Oecologia (1988) 76:273-277 Oecologia Springer-Verlag 1988 Distribution of C3 and C4 grasses at different altitudes in a temperate arid region of Argentina J.B. Cavagnaro Ecofisiologia Vegetal, IADIZA (Instituto Argentino de Invest. de Zonas Aridas), C.C. 507, 5500 Mendoza, Argentina Summary. The distribution of native C3 and C4 grasses seems to be linked to certain environmental factors such in a temperate arid region of Mendoza, Argentina, was as temperature and water availability (Teeri and Stowes studied in six areas at different altitudes. C4 species predom- 1976; Tiezsen et al. 1979; Rundel 1980; Barnes and Harr- inate at low elevations in both relative species abundance ison 1982; Barnes et al. 1983; Hattersley 1983). In addition, and plant cover. At high elevations C3 species are dominant in this family most of the species have been clearly deter- in cover and composition. At medium altitudes mined as C3 or C~ on the ground of their anatomical and (1100-t600 m) grass species composition is balanced but physiological characteristics (Smith and Brown 1973; plant cover of Cs species is greater. Of 31 genera in the Downton 1975; Hattersley and Watson 1975). whole area, 19 were C4. Only the genera Stipa (C3) and The aim of this paper is to report the relative distribu- Aristida (C4) were present in all the six areas surveyed. tion and coverage of C3 and C4 grasses in areas located The pattern of grass distribution shows high correlation at different altitudes in a temperate arid region of Mendoza, with evapotranspiration and temperature parameters, but Argentina. The relation between these aspects and some low correlation with rainfall. The relation between grass meteorological parameters from these areas is discussed. distribution and different climatic parameters is discussed. Key words: Grasses - Photosynthetic type - Distribution Material and methods - Climate - Altitude - Argentina The C4 type was established by the presence of Kranz anat- omy in cross-sections of leaf blades or from the data com- piled by other authors (Smith and Epstein 1971 ; Smith and Brown 1973 ; Downton 1975 ; Hattersley and Watson 1975). The most important characteristics of plants with different Leaf blades were obtained from field plants or from herbar- CO2 fixation pathways (C3, C4, CAM) have been summa- ium material. rized by Black (1973). Plants belonging to these groups The region surveyed is located between 32~ , and show different anatomical, biochemical, physiological, and 34~ and 69007 , and 68~ (Fig. 1). The study areas ecological characteristics. Thus, C, species have a higher are located at different elevations ranging from 570 to optimum temperature for photosynthesis, higher light in- 2400 m (Fig. 2): tensity for saturation, higher water use efficiency and lack detectable photorespiration. In contrast, C3 plants achieve Area I: plain, 560-580 m, shrubland their maximum photosynthetic rates at lower temperatures Area II: piedmont, 750-1100 m, shrubland and lower light intensities, and they show photorespiration. On the basis of previous statements, it has been postu- Area III: piedmont, 940-1400 m, shrubland lated that the photosynthetic type confers adaptive advan- Area IV: piedmont, 1200-1600 m, shrubland tages under certain environmental conditions. C4 plants should be favoured by high temperature, high irradiance, Area V: piedmont, 1300-1800 m, shrubland and limited water supply. C3 species should be favoured by Area VI: highland plain, 2200-2600 m, grassland cool, shade, and humid conditions (Ehleringer and Bj6rk- man 1977; Ehleringer 1978). Despite these generalizations, According to the phytogeographical classification of Ca- some exceptions have been reported where C4 species can brera (1976) areas I, II, and III correspond to the "Monte" succesfully compete in cool or shaded habitats (Caldwell province. Areas IV and V would be transitional between etal. 1977; Pearcy and Troughton 1975). Besides, other "Monte" and "Prepuna", and finally area VI belongs to plant features, apart from the photosynthetic pathway, can "Prepuna" province. Those areas related to the "Monte" play a major role in the competitive ability of plants (Baskin are characterized by the dominance of Zygophyllaceae, spe- and Baskin 1978; Pearcy and Ehleringer 1984). Moreover, cially of the genus Larrea (Morello 1958). Syvertsen et al. (1976) have reported that in some desert The species list for area I was compiled by the author. communities C3 species surpass C4 ones in presence and The rest of the distribution data was taken from: Roig biomass. (1976) (areas II and IV); Martinez Carretero (1982, 1985) In the family Poacea, C3 and C4 species show a well (areas III and V) and Passera et al. (1983) (area VI). Species defined pattern of geographical