INTERNATIONAL GORILLA CONSERVATION PROGRAM

Biodiversity Monitoring Program in the Mwaro ecological corridor,
Mikeno Sector, Parc National des Virunga

Augustin K. BASABOSE^*, M. Gratien BASHONGA^** and Z. BALEZI^***

* IGCP Species Conservation Coordinator

**

Independent Consultant, Botanist

***

Université Officiele de Bukavu
June 2010

ibution of the ve

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Table of Contents

Acronyms 4

Executive Summary 5

Acknowledgements 6

1. INTRODUCTION 7

1.1. Background 7

1.2. Objective of IGCP Monitoring Program in Mwaro corridor 7

1. 3. Study Site 8

1.3.1. Location 8

1.3.2. Climate 8

1.3.3. The Virunga National Park, the Mikeno sector and climate change 8

1.3.4. Vegetation and biological value of the Mikeno sector 9

1.3.5. Mikeno Sector Management 9

1.3.6. Human Environment 10

1.3.6.1. Demographical context 10

1.3.6.2. Economic and Social Context 10

1.3.7. Role of the International Gorilla Conservation Program in

the Mikeno sector 10

2. METHOD 11

2.1. Study techniques 11

2.1.1. Site Selection of permanent transect and plot 11

2.1.2. Establishment of the permanent transect and plot 12

2.1.2.1 Opening the transect 12

2.1.2.2. Establishment of the plot 12

2.1.3. Data Collection 13

2.1.3.1. Data collection on the transect 13

2.1.3.2. Data sampling within the plot 15

2.1. 4. Data processing 15

2.1.4.1. Floristic richness 15

2.1.4.2. Quantitative study of the flora 15

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

2.1.4.3. Vegetation stratification 16

2.1.4.4. Geographic data 17

2.1.5. Documentary research 17

2.2. Material 17

3. RESULTS 18

3.1. Floristic richness of Muwaro corridor 18

3.2. Morphological types of identified species 19

3.3. Vegetation description of the Mwaro corridor 20

3.3.1. Vegetation structure within the 1-ha plot 20

3.3.2. Dynamic of vegetation prospected in the 1-ha plot 21

3.3.3. Altitudinal distribution of the vegetation in the Mwaro

ecological corridor 24

3.3.3.1. Quantitative observation of vegetation in Muwaro corridor 26

3.3.3.2. Assessment of plant species diversity in the 7 segments 35

3.3.4. Herbaceous plant species identified in Mwaro corridor. 36

3.4. Animals signs identified in Mwaro ecological corridor 40

3.5. Human Activities in Mwaro ecological corridor. 41

4. DISCUSSION 42

4.1. Floristic richness and variation between different phytocenoses 42

4.2. Altitudinal variations along the line transect. 43

4.3. Wildlife presence in the Mwaro ecological corridor 44

4.4. Human Activities 44

4.5. Flora of interest to the Mountain Gorilla 45

4.6. Comparison of plant species consumed by gorillas according to different sites 46

5. CONCLUSION 47

6. REFENCES 48

7. ANNEX 50

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Acronyms

PNVi Parc National des Virunga

VNP Volcanoes National Park

IGCP International Gorilla Conservation Program

MGNP Mgahinga Gorilla National Park

ICCN Institut Congolais pour la Conservation de la Nature

FARDC Forces Armées de la République Démocratique du Congo

CNDP Congres National pour la Défense du Peuple

GPS Geograpical Positioning System

DBH Diameter at breast height

DRC Democratic Republic of Congo

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Executive Summary

The present study conducted from October 2009 to January 2010 aimed to assess the ecological role and conservation status of Mwaro corridor, connecting the mountain gorilla habitat in Mikeno sector to the rest of Virunga National Park.

Permanent botanical transect and plot methods were used to assess the dynamic of vegetation within the corridor, specifically assessing spatio-temporal availability of mountain gorilla foods and document seasonal movement of animals using the corridor.

A total of 181 plant species were sampled in Mwaro corridor with only 44.7 % of woody species and 55.3 % of herbaceous plants. Among the woody species, trees (23.2 %) were the most dominant morphological type followed by shrubs (13.2%) and woody lianas (8.3%) while herbs (35.3 %) were most represented among the herbaceous plants followed by herbaceous lianas (12,7 % and ferns (7.2 %).

Out of 181 plant species identified within a 1-ha plot and 7 Km long line transect, only 45 (24.9 %) plant species were reported as consumed by mountain gorilla in Mikeno sector, some of which with a wider distribution across different altitudinal layers in Mwaro corridor.

Signs of 11 species of mammals were identified in Mwaro corridor, among which six were primates (Colobus angolensis, Cercopithecus mitis spp., Cercopithecus mitis kandti, Pan troglodytes, Papio anubis, and Gorilla beringei beringei).

Signs of blue monkey (Cercopithecus mitis) and those of chimpanzee (Pan troglodytes) and black and white colobus (Colobus angolensis) were encountered in lower altitudes of the corridor in the forest dominated by Olea hochtetteri, while calls of golden monkey were heard in both the lower and higher altitudes. Foot prints of Buffaloes have been recorded in the Neoboutonia macrocalyx dominated forest, while fresh trails, droppings and nests of mountain gorillas were found in the highest elevations in Hagenia abyssinica and Hypericum revolutum dominated forest.

In Mwaro corridor, the vegetation is intact with a rich and diverse flora. According to our observations, Mwaro may be seen as a transitional zone where both medium altitude (Sclerophylles forest on lava flow) and high altitude plant species are found. The vegetation evolution looks progressive in Mwaro, with several plant species characteristic of primary mountain forest and with different diameter classes, such as Strombosia scheffleri, Olea hochstetteri, Entandrophragma excelsum, Ekebergia campensis, Schreber alata and Prunus africana.

Mwaro corridor is affected by many illegal human activities, including poaching activities. In fact most of these activities happened in lower elevations of the corridor.

Despite most tragic human conflicts that affected the Mikeno sector in general and particularly the ecological corridor of Mwaro, the corridor could continue playing its ecological role through its rich flora and fauna species.

Acknowledgements

This study was generously funded by the International Gorilla Conservation Programme We express our gratitude to Dr. Emmanuel De Merode, Provincial Director of ICCN and site manager of Virunga National Park who granted a permission to carry out this study in Virunga National Park. During the collection of field data, we have benefited from technical assistance from Warden in Charge of PNVi South and his staff including rangers and trackers to whom we address our thanks. We also thank the Responsible of the Herbarium at the Research Center in Natural Sciences at Lwiro who identified plant samples which we couldn't determine during our field works. To all, we express our gratitude for the work well done.

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Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

1. INTRODUCTION 1.1. Background

The Mikeno sector is the largest component of the Virunga Massif, both in terms of biodiversity and area (about 250 square kilometers, more than half the total area of the Virunga Massif estimated at 440 km²). This is the only component that has remained almost intact in the lower altitude (1800 m above sea level), which was retained in the Mwaro corridor, and which plays an important ecological role for the seasonal movements of a number of animal species such as buffaloes, elephants and sometimes chimpanzees, between Nyamulagira and the Mikeno sector.

