Skip to main content
SpringerLink
Log in

Nitrogen fertilisation reduces grass-induced N2 fixation of tree seedlings from semi-arid savannas

  • Regular Article
  • Published:
Plant and Soil Aims and scope Submit manuscript

Abstract

Aims

Coexistence of trees and grasses in nutrient-poor arid savannas may result in competition for soil N. While grasses may be more effective than woody plants in acquiring N from the soil, some leguminous woody species rely on N2 fixation. We assessed the role of N2 fixation in the N-budget of Acacia mellifera seedlings by varying N supply and grass competition.

Methods

The contribution of N2 fixation to the N-budget of Acacia mellifera seedlings with varying N supply and grass competition was determined by measuring growth, nutrient concentrations, and 15N values.

Results

Tree seedlings were 4-fold taller and had 20-fold more biomass in the absence of grass. Tree foliar δ15N was lower with (−0.25 ± 0.2‰, n = 9) than without grasses (5.2 ± 0.1‰, n = 64). The contribution of N2-fixation to the N budget decreased with increasing N supply. Greater reliance on N2-fixation by trees in the presence of grasses did not result in greater biomass accumulation or tissue [N] relative to tree seedlings grown without grass competition. Tree seedlings competing with grass had significantly more negative δ13C (−29.5 ± 0.6‰) than seedlings without grass competition (−28.8‰ ± 0.5‰).

Conclusions

Induction of N2-fixation by grass may have resulted from competition for nutrients. N2-fixation enables tree seedlings to compensate for limited soil N and survive grass competition at a critical and vulnerable developmental stage of germination and establishment.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4

Similar content being viewed by others

References

  • Allen ON, Allen EK (1981) The Leguminosae: a source book of characteristics, uses and nodulation. Macmillan, London

    Google Scholar 

  • Almeida JPF, Hartwig UA, Frehner M, Nösberger J, Lüscher A (2000) Evidence that P deficiency induces N feedback regulation of symbiotic N2 fixation in white clover (Trifolium repens L.). J Exp Bot 51:1289–1297

    Article  PubMed  CAS  Google Scholar 

  • Aranibar JN, Macko SA, Anderson IC, Potgieter ALF, Sowry R, Shugart HH (2003) Nutrient cycling responses to fire frequency in the Kruger National Park (South Africa) as indicated by stable isotope analysis. Isot Environ Heal Stud 39:141–158

    Article  CAS  Google Scholar 

  • Aranibar JN, Otter L, Macko SA, Feral CJW, Epstein HE, Dowty PR, Eckardt F, Shugart HH, Swap RJ (2004) Nitrogen cycling in the soil-plant system along a precipitation gradient in the Kalahari sands. Global Change Biol 10:359–373

    Article  Google Scholar 

  • Archer S (1989) Have southern Texas savannas been converted to woodlands in recent history? Am Nat 134:545–561

    Article  Google Scholar 

  • Barea JM, Azcón R, Azcón-Aguilar C (1989) Time-course of N2-fixation (15N) in the field by clover growing alone or in mixture with ryegrass to improve pasture productivity, and inoculated with vesicular-arbuscular mycorrhizal fungi. New Phytol 112:399–404

    Article  Google Scholar 

  • Belsky AJ (1994) Influences of trees on savanna productivity: tests of shade, nutrients and tree-grass competition. Ecology 75:922–932

    Article  Google Scholar 

  • Bloor JMG, Barthes L, Leadley PW (2008) Effects of elevated CO2 and N on tree–grass interactions: an experimental test using Fraxinus excelsior and Dactylis glomerata. Funct Ecol 22:537–546

    Article  Google Scholar 

  • Boddey RM, Peoples MB, Palmer B, Dart PJ (2000) Use of the 15N abundance technique to quantify nitrogen fixation by woody perennials. Nutr Cycl Agroecosyst 57:235–270

    Article  Google Scholar 

  • Bond WJ, Smith K, Balfour DA (2001) Acacia species turnover in time and space in an African savanna. J Biogeogr 28:117–128

