Abstract
Plants face different environmental pressures in different patches of vegetation mosaics, so their demography cannot be completely understood if it is not studied in each patch-type. Banded patterns of vegetation surrounded by bare areas occur in semiarid landscapes. At one level, two phases of the mosaic are the banded vegetation-patches (vegetation arcs) and the bare areas, but at another level two phases can be distinguished inside the vegetation arc. One phase (frontal zone) is always in the upslope boundary of the arc, has only herbs and it has been suggested that it functions as a colonization area, while the other one (central zone) is at the middle of the arcs and has both shrubs and herbs. The demography of a tussock grass (Hilaria mutica) growing in the two phases of the vegetation arcs was studied under the hypothesis that it will show the demographic parameters of a ruderal species in the frontal zone and those of a more competitive species in the central zone. Temporal variability was assessed through annual, average, periodic and stochastic matrices. λ-values are higher in the frontal than in the central zone, and lower in dry years than in years with moderate precipitation. The influence of the demographic processes on λ-values shows spatial and temporal variation. In dry years, λ-values are more sensible to stasis (permanence in the same size class) and retrogression (transition to a smaller size class) in both zones, whereas in years of moderate precipitation the influence of fecundity and growth increases in the frontal zone and the influence of stasis and retrogression continue to be the most important in the central zone. Variations in the demographic parameters observed in the frontal zone are evidences of a life history plasticity finely tuned with environmental variation, and these results support the hypothesis that frontal zones function as colonization areas.
Similar content being viewed by others
References
Benton T.G. and Grant A. 1996. How to keep fit in the real world: elasticity analyses and selection pressures on life histories in a variable environment. American Naturalist 147: 115–139.
Bierzychudek P. 1982. The demography of jack-in-the-pulpit, a forest perennial that changes sex.. Ecological Monographs 52: 335–351.
Boaler S. and Hodge C.A. 1964. Observations on vegetation arcs in the northern region, Somali Republic. Journal of Ecology 52: 511–544.
Callaway R.M. 1995. Positive interactions among plants. The Botanical Review 61: 306–349.
Caswell H. 1986. Life cycle models for plants. Lectures on Mathematics in the Life Sciences 18: 171–233.
Caswell H. 2001. Matrix Population Models. Construction, analysis and interpretation.. Sinauer Associates Inc. Publishers, Sun-derland, Massechusetts, USA.
Caswell H. and Trevisan M.C. 1994. Sensitivity analysis of periodic matrix models. Ecology 75: 1299–1303.
Cornet A., Montaña C., Delhoume J.P. and López-Portillo J. 1992. Water flows and the dynamics of desert vegetation stripes,. pp. 327–345. In: Hansen A.J. and Di Castri F. _eds_, Landscape boundaries. Consequences for biotic diversity and ecological flows. Ecological Studies 92. Springer-Verlag, New York, New York, USA.
Crowley P.H. 1992. Resampling methods for computation-intensive data analysis in ecology and evolution. Annual Review of Ecology and Systematics 23: 405–447.
de Kroon A., Plaisier H.A., van Groenendael J. and Caswell H. 1986. Elasticity: the relative contribution of demographic parameters to population growth rate. Ecology 67: 1427–1431.
Dixon P.M. 1993. The Bootstrap and the Jackknife: Describing the Precision of Ecological Indices,. pp. 290–318. In: Scheiner S.M. and Gurevitch J. _eds_, Design and analysis of ecological experiments. Chapman and Hall, USA.
Ezcurra E. and Rodrigues V. 1986. Rainfall patterns in the Gran Desierto, Sonora, México. Journal of Arid Environments 10: 13–28.
Fair J., Lauenroth W.K. and Coffin D.P. 1999. Demography of Bouteloa gracilis in a mixed prairie: analysis of genets and individuals. Journal of Ecology 87: 233–243.
Floyd S.K. and Ranker T.A. 1998. Analysis of a transition matrix model for Gaura neomexicana spp. Coloradensis Onagraceae. reveals spatial and temporal demographic variability. International Journal of Plant Science 159: 853–863.
Greig-Smith P. 1979. Pattern in vegetation. Journal of Ecology 67: 755–779.
Grime J.P. 1977. Evidence for the existence of three primary strategies in plants and its relevance to ecological and evolutionary theory. American Naturalist 11: 1169–1194.
Guardia R., Raventos J. and Caswell H. 2000. Spatial growth and population dynamics of a perennial tussock grass Achnaterum calamagrostis. in a badland area. Journal of Ecology 88: 950–963.
Horvitz C and Schemske D. 1995. Spatiotemporal variation in demographic transitions of a tropical understory herb: projection matrix analysis. Ecological Monographs 65: 155–192.
Kadmon R. 1993. Population dynamic consequences of habitat heterogeneity: an experimental study. Ecology 74: 816–825.
Kadmon R. and Shimda A. 1990a. Patterns and causes of spatial variation in the reproductive success of a desert annual. Oecologia 83: 139–144.
Lefkovich L.P. 1965. The study of population growth in organisms grouped by stages. Biometrics 21: 1–18.
