Carbon Research This project focuses on increasing the carbon in N'hambita by maintaining existing woodland, planting trees in a number of systems including woodlots and boundary planting and by increasing the carbon stored on machambas (farms) by planting nitrogen fixing trees. A wider study (Grace et al. 2006) was undertaken to determine the potential carbon benefit from protecting and managing tropical savannas across the globe. Our overall research goal is to quantify and understand the carbon dynamics of the miombo woodlands of the Gorongosa area of Mozambique. Mature miombo woodland, July 2004

Current research tools:

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Field Sites: Abandoned Machamba Plots

These were selected to enable measurements to be taken of which could help determine the relationship between time since abandonment and amount of carbon in the plot. These plots were selected from 1 - 30 year old fallows.

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Field Sites: Permanent Sample Plots

In order to determine the amount of additional carbon sequestered by these project activities, information is gathered from a number of permanent sample plots (PSP's) which range from newly abandoned areas to relatively pristine miombo. These were selected randomly and were only rejected if there was a farm in the plot. Stem diameter and the dynamics of tree growth, seasonal records of canopy cover and understory cover are among the measurements recorded from the plots. Recently the excavation of tree roots has provided valuable information on the capacity of the ecosystem to store carbon. Soil carbon and nitrogen is also monitored in the PSP's.

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Remote sensing data

See 'Miombo Woodlands' for more information about the use of remote sensed information in the project.

This image shows the location of the 15 PSP's in the project. These images are 16 day MODIS NDVI 250m resolution. The NDVI - Normalised Difference Vegetation Index can be used to measure the vegetation on the land surface. Plant density shows in the image as different colour intensities. These represent the wavelength of reflected sunlight.

Permenant sample plots 16 day MODIS NDVI 250m resolution December 2000 - January 2001

Mashambas have also been mapped using satellite imagery.

Mashambas 16 day MODIS NDVI 250m resolution December 2000 - January 2001.

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Models

The model CO2FIX is used to estimate the amount of stored carbon in addition to dynamic simulation models of carbon dynamics. This model is integral to the technical specifications in which it is used to estimate the carbon stored by the different land use systems.

The Carbon Calculator is the model used to calculate the exact volume of the carbon sink in each site. The information required for this is relatively easy to gather, and includes the area replanted and the length of time the plot had been abandoned if it is reforestation / agroforestry of an abandoned mashamba. This means it can be used on site by the project team in country. This calculator also provides valuable information such as the value of payments to farmers, and a payment schedule.

Estimates of future trends are made by modelling the growth rates of the woody vegetation in the ecosystem to store carbon.

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Soil Carbon Measurements

In Miombo woodlands, often the amount of carbon in the soil is more than in the above ground vegetation. However the amount of carbon that the soil contains is very variable, and currently work is being completed to quantify the amount of carbon in the soils in the PSP's.

Soil pits are dug in the PSPs, June 2007

Soil samples are taken at varying depths including as deep as possible, so diggers are used where the site is accessible. Soil is sieved and analysed in Edinburgh University laboratories, where density, texture, carbon and nitrogen levels can be assessed.

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Vegetation Data

Leaf litter, grass yield and ground vegetation measurements are all taken in the PSP's. Specific measurements are taken on the trees including dbh, and canopy cover (as described in Miombo Woodlands). The relationship between these attributes is described, and growth and mortality estimates can be made of miombo trees.

Litter is collected and processed in the PSPs. Nets positioned under the canopy collect fallen leaves, and this is processed (leaves and grass are dried and weighed) to calculate its carbon content.

The bulk dry density of different species of tree in each sample plot is taken, both of the heart wood and the branches.

Roots of different sizes are extracted for analysis from the PSP's. These are dried in ovens and are weighed so the water and carbon content of a tree's roots can be estimated.

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Plant Physiology

Wood densities of approximately 40 species have been taken from the project area. Some destructive sampling of trees is used for these measurements. Sap content of wood is taken and the density of the bark, sapwood and heartwood can be measured.

Fish-eye photo method of calculating Leaf Area Index (LAI) has been corroborated with the results from the LICOR canopy analyser.

Dendrometer bands on trees in the PSPs accurately measure the diameter of trees. Measurements are recorded throughout the year and growth rates can be calculated.

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