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Spatial pattern analysis of encroaching tree species (Vachellia karroo and Vachellia nilotica) after fire suppression in a semi-arid savanna

Published online by Cambridge University Press:  15 December 2017

Justice Muvengwi ,
Hilton G.T. Ndagurwa ,
Tatenda Nyenda ,
Richard Mwembe  and
Monicah Mbiba Open the ORCID record for Monicah Mbiba [Opens in a new window]
Justice Muvengwi
Affiliation:
Department of Natural Resources, Bindura University of Science Education, Private Bag, 1020 Bindura, Zimbabwe School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa
Hilton G.T. Ndagurwa
Affiliation:
Department of Forest Resources & Wildlife Management, Faculty of Applied Science, National University of Science & Technology, P.O. Box AC 939 Ascot, Bulawayo, Zimbabwe Forest Ecology Laboratory, Faculty of Applied Science, National University of Science & Technology, P.O. Box AC 939 Ascot, Bulawayo, Zimbabwe
Tatenda Nyenda
Affiliation:
Department of Natural Resources, Bindura University of Science Education, Private Bag, 1020 Bindura, Zimbabwe
Richard Mwembe
Affiliation:
Matopos Research Station, P Bag K5137, Bulawayo, Zimbabwe
Monicah Mbiba*
Affiliation:
Department of Natural Resources, Bindura University of Science Education, Private Bag, 1020 Bindura, Zimbabwe School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa
*
*Corresponding author. Email: [email protected]
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Abstract:

Bush encroachment has serious consequences on ecosystem functioning through alteration of species composition and ecosystem productivity. However, little is known regarding the spatial patterning of invading shrubs in semi-arid savannas. Cartesian coordinates of two invading woody species (Vachellia karroo and V. nilotica), were recorded in a 20 × 20-m plot on a grassland at Matopos research station, south-west Zimbabwe. We recorded a total of 308 plants including both saplings and shrubs from the two study plant species. Second-order spatial statistics was applied in order to understand the spatial pattern of encroaching plants. We predicted that the encroaching plants would be spatially aggregated because of facilitation that occurs in harsh environmental conditions. Consistent with our predictions, the two species were aggregated, with no evidence of inter- and intra specific species competition. This study demonstrates that encroaching trees in semi-arid savanna generally do not show self organization during early growth stages.

Keywords

Bush encroachmentsavannaspatial statisticsVachellia karrooV. niloticaVoronoi
Type
Short Communication
Information
Journal of Tropical Ecology , Volume 33 , Issue 6 , November 2017 , pp. 411 - 414
Copyright
Copyright © Cambridge University Press 2017 

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References

LITERATURE CITED

ARCHIBALD, S. 2008. African grazing lawns – how fire, rainfall, and grazer numbers interact to affect grass community states. Journal of Wildlife Management 72:492–501.CrossRefGoogle Scholar
BADDELEY, A., DIGGLE, P. J., HARDEGEN, A., LAWRENCE, T., MILNE, R. K. & NAIR, G. 2014. On tests of spatial pattern based on simulation envelopes. Ecological Monographs 84:477–489.Google Scholar
CALLAWAY, R. M., BROOKER, R. W., CHOLER, P., KIKVIDZE, Z., LORTIEK, C. J., MICHALET, R., PAOLINI, L., PUGNAIREQ, F. I., NEWINGHAM, B., ASCHEHOUG, E. T., ARMASQ, C., KIKODZE, D. & COOK, B. J. 2002. Positive interactions among alpine plants increase with stress. Nature 417:844–847.CrossRefGoogle ScholarPubMed
GOREAUD, F. & PÉLISSIER, R. 2003. Avoiding misinterpretation of biotic interactions with the intertype K12-Function: population independence vs. random labelling hypotheses. Journal of Vegetation Science 14:681–692.Google Scholar
MCINTIRE, E. J. B. & FAJARDO, A. 2009. The active and effective way to infer processes from spatial patterns. Ecology 90:46–56.Google Scholar
O'CONNOR, T. G. 1995. Acacia karroo invasion of grassland: environmental and biotic effects influencing seedling emergence and establishment. Oecologia 103:214–223.Google Scholar
O'CONNOR, T. G., PUTTICK, J. R. & HOFFMAN, M. T. 2014. Bush encroachment in southern Africa: changes and causes. African Journal of Range and Forage Science 31:67–88.CrossRefGoogle Scholar
PILLAY, T. & WARD, D. 2012. Spatial pattern analysis and competition between Acacia karroo trees in humid savannas. Plant Ecology 213:1609–1619.Google Scholar
RATTRAY, J. M. 1957. The grasses and grass associations of southern Rhodesia. Rhodesia Agriculture Journal 54:197–234.Google Scholar
RIETKERK, M., BOERLIJST, M. C., VAN LANGEVELDE, F., HILLERISLAMBERS, R., VAN DE KOPPEL, J., KUMAR, L., PRINS, H. H. T. & DE ROOS, A. M. 2002. Notes and comments: self organization of vegetation in arid ecosystems. American Naturalist 160:525–530.Google Scholar
ROQUES, K. G., O'CONNOR, T. G. & WATKINSON, A. R. 2001. Dynamics of shrub encroachment in an African savanna: relative influences of fire, herbivory, rainfall and density dependence. Journal of Applied Ecology 38:268–280.Google Scholar
SANKARAN, M., HANAN, N. P., SCHOLES, R. J., RATNAM, J., AUGUSTINE, D. J., CADE, B. S., GIGNOUX, J., HIGGINS, S. I., LE ROUX, X., LUDWIG, F., ARDO, J., BANYIKWA, F., BRONN, A., BUCINI, G., CAYLOR, K. K., COUGHENOUR, M. B., DIOUF, A., EKAYA, W., FERAL, C. J., FEBRUARY, E. C., FROST, P. G. H., HIERNAUX, P., HRABAR, H., METZGER, K. L., PRINS, H. H. T., RINGROSE, S., SEA, W., TEWS, J., WORDEN, J. & ZAMBATIS, N. 2005. Determinants of woody cover in African savannas. Nature 438:846–849.CrossRefGoogle ScholarPubMed
VELÁZQUEZ, E., MARTÍNEZ, I., GETZIN, S., MOLONEY, K. A. & WIEGAND, T. 2016. An evaluation of the state of spatial point pattern analysis in ecology. Ecography 39:1042– 1055.CrossRefGoogle Scholar
WIEGAND, T. & MOLONEY, K. A. 2004. Rings, circles, and null models for point pattern analysis in ecology. Oikos 104:209–229.Google Scholar