et al 2007), but the reverse pattern, sometimes associated with increased [N] and shoot growth, has also been detected (e.g . Scogings 1998;Rooke and Bergström 2007).…”

Section: Introductionmentioning

confidence: 99%

Secondary metabolites and nutrients of woody plants in relation to browsing intensity in African savannas

Scogings

Hjältén

Skarpe³

2011

Oecologia

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Carbon-based secondary metabolites (CBSMs) are assumed to function as 26 defences that contribute to herbivore-avoidance strategies of woody plants. Severe 27 browsing has been reported to reduce concentrations of CBSMs and increase N 28 concentrations in individual plants, causing heavily browsed plants to be characterised 29 by N-rich/C-poor tissues. We hypothesised that concentrations of condensed tannins 30 (CT) and total polyphenols (TP) should decrease, or N increase, in relation to 31 increasing intensity of browsing, rendering severely browsed plants potentially more 32 palatable (increased N:CT) and less N-limited (increased N:P) than lightly browsed 33 ones. We sampled naturally browsed trees (taller than 2 m) of four abundant species 34 in southern Kruger National Park, South Africa. Species-specific relationships 35 between N:CT, CT, TP and P concentrations and increasing browsing intensity were 36 detected, but N and N:P were consistently invariable. We developed a conceptual 37 post-hoc model to explain diverse species-specific CBSM responses on the basis of 38 relative allocation of C to total C-based defence traits (e.g., spines/thorns, 39 tough/evergreen leaves, phenolic compounds). The model suggests that species with 40 low allocation of C to C-based defence traits become C-limited (potentially more 41 palatable) at higher browsing intensity than species with high allocation of C to C-42 based defences. The model also suggests that when N availability is high, plants 43 become C-limited at higher browsing intensity than when N availability is low. 44 45

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Induced chemical defences in Colophospermum mopane trees

Cited by 31 publications

References 26 publications

Seasonal diet changes in elephant and impala in mopane woodland

Seasonal diet changes in elephant and impala in mopane woodland

Inter- and intra-plant variations in nitrogen, tannins and shoot growth of Sclerocarya birrea browsed by elephants

Secondary metabolites and nutrients of woody plants in relation to browsing intensity in African savannas

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