Biomass increases go under cover: Woody vegetation dynamics in South African rangelands

Penelope J. Mograbi, Barend F.N. Erasmus, E. T.F. Witkowski, Gregory P. Asner, Konrad J. Wessels, Renaud Mathieu, David E. Knapp, Roberta E. Martin, Russell Main

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Woody biomass dynamics are an expression of ecosystem function, yet biomass estimates do not provide information on the spatial distribution of woody vegetation within the vertical vegetation subcanopy. We demonstrate the ability of airborne light detection and ranging (LiDAR) to measure aboveground biomass and subcanopy structure, as an explanatory tool to unravel vegetation dynamics in structurally heterogeneous landscapes. We sampled three communal rangelands in Bushbuckridge, South Africa, utilised by rural communities for fuelwood harvesting. Woody biomass estimates ranged between 9 Mg ha-1 on gabbro geology sites to 27 Mg ha-1 on granitic geology sites. Despite predictions of woodland depletion due to unsustainable fuelwood extraction in previous studies, biomass in all the communal rangelands increased between 2008 and 2012. Annual biomass productivity estimates (10-14% p.a.) were higher than previous estimates of 4% and likely a significant contributor to the previous underestimations of modelled biomass supply. We show that biomass increases are attributable to growth of vegetation <5 m in height, and that, in the high wood extraction rangeland, 79% of the changes in the vertical vegetation subcanopy are gains in the 1-3m height class. The higher the wood extraction pressure on the rangelands, the greater the biomass increases in the low height classes within the subcanopy, likely a strong resprouting response to intensive harvesting. Yet, fuelwood shortages are still occurring, as evidenced by the losses in the tall tree height class in the high extraction rangeland. Loss of large trees and gain in subcanopy shrubs could result in a structurally simple landscape with reduced functional capacity. This research demonstrates that intensive harvesting can, paradoxically, increase biomass and this has implications for the sustainability of ecosystem service provision. The structural implications of biomass increases in communal rangelands could be misinterpreted as woodland recovery in the absence of three-dimensional, subcanopy information.

Original languageEnglish (US)
Article numbere0127093
JournalPloS one
Volume10
Issue number5
DOIs
StatePublished - May 13 2015
Externally publishedYes

Fingerprint

rangelands
Biomass
vegetation
biomass
fuelwood
Geology
geology
woodlands
Ecosystems
Ecosystem
Wood
lidar
rural communities
Rural Population
ecosystem services
aboveground biomass
South Africa
Spatial distribution
Sustainable development
shrubs

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Cite this

Mograbi, P. J., Erasmus, B. F. N., Witkowski, E. T. F., Asner, G. P., Wessels, K. J., Mathieu, R., ... Main, R. (2015). Biomass increases go under cover: Woody vegetation dynamics in South African rangelands. PloS one, 10(5), [e0127093]. https://doi.org/10.1371/journal.pone.0127093

Biomass increases go under cover : Woody vegetation dynamics in South African rangelands. / Mograbi, Penelope J.; Erasmus, Barend F.N.; Witkowski, E. T.F.; Asner, Gregory P.; Wessels, Konrad J.; Mathieu, Renaud; Knapp, David E.; Martin, Roberta E.; Main, Russell.

In: PloS one, Vol. 10, No. 5, e0127093, 13.05.2015.

Research output: Contribution to journalArticle

Mograbi, PJ, Erasmus, BFN, Witkowski, ETF, Asner, GP, Wessels, KJ, Mathieu, R, Knapp, DE, Martin, RE & Main, R 2015, 'Biomass increases go under cover: Woody vegetation dynamics in South African rangelands', PloS one, vol. 10, no. 5, e0127093. https://doi.org/10.1371/journal.pone.0127093
Mograbi PJ, Erasmus BFN, Witkowski ETF, Asner GP, Wessels KJ, Mathieu R et al. Biomass increases go under cover: Woody vegetation dynamics in South African rangelands. PloS one. 2015 May 13;10(5). e0127093. https://doi.org/10.1371/journal.pone.0127093
Mograbi, Penelope J. ; Erasmus, Barend F.N. ; Witkowski, E. T.F. ; Asner, Gregory P. ; Wessels, Konrad J. ; Mathieu, Renaud ; Knapp, David E. ; Martin, Roberta E. ; Main, Russell. / Biomass increases go under cover : Woody vegetation dynamics in South African rangelands. In: PloS one. 2015 ; Vol. 10, No. 5.
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