A two week trip to the Bayang-Mbo Nature Reserve and the University of Yaoundé, Cameroon was undertaken, beginning 28 November 2000. The aim of the trip was to establish collaboration on the first systematic study in Central African rainforests into the ability of the legume flora (plants related to our familiar peas, beans and clovers) to nodulate and fix nitrogen. The first 10 days were spent excavating root systems of legume trees in the forest with Dr Nwaga Dieudonné and his PhD student Kiam Angele. This was made possible using the logistic support of a Darwin Initiative programme led by Dr Martin Cheek of the Royal Botanic Gardens, Kew. Many new records of nodulation (both positive and negative) were made and samples were taken to Yaoundé. In Yaoundé I gave a two hour seminar to a general biological audience, in which we discussed the significance of the legume component of tropical rainforests and the need for Cameroon-based research in this area. I also gave two one hour specialist lectures to research staff from Yaoundé and other Institutions, which were followed by some practical work in which nodule material was examined. Future work was planned and an outline publication drafted which will be submitted to a refereed journal early in 2001. Samples were brought back to Dundee for examination by electron microscopy. It is hoped that the student, Kiam Angele, will be able to visit Scotland to learn the relevant techniques.

The whole trip was a great success. In addition to setting up the planned collaboration with Cameroonian scientists, while camping in the reserve I met Darwin Fellows from other parts of Africa and established links with some of these to carry out nodulation surveys in their own countries.

This was carried out at the Bayang-Mbo Nature Reserve, run by Earthwatch International. Earthwatch have a base camp there with very simple accommodation, staffed by local people. This facility was being used in a Darwin Initiative (DETR) project led by Dr Martin Cheek of the Royal Botanic Gardens, Kew in which plant taxonomists from Kew and Cameroon train Darwin Fellows from various African countries in plant identification and herbarium techniques. Duplicate specimens are collected under a memorandum of understanding with the Cameroon authorities and are lodged herbaria in Cameroon and Kew, with the final aim of completing the first inventory of plant species in this Reserve. One of the Kew experts, Barbara Mackinder, is a legume specialist: she travelled to Cameroon a few days before me and carried out a preliminary survey of the most likely areas to contain legumes. Also present in the field, as part of the national team, were Dr Nwaga Dieudonné and his PhD student Kiam Angele, with whom I have been corresponding for about a year. Dr Nwaga (who visited me in Dundee in 1994) and his research group in the University of Yaoundé are studying plant/microbial symbioses, mainly on crop species. The four of us set up a collaborative programme to look at the legume flora of their forests, initially in Bayang-Mbo, for nodulation ability.

From the camp we were able to walk into the forest and excavate roots of legume plants, all of which were either trees or lianas. Inter alia, I was able to test the practical utility of nodule structure and morphology as a taxonomic tool for legumes (Sprent, 2000). For example, on one occasion we found nodules which I predicted would come from one of two genera known from Cameroon, Pterocarpus and Dalbergia, but could see no specimens of these genera in the vicinity. After hours of hard work tracing root systems, about 30m away we connected them to a very large tree of Pterocarpus osun (not previously reported to nodulate). The frequency of nodules on this and other specimens, together with the wide area over which they are dispersed suggest that they play an important role in the nitrogen economy of this ecosystem. Nodule samples were taken and placed over desiccant for later examination in the laboratory and shoot samples were dried for plant identification by Mrs Mackinder. When the latter is complete (samples have to be shipped back to the UK with the relevant paperwork) we hope to have many new reports (both positive and negative) on nodulation. These will form the basis of a publication which we have already outlined and which will be co-authored by all collaborators. An unexpected benefit arose when some of the Darwin Fellows, who were there to identify plants from their above-ground features realised that interesting structures can also be found below ground! One, from Tanzania, offered to carry out searches in his own country, which also has many legumes unexamined for nodulation, and we have already been in communication about this.

This, the first detailed study of nodulation in African rainforest legumes, has already produced a considerable body of new information. Plans have been drawn up to continue the work both in the field and in laboratory studies examining the details of nodulation processes. These should result in a better understanding of how rainforest ecosystems function in Africa and also be of use in their proper management. Trees such as Pterocarpus species are greatly prized as timber and are being heavily cut in non-protected areas of Cameroon. I am grateful to the Royal Society of Edinburgh for making it possible to initiate this work: the results certainly exceeded my most optimistic expectations.

Reference. Sprent, J.I. (2000). Nodulation as a taxonomic tool. Advances in Legume Systematics, 9, 21-44.