Hostname: page-component-cd9895bd7-dzt6s Total loading time: 0 Render date: 2024-12-23T13:25:21.637Z Has data issue: false hasContentIssue false
  • English
  • Français

Strong competitive effects of African savanna C4 grasses on tree seedlings do not support rooting differentiation

Published online by Cambridge University Press:  31 January 2018

Benjamin L. Ketter  and
Ricardo M. Holdo
Benjamin L. Ketter
Affiliation:
Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
Ricardo M. Holdo*
Affiliation:
Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
*
*Corresponding author. Email: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract:

Rooting differentiation between established trees and grasses has been well documented in savannas, but it remains unclear to what extent tree-grass rooting differences affect competition between newly established seedlings and grasses. To examine this question, a greenhouse experiment was conducted at the University of Missouri, USA. Twenty 3-mo-old seedlings each of two African savanna tree species (Acacia nigrescens and Colophospermum mopane) were grown for 8 mo with two crossed factors: grass competition and irrigation depth. Strong negative effects of grass competition on final seedling biomass and leaf photosynthetic and stomatal conductance occurred in both tree species, but no effects of irrigation depth were detected. There was a clear tree species by grass competition interaction, suggesting interspecific variation in competitive response. The results emphasize the importance of below-ground competition with grasses for physiological and morphological responses of tree seedlings, while minimizing the importance of tree-grass rooting depth differences as a factor in modulating the competitive response of trees to grasses at the seedling stage.

Keywords

Africasoil moisturestomatal conductancetree growthtree-grass competitiontropical savanna
Type
Research Article
Information
Journal of Tropical Ecology , Volume 34 , Issue 1 , January 2018 , pp. 65 - 73
Copyright
Copyright © Cambridge University Press 2018 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

