Abstract
Introduced African grasses are invading Neotropical savannas and displacing the native herbaceous community. This work, which is part of a program to understand the success of the African grasses, specifically investigates whether introduced and native grasses differ in their water relations. The water relations of the native Trachypogon plumosus and the successful invader Hyparrhenia rufa were studied in the field during two consecutive years in the seasonal savannas of Venezuela. The two C4 grasses differed clearly in their responses to water stress. H. rufa consistently had higher stomatal conductance, transpiration rate, leaf water and osmotic potential and osmotic adjustment than the native T. plumosus. Also, leaf senescence occurred much earlier during the dry season in H. rufa. Both grasses showed a combination of water stress evasion and tolerance mechanisms such as stomatal sensitivity to atmospheric or soil water stress, decreased transpiring area and osmotic adjustment. Evasion mechanisms are more conspicuous in H. rufa whereas T. plumosus is more drought tolerant and uses water more “conservatively”. The evasion mechanisms and oportunistic use of water by H. rufa, characteristic of invading species, contribute to, but only partially explain, the success of this grass in the Neotropical savannas where it displaces native plants from sites with better water and nutrient status. Conversely, the higher water stress tolerance of t. plumosus is consistent with its capacity to resist invasion by alien grasses on shallow soils and sites with poorer nutrient and water status.
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References
Baker HG (1978) Invasion and replacement in Californian and Neotropical grasslands. In: Wilson JR (ed) Plant relations in pastures. CSIRO, Melbourne, pp 368–384
Baruch Z, Ludlow MM, Davis R (1985) Photosynthetic responses of native and introduced C4 grasses from Venezuelan savannas. Oecologia 67:288–293
Baruch Z, Hernández AB, Montilla MG (1989) Dinámica del crecimiento, fenología y repartición de biomasa en gramíneas nativas e introducidas de una sabana Neotropical. Ecotropicos 2:1–13
Bazzaz FA (1986) Life history of colonizing plants: some demographic, genetic and physiological features. In: Mooney HA, Drake JA (eds) Ecology of biological invasions of North America and Hawaii (Ecological Studies 58). Springer, New York, pp 96–110
Cáceres A (1983) Caracteristicas fisicas y químicas del suelo y contenido de nutrientes en la vegetación en un transecto matapastizal de una sabana de Trachypogon. Thesis, Universidad Central de Venezuela, Caracas
Christie EK (1975) Physiological responses of semi-arid grasses. IV. Photosynthetic rates of Thyridolepis mitcheliana and Cenchrus ciliaris leaves. Aust J Agric Res 26:459–466
Christie EK, Moorby J (1975) Physiological responses of semi-arid grasses. I.-The influence of phosphorus supply on growth and phosphorus absorption. Aust J Agric Res 26:423–436
Cutler JM, Rains DW, Loomis RS (1977) The importance of cell size in the water relations of plants. Physiol Plant 40:255–260
D'Antonio CM, Vitousek PM (1992) Biological invasions by exotic grasses, the grass/fire cycle, and global change. Annu Rev Ecol Syst 23:63–87
Daubenmire R (1972) Ecology of Hyparrhenia rufa Nees. in derived savannas in northeastern Costa Rica. J Appl Ecol 9:11–23
Fonseca AS (1983) Identificación de los cuerpos silicosos de las gramíneas de la sabana de Trachypogon de los Llanos Altos Centrales. Bol Soc Venez Cienc Nat 141:17–83
Ford CW, Wilson JR (1981) Changes in levels of solutes during osmotic adjustment to water stress in leaves of four tropical pasture species. Aust J Plant Physiol 8:77–91
Frost F, Medina E, Menaut JC, Solbrig O, Swift M, Walker B (1985) Responses of savannas to stress and disturbance International Union of Biological Sciences, Special Issue 10. Paris
García MJ, Cáceres A (1990) Soil chemistry changes in a forestgrassland vegetation gradient within a fire and grazing protected savanna from the Orinoco Llanos, Venezuela. Acta Oecol 11:775–781
Gollan T, Passioura JB, Munns R (1986) Soil water status affects the stomatal conductance of fully turgid wheat and sunflower leaves. Aust J Plant Physiol 13:459–464
Henson IE (1982) Osmotic adjustment to water stress in pearl millet (Pennisetum americanum (L.) Leeke) in a controlled environment. J Exp Bot 33:78–87
Hsiao TC, Acevedo E, Ferreres E, Henderson DW (1976) Water stress, growth, and osmotic adjustment. Philos Trans R Soc Ser B 273:479–500