Unfortunately, since 1990, Mikeno sector has become the drama of the most tragic human conflicts. A series of wars since 1996 has caused many deaths and significant cross-border migrations. These wars have also destroyed human institutions, resulting in massive deforestation and the slaughter of many wild animals, including the endangered mountain gorilla (Gorilla beringei beringei).

Military units and several thousand refugees engaged in agricultural activities within the park, both in the Mikeno sector of the Virunga National Park in the Democratic Republic of Congo, and in the Volcano NationalPark in Rwanda, cultivating exotic plants such as potato, tobacco, wheat and hemp (Rutagarama, 1999).

We also witnessed massive deforestation by armed groups for strategic purposes. It is in the ecological corridor of Mwaro that links Mikeno sector to Nyamulagira sector in the Virunga National Park that the deforestation has had the greatest impact. To limit the risk of ambush, the military forces cleared the road side vegetation. The cleareance which sometimes went 70 m deep into the forest had negative consequences for this very important ecological link that populations of elephants and other animals used in their seasonal movements.

Additionally, the armed rebel groups have freely used and roamed different parts of the forest in Virunga National Park in particular in the areas around the Mikeno volcano positioning their troops in park rangers' outposts in Gatovu, Kibumba, Bukima and Bikenge. This has had enormous repercussions on the living animal populations inhabiting Mikeno sector as protection from park staff diminished. The ecological role of the Mwaro corridor remains today unclear because its current status has been poorly studied. To fill this gap in information, the IGCP has initiated a program of ecological monitoring within the corridor.

1.2. Objective of IGCP Monitoring Program in Mwaro corridor

The overall objective of the IGCP Monitoring program in the Mwaro corridor is to assess the current ecological role and establish the conservation status of this important corridor connecting two ecosystem blocs (mountain gorilla habitat in Mikeno sector and Nyamulagira sector). To achieve this overall objective, the program should fulfill the following specific objectives:

a.

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Install a permanent transect and plot for collecting data on plant species composition, phenology, and species distribution.

b. Document the seasonal movements of animals between Nyamulagira and Mikeno sectors through the corridor using data collected along the permanent transect and within the plot.

c. Discribe different types of vegetation in the corridor by an altitudinal gradient and assess availability of plant species known eaten by gorillas in this part of the park.

1. 3. Study Site

1.3.1. Location

The Mikeno sector (29 ° 21 'E - 29 ° 36' E and 1 ° 20 'S - 1 ° 31' S) is part of the southern sector of Virunga National Park (Mikeno and Nyamulagira), forming the Congolese component of the Virunga Volcano Range. The Mikeno area is adjacent to and contiguous with the Parc National des Volcans (Rwanda) and Mgahinga Gorilla National Park (Uganda).

1.3.2. Climate

Data on the climate of the Mikeno sector are only available for over 50 years ago. Rainfall surveys taken from 1930 to 1957 using a rain gauge installed at the top of Mount Karisimbi at 4500 m above the sea level, showed an average annual rainfall of only 940 mm , but with quite large variations between years: an annual minimum of 562 mm versus a maximum of 1329 mm, more than double. Coarsely speaking, the Virunga National Park in general and in particular the Mikeno sector, analysis of temperature (averages, maximum and minimum) in both low altitude and high mountains, shows that they have remained stable for several decades (Languy and Merode, 2006).

The IGCP, in its new conservation strategy taking into account the effects of climate change envisages the installation of a network of micro-climate stations around the entire Virunga Massif aiming to study how climate changes at micro-habitat level may affect mountain gorilla behaviour.

1.3.3. The Virunga National Park, the Mikeno sector and climate change

Languy and Merode (2006) showed that the geological history of the Virunga National Park is closely linked to that of the Albertine Rift, which includes it. The formation of the latter is still ongoing; the two sides of the rift follow the tectonic plates which separate eastern Africa from the rest of the continent. Witnesses of this evolution, active Nyiragongo and Nyamulagira volcanoes are among the most active in the world. This geological dynamism has had always an evident impact on the history of park's habitats and plant communities. The succession of the different phases of climate change through history explains the current species rich biodiversity observed in Virunga National Parks.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

1.3.4. Vegetation and biological value of the Mikeno sector

The vegetation of the Mikeno sector is Afromontane. It is, according to the typical classification, that which grows at different altitudes on the African continent according to the latitude and local climates (especially dependent on the importance and frequency of rains). In the Mwaro ecological corridor, mountain forest begins at about 1800 m above sea level.

Data gathered in the present study will be used to update information regarding the area's vegetation.

According to Languy and Merode (2006), the range between 1800 and 2800 meters contains a dense humid forest dominated by Ficalhoa laurifolia and Podocarpus milanjianus, but generally very diverse and rich in plant species. The trees reach 25 m with usually small leaves. At the same altitudinal band, recently deforested areas are evident by the presence of a secondary forest dominated by Neoboutonia macrocalyx.

The bamboo forest is generally between 2300 and 2600 meters on loose soil rich in humus. This is monospecific vegetation of the species Sinarundinaria alpina. Bamboos are enormous fast-growing grasses whose young shoots are eaten by mountain gorillas. Apart from the glades, this type of forest is not conducive to the development of rich and diversified undergrowth. Several herbaceous plants including Viola abyssinica and Clematis sinensis are found in this type of vegetation.

The main vegetation type around 3000 m is the Hagenia abyssinica dominated forest which is an open forest. At this elevation, precipitation decreases significantly and the average temperature drops rapidly.

At higher altitudes, grows a forest of heath, consisting mainly of the species Philippia johnstonii rising up to 10 m high and Erica arborea growing on the dry slopes. The ground is typically covered with a thick layer of moss.

At the upper limit of Hagenia abyssinica and heather trees (Afro-Alpine floor) towards 3700 meters, appear large clearings. The most typical species of these elevations are the Lobelia and Senecio, reaching about 8 m high.

The upper surfaces of Mikeno are steep, contrary to what is observed on other extinct volcanoes in Virunga massif. The biological value of the Mikeno sector is mainly linked to its rich and unequaled biodiversity, compared to other sectors. Central to this diversity is the mountain gorilla, endemic to this area as far as the DRC is concerned. The preservation of the mountain gorilla was the very purpose of the creation of the Virunga National Park, formerly Albert National Park in 1925, as a result of the ideas and pressures of the naturalist and taxidermist, Carl Akeley. Akeley has stated with certainty the idea that gorillas in the sector were few, not suspicious or dangerous and that, consequently, the extinction of this subspecies was imminent if conservation measures were not taken (Languy and Merode, 2006).

1.3.5. Mikeno Sector Management

Management of the Mikeno sector like the whole park in DRC has been entrusted by the Congolese government to ICCN. To better monitor and manage the sector, 5 posts of patrols have been installed including: Gatovu, Bukima, Bikenge, Jomba and Gikeri park ranger outposts.

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1.3.6. Human Environment

1.3.6.1. Demographical context

As elsewhere around the Virunga National Park, the Mwaro corridor is surrounded by a dense human population characterized by about 600 people / km2. One of the serious consequences of rapid population growth in this region is the pressure exerted on the natural resources of the Virunga National Park.

