Article
Ecology
Joel R. Lewis, George A. Verboom, Edmund C. February
Summary: This study investigated the functional trait differences between two dominant genera responsible for bush encroachment in Africa, Senegalia and Vachellia, during seedling establishment. The research found that the two genera coexist at a local scale, with Vachellia exhibiting faster growth in the absence of competition from grasses, while Senegalia increased root tissue density in the presence of grasses. Differences in seed morphology and the speculated dispersal modes were also observed. The study suggests a potential role for regeneration niche in structuring local co-occurrence.
FUNCTIONAL ECOLOGY
(2021)
Article
Ecology
Franziska Koch, Britta Tietjen, Katja Tielboerger, Korinna T. Allhoff
Summary: Savannas are characterized by the coexistence of woody and herbaceous vegetation, but overgrazing can lead to bush encroachment. Using a mathematical model, we investigated the role of grazing and found that farmer support levels affect the stability of the ecosystem. Disturbances such as drought events can also trigger abrupt transitions in the savanna.
Article
Plant Sciences
Quanita Farrah Daniels, Heather L. Throop
Summary: The study found that Terminalia sericea is insensitive to fire history, with no significant differences in ecophysiological variables among plants in areas with different fire histories, despite high leaf-level photosynthetic rates. However, changes in light levels significantly affected photosynthetic rates, suggesting that canopy structural differences may impact carbon fixation and growth rates at the whole-plant level.
SOUTH AFRICAN JOURNAL OF BOTANY
(2022)
Article
Environmental Sciences
Malicha L. Hare, Yong D. Wang, Xin W. Xu, You Yuan, Zhou Na, Abule E. Gedda
Summary: The study investigated the impact of bush control techniques on woody sapling recruitment in lowland savanna region. Different treatments showed varying effects on sapling densities, with the clearing, thinning, and thinning and grazing treatments resulting in positive changes. The findings suggest that postthinning techniques can help sustain open savanna landscapes by reducing woody tree recruitment.
FRONTIERS IN ENVIRONMENTAL SCIENCE
(2021)
Article
Ecology
Tshepiso Mangani, Arnim Marquart, George Chirima, Klaus Kellner
Summary: Many semi-arid savannahs in South Africa are experiencing degradation due to bush encroachment, causing a decline in biodiversity. This study tested different restoration treatments and found that bush clearing, brush packing, reseeding, and a combination of these methods had varying effects on grass diversity, especially in communal areas. Brush packing was found to promote grass diversity under high grazing pressure, while also altering the composition of grass species communities.
JOURNAL OF ARID ENVIRONMENTS
(2022)
Article
Environmental Sciences
Malicha Loje Hare, Xin Wen Xu, Yong Dong Wang, You Yuan, Abule Ebro Gedda
Summary: Encroachment of woody plants has negative effects on grass species and livestock production in semi-arid savanna, while thinning of bushes can significantly increase grass biomass and composition, especially in heavy thinning intensities. The interaction of thinning and rainfall plays a key role in influencing grass values, with the highest values recorded in the rainy season. Thinning to 75% of tree density can sustain the original savanna and maximize forage production.
FRONTIERS IN ENVIRONMENTAL SCIENCE
(2021)
Article
Green & Sustainable Science & Technology
Klaus Kellner, Jaco Fouche, David Tongway, Ricart Boneschans, Helga van Coller, Nanette van Staden
Summary: Bush encroachment has negative effects on ecosystem functioning and services in semi-arid rangelands, highlighting the need for management, conservation, and restoration. A study in the Molopo region, South Africa, used landscape function analysis (LFA) to assess the landscape functioning of bush-encroached and controlled savanna rangelands.
Article
Ecology
Regina Mogashoa, Phesheya Dlamini, Masibonge Gxasheka
Summary: Increasing tree density in savanna grasslands leads to a decrease in grass species richness and composition, while also increasing nutrient concentrations in the topsoil layer. These findings demonstrate the complex interactions between trees, grasses, and soil in savannas.
Article
Ecology
Arnim Marquart, Helga Van Coller, Nanette Van Staden, Klaus Kellner
Summary: Climate change and inappropriate management practices often lead to shrub encroachment in semi-arid savannas. Chemical shrub control is commonly used to counter this encroachment. In southern Africa, there is a recent transition from cattle to wildlife farming. This study compares the effects of selective chemical shrub control on herbaceous diversity and composition in these two land use types.