López-Portillo J. and Montaña C. 1999. Spatial distribution of Prosopis galndulosa var. torreyana in vegetation stripes of the southern Chihuahuan desert. Acta Oecologica 20: 197–208.
Mabbutt J.A. and Fanning P.C. 1987. Vegetation banding in western Australia. Journal of Arid Environments 12: 41–59.
Mandujano M.C., Montaña C., Franco M., Golubov J. and Martínez A.F. 2001. Integration of demographic annual variability in a clonal desert cactus. Ecology 82: 344–359.
Mauchamp A., Montaña C., Lepart J. and Rambal S. 1993. Ecotone dependent recruitment of a desert shrub, Flourensia cernua, in vegetation stripes. Oikos 68: 107–116.
Mauchamp A., Rambal S. and Lepart J. 1994. Simulating the dynamics of a vegetation mosaic: a spatialized functional model. Ecological Modelling 71: 107–130.
Moloney K. 1988. Fine-scale spatial and temporal variation in the demography of a perennial bunch grass. Ecology 69: 1588–1598.
Montaña C., López-Portillo J. and Mauchamp A. 1990. The response of two woody species to the conditions creates by a shifting ecotone in an arid ecosystem. Journal of Ecology 78: 789–798.
Montaña C. 1992. The colonization of bare areas in two phase mosaics of an arid ecosystem. Journal of Ecology 80: 315–327.
Niering W.A., Whittaker R.H. and Lowe C.H. 1963. The saguaro: a population in relation to environment. Science 142: 15–23.
Nault A. and Gagnon D. 1993. Ramet demography of Allium tric-occum, a spring ephemeral, perennial forest herb. Journal of Ecology 81: 101–119.
Noy-Meir I. 1985. Desert ecosystems: structure and function,. pp. 93–102. In: Evenari M., Noy-Meir I. and Goodall D.W. _eds_, Hot deserts and arid shrublands, Ecosystems of the world, vol. 12A. Elsevier, Amsterdam, The Netherlands.
O'Connor T.G. 1993. The influence of rainfall and grazing an the demography of some African savanna grasses: a matrix modeling approach. Journal of Applied Ecology 30: 119–132.
Oostermeijer J.G.B., Brugman M.L., de Boer E.R. and den Nijs H.C.M. 1996. Temporal and spatial variation in the demography of Gentiana pneumonanthe, a rare perennial herb. Journal of Ecology 84: 153–166.
Sarukhán J. and Gadgil M. 1974. Studies on plant demography: Ranunculus repens L., R. bulbosus L. and R. acris L. III. A mathematical model incorporating multiple modes of reproduction. Journal of Ecology 62: 921–937.
SAS Institute 1995. JMP Statistics and Graphics Guide. SAS Institute Inc., Cary, North Carolina, USA.
Shmida A., Evenari M. and Noy-Meir I. 1985. Hot deserts ecosystems: an integrated view,. pp. 379–387. In: Evenari M., Noy-Meir I. and Goodall D.W. _eds_, Hot deserts and arid shru-blands, vol. 12B. Elsevier, Amsterdam, The Netherlands.
Silva J.F., Raventos J., Caswell H. and Trevisan M.C. 1991. Population responses to fire in a tropical savanna grass Andropogon semiberbis: a matrix model approach. Journal of Ecology 79: 345–356.
Silvertown J., Franco M., Pisanty I. and Mendoza A. 1993. Comparative plant demography-relative importance of life-cycle components to the finite rate of increase in woody and herba-ceous perennials. Journal of Ecology 81: 465–476.
Stuefer J.F., During H.J. and de Kroon H. 1994. High benefits of clonal integration in two stoloniferous species in response to heterogeneous ligth environments. Journal of Ecology 82: 511–518.
Tuljapurkar S.D. 1989. An uncertain life: demography in random environments. Theoretical Population Biology 35: 227–294.
Valentin C., d´Herbes J.M. and Poesen J. 1999. Soil and water components of banded vegetation patterns. Catena 37: 1–24.
Valverde T. and Silvertown J. 1997. A metapopulation model for Primula vulgaris, a temperate forest understorey herb. Journal of Ecology 85: 193–210.
Watson I.W., Westoby M. and Holm A. 1997. Continuous and episodic components of demographic change in arid zone shrubs: models of two Eremophila species from Western Australia compared with published data on other species. Journal of Ecology 85: 833–846.
Wiens J.A. 1985. Vertebrate responses to environmental patchiness in arid and semiarid ecosystems,. pp. 169–193. In: Pickett S.T.A. and White P.S. _eds_, The ecology of natural disturbance and patch dynamics. Academic Press, New York, New York, USA.
Zar J.H. 1984 1Biostatistical Analysis. Prentice Hall, USA.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Vega, E., Montaña, C. Spatio-temporal variation in the demography of a bunch grass in a patchy semiarid environment. Plant Ecology 175, 107–120 (2004). https://doi.org/10.1023/B:VEGE.0000048094.21994.74
Issue Date:
DOI: https://doi.org/10.1023/B:VEGE.0000048094.21994.74