Abstract
Above-and belowground biomass distribution, isotopic composition of soil and xylem water, and carbon isotope ratios were studied along an aridity gradient in Patagonia (44–45°S). Sites, ranging from those with Nothofagus forest with high annual rainfall (770 mm) to Nothofagus scrub (520 mm), Festuca (290 mm) and Stipa (160 mm) grasslands and into desert vegetation (125 mm), were chosen to test whether rooting depth compensates for low rainfall. Along this gradient, both mean above-and belowground biomass and leaf area index decreased, but average carbon isotope ratios of sun leaves remained constant (at-27‰), indicating no major differences in the ratio of assimilation to stomatal conductance at the time of leaf growth. The depth of the soil horizon that contained 90% of the root biomass was similar for forests and grasslands (about 0.80–0.50 m), but was shallower in the desert (0.30 m). In all habitats, roots reached water-saturated soils or ground water at 2–3 m depth. The depth profile of oxygen and hydrogen isotope ratios of soil water corresponded inversely to volumetric soil water contents and showed distinct patterns throughout the soil profile due to evaporation, water uptake and rainfall events of the past year. The isotope ratios of soil water indicated that high soil moisture at 2–3 m soil depth had originated from rainy periods earlier in the season or even from past rainy seasons. Hydrogen and oxygen isotope ratios of xylem water revealed that all plants used water from recent rain events in the topsoil and not from water-saturated soils at greater depth. However, this study cannot explain the vegetation zonation along the transect on the basis of water supply to the existing plant cover. Although water was accessible to roots in deeper soil layers in all habitats, as demonstrated by high soil moisture, earlier rain events were not fully utilized by the current plant cover during summer drought. The role of seedling establishment in determining species composition and vegetation type, and the indirect effect of seedling establishment on the use of water by fully developed plant cover, are discussed in relation to climate change and vegetation modelling.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Aguiar MR, Sala OE (1994) Competition, facilitation, seed distribution and the origin of patches in a Patagonian steppe. Oikos 70:26–34
Aguiar MR, Soriano A, Sala OE (1992) Competition and facilitation in the recruitment of seedlings in Patagonian steppe. Funct Ecol 6:66–70
Caldwell MM (1994) Exploiting nutrients in fertile soil microsites. In: Caldwell MM, Pearcy RW (eds) Exploitation of environmental heterogeneity by plants. Academic Press, San Diego, pp 325–348
Canadell J, Jackson RB, Ehleringer JR, Mooney HA, Sala OE, Schulze E-D (1996) Maximum rooting depth of vegetation at the global scale. Oecologia (in press)
Coleman ML, Shepherd TJ, Durham JJ, Rousse JE, Moore GR (1982) Reduction of water with zinc for hydrogen isotope analysis. Anal Chem 54:993–995
Dawson TE (1993) Water sources of plants as determined from xylem-water isotopic composition: perspectives on plant competition, distribution, and water relations. In: Ehleringer JR, Hall AE, Farquhar GD (eds) Stable isotopes and plant carbonwater relations. Academic Press, San Diego, pp 465–496
Farquhar GD, O'Leary MHO, Berry JA (1982) On the relationship between carbon isotope discrimination and the intercellular carbon dioxide concentration in leaves. Aust J Plant Physiol 9:121–137
Jackson RB, Canadell J, Ehleringer JR, Mooney HA, Sala OE, Schulze E-D (1996) A global analysis of root distributions for terrestrial biomes. Oecologia 108:389–411
Melillo J, Prentice C, Schulze E-D, Farquhar G, Sala OE (1996) Terrestrial ecosystems: responses to global environmental change and feedbacks to climate. IPCC Chapter 9. Cambridge Univ. Press, Cambridge, UK pp 445–481
Prentice IC (1992) Climate change and long-term vegetation dynamics. In: Glenn-Lewin DC, Peet RA, Veblen T (eds) Plant succession: theory and predictions. Chapman and Hall, New York, pp 293–339
Rawls WJ (1983) Estimating soil bulk density from particle size analysis and organic matter content. Soil Sci 135:123–125
Sala OE, Golluscio RA, Lauenroth WK, Soriano A (1989) Resource partitioning between shrubs and grasses in the Patagonian steppe. Oecologia 81:501–505
Schulze E-D, Schulze W, Kelliher FM, Vygodskaya NN, Ziegler W, Kobak KI, Koch H, Arneth A, Kusnetsova WA, Sogachev A, Issajev A, Bauer G, Hollinger DY (1995) Above-ground biomass and nitrogen nutrition in a chronosequence of pristine Dahurian Larix stands in Eastern Siberia. Can J For Res 25: 943–960
Socki RA, Karisson HA, Gibson EK Jr (1992) Extraction technique for the determination of oxygen-18 in water using preevacuated glass vials. Anal Chem 64:829–830
Soriano A (1983) Deserts and semi-deserts of Patagonia. In: West NE (ed) Temperate deserts and semi-deserts. Elsevier, Amsterdam, pp 423–459
Soriano A (1990) Missing strategies for water capture in the Patagonian semidesert. Acad Nat Cienc Ex Fis Nat Buenos Aires Monogr 5:135–139
Soriano A, Sala OE (1986) Emergence and survival of Bromus setifolius seedlings in different microsites of a Patagonian arid steppe. Isr J Bot 35:91–100
Soriano A, Golluscio RA, Satorre E (1987) Spatial heterogeneity of the root system of grasses in the Patagonian arid steppe. BullTorrey Bot Club 114:103–108
Stitt M, Schulze E-D (1994) Plant growth, storage, and resource allocation: from flux control in a metabolic chain to the whole plant level. In: Schulze E-D (ed) Flux control in biological systems. From enzymes to populations and ecosystems. Academic Press, San Diego, pp 57–118
Walter H (1939) Grasland, Savanne und Busch der ariden Teile Afrikas in ihrer ökologischen Bedingtheit. Jb Wiss Bot 87:750–860
Walter H (1966) Die Vegetation der Erde, Bd. II. Die gemäßigten und arktischen Zonen. Fischer, Stuttgart
Whittaker RH, Niering WA (1975) Vegetation of the Santa Catalina Mountains, Arizona. V. Biomass, production, and diversity along the elevation gradient. Ecology 56:771–790
Witt CT de (1958) Transpiration and crop yields (Agricultural research report 64). PUDOC, Wageningen
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Schulze, E.D., Mooney, H.A., Sala, O.E. et al. Rooting depth, water availability, and vegetation cover along an aridity gradient in Patagonia. Oecologia 108, 503–511 (1996). https://doi.org/10.1007/BF00333727
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00333727