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Primates play important roles in tropical forests through seed dispersal and herbivory. They comprise a large part of the biomass of forest communities and tend to have clumped patterns of defecations (i.e. at favoured food trees or sleeping sites). Therefore, they may also play important roles in accelerating ecosystem nutrient cycling. Here we conduct a controlled growth experiment to quantify the effect of the addition of primate dung on the growth of both light‐demanding and shade‐tolerant seedlings over 1 year in Kibale National Park, Uganda. A mixed model analysis revealed that light‐demanding species were affected by the natural dung treatment and plants with small initial size had accelerated growth, whereas there was no effect on plant growth for shade‐tolerant species. The long‐term implications of increased dung deposition on the local tree community are unclear as shade‐tolerant species may only show an effect over the long‐term and light‐demanding species may only be able to take advantage of the increased growth if subsequently exposed to high light conditions, such as a treefall gap. [ABSTRACT FROM AUTHOR]

Ecological restoration of abandoned, formerly forested farmland can improve the delivery of ecosystem services and benefit biodiversity conservation. Restoration programs can involve removing isolated, non-native trees planted by farmers for fruit or wood. As such 'legacy' trees can attract seed dispersers and create microclimates that help native seedlings to establish, removing them may actually slow forest recovery. Working on abandoned farmland in Kibale National Park, Uganda, we evaluated the effect of legacy trees on forest recovery by measuring the number, diversity, and biomass of native seedlings and saplings regenerating in plots centered on avocado ( Persea americana), mango ( Mangifera indica), and Eucalyptus legacy trees compared with adjacent plots without legacy trees. The assemblages of native, forest-dependent tree species in plots around avocado and mango trees were distinct from each other and from those around eucalyptus and all the near-legacy plots. In particular, avocado plots had higher stem density and species richness of forest-dependent species than near-avocado plots, particularly large-seeded, shade-tolerant, and animal-dispersed species-key targets of many restoration plans. Furthermore, many of the species found in high numbers were among those failing to establish in ongoing large-scale forest restoration in Kibale. Taken together, our results demonstrate that the legacy trees facilitate the dispersal and establishment of native tree species. Retaining the existing legacy trees for a number of years could usefully complement existing management strategies to restore more biodiverse native forest in degraded lands. However, careful monitoring is needed to ensure that the legacy trees do not themselves establish. [ABSTRACT FROM AUTHOR]

Highlights: [•] Determinants of tropical forest tree richness and spatial distribution. [•] Red colobus monkeys influence the abundance of Markhamia lutea. [•] 14Years of data on M. lutea flower and fruit production. [•] 21Years of data on stand structure. [•] Red colobus are important for structuring the distribution of M. lutea in Kibale. [ABSTRACT FROM AUTHOR]

Animals can play important roles in structuring the plant communities in which they live. Some species are particularly influential in that they modify the physical environment by changing, maintaining, and/or creating new habitats; the term ecosystem engineer has been used to describe such species. We here assess the two major foraging strategies of primates, frugivory and folivory, in terms of the potential for primates to function as ecosystem engineers. We argue that whereas the role of primates as seed dispersers has received a great deal of attention, the potential role that folivorous primates play in structuring their environment through herbivory has received much less attention. Further, while quantifying if frugivorous primates are ecosystem engineers through their seed dispersal has proved very difficult, it is not as difficult to ascertain whether folivorous primates are ecosystem engineers. We document situations in which folivorous primates act as ecosystem engineers by 1) eating the leaves and/or bark of trees to the extent that they kill trees, 2) feeding on trees to the degree that they slow their growth relative to nonpreferred tree species, 3) eating the flowers of species to the extent that it does not set fruit, or 4) feeding on plants in such a way as to increase their productivity and abundance. Because evidence from the literature is very limited, where possible we present new evidence of these processes from the colobus monkeys at our long-term field site in Kibale National Park, Uganda. We conclude by discussing promising research programs that could be established to refine our understanding of the role primates play in shaping the structure of plant communities, especially tropical forests. [ABSTRACT FROM AUTHOR]

The article discusses the feasibility and systems capabilities of a 12-channel backpack global positioning system (GPS) with satellite-based differential correction in a rain forest environment in Uganda. Dense forest canopy posed a barrier to quality GPS signal reception. A satellite subscription service was chosen for producing measurements. Post-processed GPS data will yield greater accuracy than data produced by real-time differential correction techniques. The use of a base station was avoided because of concerns regarding theft. The manufacturer's accuracy specifications may only be used as a guideline in a rain forest environment.

The relationship between seedling recruitment (under and away from parent trees) and the behaviour of seed dispersers and predators, was explored in a three-year study in Kibale National Park, Uganda. On the basis of 1261 hours of observation, the foraging activity of the diurnal frugivores which fed on fruit from six tree species was quantified. The fate of dispersed and non-dispersed seeds and seedlings was examined experimentally. The findings suggest that a trade-off exists between factors that promote seedling growth in areas with high seedling density and factors that promote dispersal by frugivores. For example, dispersal of Mimusops bagshawei increases both seed and seedling survival; seeds placed away from adult conspecifics had a 8% lower probability of disappearing than seeds placed under adults and seedlings away from adults had a 30% greater probability of surviving than seedlings grown under adults. In contrast, for Uvariopsis congensis, dispersed seeds had a 56% greater probability of disappearing than seeds directly under a parent tree, while the survival of dispersed and non-dispersed seedlings was similar. Non-dispersed seed and seedling disappearance were correlated with the percentage of the fruit crop removed from focal trees, suggesting that the ability to survive under an adult maybe related to other aspects of the tree's life history. [ABSTRACT FROM PUBLISHER]

Since the completion of the Navstar Global Positioning System (GPS) in 1995, the integration of GPS and Geographical Information Systems (GIS) technology has expanded to a great number of ecological and conservation applications. In tropical rain forest ecology, however, the technology has remained relatively neglected, despite its great potential. Notwithstanding cost, this is principally due to (1) the difficulty of quality satellite reception beneath a dense forest canopy, and (2) a degree of spatial error unacceptable to fine-scale vegetation mapping. Here, we report on the technical use of GPS/GIS in the rain forest of Kibale National Park, Uganda, and the methodology necessary to acquire high-accuracy spatial measurements. We conclude that the stringent operating parameters necessary for high accuracy were rarely obtained while standing beneath the rain forest canopy. Raising the GPS antenna to heights of 25-30 m resolved this problem, allowing swift data collection on the spatial dispersion of individual rain forest trees. We discuss the impact of the 1996 Presidential Decision Directive that suspended U.S. military-induced GPS error on 1 May 2000, and comment on the potential applications of GPS/GIS technology to the ecological study and conservation of tropical rain forests.