    Article  Google Scholar 

  • Breman H, de Wit CT (1983) Rangeland productivity and exploitation in the Sahel. Science 221:1341–1347

    Article  PubMed  CAS  Google Scholar 

  • Burke IC, Lauenroth WK, Parton WJ (1997) Regional and temporal variation in net primary production and nitrogen mineralization in grasslands. Ecology 78:1330–1340

    Article  Google Scholar 

  • Carlsson G (2005) Input of nitrogen from N2 fixation to northern grasslands. Dissertation, Swedish University of Agricultural Sciences, Umeå

  • Cohn EJ, Van Auken OW, Bush JK (1989) Competitive interactions between Cynodon dactylon and Acacia smallii seedlings at different nutrient levels. Am Midl Nat 121:265–272

    Article  Google Scholar 

  • Cramer MD, Chimphango SBM, van Cauter A, Waldram MS, Bond WJ (2007) Grass competition induces N2 fixation in some species of African Acacia. J Ecol 95:1123–1133

    Article  CAS  Google Scholar 

  • Cramer MD, Van Cauter A, Bond WJ (2010) Growth of N2-fixing African savanna Acacia species is constrained by belowground competition with grass. J Ecol 98:156–167

    Article  CAS  Google Scholar 

  • Crews TE (1999) The presence of nitrogen fixing legumes in terrestrial communities: evolutionary vs. ecological considerations. Biogeochemistry 46:233–246

    CAS  Google Scholar 

  • Deans JD, Ali OM, Lindley DK, Abdelnour HO (1993) Rhizobial nodulation of Acacia tree species in Sudan: soil inoculum potential and effects of peat. J Trop For Sci 6:56–64

    Google Scholar 

  • Debain S, Curt T, Lepart J (2005) Indirect effects of grazing on the establishment of Pinus sylvestris and Pinus nigra seedlings in calcareous grasslands in relation to resource level. EcoSci 12:192–201

    Article  Google Scholar 

  • DeFaria SM, Lewis GP, Sprent JI, Sutherland JM (1989) Occurrence of nodulation in the Leguminosae. New Phytol 111:607–619

    Article  Google Scholar 

  • De Klerk JN (2004) Bush encroachment in Namibia. Report on phase 1 of the bush encroachment research, monitoring and management project. Ministry of Environment and Tourism, Windhoek, Namibia

  • Doughton JA, Saffigna PG, Vallis I, Mayer RJ (1995) Nitrogen fixation in chickpea. II. Comparison of 15N enrichment and 15N natural abundance methods for estimating nitrogen fixation. Aus J Agric Res 45:225–236

    Article  Google Scholar 

  • Ehleringer JR, Rundel PW (1989) History, units and instrumentation. In: Rundel PW, Ehleringer JR, Nagy KA (eds) Stable isotopes in ecological research. Ecological Studies 68. Springer, Berlin, pp 1–15

    Chapter  Google Scholar 

  • Evans JR (1989) Photosynthesis and nitrogen relationships in leaves of C3 plants. Oecologia 78:9–19

    Article  Google Scholar 

  • Evans DR (2001) Physiological mechanism influencing plant nitrogen isotope composition. Trends Plant Sci 6:121–126

    Article  PubMed  CAS  Google Scholar 

  • Farquhar GD, O’Leary MH, Berry JA (1982) On the relationship between carbon isotope discrimination and intercellular carbon dioxide concentration in leaves. Aust J Plant Physiol 9:121–137

    Article  CAS  Google Scholar 

  • Fetene M (2003) Intra- and inter-specific competition between seedlings of Acacia etbaica and a perennial grass (Hyparrhenia hirta). J Arid Environ 55:441–451

    Article  Google Scholar 

  • Fried M, Broeshart H (1975) An independent measurement of the amount of nitrogen fixed by legume crops. Plant Soil 43:707–711

