Category Archives: bwindi phenology

Phenology week at ITFC

This week we joined Frederick Ssali (ITFC’s research officer) and other ITFC research assistants conducting their long-term phenology monitoring project. This programme was borne from a long-term phenology project started in 2004, focusing on gorilla food trees, which itself began after a PhD student conducted phenology studies linked to gorillas in 2000. The data from gorilla-focused studies was limited, so this more general project was started in 2011, thanks to a grant from WCS for Climate Change Studies in Bwindi.

photo by Andrew Kirkby

Photo by Andrew Kirkby

Every month, a team of highly trained field assistants collect data on 52 species of selected trees from plots on three transects. The team’s skilled eyes examine fruit, flowers and leaves using binoculars. Information is collected for both the canopy and the ground, on the number of ripe, unripe and rotten fruit, as well as the number of flower buds and open flowers and the number of new, old, dead and damaged leaves. The observational ability of the field assistants is amazing!

ITFC researcher observing a tree for phenology.

Photo by Andrew Kirkby

This project aims to link plant cues for flowering, fruit and leafing to climate change and plants’ responses to climate change. It is also relevant for agriculture as it can help inform farmers about pollination issues and timing of when to plant crops. Such general forest ecology knowledge is highly important for understanding the forest ecosystem and contributes greatly to other studies in Bwindi. It can, for example, inform about when certain food items as available for particular animals.

fruits and leaves of Olinia rochetiana (photo by Andrew Kirkby)

Fowers of Allophylus abyssinica (both photos by Andrew Kirkby)


The first analysis of the data is ongoing and Frederick aims to publish the results this year. Although the funding is coming to an end, the hope is that the value of this project will be recognised so that ITFC receives funding to continue this on a long-term basis.

Photo by Andrew Kirkby

Photo by Andrew Kirkby

Lucy and Andrew

The impenetrable challenge of an overwhelming understorey

The following is a text I wrote for tthe British Ecological Society Bulletin — that was published last month (June 2012). I wrote it to attract interest to a challenge that requires more attention from ecologists and others.  I hope you find it of interest.


Science journals favour tidy theory and rigorous results, but ecological science can also be advanced through highlighting unfamiliar unknowns and quirky questions. For many of us such unknowns are what makes research fun. I want to share a problem (don’t worry, it is about ecology). Maybe you can help.

Our understanding of tropical forest dynamics has advanced considerably over recent decades. We now have vast data-sets tracking hundreds of thousands of tree stems over areas of 50 hectares or more. Numerous processes have been quantified in detail. Remaining unknowns may appear to be minor gaps that will soon be filled. But, for some locations, these impressions are misleading.

For the last few years I have been based in the Bwindi Impenetrable National Park – a World Heritage Site in Southwest Uganda. We can see Rwanda and the Democratic Republic of Congo from here. The site is known for supporting half the World’s remaining mountain gorillas; a major “see them before you die”-tourist-draw that brings in significant revenues to support conservation and the region’s economy. I help run a research station that focuses on the needs of local conservation practitioners (see We have various day-to-day challenges ourselves – of which I may share more another time – but here I want to focus on our inadequate grasp of forest dynamics.

Living in a salad bowl: fewer than 800 mountain gorillas remain (Photograph Douglas Sheil)

What’s in a name

First, consider the name Bwindi Impenetrable National Park. That “Impenetrable” often leads to raised eyebrows, disbelieving laughter and accusations of ill-judged humour. But it is not a joke: “Impenetrable” is there in the official name. Ask why and you reveal you have not yet been here. Bwindi is rugged, steep and divided by cliffs but the key feature is the thick understorey. It is near impossible to walk through. The main element of this understorey challenge, superseding even the impressively rich flora of noxious nettles, barbed briars and spiny Acanthus, is its remarkable density. Understanding this forest by looking at the trees alone is probably harder than walking through it without tripping over the understorey.

Impenetrable forest – where are the seedlings? (Photograph Douglas Sheil)

Let me sketch out a few local features. The climate here is cool with altitudes up to 2,600m (we huddle at the fire at night). Being one degree south of the equator, seasonal variation is limited but we have two wetter and two drier seasons. Much of the forest canopy is open and there are extensive clearings – this likely reflects slow or stalled recovery from past disturbance (human activities, fires, landslides and elephants are all blamed). Small trees are scarce over large areas – suggesting limited regeneration. Many clearings are filled with persistent bracken fern Pteridium aquilinum (L.) Kuhn.reminiscent of the forests near where I grew up in Ireland. Other understorey species dominate other areas both with and without tree cover. Many of the common understorey species are synchronously monocarpic, living for a decade or more before flowering, seeding and dying en masse. . Examples include the African mountain bamboo (Yushania alpina (K. Schum.) Lin. Poaceae). Like many gregarious bamboo species elsewhere, it forms extensive stands and flowers only every few decades. Other monocarpic understorey plants include various Acanthaceae including several Mimulopsis spp.. One thicket forming species is Mimulopsis arborescens C.B. Clarke. It grows to 4 meters tall and bears multiple soft-woody stems with interlocking stilt-roots that are near impossible to walk through – this plant covers large areas of the forest. Along with another common monocarpic Mimulopsis species (M. solmsii Schweinf.) this is among the mountain gorillas’ most plentiful food plants. Both these Mimulopsis species flowered, seeded and died over the last two years.