JOURNAL OF ARID ENVIRONMENTS
(2023)
Article
Ecology
Zinabu Bora, Yongdong Wang, Xinwen Xu, Ayana Angassa, Yuan You
Summary: Research shows that the canopy of encroaching and non-encroaching woody plant species has different effects on herbaceous vegetation biomass, with encroaching species showing a higher ability in resource acquisition and competition.
JOURNAL OF ARID ENVIRONMENTS
(2021)
Article
Biology
Alanna Hoyer-Leitzel, Sarah Iams
Summary: The study investigates the impact of fire frequency and intensity on savanna ecosystems using ODE models and impulsive dynamical systems, revealing rich bifurcation structures in the impulsive model. Social value shows resilience to disturbance regimes, with small changes potentially triggering large transitions in the valued quantity.
BULLETIN OF MATHEMATICAL BIOLOGY
(2021)
Article
Ecology
R. James Ansley, Michael J. Castellano
Summary: Managing woody species that encroach into grasslands and can resprout following top-kill is a growing problem. Costly treatments that yield complete mortality are not feasible at a large scale, while less expensive top-kill treatments need frequent application to maintain regrowth suppression. A low rate of clopyralid-only herbicide root-killed some honey mesquite but caused partial top-kill, leading to increased herbaceous productivity. Higher rates of clopyralid increased mesquite root-kill and maintained partial top-kill in surviving plants. The best option was clopyralid at 0.42 kg.ha(-1) due to lower cost, offering a method to reduce woody competition with grasses while maintaining landscape heterogeneity.
RANGELAND ECOLOGY & MANAGEMENT
(2023)
Article
Plant Sciences
Aili Amutenya, Ezekeil Kwembeya, Rosemary Shikangalah, Zivanai Tsvuura
Summary: Mistletoe can have negative effects on host trees, reducing their growth and productivity. This study found that mistletoe-infected host trees had lower photosynthetic rates compared to non-infected trees.
SOUTH AFRICAN JOURNAL OF BOTANY
(2023)
Article
Ecology
Mthunzi Mndela, Ignacio C. Madakadze, Julius T. Tjelele, Mziwanda Mangwane, Florence Nherera-Chokuda, Sikhalazo Dube, Abel Ramoelo, Ngoako L. Letsoalo
Summary: Woody plant encroachment poses a threat to herbaceous plant productivity in many rangelands worldwide. Research conducted in two rangelands in South Africa's North-West Province showed that bush clearing improved grass productivity and performance, but the responses varied among different species.
Article
Ecology
N. van Staden, A. Marquart, K. Kellner
Summary: Land degradation caused by bush encroachment and drought has negative impacts on land users and forage production in southern African savannas. This study examined the recovery of herbaceous vegetation in the Kalahari savanna after a drought, and the effects of previous bush control measures. Results showed that diversity significantly decreased in the post-drought year, with annual species being replaced by perennial forbs and dwarf shrubs. Selective bush control enhanced herbaceous species abundance and richness. Differences in herbaceous abundance and species richness were observed between game and livestock areas, likely due to management strategies, feeding behavior, and animal movement. This study highlights the rapid recovery of herbaceous plant communities after drought and the benefits of bush control measures.
AFRICAN JOURNAL OF RANGE & FORAGE SCIENCE
(2023)
Article
Ecology
Zander S. Venter, Heidi-Jayne Hawkins, Michael D. Cramer
Summary: The study found that grass growth is sensitive to grazing frequency and intensity, but can be mitigated by higher soil nutrients. It is recommended that grazing frequency be increased only on relatively high-nutrient soils, while maximizing recovery on poorer nutrient soils.
AFRICAN JOURNAL OF RANGE & FORAGE SCIENCE
(2021)
Article
Ecology
Ruan van Mazijk, Michael D. Cramer, G. Anthony Verboom
Summary: The study found that the Greater Cape Floristic Region is generally more environmentally heterogeneous and species-rich than the Southwest Australian Floristic Region. There is a significant relationship between species richness per unit area and the major axis of heterogeneity across both regions, but this relationship differs between the two regions at the finest spatial scale.
