Changes in Elephant Abundance Affect Forest Composition or Regeneration?

Omeja, Patrick A.; Jacob, Aerin L.; Lawes, Michael J.; Lwanga, Jeremiah S.; Rothman, Jessica M.; Tumwesigye, Charles; Chapman, Colin A.

doi:10.1111/btp.12154

Cited by 37 publications

(48 citation statements)

References 70 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An alternative explanation is that there are multiple forest-wide perturbations simultaneously operating on the vegetation in Kibale independent of the selective logging event 45 years ago. Three main sources of forest-wide disturbance in Kibale have been reported including changing rainfall patterns (Hartter et al, 2012), concentrated elephant abundance and activities (Omeja et al, 2014), and intense competition from non-tree vegetation (Duclos et al, 2013). Synergistic interactions among multiple perturbations are thought to result in long-term changes in fundamental aspects of the structure and function of biological communities (Paine et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

Selective logging: Do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? – A 45year perspective

Osazuwa‐Peters

Jiménez

Oberle

et al. 2015

Forest Ecology and Management

Self Cite

View full text Add to dashboard Cite

Selective logging, the targeted harvesting of timber trees in a single cutting cycle, is globally rising in extent and intensity. Short-term impacts of selective logging on tropical forests have been widely investigated, but long-term effects on temporal dynamics of forest structure and composition are largely unknown. Understanding these long-term dynamics will help determine whether tropical forests are resilient to selective logging and inform choices between competing demands of anthropogenic use versus conservation of tropical forests. Forest dynamics can be studied within the framework of succession theory, which predicts that temporal turnover rates should decline with time since disturbance. Here, we investigated the temporal dynamics of a tropical forest in Kibale National Park, Uganda over 45 years following selective logging. We estimated turnover rates in stems, species composition, and functional traits (wood density and diameter at breast height), using observations from four censuses in 1989, 1999, 2006, and 2013, of stems ≥ 10 cm diameter within 17 unlogged and 9 logged 200 × 10 m vegetation plots. We used null models to account for interdependencies among turnover rates in stems, species composition, and functional traits. We tested predictions that turnover rates should be higher and decrease with increasing time since the selective logging event in logged forest, but should be less temporally variable in unlogged forest. Overall, we found higher turnover rates in logged forest for all three attributes, but turnover rates did not decline through time in logged forest and was not less temporally variable in unlogged forest. These results indicate that successional models that assume recovery to pre-disturbance conditions are inadequate for predicting the effects of selective logging on the dynamics of the tropical forest in Kibale. Selective logging resulted in persistently higher turnover rates, which may compromise the carbon storage capacity of Kibale’s forest. Selective logging effects may also interact with effects from other global trends, potentially causing major long-term shifts in the dynamics of tropical forests. Similar studies in tropical forests elsewhere will help determine the generality of these conclusions. Ultimately, the view that selective logging is a benign approach to the management of tropical forests should be reconsidered in the light of studies of the effects of this practice on long-term forest dynamics.

show abstract

Section: Discussionmentioning

confidence: 99%

Selective logging: Do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? – A 45year perspective

Osazuwa‐Peters

Jiménez

Oberle

et al. 2015

Forest Ecology and Management

Self Cite

View full text Add to dashboard Cite

show abstract

“…), and allows herbs and grasses to colonize disturbed areas (Omeja et al. ). Elephants also alter the composition of the plant community through preferential browsing, which selects for browsing‐tolerant plants that invest in chemical or physical defenses (Höft & Höft ).…”

Section: Ecological Effects Of Forest Elephants On Tropical Forestsmentioning

confidence: 99%

“…Forest elephants are requisite generalists, consuming over 500 species of plants and a wide range of plant parts (Blake 2002); thus, through herbivory they may affect community-level vegetation structure and species composition. In savannas high rates of elephant disturbance suppress woody vegetation (Cumming et al 1997;Shannon et al 2008), which stalls succession, prevents development of the shade canopy (Laws et al 1970 and allows herbs and grasses to colonize disturbed areas (Omeja et al 2014). Elephants also alter the composition of the plant community through preferential browsing, which selects for browsing-tolerant plants that invest in chemical or physical defenses (Höft & Höft 1995).…”

