Determinants of woody cover in African savannas

@article{Sankaran2005DeterminantsOW,
  title={Determinants of woody cover in African savannas},
  author={Mahesh Sankaran and Niall P. Hanan and Robert J. Scholes and Jayashree Ratnam and David J. Augustine and Brian S. Cade and Jacques Gignoux and Steven I. Higgins and Xavier Le Roux and Fulco Ludwig and Jonas Ardo and Feetham F. Banyikwa and Andries Bronn and Gabriela Bucini and Kelly K. Caylor and Michael B. Coughenour and Aliou Diouf and Wellington. N Ekaya and C.J.W. Feral and Edmund Carl February and Peter G. H. Frost and Pierre Hiernaux and Halszka Hrabar and Kristine L. Metzger and Herbert H. T. Prins and Susan Ringrose and William Sea and Joerg Tews and Jeffrey S. Worden and Nick Zambatis},
  journal={Nature},
  year={2005},
  volume={438},
  pages={846-849}
}
Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854… 
Determinants of woody encroachment and cover in African savannas
TLDR
It is postulated that woody encroachment is most likely driven by CO2 enrichment and a two-system conceptual framework is proposed, whereby mechanisms of wooded encroachment differ depending on whether the savanna is a wet or dry system.
Invasive Plant Species and Biomass Production in Savannas
Savannas are the second largest biome accounting for c. 30% of terrestrial production. Tropical savannas are distributed largely in Africa, Australia and South America occurring between tropical
Woody cover in African savannas: the role of resources, fire and herbivory
Aim  To determine the functional relationships between, and the relative importance of, different driver variables (mean annual precipitation, soil properties, fire and herbivory) in regulating woody
The effects of fire on the characteristics of woody vegetation and encroachment in an African savanna
Savannas are an integral part of African ecosystems and sustain the livelihoods of millions of people. Woody encroachment in savannas is a widespread phenomenon but its causes are widely debated. I
Predicting the Effects of Woody Encroachment on Mammal Communities, Grazing Biomass and Fire Frequency in African Savannas
TLDR
The results suggest that woody encroachment will have cascading consequences for Africa’s grazing systems, fire regimes and iconic wildlife, which will pose challenges and require adaptation of livelihoods and industries dependent on conditions currently prevailing.
Woody plants in grasslands: post-encroachment stand dynamics.
TLDR
If woody cover has transitioned from directional increases to a dynamic equilibrium, biomass projections will require monitoring and modeling patch dynamics and stand structure rather than simply changes in total cover.
Vegetation structure shapes small mammal communities in African savannas
TLDR
It is suggested that an increase in grass biomass enhances whole-community occupancy of small mammals, but regional diversity is likely to be higher in areas that contain patches of high grass biomass as well as patches of woody cover.
Woody cover in African savannas: Mapping strategies and ecological insights at regional and continental scales
OF DISSERTATION WOODY COVER IN AFRICAN SAVANNAS: MAPPING STRATEGIES AND ECOLOGICAL INSIGHTS AT REGIONAL AND CONTINENTAL SCALES Savanna ecosystems are characterized by the coexistence of woody and
Human impacts in African savannas are mediated by plant functional traits.
TLDR
It is argued that the unique combinations of plant functional traits characterizing the major floristic assemblages of African savannas make them differentially susceptible and resilient to anthropogenic drivers of ecosystem change.
...
...

References

SHOWING 1-10 OF 38 REFERENCES
STABILITY OF SEMI-ARID SAVANNA GRAZING SYSTEMS
SUMMARY (2) The model is based on Walter's two layer hypothesis. Woody vegetation and grasses compete for water in the surface layers of the soil, but woody vegetation has exclusive access to a
The importance of low atmospheric CO2 and fire in promoting the spread of grasslands and savannas
The distribution and abundance of trees can be strongly affected by disturbance such as fire. In mixed tree/grass ecosystems, recurrent grass‐fuelled fires can strongly suppress tree saplings and
Tree-grass interactions in Savannas
TLDR
Understanding of the widely observed increase in tree biomass following introduction of commercial ranching into savannas requires inclusion of interactions among browsers, grazers, and fires, and their effects on tree recruitment.
EFFECTS OF FIRE AND HERBIVORY ON THE STABILITY OF SAVANNA ECOSYSTEMS
Savanna ecosystems are characterized by the co-occurrence of trees and grass- es. In this paper, we argue that the balance between trees and grasses is, to a large extent, determined by the indirect
Ecosystem carbon loss with woody plant invasion of grasslands
TLDR
A clear negative relationship between precipitation and changes in soil organic carbon and nitrogen content when grasslands were invaded by woody vegetation is found, with drier sites gaining, and wetter sites losing, soilorganic carbon.
Ecological buffering mechanisms in savannas: A unifying theory of long-term tree-grass coexistence
Despite the large spatial extent and the obvious importance of the savanna biome, not to mention several decades of savanna research, the origin, age, nature, and dynamics of savannas are not well
Tree–grass coexistence in savannas revisited – insights from an examination of assumptions and mechanisms invoked in existing models
TLDR
An integration of competition-based and demographic approaches is required if a comprehensive model that explains both coexistence and the relative productivity of the tree and grass components across the diverse savannas of the world is to emerge.
Changing precipitation regimes and terrestrial ecosystems : a North American perspective
By the beginning of the twenty-first century, few people could deny the reality of global change. But while most alarm has been over increasing temperatures, other changes are occurring in
The propagation of disturbance in savannas through food webs
TLDR
The reconstructed effects of rinderpest upon African savannas, acting directly upon susceptible grazers and browsers but in directly upon many other ecosystem components, are used as a case history illustrating the propagation of disturbance in savanna ecosystems.
...
...