    Article  Google Scholar 

  • Frost PG, Medina E, Menaut JC, Solbrig O, Swift M, Walker BH (1986) Response of savannas to stress and disturbance. Biology International Special Issue, 10, IUBS, Paris

  • Gehring C, Vlek PLG (2004) Limitations of the 15N natural abundance method for estimating biological nitrogen fixation in Amazonian forest legumes. Basic Appl Ecol 5:567–580

    Article  CAS  Google Scholar 

  • Grellier S, Janeau J-L, Barot S, Ward D (2012) Grass competition is more important than seed ingestion by livestock for Acacia recruitment in South Africa. Plant Ecol 213:899–908

    Article  Google Scholar 

  • Grubb PJ (1977) The maintenance of species richness in plant communities: the importance of the regeneration niche. Biol Rev 52:107–145

    Article  Google Scholar 

  • Handley LL, Odee D, Scrimgeour CM (1994) 15N and 13C patterns in savanna vegetation: dependence on water availability and disturbance. Funct Ecol 8:306–314

    Article  Google Scholar 

  • Hansen AP, Pate JS (1987) Evaluation of the 15N natural abundance method and xylem sap analysis for assessing N2 fixation of understorey legumes in jarrah (Eucalyptus marginata Donn ex Sm) forest in S.W. Australia. J Exp Bot 38:1446–1458

    Article  CAS  Google Scholar 

  • Harrington GH (1991) Effects of soil moisture on shrub seedling survival in semi-arid grassland. Ecology 72:1138–1149

    Article  Google Scholar 

  • Hellsten A, Huss-Danell K (2000) Interaction effects of nitrogen and phosphorus on nodulation in red clover (Trifolium pratense L.). Acta Agric Scand B 50:35–142

    Google Scholar 

  • Herridge DF, Marcellos H, Felton WL, Turner GL, Peoples MB (1995) Chickpea increases soil-N fertility in cereal systems through nitrate sparing and N2-fixation. Soil Biol Biochem 27:545–551

    Article  CAS  Google Scholar 

  • Higgins SI, Bond WJ, Trollope WSW (2000) Fire, resprouting and variability: a recipe for grass-tree coexistence in savannas? J Ecol 88:213–229

    Article  Google Scholar 

  • Högberg P (1986) Nitrogen-fixation and nutrient relations in savanna woodland trees (Tanzania). J Appl Ecol 23:675–688

    Article  Google Scholar 

  • Hooper DU, Johnson L (1999) Nitrogen limitation in dryland ecosystems: responses to geographical and temporal variation in precipitation. Biogeochemistry 46:247–293

    CAS  Google Scholar 

  • House JI, Archer S, Breshears DD, Scholes RJ, Tree-Grass Interactions Participants NCEAS (2003) Conundrum in mixed woody-herbaceous plant systems. J Biogeogr 30:1763–1777

    Article  Google Scholar 

  • Hudak AT, Wessman CA (2001) Textural analysis of high resolution imagery to quantify bush encroachment in Madikwe Game Reserve, South Africa, 1955-1996. Int J Remote Sens 22:2731–2740

    Google Scholar 

  • Huss-Danell K (1997) Actinorrhizal symbioses and their N2 fixation. New Phytol 136:375–405

    Article  CAS  Google Scholar 

  • Jeltsch F, Milton SJ, Dean WRJ, van Rooyen N (1996) Tree spacing and coexistence in semi-arid savannas. J Ecol 84:583–595

    Article  Google Scholar 

  • Jeltsch F, Milton SJ, Dean WRJ, van Rooyen N, Moloney KA (1998) Modelling the impact of small-scale heterogeneities on tree-grass coexistence in semi-arid savannas. J Ecol 86:780–791

    Article  Google Scholar 

  • Johns GG (1984) Soil water storage in a semi-arid Eucalyptus populnea woodland invaded by woody shrubs, and the effects of shrub clearing and tree ring-barking. Rangel J 6:75–85

