The combined effect of termite bioturbation and water erosion on soil nutrient stocks along a tropical forest catena in Ghana

Research output: Contribution to journalArticle

Abstract

In the tropical moist semi-deciduous forests of West Africa, soil catenas with extremely gravel-rich soil horizons at the summits and upper slopes and largely gravel-free profiles at the lower slope are common. Previous investigations have suggested that these gravel layers are the result of macro-invertebrates mining of fine-grained soil material from the subsoil leaving behind the gravel, to build galleries at the surface subsequently exposing it to water erosion transport downslope. We examined the indirect effect of this process on the distribution along a soil catena of crucial base cations (Ca 2+ , Mg 2+ , K + ) and plant available phosphorous (P), which is often growth-limiting in these tropical ecosystems. We found that the export of fine-grained soil material at the top of the catena reduces the soil stocks (to 1 m) of these elements by up to 60%, while the soil fertility downslope did not change significantly. This important long-term (100–1000 yr scale) reduction in soil fertility at the top of slopes resulting from bioturbation and water erosion is overlooked in contemporary literature, which primarily focus on the beneficial impact termites and ants have on ecosystem functioning in more level savannah landscapes. As the type of catena studied is widespread across tropical environments, this effect is likely ecologically substantial. Future research should aim at understanding such long-term consequences of bioturbation on landscape ecology as well as soil heterogeneity and fertility, so we do not overlook potential negative ecosystem effects.

Details

Authors
Organisations
External organisations
  • University of Copenhagen
  • University of Ghana
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Geography

Keywords

  • Ecosystem functioning, Nutrient stock depletion, Soil erosion, Termite bioturbation, Tropical forest catena, West Africa
Original languageEnglish
Pages (from-to)307-312
Number of pages6
JournalCatena
Volume178
Publication statusPublished - 2019
Publication categoryResearch
Peer-reviewedYes