distribution. This pattern list in these papers are based on extensive and detailed phy- 274 Table l. C4 grasses and plant cover in the study areas Species Areas I II III IV V VI * Aristida adscencionis + + + + + -- Aristida aft. humilia ..... + - * Aristida mendocina 2 - + - + - * Aristida spegazzini -- -- + -- + + Bothriochloa springfieldii - - 1 - + + * Bouteloua aristidoide + ..... Bouteloua barbata + + .... Bouteloua curtipendula - - + - + - * Bouteloua lophostachya - + - + - - * Chloris castilloniana + ..... * Cottea pappophoroides + + - + - - * Dig#aria californica 1 -- + + + - * Diplachne dubia + + + + + - * Eragrostis eilianensis + + - + -- -- Eragrostis lugens .... + + * Eragrostis pilosa + + - + -- -- * Erioneurum pilosum -- -- + -- + -- Muehlenbergia asperifolia - - + - - - Muehlenbergia torreyi ..... + * Munroa mendocina + 1 - + - - * Neobouteloua lophostachya + -- + -- -- -- N. * Panicum urvilleanum + ..... * Pappophorum caespitosum 2 + + + + - * Pappophorum philippianurn + + + + + - * Scleropogon brevifolius + ..... * Setaria leucopila + + + + + -- Fig. 1. The location of the study area in Mendoza, west Argentina * Setaria mendocina + ..... Setaria pampeana - - + - - - * Sporobolus cryptandrus 1 - + 1 + - * Tragus berteronianus + ..... * Trichloris crinita 1 + + + - - I00. Total species present 21 12 16 13 14 4 C4 gr=~asse"~ C 3 grasses -, species absent; +, less than 0.1% of plant coverage; 1, 0-5% 80. cover; 2, 5%-25% cover; 3, 25%-50% cover. * Kranz anatomy; e.. inspected by the author o 8 60. E tosociological work and the species mentioned are included 0 r 40. t"-.../",,.. in the IADIZA Herbarium (MERL). ill -1 The region has a temperate-arid climate. Rainfall occurs mainly in summer and originates in convective storms. 20 / -.... Snow is important only in area VI, where 100-120 mm per ! year have been measured. The climatic data were obtained from meteorological 0 s6o 660 e6o ,ioo ,. oo ,goo aioo z,ioo stations located in the study areas (Estrella, unpublished data; Vich 1987). Values for temperature and rainfall are altitude [meters) averaged over 15 and 11 years respectively. Potential evapo- transpiration and water deficits were estimated according to Burgos and Vidal (1951). Grass cover values in Table 1 E W follow the abundance-dominance criterium of Braun-Blan- quet's phytosociological method (Roig 1973). 5000 oE 2000 Results "O .m A clear pattern of grass distribution as a function of altitude is observed in Fig. 2. C4 species are dominant at lower a I000 elevations. Between 1100 and 1600m the relative abun- dance of both types is quite similar. At the highest eleva- tions C3 species are dominant. 6 // 9o ,oo Out of 31 genera found, 12 were C3 and 19 were CA, Fig. 2. Relative grass species abundance and altitudes of the study though the latter includes the genus Panicum which has areas both C3 and C4 species. In this case only Panicum urviI- 275 Table 2. C3 grasses and plant cover in the study areas Table 3. Altitude and climatic parameters of the study areas Species Areas I II III IV V IV Parameters Areas I II III IV V VI * Bromus araucanus ..... + Altitude (m) 570 920 1170 1450 ~1600 2400 * Bromus brevis - - - + + 1 Mean annual 15.7 16.3 13.6 14.2 10.5 7.8 * Bromus sp. - - -- -- + + temperature (~ Cortaderia rudiuscula - - + - - - Elymus erianthus _ _ + + + _ January 24.4 24.2 21.5 21.0 17.1 13.5 Elytrigia atternuatta ..... + mean temperature (~ * Elytrigia mendocina ..... + July mean temperature 6.9 8.1 6.1 7.4 5.0 2.4 * Festuca rubra ..... + (~ * Koeleria mendocinensis ..... + January mean maximum 32.5 30.0 28.3 25.0 22.7 18.7 Melica andina .... + + temperature (~ * Piptochaetium napostaense - - + + + + * Poa lanuginosa .... + + January mean minimum 16.4 18.5 14.0 13.3 12.9 8.4 * Poa resinulosa .... + 2 temperature (~ Poa ligularis - - + - + + Annual rainfall (mm) 344 255 164 200 194 421 * Polypogon monspeliensis - - + - + + October-March 264 192 135 157 153 344 Sehismus barbatus .... + - rainfall (mm) Stipa debilis - - + - + - Annual 829 828 726 727 630 558 * Stipa ichu + - 2 + 2 + Stipa paramilloensis .... + + evapotranspiration * Stipa plumosa _ + + + + _ (ram) Stipa psittacorum - - + - + - October-March 642 645 558 554 466 411 Stipa sanluisensis - - 1 + 2 - evapotranspiration Stipa scirpea - - + - 1 + (mm) * Stipa tenuis - - + 1 + - Water deficit from 378 454 423 397 313 67 * Stipa tenuissima - - + - 1 3 October to March (ram) * Stipa vaginata - - 1 1 1 + C4 grass percentage 95.5 92.3 53.3 61.9 41.1 18.2 Total species present 1 1 14 8 20 18 Ca grass percentage 4.5 7.7 46.7 38.1 58.9 81.8 -, species absent; +, less than 0.1% of plant cover; 1, 0-5% cover; 2, 5%-25% cover; 3, 25%-50% cover. * Lack of Kranz anatomy; inspected by the author Table 4. Linear regression analysis