LITERATURE CITED

BARBOSA, E. R. M., VAN LANGEVELDE, F., TOMLINSON, K. W., CARVALHEIRO, L. G., KIRKMAN, K., DE BIE, S. & PRINS, H. H. T. 2014. Tree species from different functional groups respond differently to environmental changes during establishment. Oecologia 174:1345–1357.CrossRefGoogle ScholarPubMed
CAMPBELL, T. A. & HOLDO, R. M. 2017. Competitive response of savanna tree seedlings to C4 grasses is negatively related to photosynthesis rate. Biotropica 49:774–777.CrossRefGoogle Scholar
CRAMER, M. D., VAN CAUTER, A. & BOND, W. J. 2010. Growth of N2-fixing African savanna Acacia species is constrained by below-ground competition with grass. Journal of Ecology 98:156–167.CrossRefGoogle Scholar
CRAMER, M., WAKELING, J. & BOND, W. 2012. Belowground competitive suppression of seedling growth by grass in an African savanna. Plant Ecology 213:1655–1666.CrossRefGoogle Scholar
DAVIS, M. A., WRAGE, K. J., REICH, P. B., TJOELKER, M. G., SCHAEFFER, T. & MUERMANN, C. 1999. Survival, growth, and photosynthesis of tree seedlings competing with herbaceous vegetation along a water-light-nitrogen gradient. Plant Ecology 145:341–350.CrossRefGoogle Scholar
EAGLESON, P. S. & SEGARRA, R. I. 1985. Water-limited equilibrium of savanna vegetation systems. Water Resources Research 21:1483–1493.CrossRefGoogle Scholar
FEBRUARY, E. C., HIGGINS, S. I., BOND, W. J. & SWEMMER, L. 2013. Influence of competition and rainfall manipulation on the growth responses of savanna trees and grasses. Ecology 94:1155–1164.CrossRefGoogle ScholarPubMed
HIGGINS, S. I., BOND, W. J. & TROLLOPE, W. S. W. 2000. Fire, resprouting and variability: a recipe for grass-tree coexistence in savanna. Journal of Ecology 88:213–229.CrossRefGoogle Scholar
HOFFMANN, W. A., GEIGER, E. L., GOTSCH, S. G., ROSSATTO, D. R., SILVA, L. C. R., LAU, O. L., HARIDASAN, M. & FRANCO, A. C. 2012. Ecological thresholds at the savanna-forest boundary: how plant traits, resources and fire govern the distribution of tropical biomes. Ecology Letters 15:759–768.CrossRefGoogle ScholarPubMed
HOLDO, R. & BROCATO, E. 2015. Tree–grass competition varies across select savanna tree species: a potential role for rooting depth. Plant Ecology 216:577–588.CrossRefGoogle Scholar
HOLDO, R. M. & NIPPERT, J. 2015. Transpiration dynamics support resource partitioning in African savanna trees and grasses. Ecology 96:1466–1472.CrossRefGoogle Scholar
KAMBATUKU, J. R., CRAMER, M. D. & WARD, D. 2013. Overlap in soil water sources of savanna woody seedlings and grasses. Ecohydrology 6:464–473.CrossRefGoogle Scholar
KULMATISKI, A. & BEARD, K. H. 2013a. Woody plant encroachment facilitated by increased precipitation intensity. Nature Climate Change 3:833–837.CrossRefGoogle Scholar
KULMATISKI, A. & BEARD, K. 2013b. Root niche partitioning among grasses, saplings, and trees measured using a tracer technique. Oecologia 171:25–37.CrossRefGoogle ScholarPubMed
KULMATISKI, A., BEARD, K. H., VERWEIJ, R. J. T. & FEBRUARY, E. C. 2010. A depth-controlled tracer technique measures vertical, horizontal and temporal patterns of water use by trees and grasses in a subtropical savanna. New Phytologist 188:199–209.CrossRefGoogle Scholar
MORDELET, P., MENAUT, J.-C. & MARIOTTI, A. 1997. Tree and grass rooting patterns in an African humid savanna. Journal of Vegetation Science 8:65–70.CrossRefGoogle Scholar
NIPPERT, J. & KNAPP, A. K. 2007. Linking water uptake with rooting patterns in grassland species. Oecologia 153:261–272.CrossRefGoogle ScholarPubMed
PINHEIRO, J. C. & BATES, M. 2000. Mixed-Effects Models in S and S-PLUS. Springer-Verlag, New York.CrossRefGoogle Scholar
PRIYADARSHINI, K. V. R., PRINS, H. H. T., DE BIE, S., HEITKÖNIG, I. M. A., WOODBORNE, S., GORT, G., KIRKMAN, K., LUDWIG, F., DAWSON, T. E. & DE KROON, H. 2016. Seasonality of hydraulic redistribution by trees to grasses and changes in their water-source use that change tree–grass interactions. Ecohydrology 9: 218–228.CrossRefGoogle Scholar
RIGINOS, C. 2009. Grass competition suppresses savanna tree growth across multiple demographic stages. Ecology 90:335–340.CrossRefGoogle ScholarPubMed
SANKARAN, M., RATNAM, J. & HANAN, N. P. 2004. Tree-grass coexistence in savannas revisited – insights from an examination of assumptions and mechanisms invoked in existing models. Ecology Letters 7:480–490.CrossRefGoogle 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
SCHOLES, R. J. & ARCHER, S. R. 1997. Tree-grass interactions in savannas. Annual Review of Ecology and Systematics 28:517–544.CrossRefGoogle Scholar
SCHOLES, R. J. & WALKER, B. H. 1993. An African savanna: synthesis of the Nylsvlei study. Cambridge University Press, Cambridge. 306 pp.CrossRefGoogle Scholar
VERWEIJ, R. J. T., HIGGINS, S. I., BOND, W. J. & FEBRUARY, E. C. 2011. Water sourcing by trees in a mesic savanna: responses to severing deep and shallow roots. Environmental and Experimental Botany 74:229–236.CrossRefGoogle Scholar
WALKER, B. H. & NOY-MEIR, I. 1982. Aspects of the stability and resilience of savanna ecosystems. Pp. 556–590 in Huntley, B. J. & Walker, B. H. (eds). Ecology of tropical savannas. Springer-Verlag, Berlin.Google Scholar
WALTER, H. 1971. Ecology of tropical and subtropical vegetation. Oliver and Boyd, Edinburgh. 539 pp.Google Scholar
WARD, D., WIEGAND, K. & GETZIN, S. 2013. Walter's two-layer hypothesis revisited: back to the roots! Oecologia 172:616–630.CrossRefGoogle ScholarPubMed
WERNER, P. A. 2012. Growth of juvenile and sapling trees differs with both fire season and understorey type: trade-offs and transitions out of the fire trap in an Australian savanna. Austral Ecology 37:644–657.CrossRefGoogle Scholar
WERNER, P. A. & MURPHY, P. G. 2001. Size-specific biomass allocation and water content of above- and below-ground components of three Eucalyptus species in a northern Australian savanna. Australian Journal of Botany 49:155–167.CrossRefGoogle Scholar
WERNER, P. A. & PRIOR, L. D. 2013. Demography and growth of subadult savanna trees: interactions of life history, size, fire season, and grassy understory. Ecological Monographs 83:67–93.CrossRefGoogle Scholar