Show simple item record Mills, Anthony J. Milewski, Antoni V. Snyman, Dirk Jordaan, Jorrie J. 2019-09-25T09:46:23Z 2019-09-25T09:46:23Z 2017-06-29
dc.identifier.issn 1932-6203
dc.description Journal article published in the journal of PLoS ONE 12(6) en_US
dc.description.abstract The causes of the worldwide problem of encroachment of woody plants into grassy vegetation are elusive. The effects of soil nutrients on competition between herbaceous and woody plants in various landscapes are particularly poorly understood. A long-term experiment of 60 plots in a South African savanna, comprising annual applications of ammonium sulphate (146–1166 kg ha-1 yr-1) and superphosphate (233–466 kg ha-1 yr-1) over three decades, and subsequent passive protection over another three decades, during which indigenous trees encroached on different plots to extremely variable degrees, provided an opportunity to investigate relationships between soil properties and woody encroachment. All topsoils were analysed for pH, acidity, EC, water-dispersible clay, Na, Mg, K, Ca, P, S, C, N, NH4, NO3, B, Mn, Cu and Zn. Applications of ammonium sulphate (AS), but not superphosphate (SP), greatly constrained tree abundance relative to control plots. Differences between control plots and plots that had received maximal AS application were particularly marked (16.3 ±5.7 versus 1.2±0.8 trees per plot). Soil properties most affected by AS applications included pH (H2O) (control to maximal AS application: 6.4±0.1 to 5.1±0.2), pH (KCl) (5.5± 0.2 to 4.0±0.1), acidity (0.7±0.1 to 2.6±0.3 cmol kg-1), acid saturation (8±2 to 40±5%), Mg (386±25 to 143±15 mg kg-1), Ca (1022±180 to 322±14 mg kg-1), Mn (314±11 to 118 ±9 mg kg-1), Cu (3.6±0.3 to 2.3±0.2 mg kg-1) and Zn (6.6±0.4 to 3.7±0.4 mg kg-1). Magnesium, B, Mn and Cu were identified using principal component analysis, boundary line analysis and Kruskal-Wallis rank sum tests as the nutrients most likely to be affecting tree abundance. The ratio Mn/Cu was most related to tree abundance across the experiment, supporting the hypothesis that competition between herbaceous and woody plants depends on the availability of anabolic relative to catabolic nutrients. These findings, based on more than six decades of experimentation, may have global significance for the theoretical understanding of changes in vegetation structure and thus the practical control of invasive woody plants. en_US
dc.format.extent 24 pages en_US
dc.language.iso en en_US
dc.publisher PLoS ONE en_US
dc.relation.requires Adobe Acrobat Reader en_US
dc.subject Catabolic nutrients en_US
dc.subject Woody plants en_US
dc.subject Anabolic nutrients en_US
dc.subject South African savanna en_US
dc.subject.lcsh Flowering woody plants en_US
dc.subject.lcsh Savanna ecology en_US
dc.subject.lcsh Herbaceous plants en_US
dc.title Effects of anabolic and catabolic nutrients on woody plant encroachment after long-term experimental fertilization in a South African savanna en_US
dc.type Article en_US

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