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Publications - Soil Science

Kotze, E., et al., (2013), Rangeland management impacts on the properties of clayey soils along grazing gradients in the semi-arid grassland biome of South Africa, Journal of Arid Enivronments, (97):220-229

The grassland biome of South Africa is a major resource for livestock farming; yet the soils of these rangelands are stressed differently by various management systems. The aim of this study was to investigate how basic soil properties respond to different management systems. For this purpose we sampled rangeland management systems under communal (continuous grazing), commercial (rotational grazing) and land reform (mixture of grazing systems) farming. Within each of these systems a grazing gradient was identified with decreasing grazing pressure with increasing distance to the water points. Results showed that communal farms with continuous grazing were generally depleted in the respective nutrient stocks. The depletion increased with rising grazing pressure. Along that line there was a breakdown of macroaggregates with losses of the C and N stored therein. However, the commercial farms also exhibited a decline of macroaggregates and their associated C content nearby the water points. Aggregate fractionation is a sensitive indicator for detecting the beginning of soil degradation in this biome; yet, degradation was less pronounced under the rotational grazing of the commercial farms than under communal property right conditions. Hence, soil analyses confirm that fences and appropriate grazing periods are needed to manage these rangelands sustainably.

Sandhage-Hofmann, A., et al., (2015), Rangeland management effects on soil properties in the savanna biome, South Africa: A case study along grazing gradients in communal and commercial farms. Journal of Arid Environments 120: 14-25

Although the savanna biome of South Africa is a major resource for rangeland management, little is known about how differences in rangeland management systems affect soil properties in such biomes. Near to Kuruman, commercial farms have practiced rotational grazing for decades. In communal areas of former homeland Bophuthatswana, similar strategies were used prior to 1994. Nowadays, a continuous grazing system is common. We hypothesized that these changes in management affected soil properties. To test this, we sampled soils at communal and commercial land along a gradient with increasing distance to water points. The results revealed that communal systems with continuous grazing showed enlarged spatial gradients. The soils were depleted in most nutrients close to the water relative to those of commercial systems. In contrast, as the distance to the water increased, the nutrient stocks of these communal systems were higher. Changes in soil nutrient stocks were related to a zone of increased bush encroachment (up to 25%). Specific analyses (phosphorus fractions, particulate organic carbon, ?13C) confirmed that the soils of the communal grazing systems benefited from the shift of grass-dominated to bush-dominated system with woody Acacia vegetation, while the rangeland degraded in the sense that it lost palatable grass species.

Linstädter, A., et al. (2016), Assessing the resilience of a real-world social-ecological system: lessons from a multidisciplinary evaluation of a South African pastoral system, Ecology and Society 21 (3):35

In the past decades, social-ecological systems (SESs) worldwide have undergone dramatic transformations with often detrimental consequences for livelihoods. Although resilience thinking offers promising conceptual frameworks to understand SES transformations, empirical resilience assessments of real-world SESs are still rare because SES complexity requires integrating knowledge, theories, and approaches from different disciplines. Taking up this challenge, we empirically assess the resilience of a South African pastoral SES to drought using various methods from natural and social sciences. In the ecological subsystem, we analyze rangelands’ ability to buffer drought effects on forage provision, using soil and vegetation indicators. In the social subsystem, we assess households’ and communities’ capacities to mitigate drought effects, applying agronomic and institutional indicators and benchmarking against practices and institutions in traditional pastoral SESs. Our results indicate that a decoupling of livelihoods from livestock-generated income was initiated by government interventions in the 1930s. In the post-apartheid phase, minimum-input strategies of herd management were adopted, leading to a recovery of rangeland vegetation due to unintentionally reduced stocking densities. Because current livelihood security is mainly based on external monetary resources (pensions, child grants, and disability grants), household resilience to drought is higher than in historical phases. Our study is one of the first to use a truly multidisciplinary resilience assessment. Conflicting results from partial assessments underline that measuring narrow indicator sets may impede a deeper understanding of SES transformations. The results also imply that the resilience of contemporary, open SESs cannot be explained by an inward-looking approach because essential connections and drivers at other scales have become relevant in the globalized world. Our study thus has helped to identify pitfalls in empirical resilience assessment and to improve the conceptualization of SES dynamics.

Sandhage-Hofmann, A., (2016), Rangeland Management. A review. In: book: Reference Module in Earth Systems and Environmental Sciences, Elsevier 1-27, DOI: 10.1016/B978-0-12-409548-9.10455-5

 Rangelands cover great parts of the world and are home of many people worldwide. They provide a wide variety of ecosystem goods and services requested by humans. This includes livestock forage, wildlife habitat, water, mineral resources, wood products, wildland recreation, open space and natural beauty. The geographic extent and the resources of rangelands make their sustainable use and management very important. Range management focuses therefore on grazing by livestock and related ecosystem goods and services. Many rangelands have been altered by persistent vegetation change, invasive species and soil degradation. Additionally, rangelands are facing social and environmental changes, for example, climate change. Future range management has to address these challenges.

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