    Article  Google Scholar 

  • Kambatuku JR, Cramer MD, Ward D (2011a) Savanna tree-grass competition is modified by substrate type and herbivory. J Veg Sci 22:225–237

    Article  Google Scholar 

  • Kambatuku JR, Cramer MD, Ward D (2011b) Intraspecific competition between shrubs in a semi-arid savanna. Plant Ecol 212:701–713

    Article  Google Scholar 

  • Kambatuku JR, Cramer MD, Ward D (2012) Overlap in soil water sources of savanna woody seedlings and grasses. Ecohydrol, published online. doi:10.1002/eco.1273

  • Knight JD, Livingston NJ, Van Kessel C (1994) Carbon isotope discrimination and water-use efficiency of six crops grown under wet and dry land conditions. Plant Cell Environ 17:173–179

    Article  Google Scholar 

  • Knoop WT, Walker BH (1985) Interactions of woody and herbaceous vegetation in a southern African savanna. J Ecol 73:235–253

    Article  Google Scholar 

  • Kraaij T, Ward D (2006) Effects of rain, nitrogen, fire and grazing on tree recruitment and early survival in bush-encroached savanna. Plant Ecol 186:235–246

    Article  Google Scholar 

  • Ladha JK, Peoples MB, Garrity DP, Cupuno VT, Dart PJ (1993) Estimating dinitrogen fixation of hedgerow vegetation using the nitrogen-15 natural abundance method. Soil Sci Soc Am J 57:732–737

    Article  CAS  Google Scholar 

  • Lambers H, Chapin FS, Pons TL (2008) Plant physiological ecology, 2nd edn. Springer, New York

    Book  Google Scholar 

  • Leavitt SW, Idso SB, Kimball BA, Burns JM, Sinha A, Stott L (2003) The effect of long-term atmospheric CO2 enrichment on the intrinsic water-use efficiency of sour orange trees. Chemosphere 50:217–222

    Article  PubMed  CAS  Google Scholar 

  • Loiseau P, Soussanna JF, Lounault F, Delpy R (2001) Soil N contributes to the oscillation of the white clover content in mixed swards of perennial ryegrass under conditions that stimulate grazing over five years. Grass For Sci 56:205–217

    Article  CAS  Google Scholar 

  • Maseyk K, Hemming D, Angert A, Leavitt S, Yakir D (2011) Increase in water-use efficiency and underlying processes in pine forests across a precipitation gradient in the dry Mediterranean region over the past 30 years. Oecologia 167:573–585

    Article  PubMed  Google Scholar 

  • McNeil AM, Pilbeam CJ, Harris HC, Swift RS (1996) Seasonal variation in the suitability of different methods for estimating biological nitrogen fixation by grain legumes under rainfed conditions. Aust J Agric Res 47:1061–1073

    Article  Google Scholar 

  • Menneer JC, Ledgard S, McLay C, Silvester W (2003) The effect of a single application of cow urine on annual N2 fixation under varying simulated grazing intensity, as measured by four 15N techniques. Plant Soil 254:469–480

    Article  CAS  Google Scholar 

  • Meyer KM, Wiegand K, Ward D, Moustakas A (2007) The rhythm of savanna patch dynamics. J Ecol 95:1306–1315

    Article  Google Scholar 

  • Midgley JJ, Bond WJ (2001) A synthesis of the demography of African acacias. J Trop Ecol 17:871–886

    Article  Google Scholar 

  • Miller AJ, Cramer MD (2005) Root nitrogen acquisition and assimilation. Plant Soil 274:1–36

    Article  CAS  Google Scholar 

  • Molele NM, Ringrose S, Matheson W, Vanderpost C (2002) More woody plants? The status of bush encroachment in Botswana’s grazing areas. J Environ Manag 64:3–11

    Article  Google Scholar 

  • O’Connor TG (1995) Acacia karroo invasion of grassland: environmental and biotic effects influencing emergence and establishment. Oecologia 103:214–223