ITFC researchers work among the woody remains and seedling carpets of the monocarpic liana Sericostachys scandens (Amaranthaceae): note the bamboo in the background (Photograph Douglas Sheil)

A liana that was abundant in Bwindi just three years ago is also monocarpic. Sericostachys scandens Gilg. & Lopr. (Amaranthaceae) used to cover almost every tree over large areas of forest. Then 3 years ago it flowered and for months its fluffy seeds were everywhere. It is now hard to spot a plant aside from seedlings. Large dead crumbling stems lie in heaps in parts of the forest.

So to recap: large areas of the forest are dominated by a dense understorey. Many of these plants are monocarpic and achieve high densities in cycles that must impact the recruitment opportunities of other plants. Trees are locally patchy and seedlings are often rare. The behaviour of the non-tree vegetation appears key in understanding the dynamics of these forests and, by implication, the animal species such as the mountain gorillas that they sustain.

These issues are not simply a matter of curiosity: major concerns have been raised about the long term management of the forest. These are practical questions. What, for example, should be done about the forest’s vulnerability to fire and to alien species (such as Lantana camara L. now spreading in the northern lower part of the forest)? Specific questions have been raised about maintaining conservation values. Recently the park authorities suggested it may be necessary to artificially maintain gorilla food species by cutting trees. We don’t have anything close to the understanding needed to address these concerns with confidence.

Fun fun fun

How can we get a handle on the key relationships within this complex patchy mountain forest vegetation? How can we, in only a few years of affordable research, grasp how outcomes are determined? If we can’t do that can we at least begin to clarify, gather and store the information that future researchers will need to better address these impenetrable problems? We have some plots with a few thousand tagged trees already. We also acknowledge valuable research elsewhere on seedling-understorey interactions, bracken control, and many other key issues. But we’ll need more, including the sustained funding to achieve it. So can we address this in easy bite-sized pieces? Ideally we would support local students and build capacity as we did it. I am hoping you may have suggestions. If you do please let me know, better still drop by and see just how impenetrable the forest here really is.

Left: Bwindi before, and right:, after last year’s understorey die-back (Photographs by Miriam van Heist)

Hope to hear your thoughts.


Using flowers and fruits as indicators of climate change in Bwindi

Dear reader,

Do you love flowers? Do you love fruits? Why do you love them? There are many answers to these questions. Let me tell you my experience with flowers and fruits of trees in Bwindi. My love for flowers and fruits has been boosted following fieldwork around ITFC to locate trees for studying ‘phenology’ i.e. the flowering and fruiting patterns of trees. Until recently, I loved watching bright flowers and fruits only for leisure. I also thought that fruits in a natural forest like Bwindi are only useful as food for animals including gorillas, elephants, chimps and monkeys. However, this fieldwork has helped improve my understanding of flowers and fruits. Every month, we go out to check on plots we set up for monitoring phenology. In this field work, I am assisted by other ITFC staff including Christopher, Savio, Margaret, Joseph Mukasa, Peter Mukasa and Anaclet Owomuhangi. We check with binoculars for the presence of flowers and fruits and we also take photos to capture their beauty.

I guess you want to ask; why do we need a study like this? Well, the answer is that it is a way to monitor the possible impacts of climate change on plants. Studies elsewhere have already shown that some plants have expanded their geographic range in response to increasing temperatures. But also, plants may respond to the changing seasons by changing the timing of their phenology. For example, trees may flower and fruit earlier than their ‘normal’ season in response to an early start of season, say rainy season. Similarly, deciduous trees may shed their leaves later than they used to in case of a delay in the dry season. Changes in the timing of flowering and fruiting by trees may have a strong influence especially on pollination of plants and feeding of fruit-eating animals in Bwindi. Although studies elsewhere have revealed phenological responses to climate change, no study of this kind has been done in Bwindi yet. Thus, we need this study to help us better understand the potential effects of climate change on plants as well as animals in Bwindi.

The pictures below show some of the flowers and fruits in our phenology fieldwork;

Picture 1: Savio (with binoculars) and I looking out for fruits and flowers in a crown of a tree

Picture 2: Flower buds of Nuxia congesta

Picture 3: The purple fruits above belong to Rapanea melanophloeos

Picture 4: at the moment, Allophylus abyssinicus trees are full of bright red fruits

Picture 5: Fruits of Pittosporum trees are yellow when ripe

Picture 6: The red and purple berries of Rubus looking splendid indeed!

Mimulopsis arborescens is common in Bwindi’s valleys but only comes once in so many years

Mimulopsis arborescens is common in Bwindi’s valleys but only comes once in so many years

I will keep you posted on our findings. Watch this space.

Fredrick Ssali