JOURNAL OF BIOGEOGRAPHY
(2021)
Article
Ecology
Tiffany Pillay, David Ward, Admore Mureva, Michael Cramer
Summary: The interaction between woody plant encroachment and nutrient availability may vary along precipitation gradients. High-precipitation sites have higher soil nitrogen stocks and greater variation in soil phosphorus, with evidence of phosphorus limitation in areas with highest precipitation. Increased nutrients mainly benefit high-precipitation sites, possibly due to water scarcity at low-precipitation sites. Woody plant encroachment has positive effects on litter quality and plant species richness, more pronounced at high-precipitation sites.
Article
Agronomy
Patrick E. Hayes, Francis J. Nge, Michael D. Cramer, Patrick M. Finnegan, Peili Fu, Stephen D. Hopper, Rafael S. Oliveira, Benjamin L. Turner, Graham Zemunik, Hongtao Zhong, Hans Lambers
Summary: The study found that the diversification of Proteaceae is strongly correlated with traits related to soil phosphorus, such as low leaf P concentration and high seed P concentration, which are likely key innovations allowing diversification. Selection for low leaf P concentration early in the evolutionary history pre-adapted ancestors of this family to diversify into oligotrophic environments.
Article
Ecology
Andrew M. Cunliffe, Karen Anderson, Fabio Boschetti, Richard E. Brazier, Hugh A. Graham, Isla H. Myers-Smith, Thomas Astor, Matthias M. Boer, Leonor G. Calvo, Patrick E. Clark, Michael D. Cramer, Miguel S. Encinas-Lara, Stephen M. Escarzaga, Jose M. Fernandez-Guisuraga, Adrian G. Fisher, Katerina Gdulova, Breahna M. Gillespie, Anne Griebel, Niall P. Hanan, Muhammad S. Hanggito, Stefan Haselberger, Caroline A. Havrilla, Phil Heilman, Wenjie Ji, Jason W. Karl, Mario Kirchhoff, Sabine Kraushaar, Mitchell B. Lyons, Irene Marzolff, Marguerite E. Mauritz, Cameron D. McIntire, Daniel Metzen, Luis A. Mendez-Barroso, Simon C. Power, Jiri Prosek, Enoc Sanz-Ablanedo, Katherine J. Sauer, Damian Schulze-Bruninghoff, Petra Simova, Stephen Sitch, Julian L. Smit, Caiti M. Steele, Susana Suarez-Seoane, Sergio A. Vargas, Miguel Villarreal, Fleur Visser, Michael Wachendorf, Hannes Wirnsberger, Robert Wojcikiewicz
Summary: This study developed a new protocol for photogrammetric height using UAV images to standardized measurements of biomass across a globally distributed field experiment. Canopy height inferred from UAV photogrammetry was found to strongly predict aboveground biomass across different plant species, providing accurate estimates. The photogrammetric approach proved to be sensitive to wind speed but robust in providing generalizable measurements across different growth forms and environments, demonstrating its potential for accurately estimating biomass in various ecosystems.
REMOTE SENSING IN ECOLOGY AND CONSERVATION
(2022)
Article
Agriculture, Multidisciplinary
H. -j. Hawkins, Z. -s. Venter, M. D. Cramer
Summary: Holistic Management (HM) is claimed to increase production of plants and animals, as well as soil organic carbon under all conditions, but peer-reviewed studies do not support these claims. Studies in the United States, Argentina, and South Africa found that HM either had no effect or reduced production, while the potential for increased carbon sequestration with changed grazing management is substantially lower than estimated by non-peer-reviewed HM literature.
AGRICULTURE ECOSYSTEMS & ENVIRONMENT
(2022)
Article
Biodiversity Conservation
Taryn L. Morris, Nichole N. Barger, Michael D. Cramer
Summary: The regulation of invasive species by indigenous generalist herbivores plays a significant role in ecosystem resistance. This study found that herbivory by striped mice is a major factor affecting the survival of Acacia cyclops seedlings, and it is influenced by vegetation density and canopy openness.