Section: Herbivory and Physical Damagementioning

confidence: 99%

Ecological consequences of forest elephant declines for Afrotropical forests

Poulsen

Rosin

Meier

et al. 2018

Conservation Biology

View full text Add to dashboard Cite

Poaching is rapidly extirpating African forest elephants (Loxodonta cyclotis) from most of their historical range, leaving vast areas of elephant-free tropical forest. Elephants are ecological engineers that create and maintain forest habitat; thus, their loss will have large consequences for the composition and structure of Afrotropical forests. Through a comprehensive literature review, we evaluated the roles of forest elephants in seed dispersal, nutrient recycling, and herbivory and physical damage to predict the cascading ecological effects of their population declines. Loss of seed dispersal by elephants will favor tree species dispersed abiotically and by smaller dispersal agents, and tree species composition will depend on the downstream effects of changes in elephant nutrient cycling and browsing. Loss of trampling and herbivory of seedlings and saplings will result in high tree density with release from browsing pressures. Diminished seed dispersal by elephants and high stem density are likely to reduce the recruitment of large trees and thus increase homogeneity of forest structure and decrease carbon stocks. The loss of ecological services by forest elephants likely means Central African forests will be more like Neotropical forests, from which megafauna were extirpated thousands of years ago. Without intervention, as much as 96% of Central African forests will have modified species composition and structure as elephants are compressed into remaining protected areas. Stopping elephant poaching is an urgent first step to mitigating these effects, but long-term conservation will require land-use planning that incorporates elephant habitat into forested landscapes that are being rapidly transformed by industrial agriculture and logging.

show abstract

“…The limited duration of field studies increases the uncertainty in their results. There is a lack of long-term tropical forest inventories with data covering multiple decades, except for a few notable sites such as Kibale National Park in Uganda and Barro Colorado Island in Panama (Wright et al 2000, Omeja et al 2014). In addition, it is difficult to find comparable regions (similar adult tree composition, disturbance history, and environmental conditions) with different defaunation histories, and to regularly monitor forest regeneration without sufficient long-term funding.…”

Section: The Challenge Of Studying Long-term Processesmentioning

confidence: 99%

Assessing the role of megafauna in tropical forest ecosystems and biogeochemical cycles – the potential of vegetation models

et al. 2018

View full text Add to dashboard Cite

Megafauna (terrestrial vertebrate herbivores > 5 kg) can have disproportionate direct and indirect effects on forest structure, function, and biogeochemical cycles. We reviewed the literature investigating these effects on tropical forest dynamics and biogeochemical cycles in relation to ecology, paleoecology, and vegetation modelling. We highlight the limitations of field‐based studies in evaluating the long‐term consequences of loss of megafauna. These limitations are due to inherent space‐time restrictions of field‐studies and a research focus on seed dispersal services provided by large animals. We further present evidence of a research gap concerning the role of megafauna in carbon cycling in tropical ecosystems. Specifically, changes in aboveground biomass might not be noticeable in short‐term studies because of slow vegetation dynamics requiring decades to respond to disturbance (i.e. defaunation). Nutrient cycling has received even less attention in relation to the role of megafauna in tropical forests. We present an approach to investigate the effects of megafauna from new perspectives and with various tools (notably, vegetation models), which can simulate long‐term dynamics in different environmental and megafauna density scenarios. Vegetation models could facilitate interaction between plant–animal ecology and biogeochemistry research. We present practical examples on how to integrate plant–animal interactions in vegetation models to further our understanding of the role of large herbivores in tropical forests.

show abstract

Changes in Elephant Abundance Affect Forest Composition or Regeneration?

Cited by 37 publications

References 70 publications

Selective logging: Do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? – A 45year perspective

Selective logging: Do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? – A 45year perspective

Ecological consequences of forest elephant declines for Afrotropical forests

Assessing the role of megafauna in tropical forest ecosystems and biogeochemical cycles – the potential of vegetation models

Contact Info

Product

Resources

About