:

Rosa Mary Hernández-Hernández1, Dimas Acevedo2, Lina Sarmiento2

1Universidad Simón Rodríguez, Miranda, Venezuela. rodama33@yahoo.com.mx

2Universidad de Los Andes, Mérida, Venezuela. dimas@ula.ve y lsarmien@ula.ve

Carbon Sequestration Potential in the Savannas Ecosystems of Venezuela

Rome, March 2017

The flatlands occupy 28% (25MM ha) of

Venezuela. They are dominated by ecosystems of savannas

with different landscapes, soils, and

vegetation, mostly adapted to acid soils,

low fertility and subjected to frequent

fires

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They are dominated by grasses that growth in dystrophic soils.

Well drained soils are predominant, but there are also extensive areas with poor drainage during the rainy season.

All soils are subjected to a dry season (4 to 6 months) and recurrent anthropic fires during this season.

EAST CENTRAL WEST

Types of Savannas in Venezuela

Site GuaricoCentral Flatlands Venezuela (2)

AraucaEastern LowlandsColombia (4)

Monagas Elevated PlateausVenezuela (3)

Soil type UltisolAlfisols

Dystrudepts Kandiustult

pH 5.1 5.13 4.9SOC (%) 1.3 1.6 0.46CEC (cmol/kg) 4.6 8.02 1.9Al saturation (%) 25.1 96.01 --P (ppm) -- 23.30 2K (cmol/kg) 0.4 0.12 TracesCa (cmol/kg) 1.4 0.07 0.3Mg (cmol/kg) 0.9 0.13 0.2Bulk density (0-20cm) (Mg.m-3)

1.46 1.27 1.55

Characteristics of some representative soil types found in the Savannas

(1) Rao, 1998; (2) Hernández and López, 2002; (3) Comerma and Chirinos, 1976; (4) IGAC, 2003 ) Tomado de Rondón et al. (2006)

Main land uses and management

The main management practice in the Llanos has been the burning of native grasses. But In recent decades it has being intensified i through the introduction of exotic grasses such as Brachiarias, Panicum and Digitaria among others. Also crop species such as sorghum, maize, beans, rice , Forest plantations of pinus , eucalyptus and teak are now also important

1.- To compile the results published about of C (%) at depths from 0 to 30 cm and its bulk density.

2.- To estimate the storage and potential sequestration of C in the soil, derived from the changes in land use in this ecoregion.

objectives

Review of bibliography of areas of the main types of landscapes, their

ecosystems, and the land use types the soil C content (%), bulk density of the first 30 cm of soil, distribution of the principal suborders of soilsThen For each paper we calculated the stock of C for 0-

30 cm (C % x bulk density x ha) Then, calculated the accumulation of C for each

landscape unit using the average of C stock, the extent of the ecosystem and the type of land use.

Methodology

Landscapes Regions C stocks (MgC.ha-1) C (%)

Recent alluvial plains Deciduous forests West 77.0 ± 19.4 5.0 ± 1.3Hyperseasonal savannas ( lowlands) 45.2 ± 17.3 3.2 ± 1.4Semiseasonal savannas (lowlands) 61.5 ± 12.0 5.2 ± 1.1

Alluvial Plains from the Pleistocene Hyperseasonal savannas ( lowlands) West 39.0 ± 8.5 2.6 ± 0.6Seasonal savannas 33.5 ± 6.4 2.2 ± 0.5Seasonal savannas East 42 0.9Seasonal savannas Central 46 2.9

Eolic Plains Poorly drained savannas West 65 ± 7.1 4.2 ± 0.3Well drained savannas 22 ± 4.2 1.4 ± 0.2

Elevated Plateaus Seasonal savannas West 24 ± 9.9 1.6 ± 0.7Seasonal savannas East 17.7 ± 7.5 0.8 ± 0.5Seasonal savannas Central 51.3 ± 22.5 3.5 ± 1.6

Rolling hills Seasonal savannas Central 31 3.3

Carbon content and stocks in the top 30 cm of soils from Venezuelan flatlands

Estimated C stocks for the main land use systems in the Venezuelan savannas

AreaEstimated Carbon stocks (0-

30 cm depth)Landscape position/land use (Mha) MgC.ha-1

Remaining natural systems Elevated plateaus 5.04 35.66 Well drained lowlands 4.81 43.16 Poorly drained low plains 5.45 59.41 Rolling hills 1.66 40.00 Gallery and deciduous forest 1.52 75.00Subtotal 18.48 Modified systems Introduced pastures 5.00 78.00 Annual crops, conventional tillage 0.83 38.10 Annual crops, reduced tillage 0.17 43.20 Tree plantations 0.80 27.00 Urban, water bodies etc. 0.90 Subtotal 7.70 Total 26.18 Published in (Rondon et al. 2006)

5 Tg C

8 Tg C

2 Mha

Annual crops under conventional tillage

148 Tg C

5 Mha 1 8 Mg/ha

1.02 Pg C(Rondón et al 2006)

Minimun tillage

AgroforestryIf we stop the burning of the savannas

Introduced pasture

If all the savannas are covered with introduced pastures

Potential carbon sequestration in the Venezuelan savannas

If we increase the area of introduced pastures

Change to minimun tillage

If all the planted areas goes to minimun tillage

conclusions I. Tropical savannas play key roles in biogeochemical cycles.

II. The alluvial and the eolic plains have the largest capacity of carbon sequestration, due to their extent and to their C content in the upper 30 cm of their soils. Data indicate that this capacity increases toward the western llanos, related to an increase in rainfall .

III. Savanna soils have a large potential to sequester up to 1.02 Pg of C, assuming that all the native land could be converted into well managed and sustainable pastures.

IV. There are currently available technologies to allow sustainable agriculture, livestock and forestry in the region. Most of these technologies also sequester atmospheric carbon in the biomass or in the soils.

V. The use of sustainable agriculture will result in more organic matter being sequestered into the soils of the Llanos. This will have important benefits for the global environment through reductions in the net fluxes of greenhouse gases but also to the health status of the soils of the region

VI. More and better data is required