    Article  Google Scholar 

  • Owen AG, Jones DL (2001) Competition for amino acids between wheat roots and rhizosphere microorganisms and the role of amino acids in plant N acquisition. Soil Biol Biochem 33:651–657

    Article  CAS  Google Scholar 

  • Pate JS, Layzell DB, Atkins CA (1979) Economy of carbon and nitrogen in a nodulated and nonnodulated (NO3-grown) legume. Plant Physiol 64:1083–1088

    Article  PubMed  CAS  Google Scholar 

  • Pate JS, Stewart GR, Unkovich M (1983) 15N natural abundance of plant and soil components of a Banksia woodland ecosystem in relation to nitrate utilization, life form, mycorrhizal status and N2-fixing abilities of component species. Plant Cell Environ 16:365–373

    Article  Google Scholar 

  • Peoples MB, Herridge DF, Ladha JK (1995) Biological nitrogen fixation: an efficient source of nitrogen for sustainable agricultural production. Plant Soil 174:3–28

    Article  CAS  Google Scholar 

  • Peoples MB, Palmer B, Lilley DM, Duc LM, Herridge DF (1996) Application of 15N and xylem ureide methods for assessing N2 fixation of three shrub legumes periodically pruned for forage. Plant Soil 182:125–137

    Article  CAS  Google Scholar 

  • Robinson D (2001) δ15N as an integrator of the nitrogen cycle. Trends Ecol Evol 16:153–162

    Article  PubMed  Google Scholar 

  • Roggy JC, Prévost ME, Garbaye J, Domenach AM (1999) Nitrogen cycling in the tropical rain forest of French Guiana: comparison of two sites with contrasting soil types using d15N. J Trop Ecol 15:1–22

    Article  Google Scholar 

  • Rutherford MC (1997) Categorization of biomes. In: Cowling RM, Richardson DM, Pierce SM (eds) Vegetation of southern Africa. Cambridge University Press, Cambridge, pp 91–98

    Google Scholar 

  • Sankaran M, Ratnam J, Hanan NP (2004) Tree-grass coexistence in savannas revisited- insights from an examination of assumptions and mechanism invoked in existing models. Ecol Lett 7:480–490

    Article  Google Scholar 

  • Sankaran M, Hanan NP, Scholes RJ, Ratnam J, Augustine DJ, Cade BS, Gignoux J, Higgins SI, Le Roux X, Ludwig F, Ardo J, Banyikwa F, Bronn A, Bucini G, Caylor KK, Coughenour MB, Diouf A, Ekaya W, Feral CJ, February EC, Frost PGH, Hiernaux P, Hrabar H, Metzger KL, Prins HHT, Ringrose S, Sea W, Tews J, Worden J, Zambatis N (2005) Determinants of woody cover in African savannas. Nature 438:846–849

    Article  PubMed  CAS  Google Scholar 

  • Sankaran M, Ratnam J, Hanan N (2008) Woody cover in African savannas: the role of resources, fire and herbivory. Global Ecol Biogeogr 17:236–245

    Article  Google Scholar 

  • Schimel DS, Participants VEMAP, Braswell BH (1997) Continental scale variability in ecosystem processes: models, data, and the role of disturbance. Ecol Monogr 67:251–271

    Article  Google Scholar 

  • Scholes RJ, Walker BH (1993) An African savanna: synthesis of the Nylsvley study. Cambridge University Press, Cambridge

    Book  Google Scholar 

  • Scholes RJ, Hall DO (1996) The carbon budget of tropical savannas, woodlands and grasslands. In: Breymeyer AI, Hall DO, Melillo JM, Agren GI (eds) Global change: effects on coniferous forests and grasslands. SCOPE V56. Wiley, Chichester, pp 69–100

    Google Scholar 

  • Scholes RJ, Archer SR (1997) Tree-grass interactions in savannas. Annu Rev Ecol Syst 28:517–544