At Kibumba (Gikieri) for example, people cut bamboo for making baskets, winnows and for other uses. A case recently observed during a visit of the permanent transect, three weeks after its establishment, is the cutting of young trees to be used as bean-stakes in the peasant bean fields. Plastic labels on our plants had even been pulled out is some cases.

Much of the population around the Mikeno sector moved into internal displaced camps during the recent clashes between the FARDC and the CNDP leaving their fields fallow. Today, they are back in their gardens looking after their crops.

1.3.6.2. Economic and Social Context

People on both sides of the Mwaro ecological corridor practise mainly agriculture on a very fertile volcanic soil and in a climate tempered by altitude to produce a variety of agricultural products. There exists great potential for agricultural production of bananas, maize, sorghum, beans, potatoes, various vegetables, various fruits such as avocado, papaya, pineapple, orange etc. (Bashonga, 2009).

Before the war, the region produced a lot of agricultural products, the surplus of which was sold in local markets at Rutshuru and Goma and occasionally in Kinshasa.

The region also has a potential to support cattle breeding. There are also small herds of goats, sheep, pigs and poultry including chickens, ducks and turkeys. But farming has been severely affected by the war to the point that many farmers no longer have livestock, although some may still raise a few head of cattle on the edge of the park.

1.3.7. Role of the International Gorilla Conservation Program in the Mikeno sector

The IGCP is a partner of ICCN and particularly active in the Mikeno sector. It provides the mechanism to increase cooperation between national parks, local communities and partners in the region and to develop a regional approach to the conservation of biodiversity and promote the revenue sharing program. The first threat to mountain gorillas comes from population growth in the region and its growing need for land and food supplies. IGCP is working with its partners to reduce specific threats against the mountain gorillas, of deforestation, disease and poaching. The IGCP conservation approach is summarized into four specific strategies, including:

a. Institutional support to strengthen the conservation capacity of ICCN

b. Promote transboundary collaboration to conserve Mikeno biodiversity collaboratively with adjacent protected areas

c. Provide alternative livelihood opportunities to local communities

d. Advocate policies favouring conservation in harmony with adjacent protected areas.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

2. METHOD

2.1. Study techniques

2.1.1. Site Selection of permanent transect and plot

From GIS shapefiles and SPOT images of the area covered by the study has been identified for the preparation of a baseline map.

This map has been enriched by a layer of contour lines which allowed us to identify the best location of the permanent transect and plot for the study of habitat variation according to an altitudinal gradient.

Using the Map Source software and Arc GIS 9.2, we created geographic coordinates of the beginning and the direction of the permanent transect. These coordinates were then uploaded into the GPS and using the «GoTo function» of GPS; thus the planned transect was established in the field.

Figure 1. Location of Mwaro ecological corridor: setting of the permanent botanical 7 km long transect and 1-ha plot

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The plot's, establishment was carried out according to the recommendations of Kuebler (2003), using a vegetation long-term monitoring method alowing to assess the biomass, the growth, the structure and composition the forest.

2.1.2. Establishment of the permanent transect and plot

2.1.2.1 Opening the transect

The coordinates created and downloaded into the GPS were: S 1.45535; E29.34112 On the ground, thanks to the «Go To» function of the GPS, we approximately located the starting point at the coordinates S1.45535, E29.3411, at an altitude of 1867 m and corresponding to the starting point of the permanent transect.

Using a compass, we ran the tracker responsible for the opening of the transect in the East of the magnetic direction corresponding to the orientation of the corridor. The tracker, who opened the transect using a machete was brought back on course at every slightest deviation. Along the transect, each 50 m was marked with a colored ribbon on which was inscribed the distance reached. The distance along the transect was known by reading the figure indicated by the pointer function "map" of GPS. This corresponds to the distances travelled measured as the crow flies (rather tan distance traveled on foot, for example), which are best suited for representation in 2 dimensions of surfaces such as those used when making maps.

2.1.2.2. Establishment of the plot

A 1 ha plot was identified and located in a vegetation of 4 ha earlier prospected on a homogenous ground in Mwaro corridor. The making of the plot started with the opening of two perpendiculars lines in the target vegetation, one towards the east and the other towards the south and each with 100m long subdivided in 5 intervals of 20cm each. The first 2 intervals of 20 m of each transects were attributed the coordinates (00, 20) and (20, 00). At 40 m of each transect the coordinates become (00, 40) et (40, 00), likewise, at 60 m they were (00, 60) and (60, 00). From this we deduce that the coordinates at the end of the transects were: (00, 100) and (100, 00).

To establish a 1ha plot easily as well as to limit 25 quadrates of 20 m X 20 m within the plot, KUEBLER (2003) recommands, to limit the first quadrat at coordinates (20, 20) which corresponds to the perpendicular point at the distances of 20 m of 2 transects. The next point of the limitation of the quadrat n° 2 had thus (40, 20) as coordinates; the third point for quadrat 3 was (60, 20, then (80, 20) for the fourth quadrat and (100, 20) for the fifth.

At this level, the next stage, according to the same method, consisted in identifying the point of limitation of quadrat n° 10 just near quadrat n° 1. This is the point of coordinates (20, 40) then the point of coordinates (20, 60), (20, 80), (20, 100). There followed the identification of point (40, 40) and in the same way the identification of point (60, 40) ; (80, 40) ; and (100,40) as well as (40, 60) and (40, 80) (40, 100). The next identified point was (60, 60) followed by (80, 60) and (100, 60) and then (80, 80) and (100, 100).

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Then the 25 quadrats were identified by reference numbers in 1 - 5, 5-6; 6-10; 10-11; 11-15; 15-16; 16-20; 20-21; 21-25 (figure 4).

20 m

Figure 2. Schematic representation of the 1-ha plot established in Mwaro corridor

2.1.3. Data Collection

2.1.3.1. Data collection on the transect

Along the transect collecting these types of data was performed on regular segments of 500 m between 0 and 500 m, 1000 and 1500 m, 2000 and 2500 m, 3000 and 3500 m, 4000 and 4500 m, 5000 and 5500 and late 6000 and 6500 m.

On each segment, sub-segments of 50 m were also taken to serve as data collection units (Gentry 1982a).

The actual qualitative and quantitative data collection on flora has been made in moving along the transect line. Any woody stem met at 1m on each side of the base line and having a circumference greater than or equal to 10 cm or DBH higher or equal to 2.5 cm was identified, measured, tagged and recorded on a data sheet.

The data sheet has been properly filled in recording the following information: date, segment

number, distance on the transect, GPS point (altitude, latitude, longitude), topography, habitat type, canopy, undergrowth, species name , vernacular name of the species in local language (Kinyabwisha), family, individual height, circumference at the height of 1.30 m above the ground, consumed or not by the gorilla, plant item consumed, phenology status of the tagged individual tree or shrub and personal observations.

For species difficult to identify directly on the transect, the vernacular name was given if known or assigned an herbarium number for further identification using different flora or by comparison with specimens kept at the herbarium.