Knapp AK (1985) Water relations and growth of three grasses during wet and drought years in a tallgrass prairie. Oecologia 65:35–43
Kramer PJ (1980) Drought, stress and the origin of adaptations. In: Turner NC, Kramer FJ (eds) Adaptation of plants to water and high temperature stress. Wiley-Interscience, New York, pp 7–20
López D, Roa F, Ramirez I (1971) Estudios en un sedimento ferruginoso llamado localmente “ripio”. Bol Soc Venez Cienc Nat 119/120:27–49
Ludlow MM (1980) Stress physiology of tropical pasture plants. Trop Grassl 14:136–145
Ludlow MM, Chu ACP, Clements RJ, Kerslake RG (1983) Adaptation of species of Centrosema to water stress. Aust J Plant Physiol 10:119–130
Medina E (1982) Physiological ecology of neotropical savanna plants. In: Huntley BJ, Walker BH (eds) Ecology of tropical savannas (Ecological Studies 42). Springer-Verlag, Berlin, pp 303–335
Morgan JM (1984) Osmoregulation and water stress in higher plants. Annu Rev Plant Physiol 35:299–348
Munns R (1988) Why measure osmotic adjustment? Aust J Plant Physiol 15:717–726
Parsons JJ (1972) Spread of African grasses to the American tropics. J Range Manage 25:12–17
Passioura JB (1986) Resistance to drought and salinity: avenues for improvement. Aust J Plant Physiol 13:191–201
Pavlik BM (1984) Seasonal changes of osmotic pressure, symplastic water content and tissue elasticity in the blades of dune grasses growing in situ along the coast of Oregon. Plant Cell Environ 7:531–539
Peake DCI, Stirk GD, Henzell ET (1975) Leaf water potentials of pasture plants in a semi-arid subtropical environment. Aust J Exp Agric 15:645–654
Ramia M (1967) Tipos de sabanas en los Llanos de Venezuela. Bol Soc Venez Cienc Nat 112:264–288
Redmann RE (1976) Plant water relationships in a mixed grassland. Oecologia 23:283–295
Sala OE, Lauenroth WK, Parton WJ, Trlica MJ (1981) Water status of soil and vegetation in a shortgrass steppe. Oecologia 48:327–331
San José JJ, Fariñas MR (1991) Temporal changes in the structure of a Trachypogon savanna protected for 25 years. Acta Oecol 12:237–247
San José JJ, Medina E (1975) Effect of fire on organic matter production and water balance in a tropical savanna. In: Golley FB, Medina E (eds) Tropical ecological systems (Ecological Studies 11). Springer-Verlag, New York, pp 251–264
Santamaria JM, Ludlow MM, Fukai S (1990) Contribution of osmotic adjustment to grain yield in Sorghum bicolor (L.) Moench under water limited conditions. I. Water stress before anthesis. Aust J Agric Res 41:51–65
Scholander PFL, Hammel HI, Broadstreet ED, Hemmingsen EA (1965) Sap pressure in vascular plants. Science 148:339–346
Schulze ED (1986) Whole plant responses to drought. Aust J Plant Physiol 13:127–142
Simoes M, Baruch Z (1991) Responses to simulated herbivory and water stress in two tropical C4 grasses. Oecologia 88:173–180
Turner NC (1986) Adaptation to water deficits: a changing perspective. Aust J Plant Physiol 13:175–190
Turner NC, O'Toole JC, Cruz RT, Yambao EB, Ahmad S, Namuco OS, Dingkuhn M (1986) Response of seven diverse rice cultivars to water deficit. II. Osmotic adjustment, leaf elasticity, leaf extention, leaf death, stomatal conductance, and photosynthesis. Fields Crop Res 13:273–286
Tyree MT, Hammel HT (1972) The measurement of the turgor pressure and water relations of plants by the pressure bomb technique. J Exp Bot 23:267–282
Velásquez J (1968) Estudio fitosociológico acerca de los pastizales de las sabanas de Calabozo, Edo. Guárico. Bol Soc Venez Cienc Nat 109:59–101
Vitousek FM (1986) Biological invasions and ecosystem properties: can species make a difference? In: Mooney HA, Drake JA (eds) Ecology of biological invasions of North America and Hawaii (Ecological Studies 58). Springer-Verlag, New York, pp 163–178
Wilson JR, Fisher MJ, Schulze ED, Dolby GR, Ludlow MM (1979) Comparison between pressure-volume dew point hygrometry for determining the water relations characteristics of grass and legume leaves. Oecologia 41:77–88
Wilson JR, Ludlow MM, Fisher MJ, Schulze ED (1980) Adaptation to water stress of the leaf water relations of four tropical forage species. Aust J Plant Physiol 7:207–220
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Baruch, Z., Fernández, D.S. Water relations of native and introduced C4 grasses in a neotropical savanna. Oecologia 96, 179–185 (1993). https://doi.org/10.1007/BF00317730
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DOI: https://doi.org/10.1007/BF00317730