Soil characteristics within vegetation patches are sensitive indicators of savanna rangeland degradation in central Namibia

By Katrin Zimmer (University of Bonn), Vistorina Amputu (University of Tübingen), Lisa-Maricia Schwarz (University of Bonn), Anja Linstädter (University of Bonn & CRC-TRR 228 Project A01 Future Carbon Storage) and Alexandra Sandhage-Hofmann (University of Bonn & CRC-TRR 228 Project A01 Future Carbon Storage).

Abstract

Savanna rangelands are threatened by increased grazing pressure, with the risk of desertification and woody plant encroachment. In this context, sensitive early-warning indicators for irreversible shifts toward degraded rangelands are urgently needed. We hypothesize that soil properties, in particular soil organic carbon (SOC) and carbon isotopes (δ13C) are suitable to detect degradation in different land management systems. We conducted a natural experiment on arid savanna rangelands on Arenosols in Namibia. As treatments, we considered two land management systems (freehold farms with rotational grazing and systematic bush thinning, and communal rangelands with free grazing without systematic bush thinning), with different grazing intensities (grazing gradients), and four vegetation patch types (dominance of bare soil, annual plants, perennial grasses, or woody plants) with four replications per land management system. Clay was considered a system-inherent confounder. SOC stocks were lower on communal rangelands (8.2 ± 2.8 Mg ha−1) than on freehold farms (9.7 ± 2.6 Mg ha−1). Besides clay content, SOC stocks correlated with perennial grass cover (r = 0.6) in freehold farms, and with woody plant cover (r = 0.54) in communal rangelands. δ13C values were higher by 2.15 ‰ on freehold farms, indicating greater origin of C4 grass derived SOC. Distance to the nearest water point – as an estimate of local grazing intensity – had a small effect on SOC stocks compared to clay. SOC was a sensitive degradation indicator in savanna rangelands when considered together with the patchy character of savanna vegetation. Under current land management and tenure, communal rangelands faced higher degradation threats than freehold farms, but were also more vulnerable due to lower clay contents.

Reference

Zimmer, K., Amputu, V., Schwarz, L.-M., Linstädter, A., Sandhage-Hofmann, A. 2024. Soil characteristics within vegetation patches are sensitive indicators of savanna rangeland degradation in central Namibia, Geoderma Regional, Volume 36, e00771, DOI

More CRC News

picture taken during a workshop in namibia

How Things Connect People: Project C05 Organizes and Conducts Workshop in Namibia

Project C05 Framing Futures investigates how concepts of age and generation shape temporal frames of reference in future-making and compare temporal frames of reference used ...
Read More »
delegations of mzumbe university and the departemnt of geography at the university of bonn

Vice-Chancellor of Mzumbe University Visits Department of Geography in Bonn

A delegation from Mzumbe University in Tanzania recently visited the University of Bonn’s Department of Geography. Mzumbe University is a a partner institution in the ...
Read More »
thumbnail for this entry of the wawili toolbox blog series

Wawili Toolbox Entry 6: Contested Roles and Expectations

The arrival at Mt. Paka and life among the pastoral community is something that will be explored below. Of course, in retrospect, many experiences appear ...
Read More »
cover for a website post

Short Film: The Southern Buffalo Fence

By Wisse van Engelen (Project A04 Future Conservation). Disease transmission is an often overlooked form of human-wildlife conflict, yet animal diseases and veterinary interventions often ...
Read More »
website of the research consortium "commodifying the wild"

Future Rural Africa Researchers Eric Kioko and Clemens Greiner named Principal Investigators in Newly Established Research Consortium “Commodifying the Wild”

The newly established, DFG funded research consortium “Commodifying the Wild” aims to contribute to a better understanding of the trans-regional ecological, social, and political dimensions ...
Read More »
Scroll to Top