N-fertilization does not alleviate grass competition induced reduction of growth of African savanna species

Michael Cramer, W.J. Bond

    Research output: Contribution to journalArticle

    8 Citations (Scopus)

    Abstract

    Background and aims: Below-ground grass competition limits woody establishment in savannas. N2-fixing legumes may, however, have a nutritional advantage over broad-leaved species. We hypothesised that broad-leaved non-legume savanna thicket species would be more severely constrained by grass competition for N and consequently respond more to N-fertilization than the legume, Acacia karroo. Methods: A. karroo and five non-legume thicket species (Maytenus senegalensis, M. heterophylla, Euclea divinorum, Ziziphus mucronata, Schotia brachypetala) were grown together in an irrigated competition experiment with clipped-, unclipped-grass and without grass with/without N-fertilizer. The biomass, foliar nutrient, δ13C and δ15N of grasses and woody species were determined. Results: Growth of both A. karroo and the non-legume species was equally sensitive (c. 90 % reduction) to both clipped- and unclipped-grass competition, regardless of N-fertilization. With grass competition, however, foliar [N] increased and δ15N decreased in response to N-fertilization. Grass biomass accumulation was also unchanged by fertilisation, despite increases in foliar [N] and decreases in δ15N. Conclusions: The N2-fixation capacity of A. karroo provided no growth advantage over non-legumes. The lack of responsiveness of biomass accumulation by both the woody species and the grasses to N-fertilization, despite evidence that plants accessed the N-fertilizer, indicates limitation by other nutrients. © 2012 Springer Science+Business Media B.V.
    Original languageEnglish
    Pages (from-to)563-574
    JournalPlant and Soil
    Volume366
    Issue number1-2
    DOIs
    Publication statusPublished - 2013

    Fingerprint

    savanna
    growth retardation
    savannas
    grass
    grasses
    Acacia karroo
    Schotia
    biomass production
    biomass
    nitrogen fertilizers
    legumes
    fertilizer
    Maytenus
    nutrient
    nutrients
    fixation

    Cite this

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    title = "N-fertilization does not alleviate grass competition induced reduction of growth of African savanna species",
    abstract = "Background and aims: Below-ground grass competition limits woody establishment in savannas. N2-fixing legumes may, however, have a nutritional advantage over broad-leaved species. We hypothesised that broad-leaved non-legume savanna thicket species would be more severely constrained by grass competition for N and consequently respond more to N-fertilization than the legume, Acacia karroo. Methods: A. karroo and five non-legume thicket species (Maytenus senegalensis, M. heterophylla, Euclea divinorum, Ziziphus mucronata, Schotia brachypetala) were grown together in an irrigated competition experiment with clipped-, unclipped-grass and without grass with/without N-fertilizer. The biomass, foliar nutrient, δ13C and δ15N of grasses and woody species were determined. Results: Growth of both A. karroo and the non-legume species was equally sensitive (c. 90 {\%} reduction) to both clipped- and unclipped-grass competition, regardless of N-fertilization. With grass competition, however, foliar [N] increased and δ15N decreased in response to N-fertilization. Grass biomass accumulation was also unchanged by fertilisation, despite increases in foliar [N] and decreases in δ15N. Conclusions: The N2-fixation capacity of A. karroo provided no growth advantage over non-legumes. The lack of responsiveness of biomass accumulation by both the woody species and the grasses to N-fertilization, despite evidence that plants accessed the N-fertilizer, indicates limitation by other nutrients. {\circledC} 2012 Springer Science+Business Media B.V.",
    author = "Michael Cramer and W.J. Bond",
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    doi = "10.1007/s11104-012-1456-4",
    language = "English",
    volume = "366",
    pages = "563--574",
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    N-fertilization does not alleviate grass competition induced reduction of growth of African savanna species. / Cramer, Michael; Bond, W.J.

    In: Plant and Soil, Vol. 366, No. 1-2, 2013, p. 563-574.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - N-fertilization does not alleviate grass competition induced reduction of growth of African savanna species

    AU - Cramer, Michael

    AU - Bond, W.J.

    PY - 2013

    Y1 - 2013

    N2 - Background and aims: Below-ground grass competition limits woody establishment in savannas. N2-fixing legumes may, however, have a nutritional advantage over broad-leaved species. We hypothesised that broad-leaved non-legume savanna thicket species would be more severely constrained by grass competition for N and consequently respond more to N-fertilization than the legume, Acacia karroo. Methods: A. karroo and five non-legume thicket species (Maytenus senegalensis, M. heterophylla, Euclea divinorum, Ziziphus mucronata, Schotia brachypetala) were grown together in an irrigated competition experiment with clipped-, unclipped-grass and without grass with/without N-fertilizer. The biomass, foliar nutrient, δ13C and δ15N of grasses and woody species were determined. Results: Growth of both A. karroo and the non-legume species was equally sensitive (c. 90 % reduction) to both clipped- and unclipped-grass competition, regardless of N-fertilization. With grass competition, however, foliar [N] increased and δ15N decreased in response to N-fertilization. Grass biomass accumulation was also unchanged by fertilisation, despite increases in foliar [N] and decreases in δ15N. Conclusions: The N2-fixation capacity of A. karroo provided no growth advantage over non-legumes. The lack of responsiveness of biomass accumulation by both the woody species and the grasses to N-fertilization, despite evidence that plants accessed the N-fertilizer, indicates limitation by other nutrients. © 2012 Springer Science+Business Media B.V.

    AB - Background and aims: Below-ground grass competition limits woody establishment in savannas. N2-fixing legumes may, however, have a nutritional advantage over broad-leaved species. We hypothesised that broad-leaved non-legume savanna thicket species would be more severely constrained by grass competition for N and consequently respond more to N-fertilization than the legume, Acacia karroo. Methods: A. karroo and five non-legume thicket species (Maytenus senegalensis, M. heterophylla, Euclea divinorum, Ziziphus mucronata, Schotia brachypetala) were grown together in an irrigated competition experiment with clipped-, unclipped-grass and without grass with/without N-fertilizer. The biomass, foliar nutrient, δ13C and δ15N of grasses and woody species were determined. Results: Growth of both A. karroo and the non-legume species was equally sensitive (c. 90 % reduction) to both clipped- and unclipped-grass competition, regardless of N-fertilization. With grass competition, however, foliar [N] increased and δ15N decreased in response to N-fertilization. Grass biomass accumulation was also unchanged by fertilisation, despite increases in foliar [N] and decreases in δ15N. Conclusions: The N2-fixation capacity of A. karroo provided no growth advantage over non-legumes. The lack of responsiveness of biomass accumulation by both the woody species and the grasses to N-fertilization, despite evidence that plants accessed the N-fertilizer, indicates limitation by other nutrients. © 2012 Springer Science+Business Media B.V.

    U2 - 10.1007/s11104-012-1456-4

    DO - 10.1007/s11104-012-1456-4

    M3 - Article

    VL - 366

    SP - 563

    EP - 574

    JO - Plant and Soil: An International Journal on Plant-Soil Relationships

    JF - Plant and Soil: An International Journal on Plant-Soil Relationships

    SN - 0032-079X

    IS - 1-2

    ER -