Ecological Importance of Large Herbivores in the Ewaso Ecosystem

Pringle, Robert M.; Palmer, Todd M.; Goheen, Jacob R.; McCauley, Douglas J.; Keesing, Felicia

doi:10.5479/si.00810282.632.43

Cited by 27 publications

(25 citation statements)

References 54 publications

(64 reference statements)

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“…The Laikipia exclosure experiments have played a fundamental role in the discovery that LMH exert a diverse range of indirect effects on smaller consumers . Keesing showed that the exclusion of large herbivores in KLEE led to a rapid and sustained doubling of small‐mammal abundance.…”

Section: Lesson #3: Lmh Play Central Roles In Trophic Cascades and Otmentioning

confidence: 99%

Conservation lessons from large‐mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments

Goheen

Augustine²,

Veblen

et al. 2018

Annals of the New York Academy of Sciences

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African savannas support an iconic fauna, but they are undergoing large-scale population declines and extinctions of large (>5 kg) mammals. Long-term, controlled, replicated experiments that explore the consequences of this defaunation (and its replacement with livestock) are rare. The Mpala Research Centre in Laikipia County, Kenya, hosts three such experiments, spanning two adjacent ecosystems and environmental gradients within them: the Kenya Long-Term Exclosure Experiment (KLEE; since 1995), the Glade Legacies and Defaunation Experiment (GLADE; since 1999), and the Ungulate Herbivory Under Rainfall Uncertainty experiment (UHURU; since 2008). Common themes unifying these experiments are (1) evidence of profound effects of large mammalian herbivores on herbaceous and woody plant communities; (2) competition and compensation across herbivore guilds, including rodents; and (3) trophic cascades and other indirect effects. We synthesize findings from the past two decades to highlight generalities and idiosyncrasies among these experiments, and highlight six lessons that we believe are pertinent for conservation. The removal of large mammalian herbivores has dramatic effects on the ecology of these ecosystems; their ability to rebound from these changes (after possible refaunation) remains unexplored.

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Section: Lesson #3: Lmh Play Central Roles In Trophic Cascades and Otmentioning

confidence: 99%

Conservation lessons from large‐mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments

Goheen

Augustine²,

Veblen

et al. 2018

Annals of the New York Academy of Sciences

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“…However, quantitative syntheses of the impacts of biodiversity loss on ecosystem functions have focused nearly exclusively on studies of small or sessile organisms like invertebrates and plants (Delgado-Baquerizo et al, 2015;Hooper et al, 2012;Soliveres et al, 2016). The lack of synthesis is surprising given that (a) large taxa are often suggested to have disproportionately influential roles on ecosystem function (Owen -Smith, 1988;Pringle, Palmer, Goheen, McCauley, & Keesing, 2010) (Figure 1), and (b) multiple efforts have attempted to synthesize effects of excluding large, wild herbivores on producers (e.g. Gruner et al, 2008, Jia et al, 2018) and smaller consumers (Daskin & Pringle, 2016;Foster, Barton, & Lindenmayer, 2014).…”

Section: Introductionmentioning

confidence: 99%

Synthesizing the effects of large, wild herbivore exclusion on ecosystem function