Figure 3. Reference label on a trunk of a tree in the transect

Each identified tree or shrub was tagged using a plastic number (Figure 2) for long term monitoring of the individual.

Figure 4. Painting the trunk in red at DBH level.

One way to ensure future monitoring of the dynamic growth of the species on the transect was to place a strip of red paint on the trunk at 1.3 m corresponding to the height where the measurement of DBH was performed (Figure3).

The GPS coordinates collected at each 50 m apart on the transect line were completed by recording data on vegetation type, dominant species of tree layer, shrub and herbaceous. We also collected wildlife and human activities data along the transectA form designed to collect these data types was completed each time animal sign or human activity was encountered.

The animal signs recorded were: dung, shouting, footprint, track or trail, nest, razing and other. As for signs of human activities, we noted cutting wood, trails, traps, abandoned objects, camp fire, cutting and others.

Each sign registered was georeferenced using GPS. Additional information was completed on the data sheet every time a sign was encountered. This includes the date, distance on the transect, the observer name, observation time, type of observation, as the case may be a case of animal or human activity, species name to which the animal belongs for the case of animal observation, type of sign, age, status, type of habitat of the place where the sign was discovered, the canopy of vegetation, the undergrowth condition and personal comments.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

2.1.3.2. Data sampling within the plot

All the individuals of any species with a circumference equal to or greater than 10 cm were identified by their scientific and/or local names, by measuring with a tape measure the circumference at breast height. In case of doubt species identification was cross-referenced by using different published references such as TROUPIN (1979, 1983, 1985), HAMILTON (1971) as well as different volumes of the Flora Congo Belgium and Rwanda Urundi, Robyns flora of central Africa (1951,1958).

For unknown species, a sample of the plant was taken and put in a herbarium for further identification at the Lwiro Research Centre herbarium.

We sampled data according to the order of quadrat from the first towards the fifth and then according to the way indicated by the arrows in figure 1 up to the twenty fith.

The following information was recorded: the name of the site, the date, the number of persons at work, the team leader, GPS points, number of the quadrat, the topography of the quadrat, type of vegetation, the configuration of the canopy in a given quadrat, name of the tree or shrub species identified, the n° of the herbarium for the collected sample, the vernacular name, the family of the plant, the circumference as well as the approximative height of the idenntified individual. On the same data sheet is indicated information about whether or not, the registered species is consumed by mountain gorilla, as well as the part consumed. These pieces of information were provided to us by park rangers and trackers who were members of the working team. The phenology of the plant has also been indicated after observation of the vegetative state of the individual recorded. For the phenology, we recorded whether the presence or absence of flowers, fruits (distinguishing ripe and unripe ones), new leaves or no leaves present at all. Besides, we have, for every identified individual plant, assigned a reference n° using plastic tags with numbers stapled on the trunk of each of the individuals measured; this, to assure long term monitoring of the evolution of the DBH and the phenology of every identified plant over time.

2.1. 4. Data processing

All data recorded have been were entered into the computer and analysed in Excel and in ArcGIS 9.2.

2.1.4.1. Floristic richness

To record plant species richness, a systematic list of plant species encountered was established. The number of families, genera and species identified was listed. For each species, the morphological type was also noted. Examples of morphological data collected included tree, shrub, woody liana, herbaceous liana, herb and fern

2.1.4.2. Quantitative study of the flora

Quantitative assessement of different observed features was based on tree identified in different habitat types using DBH data, average height (Hm), basal area (BA), the relative dominance (RDO) and the relative density (RD).

Then determination of the diversity and equitability (H 'and Hmax) of different habitat types was made by calculating the Shannon index for each segment along the permanent transect. Hence, parameters measured for plants with DBH = 10 cm and diversity are:

4 (d= diameter of the individual); (BA in m2/ha)

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Number of indiv. of a species or a familly

Total mumber of indiv. BA of a species

100

Do R =

. ×

Total BA of all the identified species Shannon's indice of diversity, H

H = - Ó Pi (ln Pi)

Pi = proportion of the'species i over the total number of the species S.

Shannon's equitability (EH) can be calculated by dividing H by Hmax (here Hmax = lnS). Equitability assumes a value between 0 and 1 with 1 being complete evenness.

EH = H / Hmax
= H /lnS

The basal area provides information on the area occupied by sections of truncks at 1.30 m above the ground.

The abundance of taxa is calculated to provide information on the number of individuals of a species or family as well as information on how to determine the relative density of taxa. The basal area was also used to calculate the dominance. This reflects the size of individual plants and allows highlighting taxa that occupy the most space in the vegetation.

Diversity of taxa is assessed taking into account the number of individuals within a species or family or in a community. It is also called specific heterogeneity and it is a unique characteristic at the level of biological organization of a community.

Thus, a vegetal community is diversified when it comprises a large number of plant species or families.

2.1.4.3. Vegetation stratification

Vegetation strata were determined according to the following considerations: Superior tree layer (A): > 30 m - 40 m;

Average tree layer (B): 25 to 30 m;

Inferior tree layer (C): 15 to 20 m;

Shrub: 4 to 10 m.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

2.1.4.4. Geographic data

The geographical coordinates collected by GPS were downloaded on a computer. We used Arc Map and Arc Catalog ArcGIS 9.2 software packages to make shapefiles delimitation of vegetation types, animals and signs of human activity on the transect. This, in combination with satellite image of Mikeno sector and other shapefiles available at IGCP Goma office, allowed us to produce various maps included in this report.

2.1.5. Documentary research

It has served to verify the identifications and spellings of species recognized and in the investigation and search for bibliographic information on the identified species.

It also allowed us to gather the necessary literature on the floristic composition of former vegetation to compare with the results of this study and other information on the diet of the mountain gorilla.

2.2. Material

Table 1. Suggested Field Equipments

3. RESULTS

3.1. Floristic richness of Muwaro corridor

The species surveyed are divided into different taxa in a phylogenetic order according to the new classification of Judd et al. (2002), Lejoly (2006-2007) and APG II (2003) and this in alphabetical order (see attached list). Table 2 presents the numbers of species identified per family in the permanent plot and transect open in Mwaro ecological corridor.

