Sexual and vegetative regeneration of three leguminous tree species in South African savannas

Munkert, H.

doi:10.1016/j.sajb.2009.04.002

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…Species with extensive root elongation, such as those that spread clonally by root‐suckering, are therefore expected to sustain higher rates of carbon assimilation without having to down‐regulate photosynthesis. The highly variable D. cinerea , a common shrub species in the KNP sites, spreads by root suckers in frequently burnt mesic savannas dominated by the variety nyassana (Neke et al ., ; Wakeling & Bond, 2007; Munkert, ). In semiarid areas, the africana form is common and populations in Hluhluwe‐iMfolozi Park, South Africa, do not form root suckers (W.J.…”

Section: Discussionmentioning

confidence: 99%

Increased tree densities in South African savannas: >50 years of data suggests CO₂ as a driver

Buitenwerf

Bond

Stevens

et al. 2011

Global Change Biology

318

248

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For the past century, woody plants have increased in grasslands and savannas worldwide. Woody encroachment may significantly alter ecosystem functioning including fire regimes, herbivore carrying capacity, biodiversity and carbon storage capacity. Traditionally, increases in woody cover and density have been ascribed to changes in the disturbance regime (fire and herbivores) or rainfall. Increased atmospheric CO 2 concentrations may also contribute, by increasing growth rates of trees relative to grasses. This hypothesis is still heavily debated because usually potential CO 2 effects are confounded by changes in land use (disturbance regime). Here we analyse changes in woody density in fire experiments at three sites in South African savannas where the disturbance regime (fire and herbivores) was kept constant for 30 and 50 years. If global drivers had significant effects on woody plants, we would expect significant increases in tree densities and biomass over time under the constant disturbance regime. Woody density remained constant in a semiarid savanna but tripled in a mesic savanna between the 1970s and 1990s. At the third site, a semiarid savanna near the southern limits of the biome, tree density doubled from the mid 1990s to 2010. Interpretation of the causes is confounded by population recovery after clearing, but aerial photograph analysis on adjacent non-cleared areas showed an accompanying 48% increase in woody cover. Increased CO 2 concentrations are consistent with increased woody density while other global drivers (rainfall) remained constant over the duration of the experiments. The absence of a response in one semiarid savanna could be explained by a smaller carbon sink capacity of the dominant species, which would therefore benefit less from increased CO 2 . Understanding how savannas and grasslands respond to increased CO 2 and identifying the causes of woody encroachment are essential for the successful management of these systems.

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Section: Discussionmentioning

confidence: 99%

Increased tree densities in South African savannas: >50 years of data suggests CO₂ as a driver

Buitenwerf

Bond

Stevens

et al. 2011

Global Change Biology

318

248

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“…Les projets de développement préconisent une série d'actions qui reposent sur une politique de décentralisation (loi forestière de 1994 du Cameroun, conçue pour le sud et peu adaptée au nord du pays), sur une meilleure connaissance des savoirs locaux au profit d'interventions fondées ou copiées sur les savoirs endogènes. Dans cette optique, la multiplication végétative à faible coût, notamment l'induction du drageonnage et les techniques de marcottage, sont aisément transposables par les populations locales [12][13][14][15][16]. Un exemple pratique de savoir faire traditionnel en Mauritanie, relatif à l'établissement de haies vives à base de Balanites aegyptiaca est révélateur : de jeunes plants issus de semis sont plantés à grand écartement sur la ligne où doit être installée la haie.…”

Section: Introductionunclassified

Multiplication végétative deBalanites aegyptiaca(L.) Del.,Diospyros mespiliformisHochst. ex. A. Rich. etSclerocarya birrea(A. Rich.) Hochst. au nord du Cameroun

Tchiagam¹,

Ndzié²,

Bellefontaine³

et al. 2011

Fruits

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“…Dichrostachys cinerea had three times more stems in the fenced relative to unfenced off‐mound plots in 2006 (Supporting Information ), only 1 yearr after fencing. D. cinerea spreads vegetatively (Munkert, ), permitting dense regeneration following the removal of browsers. On the other hand, the stem density of A. gerrardii reduced off‐mound with fencing ( p = 0.02; Supporting Information ).…”

Section: Discussionmentioning

confidence: 99%

Termites confer resistance to changes in tree composition following reduced browsing in an African savanna

Acanakwo

Okullo²,

Sheil

et al. 2018

J Vegetation Science

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Questions Ungulates affect plant community structure and composition. Vegetation response to these effects are variable. Wild large herbivore populations are declining globally, but how tree communities respond to this change is not clear. We experimentally examined how tree communities respond to changes in ungulate abundance in a heterogeneous landscape. Location Lake Mburo National Park, Uganda. Methods We recorded tree species in nine replicate sites each with four treatment plots: fenced off‐mound (excluding ungulates), unfenced off‐mound, fenced and unfenced on‐mound. Each species was assessed for fruit type, leafing strategy, spinescence and bark thickness. We compared tree communities on‐ and off‐mound, with and without ungulates using PERMANOVA, and the effects of habitat, fencing and time on stem density and traits using generalized linear mixed effects model. Results Stem density increased by 88% off‐mound and 138% on‐mound (p = 0.005) with fencing, between 2006 and 2015. Whether tree communities occurred on‐ or off‐mound determined species composition, but fencing had little effect. Tree traits were not markedly altered by fencing on‐mound. Off‐mound, fencing was associated with a 38% increase in the proportion of fleshy‐fruited tree stems (p < 0.001), 18% decline in armed tree stems (p = 0.035) and a 44% reduction in mean bark thickness (p = 0.001). Conclusion Our study highlights the important role mounds play in maintaining tree community composition with declining ungulate abundance. While ungulates influence tree communities off‐mounds they have little effect on tree composition and traits of mound‐borne trees. Thus, Macrotermes mounds support distinct tree communities that are robust to exclusion of ungulates.

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Sexual and vegetative regeneration of three leguminous tree species in South African savannas

Cited by 6 publications

References 15 publications

Increased tree densities in South African savannas: >50 years of data suggests CO₂ as a driver

Increased tree densities in South African savannas: >50 years of data suggests CO₂ as a driver

Multiplication végétative deBalanites aegyptiaca(L.) Del.,Diospyros mespiliformisHochst. ex. A. Rich. etSclerocarya birrea(A. Rich.) Hochst. au nord du Cameroun

Termites confer resistance to changes in tree composition following reduced browsing in an African savanna

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Sexual and vegetative regeneration of three leguminous tree species in South African savannas

Cited by 6 publications

References 15 publications

Increased tree densities in South African savannas: >50 years of data suggests CO2 as a driver

Increased tree densities in South African savannas: >50 years of data suggests CO2 as a driver

Multiplication végétative deBalanites aegyptiaca(L.) Del.,Diospyros mespiliformisHochst. ex. A. Rich. etSclerocarya birrea(A. Rich.) Hochst. au nord du Cameroun

Termites confer resistance to changes in tree composition following reduced browsing in an African savanna

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Increased tree densities in South African savannas: >50 years of data suggests CO₂ as a driver

Increased tree densities in South African savannas: >50 years of data suggests CO₂ as a driver