et al. 2019

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Wild large herbivores are declining worldwide. Despite extensive use of exclosure experiments to investigate herbivore impacts, there is little consensus on the effects of wild large herbivores on ecosystem function. Of the ecosystem functions likely impacted, we reviewed the five most‐studied in exclosure experiments: ecosystem resilience/resistance to disturbance, nutrient cycling, carbon cycling, plant regeneration, and primary productivity. Experimental data on large wild herbivores' effects on ecosystem functions were predominately derived from temperate grasslands (50% grasslands, 75% temperate zones). Additionally, data were from experiments that may not be of adequate size (median size 400 m2 despite excluding all experiments below 25 m2) or duration (median duration 6 years) to capture ecosystem‐scale responses to these low‐density and wide‐ranging taxa. Wild herbivore removal frequently impacted ecosystem functions; for example, net carbon uptake increased by three times in some instances. However, the magnitude and direction of effects, even within a single function, were highly variable. A focus on carbon cycling highlighted challenges in interpreting effects on a single function. While the effect of large herbivore exclusion on carbon cycling was slightly positive when its components (e.g. pools vs. fluxes of carbon) were aggregated, effects on individual components were variable and sometimes opposed. Given modern declines in large wild herbivores, it is critical to understand their effects on ecosystem function. However, this synthesis highlights strong variability in direction, magnitude, and modifiers of these effects. Some variation is likely due to disparity in what components are used to describe a given function. For example, for the carbon cycle we identified eight distinctly meaningful components, which are not easily combined yet are potentially misrepresentative of the larger cycle when considered alone. However, much of the observed difference in responses likely reflects real ecological variability across complex systems. To move towards a general predictive framework we must identify where variation in effect is due to methodological differences and where due to ecosystem context. Two critical steps forward are (a) additional quantitative synthetic analyses of large herbivores' effects on individual functions, and (b) improved, increased systematic exclosure research focusing on effects of large herbivores' exclusion on functions. A free Plain Language Summary can be found within the Supporting Information of this article.

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“…In water‐limited savannas, for example, soil effects on plant‐available moisture may trump or modulate the effects of nutrient availability on productivity. Moreover, mammalian herbivory is a potent top‐down force in these systems (Augustine and McNaughton , Skarpe and Hester , Pringle et al ) and interacts with bottom‐up forces to structure savanna vegetation (Scholes and Archer , Bond ). Thus, soil × herbivory interactions may be a potent and widespread force in savanna‐plant community assembly, and to understand them, we may need to account for other dimensions of soil quality than nutrient availability alone.…”

Section: Introductionmentioning

confidence: 99%

Large herbivores promote habitat specialization and beta diversity of African savanna trees

Pringle

Prior

Palmer

et al. 2016

Ecology

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Edaphic variation in plant community composition is widespread, yet its underlying mechanisms are rarely understood and often assumed to be physiological. In East African savannas, Acacia tree species segregate sharply across soils of differing parent material: the ant-defended whistling thorn, A. drepanolobium (ACDR), is monodominant on cracking clay vertisols that are nutrient rich but physically stressful, whereas poorly defended species such as A. brevispica (ACBR) dominate on nutrient-poor but otherwise less-stressful sandy loams. Using a series of field experiments, we show that large-mammal herbivory interacts with soil properties to maintain this pattern. In the absence of large herbivores, transplanted saplings of both species established on both soil types. Browsers strongly suppressed survival and growth of ACDR saplings on sandy soil, where resource limitation constrained defensive investment. On clay soil, ACBR saplings established regardless of herbivory regime, but elephants prevented recruitment to maturity, apparently because trees could not tolerate the combination of biotic and abiotic stressors. Hence, each tree species was filtered out of one habitat by browsing in conjunction with different edaphic factors and at different ontogenetic stages. Browser abundance was greater on sandy soil, where trees were less defended, consistent with predicted feedbacks between plant community assembly and herbivore distributions. By exploring two inversely related axes of soil "quality" (abiotic stress and nutrient content), our study extends the range of mechanisms by which herbivores are known to promote edaphic specialization, illustrates how the high cost of a protection mutualism can constrain the realized niche of host trees, and shows that large-scale properties of savanna ecosystems are shaped by species interactions in cryptic ways that mimic simple abiotic determinism. These results suggest that ongoing declines in large-herbivore populations may relax spatial heterogeneity in plant assemblages and reduce the beta diversity of communities.

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Ecological Importance of Large Herbivores in the Ewaso Ecosystem

Cited by 27 publications

References 54 publications

Conservation lessons from large‐mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments

Conservation lessons from large‐mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments

Synthesizing the effects of large, wild herbivore exclusion on ecosystem function

Large herbivores promote habitat specialization and beta diversity of African savanna trees

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