Table 2: Number of species per family in Mwaro ecological corridor

N. espèces

Famille

Famille

N°

N. espèces

N°

1

Amaranthaceae

1

Asteraceae

21

32

1

Amygdalaceae

2

13

33

Ferns

1

Apocynaceae

3

Urticaceae

11

34

1

Aquifoliaceae

4

Rubiaceae

10

35

1

Asclepiadaceae

Acanthaceae

36

5

7

1

Basellaceae

6

Fabaceae

7

37

1

Begoniaceae

6

Euphorbiaceae

38

7

1

Boraginaceae

6

8

39

Rosaceae

1

Capparaceae

5

Cucurbitaceae

9

40

1

Clusiaceae

5

Poaceae

10

41

1

Conaraceae

4

Lamiaceae

11

42

1

Convolvulaceae

Araliaceae

12

3

43

1

Cornaceae

Liliaceae

13

3

44

1

Cyperaceae

Meliaceae

14

3

45

1

Dioscoreaceae

15

Moraceae

3

46

1

Ericaceae

Oleaceae

16

3

47

1

Flacourtiaceae

17

Polygonaceae

3

48

1

Geraniaceae

18

Ranunculaceae

3

49

1

Lobeliaceae

19

3

50

Rutaceae

1

Loganiaceae

20

Apiaceae

2

51

1

Maesaceae

21

Araceae

2

52

1

Melianthaceae

22

Asparagaceae

2

53

1

Menispermaceae

23

Balsaminaceae

2

54

1

Monimiaceae

2

Bignoniaceae

24

55

1

Musaceae

2

Celastraceae

25

56

1

Olacaceae

2

Malvaceae

26

57

1

Passifloraceae

27

Myrsinaceae

2

58

1

Phyllantaceae

28

Piperaceae

2

59

1

Pittosporaceae

Rhamnaceae

29

2

60

1

Smilacaceae

Sapindaceae

30

2

61

1

Ulmaceae

Alangiaceae

31

1

62

173

Total

Table 2 presents a total of 173 species grouped into 61 families. Families most specificaly represented are Asteraceae (21 species); Urticaceae (11 species); Rubiaceae (10 species); Acanthaceae and Fabaceae (7 species); Euphorbiaceae and Rosaceae (6 species) and finaly Cucurbitaceae and Poaceae (5 species). The total number of species identified is 181, when

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

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Page 19

including 8 not yet determined and not listed in Table 2. Additionaly, ferns were not identified at species level due to lack of adequate documentation.

3.2. Morphological types of identified species

So far, a total of 181 species have been identified in the permanent 1-ha plot and 7 km long transect in the Mwaro ecological corridor. Morphological types of the identified species are presented in Table 3.

Table 3: Morphological types of species inventoried

The reading of Table 3 shows a dominance of herbaceous species over other species with 87 species (herbs and herbaceous lianas), versus 81 woody species (Trees, Shrubs and woody lianas). This is likely attributable to the fact that the line transect was done across Mikeno mountain and the higher we went in altitude, the rarer woody species became.

Table 4: Distribution of species in morphological types in prospected phytocenoses

*total area of the 7 segments of 0.1 ha each. Each Segment has 500 m long and 2 m wide. 500 m segment has been suggested as best method for rapid assessment of forest habitats and plant diversity. It is useful to compare different habitats in terms of forest structure and composition of their flora (GENTRY 1982).

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

When examining Table 4, we notice that, though the plot surface is slightly bigger than the transect, it is on the line transect where we found a high specific diversity with a good proportion between the different morphological types, probably because the transect covers differet altitudes, given that some plant species are specific to a type of altitude. We also notice a great dominance of herbaceous species in both phytocenoses.

3.3. Vegetation description of the Mwaro corridor

3.3.1. Vegetation structure within the 1-ha plot

The plot established at Mwaro presents distinct stratified vegetation with all the forest strata well represented. A total of 1246 individuals with a circumference superior or equal to 10 cm has been inventoried among which trees, shrubs and sub- shrub. Figure 5 schematizes the stratification of the vegetation of Mwaro as observed from the results of the 1-ha plot.

8 species of which Schrebera alata, Prunus africana, Olea hochstetteri, Croton macrostachyus, Ehretia cymosa, Bersama abyssinica ssp. paullinioides, Polyscias fulva and an unknown (Umuhanamambo in the local dialect, the Kinyabwisha) occupy the superior arborescent stratum (35 - 40 m). A woody liana Cissus humbertii is found in this stratum.

The middle arborescent stratum is on its part occupied by the species Albizia adiantifolia., Alangium chinense, Erythrina mildbraedii, Ekebergia capensis as well as the lianas Gouania longispicata, Mezoneuron angolense and Mimulopsis solmsii.

In the lower arborescent stratum we find some trees such as Afrocrania volkensii, Bridelia micrantha, Maesa lanceolata, Tabernaemonta johnstonii, Drypetes ugandensis and Kigelia africana as well as of the lianas Urera hypselodendron, Adenia rumicifolia, Rhamnus prinioides, Clerodendron johnstonii and Toddalia asiatica.

The species, Xymalos monospora, Lepidotrichilia volkensi, Allophyllus kivuensis, Maytenus arguta constituting the essential of the sub-wood are at the same time present in the lower arborescent stratum and the shrubby stratum while Psychotria mahonii, Markhamia lutea, Galliniera coffeoide. Leptonichia mildbraedii and Oxyanthus speciosus occupy the shrubby stratum exclusively.

Page 21

Figure 5. Structure of the vegetation in the plot at Mwaro (Y = height in m and X = Plant species)

3.3.2. Dynamic of vegetation prospected in the 1-ha plot

According to our observations, the phytocenose represented by the 1-ha permanent plot is an ecotone bearing vegetation of both the average altitude (sclerophylles forest on stream of lava) and high altitude vegetation. The evolution of this vegetation seems progressive concidering its state and the presence of several young plants characteristic to primary mountain forest such as Strombosia scheffleri, Olea hochstetteri, Entandrophragma excelsum, Ekebergia campensis, Schrebera alata and Prunus africana (Figure 5). We also noticed presence of some individuals belonging to primary forest species, sometimes seen with big circumferences, but without remarkable promising succession.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Figure 8. Diameter classes for Bersama abyssinica ssp. paullinioides

Figure 6. Diameter classes for Olea hochtetteri

Figure 7. Diameter classes for Entandrophragma excelsum

Figure 9. Diameter classes for Afrocrania volkensi

In Figures 6 and 7 we observe young individuals of Olea hochstetteri and Entandrophragma excelsum growing in the corridor and ready to generate a future stable primary forest provided that no external factors disturb this natural evolution. Observed adult individuals of Olea hochstetteri are expected to ensure good successors for the maintenance of this important species. This is similar to the observations of Bersama abyssinica ssp. paullinioides and Afrocrania volkensii (Figures 8 and 9), two important species typical of Sclerophyles forests growing on the slope of the northern side of Nyamulagira Mountain on recent lava streams.

This is not the case for Entandrophragma excelsum, all individuals of which are young (Figure 7). A long term monitoring program should be initiated to assess the establishment of this important species within Mwaro corridor. A similar observation is made for 2 other species (Ekebergia capensis and Schrebera alata, figures 10 and 11), with the presence of young individuals predicting a good future representation of a primary forest in the Mwaro corridor, though young individuals of these two species were limited in number.

Figure 10. Diameter classes for Ekebergia capensis

Figure 11. Diameter classes for Schrebera alata

Figure 12. Diameter classes for Prunus africana

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Prunus africana (Figure 12) represents a better distribution of the size classes according to the plot established in the Mwaro ecological corridor of. Indeed, the tendency of distribution of diameter classes for this species is a reverse curve in" J ", with a lot of trees of small size (or young trees) than adult ones. This big number decreases with regard to the number of individuals of 30 to 60 cm of diameter.

We, however observed, some individuals of very large size (>60 cm of diameter) that, once extinct will let new generations ensuring a good conservation status of the species in the Mwaro corridor for long term.

