Biomass and nutrient dynamics in a littoral savanna subjected to annual fires in Congo

Laclau, Jean‐Paul; Sama-Poumba, Wildfrid; Nzila, Jean de Dieu; Bouillet, Jean‐Pierre; Ranger, Jacques

doi:10.1016/s1146-609x(02)01132-3

Cited by 36 publications

(23 citation statements)

References 16 publications

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“…A high abundance of herbaceous legumes has, indeed, been reported in fire-prone forest ecosystems in Australia, Europe and North America (Bell & Koch 1980, Kazanis & Arianoutsou 1994, Hendricks & Boring 1999, and Vitousek and Field (1999) have proposed a simple model showing how legumes may coexist with nonfixing species under conditions of frequent fires. In African savannas, however, which are among the most frequently burnt ecosystems in the world (Bond et al 2005), herbaceous legumes are usually scarce, often making up o 1 percent of the biomass (Ezedinma et al 1979, Menaut & Cesar 1979, Huntley 1982, Isichei 1995, Laclau et al 2002. A similar scarcity of herbaceous legumes has also been reported for prairies and semiarid grasslands in the United States (Woodmansee 1978, Collins et al 1995, Ritchie & Tilman 1995, and for savannas in northern part of South America (San Jose et al 1985, Medina 1987.…”

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confidence: 83%

Why is Abundance of Herbaceous Legumes Low in African Savanna? A Test with Two Model Species

2010

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Although fire is frequent in African savanna ecosystems and may cause considerable loss of nitrogen (N), N 2 -fixing herbaceous legumes-which could be expected to benefit from low N conditions-are usually not abundant. To investigate possible reasons for this scarcity, we conducted a pot experiment using two common plants of humid African savannas as model species, the legume Cassia mimosoides and the C 4 grass Hyperthelia dissoluta. These species were grown at different levels of water, N and phosphorus (P), both in monoculture and in competition with each other. In the monocultures, yields were significantly increased by the combined addition of N and P in pots receiving high water supply. In pots with interspecific competition, the legume grew poorly unless P was added. Foliar d 15 N values of legume plants grown in mixtures were considerably lower than those in monocultures, suggesting that rates of symbiotic N-fixation were higher in the presence of the grass. Grass d 15 N values, however, were also lower in mixtures, while N concentrations were higher, indicating a rapid transfer of N from the legume to the grass. We conclude that the main reason for the low abundance of C. mimosoides is not low P availability as such, but a greater ability of H. dissoluta to compete for soil N and P, and a much higher N-use efficiency. If other C 4 grasses have a similar competitive advantage, it could explain why herbaceous legumes are generally sparse in African savannas. We encourage others to test these findings using species from other types of savanna vegetation.

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confidence: 83%

Why is Abundance of Herbaceous Legumes Low in African Savanna? A Test with Two Model Species

2010

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“…1A). Over 90% of the biomass burned in savanna fires is broken down and mobilized, leaving less than 10% of the original mass as ash (LaClau et al, 2002). Opaline phytoliths likely make up a significant component of that ash, which, in a denuded landscape, will be eroded readily and transported by wind and water.…”

Section: Silica Mobilization By Grassesmentioning

confidence: 99%

“…Macroscopic plant material can be transported at least 20 km via fires (Pisaric, 2002); thus, microscopic phytoliths should be even more mobile. Conservative estimates derived from LaClau et al (2002) suggest that about 5 g of silica per m 2 are released by fire from the nutrient-poor savannas of Congo. Several additional lines of evidence support escape of phytolith silica from grasslands.…”

Section: Silica Mobilization By Grassesmentioning

confidence: 99%

“…Grasslands typically take up several times more silica per unit of carbon than other terrestrial ecosystems (Jones and Handreck, 1967;Raven, 1983;Epstein, 1999). In doing so, they create a reservoir of soluble opal phytoliths, some of which are released quickly, such as during fires (e.g., Laclau et al, 2002;Pisaric, 2002), whereas others are stored in soil for later release (Meunier et al, 1999). Volcanism is a viable supplier of silica for diatomite deposition, and rivers draining volcanic-source terranes carry dissolved silica loads that rival the most silica-rich tropical rivers, such as the Amazon (Berner and Berner, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Impact of Grassland Radiation on the Nonmarine Silica Cycle and Miocene Diatomite

Kidder¹,

Gierlowski‐Kordesch²

2005

PALAIOS

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“…Fire in savannas has been the subject of several studies conducted worldwide (Greig-Smith 1991, Biddulph and Kellman 1998, Laclau et al 2002, Fensham et al 2003, Wilson and Witkowski 2003, Harcombe et al 2004, Townsend and Douglas 2004, Barbosa and Fearnside 2005, Cardoso et al 2008. However, the influence of the soil on the characteristics of savanna plant formations has also held the interest of investigators, such as Furley and Ratter (1988Ratter ( , 1990, Sankaran et al (2005) and Banfai and Bowman (2007).…”

Section: Introductionmentioning

confidence: 99%

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

Pinheiro

Azevedo

Monteiro

2010

An. Acad. Bras. Ciênc.

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The analysis of the influence of edaphic finer textures, as a facilitating factor for the expansion of forest formations in the absence of fire, was possible thanks to rare characteristics found in a savanna fragment located in the State of São Paulo, Brazil. The total suppression of fire for over four decades, and the occurrence of two savanna physiognomies, cerrado sensu stricto and cerradão, allowed the conduction of this study based on the hypothesis that cerradão, a physiognomy of forest aspect consisting of fire-sensitive tree and shrubs species, is favored by fire absence and higher soil hydric retention capacity. Edaphic samples were collected from a regular grid of 200 m 2 for the production of isopletic maps of the distribution of clay, fine sand, coarse sand and silt edaphic textures by the geostatistic method of ordinary kriging. Changes in the areas occupied by both savanna physiognomies, defined on the basis of aerial photographs taken over a period of 43 years, were assessed through mean variation rates. Besides corroborating the hypothesis of edaphic hydric retention as a facilitating factor for the expansion of forest physiognomies in savanna areas, we were able to infer the positive influence of higher precipitation on the increase in cerradão expansion rates.

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Biomass and nutrient dynamics in a littoral savanna subjected to annual fires in Congo

Cited by 36 publications

References 16 publications

Why is Abundance of Herbaceous Legumes Low in African Savanna? A Test with Two Model Species

Why is Abundance of Herbaceous Legumes Low in African Savanna? A Test with Two Model Species

Impact of Grassland Radiation on the Nonmarine Silica Cycle and Miocene Diatomite

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

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