Department of Natural Resources
Permanent URI for this collectionhttp://localhost:4000/handle/20.500.12092/1949
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Item Synergistic effects of long-term herbivory and previous fire on fine-scale heterogeneity of prescribed grassland burns(Ecology, 2020-10) Kimuyu, Duncan; Werner, Chhaya M.; Veblen, Kari E.; Sensenig, Ryan L.; LaMalfa, Eric; Young, Truman P.Grassland and savanna ecosystems, important for both livelihoods and biodiversity conservation, are strongly affected by ecosystem drivers such as herbivory, fire, and drought. Interactions among fire, herbivores and vegetation produce complex feedbacks in these ecosystems, but these have rarely been studied in the context of fuel continuity and resultant fire heterogeneity. We carried out 36 controlled burns within replicated experimental plots that had allowed differential access by wild and domestic large herbivores since 1995 in a savanna ecosystem in Kenya. Half of these were reburns of plots burned five years previously. We show here that the fine-scale spatial heterogeneity of fire was greater in plots a) previously burned, b) accessible to large herbivores, and especially c) these two in combination. An additional embedded experiment demonstrated that even small experimental burnfree patches can have strong positive effects on tree saplings, which experienced less damage during controlled burns and quicker post-fire recovery. This work highlights the importance of simultaneously examining the interactions between fire and herbivory on fuel heterogeneity, which can have important impacts on the growth of woody saplings in savanna grasslands.Item Fine-scale habitat heterogeneity influences browsing damage by elephant and giraffe(Wiley Publishers, 2020-06) Kimuyu, Duncan M; Kenfack, David; Musili, Paul M.; Ang’ila, Robert O.Effects of large mammalian herbivores on woody vegetation tend to be heterogeneous in space and time, but the factors that drive such heterogeneity are poorly understood. We examined the influence of fine-scale habitat heterogeneity on the distribution and browsing effects of two of the largest African terrestrial mammals, the elephant and giraffe. We conducted this study within a 120-ha (500 x 2,400 m) ForestGEO long-term vegetation monitoring plot located at Mpala Research Center, Kenya. The plot traverses three distinct topographic habitats (“plateau,” “steep slopes,” and “valley”) with contrasting elevation, slope, soil properties, and vegetation composition. To quantify browsing damage, we focused on Acacia mellifera, a palatable tree species that occurs across the three habitat categories. Overall tree density, species richness, and diversity were highest on the steep slopes and lowest on the plateau. Acacia mellifera trees were tallest and had the lowest number of stems per tree on the steep slopes. Both elephant and giraffe avoided the steep slopes, and their activity was higher during the wet season than during the dry season. Browsing damage on Acacia mellifera was lowest on the steep slopes. Elephant browsing damage was highest in the valley, whereas giraffe browsing damage was highest on the plateau. Our findings suggest that fine-scale habitat heterogeneity is an important factor in predicting the distribution of large herbivores and their effects on vegetation and may interact with other drivers such as edaphic variations to influence local variation in vegetation structure and composition.