As for Strombosia scheffleri, the recorded individuals were less than 10 cm in diameter or were seedlings met in the herbaceous stratum. With time, these individuals will grow up in classes of diameter = 10 and with the dynamics of the aforesaid vegetation will be part of the climax forest the environment conditions allow.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Figure 13. Description of different vegetation types along the permanent line transect

3.3.3. Altitudinal distribution of the vegetation in the Mwaro ecological corridor

According to the vegetation data collected along the line transect, the altitudinal distribution of Mwaro corridor is presented in Figure 13.

Six different types of vegetation have been described on the line transect (Figure13). From the point of distance 0 m (S1.45535, E29.34111) at around the altitude of 1867 m and moving eastward to the point of contact S1.45663, E29.34778 at 1915 m above sea level corresponding to the distance of 750 m on the line transect, we noted a primary forest of Olea hochtetteri with undergrowth dominated by Lepidotrichilia volkensi and Xymalos monosporous.

From this contour line at about 1200 m of distance on the line transect grows a forest type dominated by Afrocrania volkensi with spread stems of Schreber alata. The end of this vegetation has been marked at the point of contact S1.45754, E29.35296 to 1962 meters above the sea level.

Page 25

Further on the line transect, we found a wider range of typical secondary forest with spread stems of Neoboutonia macrocalyx estimated at 3.35 km as the crow flies on the line transect. The undergrowth was very dense and is made up of Acanthus pubescens lining up to the foot of Mount Mashahi around the contour line of 2400 m of altitude.

This vegetation type is associated with Dombeya goetzenii. We have noted this change in vegetation at 2372 m above sea level. The vegetation Neoboutonia macrocalyx and Dombeya Goetzens described above have their upper limit at a distance of 5150 m along the line transect corresponding to the altitude of 2552 m at the point of contact noted S1.46294 E29.38812. At this point begins Hagenia forest where we also observe several stems of Hypericum revolutum until about 3000 m above sea level at 6600 m of distance on the line transect. The GPS coordinates collected at this level are S1.46522 E29.39963. Vegetation dominated by Prunus africana grows from this altitude on steep slopes and grows until the end of our line transect at 7000 m of distance. The altitude taken this point was at 3190 m. The shape of the topography of the Mwaro corridor is presented in Figure 14.

Distance on transect (m)

Mashahi Hill

Altitude (m)

Fig.14. Topographic shape of Mwaro ecological corridor

In general, the topography of the Mwaro corridor presents the appearance of a slight slope to the
foot of Mount Mashahi around 2200 meters. Beyond Mashahi, it presents a valley where grows

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

a vegetation dominated by Sphagnum moss. Further, the slope becomes gradually steeper and beyond 2500 m even steeper.

3.3.3.1. Quantitative observation of vegetation in Muwaro corridor

We represent in Tables, 3, 4, 5, 6, 7 and 8 the results of our study on the structure of vegetation according to the data we collected in the permanent 1-ha plot and the 7 Km line transect. Figures 15 to 20 are graphs representing the stratification of vegetation for segments 1 to 4 of 7 segments delineated on our line transect.

Table 5. Species with circumference = 10 cm identified within the 1-ha permanent plot in the Mwaro corridor

Page 27

We observed (Table 5) a good representation of woody species with 1246 individuals belonging to 55 different species. The mean height of trees is 8.2 m ranging from 2 to 40 m, with all the forest stata being represented. However the undergrowth of the 1-ha plot is very dense, dominanted by Xymalos monospora, Lepidotrichilia volkensi and Allophylus kivuensis among the most represented species. In this phytocenose, the herbaceous strata is dominated by Acanthopale pubescens and Mimulopsis solmsii.

Table 6. Species with DBH = 10 cm of segment 1 of the 7 Km line transect in Mwaro corridor

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Figure 15. Stratification of the vegetation in segment 1 at Mwaro ecological corridor

Table 6 highlights a good representation of woody species with 252 individuals distributed

in 36 species. In this phytocenose, species of Lepidotrichilia volkensi and Xymalos monosporous are best represented in number of individuals followed, by species of Alangium chinense, Afrocrania volkensii and Olea hochstetteri.

Olea hochstetteri dominates in this phytocenose with a relative dominance (DOR) of 51.66, followed by Lepidotrichilia volkensi and Xymalos monosporous.

In terms of stratification of the vegetation in segment 1 (Figure 4), the upper tree layer is exclusively occupied by Olea hochstetteri, while the average tree layer is dominated by woody lianas such as Cissus humbertii, Toddalia asiatica, Adenia rumicifolia, Dalbergia lactea and Mikaniopsis ruandensis accompanied by tree species typical of secondary forest like Polyscias fulva, Ilex mitis, Macaranga neomildbraediana and Ehretia cymosa. Lepidotrichilia volkensi and Xymalos monospora are characteristic of the shrub strata.

The calculated values of basal area (BA), relative density (RD) and relative dominance (RDO) of species inventories in segment 2 are presented in Table 7 below.

Page 29

Table 7: Species with DBH = 10 cm segment 2 of the 7 Km line transect in the Mwaro corridor

Table 7 presents the data collected in segment 2 with a total of 185 individuals grouped into 31 species. In this phytocenose, species Lepidotrichilia volkensi, Maytenus arguta, Afrocrania volkensi are the most represented as far as number of individuals is concerned. They occupy the shrub layer, while woody lianas like Urera hypselodendron, Mezoneuron angolense, Gouania longispicata and Sheffleura myrianta occupy the tree stratum (Figure16).

Afrocrania volkensi occupies more space in this phytocenose (RDO = 32.55). Its many young
individuals (Figure 7) show good regeneration implying that this species will remain for long

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Page 30

time again in this habitat to which it is characteristic, though in the dense shrub layer, some of its individuals reach the lower tree layer (Figure 9).

12

12

²

Nbre eso.

Hauteur 1m1

10

10

8

8

6

a 43. 0) CO ti

6

4

4

0

2

20.1-30 cm

40.1-50 cm

30.1-40 cm

50.1-60 cm

1-10 cm

10.1-20 cm

0

Classes de diamètre

Classes de hauteur

4-10 m 11-14 m 15-20 m 21-25 m 26-30 m >30 m

Figure 16. Stratification of the vegetation in segment 2

Figure 17. Diameter Classes for Figure 18. Height Classes for Afrocrania

frocrania volkensi volkensi

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

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The calculated values of basal surface (BA), relative density (RD) and relative dominance (RDO) species inventoried in segment 3 are presented in Table 8 below.

Table 8. Species with DBH = 10 cm segment 3 of the 7 Km line transect in Mwaro corridor

Hauteur moyenne (m)

12

10

8

6

4

2

0

Urera
hypselodendron

Lepidotrichilia
volkensi

Neoboutonia
macrocalyx

Alangium
chinense

Drypetes
ugandensis

Croton
macrostachyus

Espèces inventoriées

Figure 19. Stratification of the vegetation in segment 3

As shown in Table 7, unlike segments 1 and 2, segment 3 has a specific poverty in term of number of species. In total only 32 individuals, grouped in 6 woody species were observed in this phytocenose. The higher relative density (RD) is that of Neoboutonia macrocalyx, species occupying at the same time the most space in this segment. It is thus the characteristic species in the vegetation of this segment. A good number of individuals occupying the tree stratum, although its average height is lower (Figure 9), given its many young individuals observed. The shrub layer in this segment is dominated by Lepidotrichilia volkensi.