    Article  Google Scholar 

  • Scholes RJ, Dowty PR, Caylor K (2002) Trends in savanna structure and composition along an aridity gradient in the Kalahari. J Veg Sci 13:419–422

    Article  Google Scholar 

  • Schulze ED, Gebauer G, Ziegler H, Lange OL (1991) Estimates of nitrogen fixation by trees on an aridity gradient in Namibia. Oecologia 88:451–455

    Article  Google Scholar 

  • Seghieri J (1995) The rooting patterns of woody and herbaceous plants in a savanna: are they complementary or in competition? Afr J Ecol 33:358–365

    Article  Google Scholar 

  • Shearer G, Kohl DH (1986) N2- fixation in field settings: estimations based on natural 15N abundance. Aus J Plant Physiol 13:699–756

    CAS  Google Scholar 

  • Shearer G, Kohl DH, Virginia RA, Bryan BA, Skeeters JL, Nilsen ET, Sharifi MR, Rundel PW (1983) Estimates of N2-fixation from the natural abundance of 15N in Sonoran desert ecosystems. Oecologia 56:365–373

    Article  Google Scholar 

  • Skarpe C (1991) Spatial patterns and dynamics of woody vegetation in an arid savanna. J Veg Sci 2:565–572

    Article  Google Scholar 

  • Skarpe C (1992) Dynamics of savanna ecosystems. J Veg Sci 3:293–300

    Article  Google Scholar 

  • Skarpe C, Bergström R (1986) Nutrient content and digestibility of forage plants in relation to plant phenology and rainfall in the Kalahari, Botswana. J Arid Environ 11:147–164

    Google Scholar 

  • Smith TM, Goodman PS (1986) The effect of competition on the structure and dynamics of Acacia savannas in southern Africa. J Ecol 74:1031–1044

    Article  Google Scholar 

  • Solbrig OT (1996) The diversity of the savanna ecosystem. In: Solbrig OT, Medina E, Silva JF (eds) Biodiversity and savanna ecosystem processes-A global perspective. Ecological Studies 121. Springer, Berlin, pp 1–27

    Chapter  Google Scholar 

  • Sprent JI (1985) Nitrogen fixation in arid environments. In: Wickens GE, Goodin JR, Field DV (eds) Plants for arid lands. George Allen and Unwin, London, pp 215–229

    Chapter  Google Scholar 

  • Stott P (1991) Recent trends in the ecology and management of the world’s savanna formations. Prog Phys Geogr 15:18–28

    Article  Google Scholar 

  • Streeter J (1988) Inhibition of legume nodule formation and N2 fixation by nitrate. Crit Rev Plant Sci 7:1–23

    Article  CAS  Google Scholar 

  • Svenning MM, Macduff JH (1996) Low root temperature retardation of the mineral nitrogen induced decline in N2 fixation by a northern ecotype of white clover. Ann Bot 77:615–621

    Article  CAS  Google Scholar 

  • Trinogga J (2010) Arid savanna shrubs affect soil chemistry and vegetation cover. Dissertation, Friedrich Schiller University, Jena

  • Unkovich MJ, Pate JS, Lefroy EC, Arthur DJ (2000) Nitrogen isotope fractionation in the fodder tree legume tagasaste (Chamaecytisus proliferus) and assessment of N2 fixation inputs in deep sandy soils of western Australia. Aus J Plant Physiol 27:921–929

    Google Scholar 

  • Van Auken OW (2000) Shrub invasions of North American semiarid grasslands. Annu Rev Ecol Syst 31:197–215

    Article  Google Scholar 

  • Vitousek PM, Howarth RW (1991) Nitrogen limitation on land and sea: how can it occur? Biogeochemistry 13:87–115

    Article  Google Scholar 

  • Vitousek PM, Turner D, Parton W, Sanford R (1994) Litter decomposition on the Mauna Loa environmental matrix, Hawaii: patterns, mechanisms and models. Ecology 75:418–429

