Cosmic ray probe to aid Mapungubwe's threatened endemic forest

How the combined impact of droughts, floods and elephants has been killing trees in the endemic gallery forest on the side of the Limpopo River in Mapungubwe National Park is well understood.

What is still not known, is how the pumping of groundwater from inside the forest for diamond mining near the park is affecting soil moisture, and therefore the growth of the trees.

In March 2015, a cosmic ray probe was installed to monitor both the soil moisture and the amount of water inside the canopy of trees. The research site is close to the confluence of the Limpopo and Shashe rivers where South Africa, Botswana, and Zimbabwe meet, and located in one of South Africa’s eight World Heritage Sites.

SAEON’s hydro-meteorologist, Colin Everson, together with Trenton Franz from the University of Nebraska-Lincoln, is testing technology developed for agriculture to create an early-warning system for detecting drought water stress in trees. The team are combining the data with detailed in-situ monitoring of the vegetation to determine if and when the forest is being affected by water stress caused by ground water pumping for the De Beers Venetia mine. Depending on the success of the early-warning system, De Beers may integrate it into its pumping operations as part of its conservation efforts.

The probe has a circular footprint of 34 ha and is non-invasive. The device, carefully installed out of reach of wild animals, sends data in real time to the COSMOS server.

The cosmic ray probe project is a collaborative effort supported by grants from the USAID-National Science Foundation (PEER) and the National Research Foundation (NRF-RISP), while the physiological and ecological work is supported by De Beers, World Wide Fund for Nature (WWF) and SANParks.

At a larger scale, SAEON will manage the South African network of five cosmic ray neutron probes linked to the global COsmic Ray Soil Moisture Observing System (COSMOS) network, providing landscape-level soil moisture data for climate change detection.