Browsing by Author "Mayengo, Gabriel"

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The importance of nutrient hotspots for grazing ungulates in a Miombo ecosystem, Tanzania
(PLOS ONE, 2020-03-30) Mayengo, Gabriel; PielI, Alex K.; Treydte, Anna C.
While movement patterns of grazing ungulates are strongly dependent on forage quality their use of nutrient hotspots such as termite mounds or grazing lawns has rarely been quantified, especially in savanna ecosystems where soil-nutrient quality is low. Additionally, few experiments have been conducted to determine the role of termite mound- and grazing lawn-derived soils in improving forage quality in the field. We studied wild ungulate grazing activities around ten termite mounds, six grazing lawns and their respective control sites in a Miombo system of Issa Valley, western Tanzania, in the same system. We used indirect observations (i.e., dung, tracks) to identify seasonal and spatial variations in habitat use of various wild mammalian grazers. Grazer visitation rates were nine and three times higher on termite mounds and grazing lawns, respectively, compared to control sites. During the rainy season, termite mounds were more frequently used than grazing lawns while the latter were used more often during the dry season. In an additional pot experiment with soils derived from different areas, we found that Cynodon dactylon in termite mound-derived soils had twice as high Nitrogen and Phosphorous contents and biomass compared to grasses planted in grazing lawn soils and control site soils. We highlight that both termite mounds and grazing lawns play a significant role in influencing seasonal nutrient dynamics, forage nutrient quality, habitat selectivity, and, hence, grazing activities and movement patterns of wild ungulate grazers in savannas. We conclude that termite mounds and grazing lawns are important for habitat heterogeneity in otherwise nutrient–poor savanna systems.
Nutrient hotspots for wild grazing ungulates in a miombo ecosystem, western Tanzania
(NM-AIST, 2020-06) Mayengo, Gabriel
While the movement pattern of grazing ungulates is strongly dependent on forage quality whose use of nutrient hotspots has rarely been quantified, especially in miombo ecosystems where soil-nutrient quality is low. Few experiments have been conducted to determine the role of nutrient hotspots derived soils in improving forage quality in miombo ecosystems. Nutrient hotspots strongly attract ungulates in nutrient poor habitats such as savanna systems. However, little is known about their seasonal importance for different grazing ungulate species. No study has quantified the potential re-distribution of nutrients into the surroundings away from hotspots. The current study assessed nutrient hotspot (i.e., grazing lawns and termite mounds) use by ungulates in a highly threatened miombo ecosystem of the Issa valley, western Tanzania. Study used indirect observation, camera traps and stable isotope analyses over a one year period to identify seasonal and spatial variations in habitat use of various wild mammalian grazers around ten termite (Macrotermes sp.) mounds, six grazing lawns and their respective control sites. Grazer visitation rates were nine and three times higher on termite mounds and grazing lawns, respectively compared to control sites. During the rainy season, termite mounds were more frequently used than grazing lawns while grazing lawns were more frequently used during the dry season. A total of 32 camera stations recorded 244 wildlife encounter events in total. Camera data show that ungulates used hotspot areas four times more frequently in comparison to their control plots. Cynodon dactylon grass planted in soils derived from termite mounds had twice as high nitrogen and phosphorous contents compared to grasses planted in grazing lawn soils and control site soils. Stable isotope analysis highlighted that dung deposited by grazers around hotspots originated from grasses within hotspot areas, hence proving that grazers are responsible for modifying nutrient stability around these hotspots. This study results highlight that nutrient hotspots play a significant role in influencing seasonal soil and forage nutrient dynamics, habitat selectivity, and hence grazing activities/ movements of wild ungulate grazers in miombo ecosystems. The study concludes that nutrient hotspots are important for various ungulates in otherwise nutrient – poor miombo systems.
Quantifying nutrient re-distribution from nutrient hotspots using camera traps, indirect observation and stable isotopes in a miombo ecosystem, Tanzania
(Elsevier B.V., 2020-09) Mayengo, Gabriel; Armbruster, Wolfgang; Treydte, Anna C.
Nutrient hotspots strongly attract mammalian herbivores in nutrient-poor habitats such as savanna systems. However, little is known about their seasonal importance for mammalian herbivore species, particularly grazers. In addition, no study has fully quantified the potential re-distribution of nutrients into the surroundings of these hotspots. We assessed nutrient hotspot (i.e., grazing lawns and termite mounds) use by herbivores in a Miombo ecosystem of the Issa valley, Tanzania, using dung counts, camera traps and stable isotope analyses over a one year period, from May 2016 to October 2017. We conducted dung counts along four transects each radiating away from ten termite mounds and six grazing lawns as well as in 16 control sites 100 m away from each nutrient hotspot. In addition, we sprayed grasses around five termite mounds with urea and traced the isotopic signature back in grazing herbivore dung. Grazer dung deposition was twice as high in hotspot areas vs control sites. A total of 32 camera stations recorded 244 wildlife encounters, with mammalian herbivores using hotspot areas four times more frequently compared to control plots. Stable isotope analyses highlighted that dung deposited by mammalian grazers around hotspots likely originated from grasses within or close to hotspot areas, indicating that grazers are responsible for maintaining nutrient stability of these hotspots. We, therefore, emphasize the importance of grazing mammal species for the long-term persistence of hotspots and, thus, their contribution to the maintenance of a heterogeneous landscape within the Miombo ecosystem.