    Article  Google Scholar 

  • Walter H (1939) Grassland, savanne und busch der ariden teile Afrika in ihrer okologischen bedingtheit. Jahrb Wissen Bot 87:750–860

    Google Scholar 

  • Walter H (1964) The vegetation of the earth in ecophysiological examination [Die Vegetation der Erde in ökophysiologischer Betrachtung]. Gustav Fischer Verlag, Stuttgart

    Google Scholar 

  • Walter H (1971) Ecology of tropical and subtropical vegetation. Oliver and Boyd, Edinburgh

    Google Scholar 

  • Walker BH, Noy-Meir I (1982) Aspects of stability and resilience of savanna ecosystems? In: Walker BJ, Huntley BH (eds) Ecology of tropical savannas. Springer, Berlin, pp 556–590

    Chapter  Google Scholar 

  • Ward D (2005) Do we understand the causes of bush encroachment in African savannas? Afr J Range For Sci 22:101–105

    Article  Google Scholar 

  • Ward D, Esler KJ (2011) What are the effects of substrate and grass removal on recruitment of Acacia mellifera seedlings in a semi-arid environment? Plant Ecol 212:245–250

    Article  Google Scholar 

  • Wiegand K, Ward D, Saltz D (2005) Multi-scale patterns and bush encroachment in an arid savanna with a shallow soil layer. J Veg Sci 16:311–320

    Article  Google Scholar 

  • Wiegand K, Saltz D, Ward D (2006) A patch-dynamics approach to savanna dynamics and woody plant encroachment – Insights from an arid savanna. Perspect Plant Ecol Evol Syst 7:229–242

    Article  Google Scholar 

  • Zapata F, Axman H (1995) 32P isotopic techniques for evaluating the agronomic effectiveness of rock phosphate materials. Nutr Cycl Agroecosyst 41:189–195

    Google Scholar 

  • Zanetti S, Hartwig UA, Lüscher A, Hebeisen T, Frehner M, Fischer BU, Hendrey GR, Blum H, Nösberger J (1996) Stimulation of symbiotic N2 fixation in Trifolium repens L. under elevated atmospheric pCO2 in a grassland ecosystem. Plant Physiol 112:575–583

    PubMed  CAS  Google Scholar 

Download references

Acknowledgements

Vanessa Stuart and Seth Hakizimana are thanked for technical assistance. Financial assistance from the National Research Foundation of South Africa to DW is gratefully acknowledged. This research was partially supported by the International Foundation for Science, Stockholm, Sweden through a grant to JRK. Slow-release fertiliser was donated by AGLUKON Spezialduenger GmbH & Co. KG, Düsseldorf, Germany through Grovida (Durban, SA). We thank the Stable Isotope Unit at the University of Cape Town for isotope analyses. John Lanham and Ian Newton are thanked for carrying out the mass spectrometer analyses. Mary K. Seely commented on versions of the manuscript. We thank the anonymous reviewers for their comments that considerably improved this ms.

Author information

Authors and Affiliations

  1. School of Life Sciences, University of KwaZulu-Natal, Scottsville, 3209, South Africa

    Jack Ratjindua Kambatuku & David Ward

  2. Department of Botany, University of Cape Town, Private Bag X1, Rondebosch, 7701, South Africa

    Michael D. Cramer

  3. Department of Integrated Environmental Sciences, University of Namibia, Ogongo, Private Bag 5520, Oshakati, Namibia

    Jack Ratjindua Kambatuku

Authors
  1. Jack Ratjindua Kambatuku
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Michael D. Cramer
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. David Ward
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to David Ward.

Additional information

Responsible Editor: Katharina Pawlowski.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Kambatuku, J.R., Cramer, M.D. & Ward, D. Nitrogen fertilisation reduces grass-induced N2 fixation of tree seedlings from semi-arid savannas. Plant Soil 365, 307–320 (2013). https://doi.org/10.1007/s11104-012-1389-y

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11104-012-1389-y

Keywords

Search

Navigation