The calculated values of basal surface (BA), relative density (RD) and relative dominance (RDO) species inventories in segment 4 are presented in Table 9.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

N. indiv.

25

20

15

10

5

0

2_10 11_15 16_25

Hauteur (m)

Page 32

Figure 20. Height classes for Neoboutonia macrocalyx

Table 9. Species with DBH = 10 cm of segment 4 of the 7 Km line transect in Mwaro corridor

We observe only 42 stems of 7 woody species in Segment 4 (Table 9). Neoboutonia macrocalyx is dominant in this phytocenose. It occupies more space DOR: 67.78. It is also more dense in this phytocenose, thought its average height is low (Figure 20) because of the many young individuals observed (Figure 21).

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Hauteur (m)

30

25

20

15

10

5

0

Albphylus
abyssinicus

Urera
hypselodendron

Maesa lanceolata

Alangium
chinense

Dombeya goetzeni

Lepidotrichilia
volkensi

Espèces inventoriées

Neoboutonia
macrocalyx

Page 33

Figure 21. Stratification of the végétation insegment 4

Table 10 shows the values of basal surface (ST), relative density (RD) and relative dominance (DOR) species inventories in segment 5.

Table 10: species DBH = 10 cm segment 5 of the 7 Km line transect in Mwaro corridor

Only five species and 45 stems were identified in phytocenose of segment 5. Neoboutonia macrocalyx and Dombeya Goetzens dominate this phytocenose in term of their relative densities as shown by the higher number of stems (Table 7).

Results of basal area (BA), relative density (RD) and relative dominance (RDO) of species identified in segment 6 are presented in Table 11.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

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Table 11: species DBH = 10 cm segment 6 of the 7 Km line transect in Mwaro corridor

Table 11displays a total of 60 stems identified in segment 6. Hagenia abyssinica appeared for the first time in this segment. It is also dominant in this new phytocenose; RDO = 63.63, followed by Hypericum revolutum another species characteristic of this phytocenose in high altitude. Neoboutonia macrocalyx which reached its optimum in the previous segment is still well represented in this phytocenose, though not dominant. Indeed, its relative dominance (RDO) is only 28, 2 against 91.6 in segment 5 where it was the most dominant species.

Table 12 lists the results of the basal surface (BA), relative density (RD) and relative dominance (RDO) species inventories for Segment 7.

Table 12: Species DBH = 10 cm segment 7 of the 7 Km line transect in Mwaro corridor

As with Segment 3, 4, 5 and 6 (Tables 8, 9, 10 and 11), Segment 7 (Table 12) shows a clear poverty in plant species, with only 5 identified species (one to be determined) in this phytocenose of 0.1 ha with only 43 stems identified. This phytocenose located at high altitude is dominated by Hypricum revolutum and Hagenia abyssinica with RDO of 41.57 and 33.36 respectively. It is therefore possible to extrapolate from what we observed in the Mwaro ecological corridor that, in the Mikeno sector, the more we climb in altitude, the rarer woody species become. The relative density of each species is low, the stems of the trees are scattered and the canopy is therefore open. This ecological condition is more fovarable to excessive growth of herbaceous vegetation, with many species that compose mountain gorilla foods.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Segment 1 Segment 2 Segment 3 Segment4 Segment5 Segment6 Segment7

N.species

45

40

25

20

35

30

15

10

5

0

Page 35

Figure 22. Cumulated curves of species with DBH =10 cm inventoried in different segments

Figure 22 shows a clear and specific diversity of plant species greater in the first two segments 1 and 2. In these phytocenoses, we gradually observed new species as we moved on the line transect; this species richness contrasted with what we observed when we reached phytocenoces located in higher altitude in segments 3,4,5,6, and 7.

3.3.3.2. Assessment of plant species diversity in the 7 segments

Table 13. Diversity and equitability of different segments surveyed in the 7 km line transect in Mwaro corridor

Legend:

H = diversity

Equitability Indice = H / Hmax Segm = segment

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

It appears from Table 13 that it is the segments 1 and 2 which have a good diversity of species, but with relatively low equitability in abundance. The similarity test below (Figure 23) provides another way to compare data obtained in the 7 segments.

Seg7

Seg6

Seg5

Seg4

Seg3

Seg2

Seg1

UPGMA

0.04 0.2 0.36 0.52 0.68 0.84 1

Jaccard's Coefficient

Figure 23. Similarity between segments taking into account the number and types of species identified with DBH = 10 cm

Figure 23 confirms the previous results showing phytocenoses of segments 1 and 2 highly diversified in plant species than segments 3, 4, 5, 6 and 7 located in higher altitude.

The dendrogram shows three different phytocenose classes as far as similarity in plant species is concerned (phtocenose of segment1 and 2; phytocenose of segments 3 and 4 and phytocenose of segments 5, 6 and 7).

Because of the altitudinal proximity between consecutive segments, there is good reason to believe that this similarity is a function of altitude.

3.3.4. Herbaceous plant species identified in Mwaro corridor.

Table 14. List of herbaceous species of the ecological corridor of Mwaro

Page 37

8

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

58

Page 39

Table 14 shows 107 species of herbs for all 7segments delimited along the 7 Km line transect. Species with wider distribution, that is to say those found on at least 5 of 7 segments are: Basella alba, Clematis simensis, Coccinia milbraedii, Desmodium rependum, Dryopteris manniana, Gynura rwenzoriensis Impatiens burtonii, Laportea ovalifolia, Mimulopsis solmsii, Oreosyce Africana, Stephania abyssinica, Thalictrum rhynchocarpum, Urera hypselodendron and Vernonia auriculifera.

Table 15. List of species eaten by mountain gorillas identified along the 7 Km line transect plotted in Mwaro.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Figure 24. Distribution of animal signs along the 7 Km line transect of Mwaro

40

It appears from Table 15 that from all identified 181 plants species in the Mwaro corridor, 45 are reported consumed by the mountain gorilla in the Mikeno sector. Ten species were registered on most of the 7 segments and, therefore, regarded as species of wider distribution in this corridor. These include Basella alba, Desmodium rependum, Discopodium penninervium Impatiens burtonii, Impatiens purpureo-violacea, Mimulopsis solmsii, Urera hypselodendron, Vernonia auriculifera and Tacazze apiculata.

3.4. Animals signs identified in Mwaro ecological corridor

Signs of 11 species of mammals were identified in the Mwaro corridor (Figure 14). Among these mammals, six species of primates were identified: Colobus angolensis, Cercopithecus mitis spp., Cercopithecus mitis kandti, Pan troglodytes, Papio anubis, and Gorilla beringei beringei.

