Vegetation biomass influences the ways in which terrestrial ecosystems interact with biogeochemical cycles such as those of carbon and water. Tracking vegetation changes, estimating biomass and cover, characterising the vegetation types and being able to track long-term changes in vegetation are crucial for understanding ecosystem fluxes of carbon and water cycles, with obvious impacts on understanding the effects and consequences of global change on carbon sequestration, water availability and the provision of ecosystem services such as grazing and regulatory services.  

In 2019, the Expanded Freshwater and Terrestrial Environmental Observation Network (EFTEON) erected two flux towers at Benfontein Nature Reserve in Kimberley to test the functioning of the eddy covariance instruments in this arid region. The eddy covariance instruments measure fluxes between terrestrial and atmospheric systems in the Savanna and Nama-Karoo biomes in the reserve.

Rationale

To aid understanding of the ecosystem fluxes from the eddy covariance instruments, EFTEON staff members kick-started a research project to characterise the vegetation around the flux tower footprints at Benfontein following a protocol developed by the Socio-Ecological Observatory for Southern African Woodlands (SEOSAW) . The protocol is widely used in various woody vegetation sampling sites in Africa, including the Skukuza Flux tower site and sites in Hluhluwe-Imfolozi Park in South Africa.

This article shares information on the fieldwork recently initiated at the savanna flux tower site at Benfontein Nature Reserve.

Surveys

EFTEON team members are currently sampling woody vegetation in the Savanna Biome at the Savanna flux tower to assess and characterise the woody vegetation around the site. We set up four plots in the traditional cardinal directions (N, S, W, E) from the flux tower. One additional plot is located near SAEON’s automated weather station (~300 m from the flux tower).

The plot located east of the flux tower covers a previously burnt patch in the landscape. The plots are one hectare in size, and the N, S, W and E plots are centred 100 m from the flux tower.

The centre of the plot was marked with a metal dropper and GPS readings were recorded. Each corner of the plot is marked by a dropper to demarcate the plot boundaries.

Woody vegetation was surveyed in each plot and parameters related to tree demography were recorded, together with other environmental variables such as signs of animal activity and the soil characteristics. We also kept track of the woody vegetation recruitment in these plots, whereby we surveyed tree and shrub seedlings and saplings.

Photographs of the site are taken from the centre of each plot at a height of 1.2 m towards the four cardinal directions (N, S, E, W). Repeat photographs will be taken from the same position when we revisit the plot.

Below are examples of photos taken by EFTEON’s Amukelani Maluleke from the centre of plot E1 in the four cardinal directions. The photos were taken from the centre of the plot at a height of 1.2 metres. The same procedure will be followed in all the other plots.

The photos below are examples of tree measurements to characterise the vegetation in the plots: