Abstract
Mediterranean fluvial ecosystems are subjected to ever-increasing water demands and to a wide variety of other human impacts with potential negative effects on riparian vegetation. Nevertheless, few studies have compared the importance of human versus natural factors in structuring riparian vegetation in this region, particularly in semi-arid areas. We examined basin-scale responses of riparian vegetation to the main environmental gradient extracted by canonical correspondence analysis in two semi-arid Mediterranean rivers in southern Spain, considering different community attributes (woody, herbaceous, functional groups, and exotics species) and using different metrics (species composition, richness, and cover). The results show two main environmental gradients for riparian vegetation: a prime altitudinal gradient of increasing salinity towards the lower sites, and a second gradient of increasing water pollution and human physical impact parallel to the hydroperiod shortening. Species richness of woody and herbaceous life forms, and cover of woody species, reacted negatively to the increasing salinity downstream, a pattern that was driven by most functional groups. This is consistent with the key role of salinity for vegetation. Furthermore, as for other semi-arid riparian ecosystems, the decline in rainfall coupled with higher temperatures and evaporative stress at the lower elevation open-canopy sites may have constrained herbaceous species. Woody richness and cover declined with shorter hydroperiod and increasing human impacts, a response that was driven by mesic and hydric species. These results agree with the idea that surface flow permanence is an outstanding limiting factor for woody vegetation in semi-arid rivers, possibly exerting more influence on species richness than flood disturbance. However, herbs showed very little response to drought or human impacts compared to woody species, which may be related to the higher recovery rate from disturbance of herbaceous life forms, due to their shorter life-span and higher colonization rates. Generally, exotic species were positively affected by dissolved nutrients (N and P), especially exotic herbaceous richness and cover by nitrogen. As in other Mediterranean rivers, percentage richness of exotics in our rivers was substantially lower compared to fluvial ecosystems in other regions.
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Literature Cited
Aguiar, F. C. and M. T. Ferreira. 2005. Human-disturbed landscapes: effects on composition and integrity of riparian woody vegetation in the Tagus river basin, Portugal. Environmental Conservation 32: 30–41.
Aguiar, F. C., M. T. Ferreira, and I. Moreira. 2001. Exotic and native vegetation establishment following channelization of a western Iberian river. Regulated Rivers: Research and Management 17: 509–26.
Aguiar, F. C., M. T. Ferreira, and P. Pinto. 2002. Relative influence of environmental variables on macroinvertebrate assemblages from an Iberian basin. Journal of North American Benthogical Society 21: 43–53.
Ali, M. M., G. Dickinson, and K. J. Murphy. 2000. Predictors of plant diversity in a hyperarid desert wadi ecosystem. Journal of Arid Environments 45: 215–30.
Allan, J. D. and A. S. Flecker. 1993. Biodiversity conservation in running waters. Bioscience 43: 32–43.
APHA. 1992. Métodos Normalizados para el Análisis de Aguas Potables y Residuales. Díaz de Santos, Madrid, Spain.
Auble, G. T. and M. L. Scott. 1998. Fluvial disturbance patches and cottonwood recruitment along the upper Missouri River, Montana. Wetlands 18: 546–56.
Bagstad, K. J., J. C. Stromberg, and S. J. Lite. 2005. Response of herbaceous riparian plants to rain and flooding on the San Pedro River, Arizona, USA. Wetlands 25: 210–23.
Baker, W. L. 1990. Climatic and hydrologic effects on the regeneration of Populus angustifolia James along the Animas River, Colorado. Journal of Biogeography 17: 59–73.
Bullock, J. 1996. Plants. p. 111–38. In W. J. Sutherland (ed.) Ecological Census Techniques: A Handbook. Cambridge University Press, Cambridge, UK.
Bunn, S. E., D. H. Edward, and N. R. Lonegran. 1986. Spatial and temporal variation in the macroinvertebrate fauna of streams of the northern jarrah forest, Western Australia: community structure. Freshwater Biology 16: 67–91.
Burnham, K. P. and D. R. Anderson. 2002. Model Selection and Multimodel Inference: A Practical Information-Theoretic Approach. Springer-Verlag, New York, NY, USA.
Busch, D. E. and S. D. Smith. 1995. Mechanisms associated with decline of woody species in riparian ecosystems of the Southwestern U.S. Ecological Monographs, 65: 347–70.
Casas, J. J., M. O. Gessner, P. H. Langton, D. Calle, E. Descals, and M. J. Salinas. 2006. Diversity of patterns and processes in rivers of eastern Andalusia. Limnetica 25: 155–70.
Chytrý, M., P. Pyšek, L. Tichý, I. Knollová, and J. Danihelka. 2005. Invasions by alien plants in the Czech Republic: a quantitative assessment across habitats. Preslia, Praha 77: 339–54.
Corbacho, C., J. M. Sánchez, and E. Costillo. 2003. Patterns of structural complexity and human disturbance of riparian vegetation in agricultural landscapes of a Mediterranean area. Agriculture, Ecosystems and Environment 95: 495–507.
Decruyenaere, J. G. and J. S. Holt. 2005. Ramet demography of a clonal invader, Arundo donax (Poaceae), in Southern California. Plant and Soil 277: 41–52.
Deferrari, C. R. and R. J. Naiman. 1994. A multi-scale assessment of exotic plants on the Olimpic Peninsula, Washington. Journal of Vegetation Science 5: 247–58.
di Castri, F. 1991. An ecological overview of the five regions of the world with a Mediterranean climate. p. 3–16. In R. H. Groves and F. di Castri (eds.) Biogeography of Mediterranean Invasions. Cambridge University Press, Cambridge, UK.
El-Ghareeg, R. and M. A. Shabana. 1990. Vegetation-environmental relationships in the bed of Wadi El-Sheikh of Southern Sinai. Vegetatio 90: 145–57.
Ferreira, M. T. and I. S. Moreira. 1995. The invasive component of river flora under the influence of Mediterranean agricultural systems. p. 117–27. In P. Pysek, K. Prach, M. Rejmanek, and M. Wade (eds.) Plant Invasions — General Aspects and Special Problems. SPB Academic Publishing, Amsterdam, The Netherlands.
Friedman, J. M., W. R. Osterkamp, M. L. Scott, and G. T. Auble. 1998. Downstream effects of dams on channel geometry and bottomland vegetation: regional patterns in the Great Plains. Wetlands 18: 619–33.
Gasith, A. and V. H. Resh. 1999. Streams in Mediterranean climate regions: abiotic influences and biotic responses to predictable events. Annual Reviews of Ecology and Systematics 30: 51–81.
Giller, P. S. and B. Malmqvist. 1998. The Biology of Streams and Rivers. Oxford University Press, Oxford, UK.
Gladwing, D. N. and J. E. Roelle. 1998. Survival of plains cottonwood (Populus deltoides subsp. monilifeva) and saltcedar (Tamarix remosissima) seedlings in response to flooding. Wetlands 18: 669–74.
Glavac, V., C. Grillenberger, W. Hakes, and H. Ziezold. 1992. On the nature of vegetation boundaries, undisturbed floodplain communities as an example-a contribution to the continuum/ discontinuum controversy. Vegetatio 101: 123–44.
Gordon, N. D., T. A. McMahon, and B. L. Finlayson. 1992. Stream Hydrology. John Wiley & Sons, Inc., Chichester, UK.
Grime, J. P. 1979. Plant Strategies and Vegetation Processes. John Wiley & Sons, Inc., Chichester, UK.
Hood, G. W. and R. J. Naiman. 2000. Vulnerability of riparian zones to invasions by exotic vascular plants. Plant Ecology 148: 105–14. http://www.rivermurray.sa.gov.au/major/salinity.html#irrigation. http://www.rjb.csic.es/floraiberica/.
Hupp, C. R. 1992. Riparian vegetation recovery patterns following stream channelization: a geomorphic perspective. Ecology 73: 1209–26.
Hupp, C. R. and W. R. Osterkamp. 1996. Riparian vegetation and fluvial geomorphic processes. Geomorphology 14: 277–95.
Jacobson, P. J., K. M. Jacobson, P. L. Angermier, and D. S. Cherry. 2000. Hydrologic influences on soil properties along ephemeral rivers in the Namib Desert. Journal of Arid Environments 45: 21–34.
Jolly, I. D., G. R. Walker, and P. J. Thorburn. 1993. Salt accumulation in semi-arid floodplain soils with implications for forest health. Journal of Hydrology 150: 589–614.
Keddy, P. A. 2000. Wetland Ecology: Principles and Conservation. Cambridge University Press, Cambridge, UK.
Lite, S. J., K. J. Bagstad, and J. C. Stromberg. 2005. Riparian plant species richness along lateral and longitudinal gradients of water stress and flood disturbance, San Pedro River, Arizona, USA. Journal of Arid Environments 63: 785–813.
Lite, S. J. and J. C. Stromberg. 2005. Surface water and groundwater thresholds for maintaining Populus-Salix forests, San Pedro River, Arizona. Biological Conservation 125: 153–67.
Lyon, J. and C. L. Sagers. 1998. Structure of herbaceous plant assemblages in a forested riparian landscape. Plant Ecology 138: 1–16.
Marier, R. J., J. C. Stromberg, and D. T. Patten. 2001. Growth response of Populus fremontii, Salix gooddingii, and Tamarix ramosissima seedlings under different nitrogen and phosphorus concentrations. Journal of Arid Environments 49: 133–46.
McCune, B. and J. A. Antos. 1981. Correlations between forest layers in the Swan Valley, Montana. Ecology 62: 1196–1204.
McIntyre, S., S. Lavorel, and R. O. Tremont. 1995. Plant life history attributes with relationships to disturbance response in herbaceous vegetation. Journal of Ecology 83: 31–41.
McQuarrie, A. D. R. and C.-L. Tsai. 1998. Regression and Time Series Model Selection. World Scientific Publishing Co., Toh Tuck Link, Singapore.
Naiman, R., H. Décamps, and M. E. McClain. 2005. Riparia: Ecology, Conservation, and Management of Streamside Communities. Elsevier/Academic Press, San Diego, CA, USA.
Nilsson, C., E. Nilsson, M. E. Johansson, M. Dynesius, G. Grelsson, S. Xiong, R. Jansson, and M. Danvind. 1993. Processes structuring riparian vegetation. Current Topics in Botany Research 1: 419–31.
Pettit, N. E., R. H. Froend, and P. M. Davies. 2001. Identifying the natural flow regime and the relationship with riparian vegetation for two contrasting western Australian rivers. Regulated Rivers: Research and Management 17: 201–15.
Petts, G. E. and C. Amoros. 1996. Fluvial Hydrosystems. Chapman & Hall, London, UK.
Phillips, F. M., J. F. Hogan, S. K. Mills, and J. M. H. Hendrickx. 2003. Environmental tracers applied to quantifying causes of salinity in arid-region rivers: preliminary results from the Rio Grande, Southwestern USA. p. 327–34. In A. S. Alsharhan and W. W. Wood (eds.) Water Resources Perspectives: Evaluation, Management and Policy. Elsevier Science, New York, NY, USA.
Planty-Tabacchi, A. M., E. Tabacchi, R. J. Naiman, C. Deferrari, and H. Décamps. 1996. Invasibility of species-rich communities in riparian zones. Conservation Biology 10: 598–607.
Pulido-Bosch, A., A. Vallejos, W. Martin-Rosales, L. Molina, J. M. Andreu, and J. M. Calaforra. 1998. La surexploitation dans certains aquifèrs du sud-est espagnol. International Conference on World Water Resources at the Beginning of the 21st Century. Proceeding: 293–98, UNESCO, Paris, France.
Ríos, S. and J. Alcaraz. 1996. Flora de las Riberas y Zonas Húmedas de la Cuenca del Río Segura. Universidad de Murcia, Murcia, Spain.
Robertson, A. I. and R. W. Rowling. 2000. Effects of livestock on riparian zone vegetation in an Australian dryland river. Regulated Rivers: Research and Management 16: 527–41.
Rogers, R. S. 1981. Mature mesophytic hardwood forest: community transitions, by layer, from east-central Minnesota to southeastern Michigan. Ecology 62: 1634–47.
Sabo, J. L., R. Sponseller, M. Dixon, K. Gade, T. Harms, J. Heffernan, A. Jani, G. Katz, C. Soycan, J. Watts, and J. Welter. 2005. Riparian zones increase regional species richness by harboring different, not more, species. Ecology 86: 56–62.
Sagers, C. L. and J. Lyon. 1997. Gradient analysis in a riparian landscape: contrast among forest layer. Forest Ecology and Management 96: 13–26.
Salinas, M. J., G. Bianca, and A. T. Romero. 2000a. Evaluating riparian vegetation in semi-arid Mediterranean watercourses in the south-eastern Iberian Peninsula. Environmental Conservation 27: 24–35.
