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2004
- handle: 10670/1.ukdqo2
- 0378-1844
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http://www.redalyc.org/revista.oa
Interciencia
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Multidisciplinarias (Ciencias Sociales) Nitrogen Mycorrhiza Phosphorus Defoliation Shoot GrowthSujets proches
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Carlos A. Busso et al., « Soil resource acquisition mechanisms, nutrient concentrations and growth in perennial grasses », Interciencia, ID : 10670/1.ukdqo2
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"Relationships among soil resource acquisitionmechanisms and componentsof shoot tissue production were studiedin the late-seral, grazing tolerant and competitive Stipa clarazii Ball and inthe earlier-seral, less grazing tolerantand competitive S. tenuis Phil and S.ambigua Speg. History of grazing and/or fire determines abundance of theseC3 perennial tussock grasses in temperate,semiarid rangelands of Argentina.We hypothesized lower values forroot length density (RLD) and percentagevesicular-arbuscular mycorrhizal(%VAM) colonization on defoliated thanon undefoliated plants, and also greatervalues for RLD and %VAM colonizationon defoliated and undefoliated plants ofS. clarazii than on those of the othertwo species, because of its greater competitiveability and defoliation tolerance.Field study was conducted withina 2-year exclosure to domestic herbivory.One group of plants was defoliatedonce to 5cm stubble height inearly spring, while another group wasdefoliated twice, in early and midspring.A third group remained undefoliated(control). Measurements wereconducted 6-10 days after each defoliation,and at the end of the growing season.RLD and %VAM colonization weresimilar on defoliated plants and on undefoliatedcontrols in all three species.Greater regrowth production in S. claraziiwas not associated with higherRLD and %VAM colonization in themore competitive species. The positiverelationship between RLD and eitherdry weight production or tissue N andP concentration in these species suggeststhat their root activity must bemaintained after defoliation to rapidlyreestablish a photosynthetic canopy andkeep resource supply at equilibrium. Allperennial grasses showed consistentlyhigh %VAM colonization, suggestingthey may function as obligate mycotrophs.The negative correlation between%VAM colonization and RLD orsoil available P for S. clarazii couldrepresent a mechanism to avoid shiftsfrom mutualism to parasitism in theplant-mycorrhizae relationship."