Department of Environmental Studies
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Item Fine‐scale variation in soil and topography influences herbaceous vegetation and the distribution of large mammalian herbivores(Wiley, 2023-04) Ang'ila, Robert O.; Kimuyu, Duncan M.; Wambugu, Geoffrey M.; Kenfack, David; Musil, Paul M.; Kartzinel, Tyler R.Current understanding of the distribution of vegetation and large mammalian herbivores (LMH) is based on a combination of biogeographic studies and highly controlled field experiments, but a more complete understanding of these patterns requires study of their natural co-occurrence patterns at intermediate spatial scales. The study was conducted in the 120-ha Mpala Forest Global Earth Observatory (ForestGEO) plot, Kenya. We examined differences in herbaceous plant communities and habitat use by LMH among three topographic habitats with distinct soil types, namely steep slopes, valley and plateau. Each pair of habitats differed in plant and animal com position. The steep slopes and plateau respectively had ≥1-fold higher percentage herbaceous cover than the valley, whereas the steep slopes and valley had >1.5-fold greater grass species richness and diversity than the plateau. The activity of LMH was ≥1.7-fold higher in the valley than the steep slopes and plateau, reflecting a positive relationship between LMH activity index and richness and diversity of grass species. Results indicate that fine-scale variation in topography and soil are associated with both the distribution of herbaceous vegetation and LMH, suggesting a need to account for local habitat characteristics when examining the distributions of plants, animals, and plant-herbivore interactions in natural systemsItem 5. Absentee owners and overlapping home ranges in a territorial species(2021-01-07) Isbell, Lynne A.; Bidner, Laura R.; Loftus, Carter; Kimuyu, Duncan M.; Young, Truman P.Abstract Understanding animals’ use of space can shed valuable light on multiple other aspects of behavioral ecology, including social organization, dispersal, and foraging efficiency. Home ranges, territories, core areas, and home range overlaps have been widely studied, but unless animals are directly observed or are tracked remotely on a fine temporal scale, how they actually use the space available to them and how they share (or partition) this space with a community of conspecifics over time cannot be fully understood. Using GPS technology, we tracked three adjacent groups of vervet monkeys (Chlorocebus pygerythrus) in Laikipia, Kenya, for 1 year to better understand the processes involved in territoriality and home range overlaps. Home ranges overlapped with any one neighboring group by 12.7–34.7%, but intergroup encounters only occurred in restricted areas within these zones, which defined territorial boundaries. The resources closest to the territorial boundaries were nocturnal core areas with preferred sleeping sites adjacent to shortgrass areas offering fewer hiding places for ambush predators and greater visibility for predator detection. Home range overlaps were not neutral zones, the result of shifting home range boundaries over time, or based on intergroup encounters at boundaries, but resulted when groups made incursions beyond their territorial boundaries while the neighbor was far away and likely unaware of the intruders. Thus, territories can be non-exclusive but may still be perceived by the animals themselves as sole-owned, as neighbors only intrude when territory owners are absent from that area.Item Evidence of nutrient translocation in response to smoke exposure by the East African ant acacia, Vachellia drepanolobium(Wiley & Sons Ltd, 2021-09) Kimuyu, Duncan M.; Martins, Dino J.; Pierce, Naomi E.; Yekwayo, Inam; Ye, Wenqing; Wu, Donghao; Perez-Martinez, Christian A.; Ziemke, Clayton H.; Kennedy-Yoon, Annina; Darling, Walker S.; Blumstein, Meghan; Dean, Brendan Z. M.; Angier, Katherine I. W.; Rabideau-Childers, Richard1. Fire is a major selective force on arid grassland communities, favoring traits such as the smoke-induced seed germination response seen in a wide variety of plant species. However, little is known about the relevance of smoke as a cue for plants beyond the seedling stage. 2. We exposed a fire-adapted savanna tree, Vachellia (=Acacia) drepanolobium, to smoke and compared nutrient concentrations in leaf and root tissues to unexposed controls. Experiments were performed on three age cohorts: 2-year-old, 9-month-old, and 3-month-old plants. 3. For the 2-year-old plants exposed to smoke, carbon and nitrogen concentrations were lower in the leaves and higher in the roots than controls. Less pronounced trends were found for boron and magnesium. 4. In contrast, smoke-exposed 3-month-old plants had lower root nitrogen concentrations than controls. No significant differences were found in the 9-month-old plants, and no significant shifts in other nutrient concentrations were observed between plant tissues for any of the three age cohorts. 5. Synthesis: Our findings are consistent with smoke-induced translocation of nutrients from leaves to roots in 2-year-old V. drepanolobium. This could represent a novel form of fire adaptation, with variation over the course of plant development. The translocation differences between age cohorts highlight the need to investigate smoke response in older plants of other species. Accounting for this adaptation could better inform our understanding of savanna community structure and nutrient flows under fire regimes altered by anthropogenic land use and climate change.Item Spatial scales influence long-term response of herbivores to prescribed burning in a savanna ecosystem(CSIRO PUBLISHING, 2017-01) Kimuyu, Duncan M.; Sensenig, Ryan L.; Chira, Robert M.; Githaiga, John M.; Young, Truman P.Both wild and prescribed fire in savanna ecosystems influence habitat use by herbivores by creating or maintaining spatial and temporal heterogeneity in forage quality and vegetation cover. Yet little is known about how spatial scales influence long-term persistence of fire effects. We examined changes over a 6-year period in herbivore preference for experimentally burned patches that varied in spatial extent and grain. Avoidance for the burns by elephants andpreferencefortheburnsbyimpalaandGrant’sgazelledecreasedsignificantly.Fortherestofthespecies(zebra,eland, oryx, hartebeest, warthog and hare), there were no significant changes in preference for the burns. Changes in preference for the burned areas depended on the spatial extent and grain of the burn, with intermediate-size (9-ha) burns and large (8-ha) patchy burns being more preferred 6–7 years after fire. Grain, but not the spatial extent of the burned area, influenced changes in grass height. Fire resulted in a delayed reduced tree density irrespective of the spatial scale of the burn. Results of this study indicate that, depending on the scale of fire prescription, the impacts of fire on herbivores may last longer than previous studies suggest