BIOLOGICAL INVASIONS
(2022)
Article
Multidisciplinary Sciences
Mingzhen Lu, William J. Bond, Efrat Sheffer, Michael D. Cramer, Adam G. West, Nicky Allsopp, Edmund C. February, Samson Chimphango, Zeqing Ma, Jasper A. Slingsby, Lars O. Hedin
Summary: Recent research suggests that plant root traits play a crucial role in shaping biome boundaries and maintaining plant communities. The study conducted in South Africa revealed that thin-rooted plant strategies are favored in biomes with low soil resources, and these strategies, along with intense belowground competition, help maintain the sharp boundary between different biomes. The findings challenge the traditional belief that external abiotic factors primarily determine biome boundaries and highlight the importance of internal biotic mechanisms in maintaining these boundaries.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Multidisciplinary Sciences
Jeremy J. Midgley, Michael D. Cramer
Summary: This study found significant differences between female and male plants in terms of sexual reproduction and vegetative growth. Female plants tend to allocate more resources to sexual reproduction, while male plants prioritize vegetative growth. However, the sex ratios and basal stem areas are equal between the sexes. This suggests that plant traits are not only related to nutrition, but also to reproduction.
SCIENTIFIC REPORTS
(2022)
Article
Geosciences, Multidisciplinary
Johanna R. C. J. von Holdt, Jeremy J. Midgley, Christopher D. von Holdt, Michael Cramer
Summary: The origins of regularly spaced mounded landscapes worldwide remains a mystery, including the Mima-like heuweltjies in South Africa. This study explored the hypothesis that these mounds retain some characteristics of aeolian deposition known as nabkhas. Aerial surveys and sedimentological analysis were conducted, revealing no evidence of heuweltjie origins as nabkhas based on mound morphology, spatial distribution, or sediment characteristics. Instead, the elongated downslope shape and steeper downslope flanks suggest soil creep and water erosion as the primary factors. This study suggests that hydrological processes and the redistribution of aeolian sediments contribute to the spatial pattern and morphology of heuweltjies.
Article
Ecology
Michael D. Cramer, David W. Hedding, Michelle Greve, Guy F. Midgley, Brad S. Ripley
Summary: Extreme changes in temperature, rainfall, and wind regimes have been correlated with plant species range expansion upslope on sub-Antarctic islands. However, non-climatic characteristics, such as soil and topographic factors, may limit the capacity for range shifts and survival of vascular plant species.
FUNCTIONAL ECOLOGY
(2022)
Article
Ecology
T. K. Aikins, M. D. Cramer, R. L. Thomson
Summary: In arid environments, the presence of sociable weaver nests alters soil properties and enhances nutrient concentrations under trees, but the area under the nests remains devoid of vegetation due to physiological drought and nutrient toxicity.
JOURNAL OF ARID ENVIRONMENTS
(2023)
Article
Ecology
Stephni van der Merwe, Michelle Greve, Andrew Luke Skowno, Michael Timm Hoffman, Michael Denis Cramer
Summary: The updating and rethinking of vegetation classifications are crucial for monitoring ecosystems in a changing world. However, the assumption of discrete and persistent plant communities that can be efficiently monitored is rarely tested. This study tested the ability to classify species-poor vegetation on Marion Island using objective techniques and compared it to previous classifications. The results showed that species composition alone is not sufficient to classify plots into previously suggested vegetation units, suggesting that species-level monitoring may be more suitable in species-poor environments.
ECOLOGY AND EVOLUTION
(2023)
Article
Plant Sciences
Michael D. Cramer, G. Anthony Verboom
Summary: The high species richness in Mediterranean ecosystems is attributed to multiple mechanisms, including resource availability, spatial and temporal heterogeneity, and biotic feedbacks. Water availability and nutrient scarcity are important factors influencing species richness.
Article
Plant Sciences
Timothy K. Aikins, Robert L. Thomson, Michael D. Cramer
Summary: Islands of fertility associated with tree/shrub patches in arid grasslands create spatial heterogeneity of soil nutrients. Faunal activities under these trees/shrubs may contribute to diverse characteristics of these fertile patches of soil due to different faecal inputs. We investigated the diversity in islands of fertility in the Kalahari Desert and found that the faecal input of sociable weavers accounts for the growth differences in these islands.