Salinas, M. J., G. Bianca, and A. T. Romero. 2000b. Riparian vegetation and water chemistry in a basin under semiarid Mediterranean climate, Andarax River, Spain. Environmental Management 26: 539–52.
Shafroth, P. B., J. M. Friedman, and L. S. Ischinger. 1995. Effects of salinity on establishment of Populus freemontii (cottonwood) and Tamarix ramosissima (saltcedar) in Southwestern United States. Great Basin Naturalist 55: 58–65.
Shafroth, P. B., J. C. Stromberg, and D. T. Patten. 2002. Riparian vegetation response to altered disturbance and stress regimes. Ecological Applications 12: 107–23.
Sobrino, E., M. Sanz-Elorza, E. Dana, and A. González-Moreno. 2002. Invasibility of a coastal strip in NE Spain by alien plants. Journal of Vegetation Science 13: 585–94.
Stromberg, J. C. 1993. Instream flow models for mixed deciduous riparian vegetation within a semiarid region. Regulated Rivers: Research and Management 8: 225–35.
Stromberg, J. C., K. J. Bagstad, J. M. Leenhouts, S. J. Lite, and E. Makings. 2005. Effects of stream flow intermittency on riparian vegetation of a semiarid region river (San Pedro River, Arizona). River Research and Applications 21: 925–38.
Stromberg, J. C., M. Briggs, C. Gourley, M. Scott, P. Shafroth, and L. Stevens. 2004. Human alterations of riparian ecosystems. p. 101–26. In M. Baker, Jr., P. Ffolliott, L. DeBano, and D. G. Neary (eds.) Riparian Areas of the Southwestern United States: Hydrology, Ecology and Management. CRC Press/ Lewis Publishers, Boca Raton, FL, USA.
Stromberg, J. C. and M. K. Chew. 1997. Herbaceous exotics in Arizona’s riparian ecosystems. Desert Plants 13: 11–17.
Stromberg, J. C., L. Gengarelly, and B. F. Rogers. 1997. Exotics herbaceous species in Arizona’s riparian ecosystems. p. 45–47. In J. H. Brock, M. Wade, P. Pysek, and D. Green (eds.) Plant Invasions: Studies from North America and Europe. Backhuys, Leiden, The Netherlands.
Tabacchi, E., D. L. Correll, R. Hauer, G. Pinay, A. M. Planty-Tabacchi, and R. C. Wissmar. 1998. Development, maintenance and role of riparian vegetation in the river landscape. Freshwater Biology 40: 497–516.
Tabacchi, E., A. M. Planty, M. J. Salinas, and H. Décamps. 1996. Landscapes structure and diversity in riparian plant communities. a longitudinal comparative study. Regulated Rivers: Research and Management 12: 367–90.
Tabacchi, E., A. M. Planty-Tabacchi, L. Roques, and E. Nadal. 2005. Seed inputs in riparian zones: implications for plant invasion. River Research and Applications 21: 299–313.
ter Braak, C. J. F. 1986. Canonical correspondence analysis: a new eigenvector technique for multivariate direct gradient analysis. Ecology 67: 1167–79.
ter Braak, C. J. F. 1987. The analysis of vegetation-environment relationships by canonical correspondence analysis. Vegetatio 69: 69–77.
ter Braak, C. J. F. and P. Smilauer. 1998. CANOCO Reference Manual and User’s Guide to Canoco for Windows: Software for Canonical Community Ordination (version 4). Microcomputer Power, Ithaca, NY, USA.
Tutin, T. G., et al. (eds.). 1964, 1968, 1972, 1976, 1980. Flora Europaea, Volumes 1–5. Cambridge University Press, Cambridge, UK.
Walker, K. F., F. Sheldon, and J. T. Puckridge. 1995. A perspective on dryland river ecosystems. Regulated Rivers: Research and Management 11: 85–104.
Wetzel, R. G. and G. E. Likens. 1991. Limnological Analyses, second edition. Springer-Verlag, New York, NY, USA.
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Salinas, M.J., Casas, J.J. Riparian vegetation of two semi-arid Mediterranean rivers: Basin-scale responses of woody and herbaceous plants to environmental gradients. Wetlands 27, 831–845 (2007). https://doi.org/10.1672/0277-5212(2007)27[831:RVOTSM]2.0.CO;2
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DOI: https://doi.org/10.1672/0277-5212(2007)27[831:RVOTSM]2.0.CO;2