The Benfontein Plant Phenology Project – A low-hanging fruit

By Marco Pauw, Field Technician, SAEON Arid Lands Node Tweet

Originally bought by De Beers in 1891 for its diamond reserves, Benfontein Nature Reserve lies in a transitional zone 14 km from Kimberley where Karoo grassland and Kalahari thornveld savanna meet.

SAEON’s Arid Lands Node and Sol Plaatje University have been collaborating at Benfontein since October 2017 on what is promising to become a highly valuable long-term dataset.

Muxe Ndlomu, Dr Kunle Adebowale (both Sol Plaatje University), Tshililo Ramaswiela and Lehlonoholo Lepholletse (both SAEON) searching for flowers and seed pods on an umbrella thorn tree.

Trial phase

The team has been observing the phenology of six woody plant species and two grass species: Ehretia alba (white puzzle bush), Searsia lancea (karee), Senegalia mellifera (blackthorn), Vachellia erioloba (camelthorn), Vachellia tortilis (umbrella thorn) and Ziziphus mucronata (buffalo thorn); Schmidtia pappophoroides (Kalahari sand quick) and Stipagrostis uniplumis (silky bushman grass). These species were selected because they are not only abundant at the site, but also occur widely in the arid savanna of South Africa.

Once a month, members of the team record four different phenological stages – flowering, fruiting, leafing and shoot growth. Notes are kept on other life history phenomena, such as germination and mortality.

An automated weather station collects meteorological data as well as soil temperature and moisture data. This dataset can be used to determine to which meteorological variables or other seasonal cues the phenology of each species responds, and in the long-term study the effect of climate change at a local scale.

A view of the study site at Benfontein. The study looks at the phenology of woody and grass species.                                                 SAEON's automated weather station provides on-site climate data crucial to understanding the relationships between plant phenology and climatic variables.

This would already be valuable information, but the project has the potential to be expanded to include studies on carbon fluxes, microclimates, plant physiology, symbionts, pathogens and trophic interactions.

The trial phase of this project ended in October 2018 and from the initial data it looks like each woody species follows a different combination of strategies for flowering, fruiting, leafing and growth. However, it has been a dry year and many species did not flower and fruit as prolifically as they potentially could.

Frequency of data collection

From the trial, the team also learned that data collection at monthly intervals is not frequent enough to capture the start, end or peaks of different phenological stages. The plan is to increase the frequency of observation to once every two weeks (or even once a week, as is done for the phenology project at Tierberg). This will require more frequent fieldwork at Benfontein than was possible in the past.

Rain clouds building over the study site. Moisture is a major driver of plant phenology.                                                                                      Open flowers on an umbrella thorn tree. Species seem to respond differently to climatic variables and many of them flower at different times.

Considering the low cost and high scientific value of the data, this project is a low-hanging fruit worth picking. The project team, consisting of Kunle Adebowale and Tendai Musvuugwa (Sol Plaatje University), and Marco Pauw and Tshililo Ramaswiela (SAEON Arid Lands Node), hope that the Benfontein Plant Phenology project will continue well beyond their own careers.