Page 41

Signs of blue monkey (Cercopithecus mitis) and those of chimpanzee (Pan troglodytes) and black and white colobus (Colobus angolensis) were identified in lower altitudes of the corridor in the forest dominated by Olea hochtetteri. Foot prints of buffaloes have been recorded in the Neoboutonia macrocalyx dominated forest, while fresh trails, droppings and nests of mountain gorillas were found in the highest elevations in Hagenia abyssinica and Hypericum revolutum dominated forest.

Old chimpanzee nests and feaces, and baboon sightings were recorded in the permanent plot located in the northern part of our line transect, while calls of golden monkey were heard in the lower altitudes but also higher towards the end of our line transect.

3.5. Human Activities in Mwaro ecological corridor.

Figure 25. Human activity signs recorded along the 7 Km line transect in Mwaro corridor

The Mwaro corridor is affected by many illegal human activities, including poaching particularly occurring in lower elevations (Figure 25). The many fresh human paths encountered, sufficiently demonstrate the frequent movement of poachers in this important ecological corridor.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Page 42

4. DISCUSSION

4.1. Floristic richness and variation between different phytocenoses

Results of this study show evidence of floristic richness in the Mwaro corridor, which connect two afromountain phytocenoses (Nyamulagira and Mikeno sectors). We noticed a good representation of the afromountain species that have been recorded by Dowselt (1990) in Nyungwe forest: Olea hochstetteri, Maesa lanceolata, Ilex mitis and Nuxia congesta.

During our investigations, we identified Dombeya goetzenii, endemic species of the eastern part of the Rift Albertine region, in one of the Mwaro habitats. The Mwaro corridor is therefore an important phytocenose were key important plant species are growing.

We compared our results with those obtained by other researchers who undertook similar studies in other ecosystems, using the transect method.

The study of plant diversity in the Mwaro ecological corridor shows a decrease of a species richness of woody plants with increase in altitude. Indeed, segments 1 and 2 located in the lower altitudes are the richest. These 2

Figure 26. Distribution of woody and herbacous species in different segments.

Number of species

40

60

50

30

20

10

0

Segl

ot Herbaceous

herbacées species Woody Espèces species ligne

Seg2

Seg3

Seg4

Seg5

Seg6

Segments

Type se

Seg7

segments are in the altitudinal edge below 2000 m.

Thirty-six wood species are noted in segment 1 and 31 in segment 2, while fewer than 10 species were found in segments located in higher altitude (segments 3, 4, 5, 6, and 7).

One species economically coveted by local communities for charcoal, Olea hochstetteri, forms an intact vegetal group in the first two segments. It is one of the bigest trees growing in mountain forests, also described by Dowselt (1990) in the Nyungwe forest.

Unlike the woody flora, qualitative study of the altitudinal distribution of herbaceous species has in contrast showed little change in its composition. The specific herbaceous composition of each segment depends on the altitude, though the trend is not as such strongly remarkable as for woody species as shown in Figure 26.

We indeed observe a decrease in the number of woody species from the segment 3 and this number remains low towards the end of the line transect (Figure 26).

In contrast, the number of herbaceous species decreased slightly in segment 3, but the maximum is observed at high altitudes (see segment 6). We therefore conclude that in the Mwaro corridor, the higher elevations are richer in herbaceous species where woody species are rare.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Page 43

4.2. Altitudinal variations along the line transect.

Figure 27. Vegetation with Prunus Africana on Mikeno slope at 3200 m of altitude

The study of altitudinal variations in vegetation along the line transect open in the Mwaro corridor has documented 3 different horizons that match those described by Lebrun and Gillbert (1944) in mountain forests. The first is the lower horizon located between 1600 and 1900 m, then the average horizon between 1900 and 2100 m, and the higher horizon between 2100 and 2400 m above sea level. Species characteristic to these horizons are those also suggested by these authors. It is for the case of the Mwaro survey the following species: Bersama abyssinica ssp. paullinioides, Alangium chinense, Lepidotrichilia volkensi, Olea hochstetteri and Xymalos monosporous. Gillbert and Lebrun (1944) describe the following synecologic features for this type of vegetation: heavy rainfall, low temperatures with frequent fog, high radiation and high atmospheric humidity. The grounds are covered with abundant litter with good composition and deep penetration of humus. According to these authors, such vegetation presents the following physiognomy and structure: species of medium size (20 to 25 m), a less dense layer due to the lower density of the upper layer and greater intensity. Thus, using these features we may classify the vegetation of the Mwaro corridor, located between 1800 and 2400 m above sea level, in the phytosociological order of FicalhoetoPodocarpetalia.

The study also highlighted the existence of a secondary forest with Neoboutonia macrocalyx and Dombeya Goetzeni from 2400 m and a development of Afro-montane vegetation from 2600 m of altitude. The latter is dominated by species associated with Hagenia abyssinica and Hypericum revolutum up to the upper limit at about 3000 meters of altitude. At this level, precipitation decreases significantly and the average temperature drops rapidly (Languy and Merode, 2006).

The transect open in Mwaro corridor and throughout the contour line of 3000 m above sea level helped to discover another type of vegetation that is still poorly known; it is a vegetation dominated by the Prunus africana rich in Lobelia giberoa, Stachys aculeolata and Crassocephalum lucis-aprutii in the herbaceous layer. At higher altitudes, which our line transect didn't reach, Languy and De Merode (2006) noted the presence of a forest heath, consisting mainly of the species of Philippia johnstonii up to 10 m high and Erica arborea on the drier slopes.

At the upper limit of tree heath (Afro-Alpine floor), according to the same authors, there are large clearings towards 3700 meters above sea level. Plant species most typical of these elevations are Lobelia and Senecio, reaching about 8 m high.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

4.3. Wildlife presence in the Mwaro ecological corridor

The Mwaro ecological corridor is historically well known for being frequently used by wildlife to migrate between the Nyamulagira and Mikeno sectors. Results of this study show the presence of 11 species of mammals including 6 primates: mountain gorillas, golden monkeys, blue monkey, Black and white colobus, chimpanzee and Baboon. Chimpanzees and baboons were inventoried in the lower altitude in the Mwaro corridor (below 2000 m above sea level) while the calls of the golden monkey were heard at around an altitude of 2900 m. The mountain gorilla in this region ranges in higher altitudes between 2900 and 3000 m above sea level. According to the trackers and park rangers who have assisted us, these are the families of gorillas not yet accustomed to human presence.

Fresh trails of elephants and buffaloes were recorded at the foot of the Mashahi hill. We have also noted signs of grazing of duiker near Mashahi. All These observations predict a rich diversity of wildlife in the area.

Figure 28. Nest of mountain gorillas at 6300 m on the line transect

Figure 29. Mountain gorilla habitat
towards 6300 m on the line transect

Three distinct zones are particularly important for wildlife that we have identified along the line transect. The first zone of wildlife concentration was noted at the origins of the 7 Km line transect in the forest dominated by Olea hochstetteri (Figure 12), the second area is in middle position of the line transect in the secondary forest dominated by Neoboutonia macrocalyx and finally the third zone is located at the highest altitudes at the end of the transect.

4.4. Human Activities

As elsewhere around the Mikeno sector, the Mwaro corridor is surrounded by a dense growing human population. The consequence of this population growth is the pressure exerted on the natural resources of the park. Indeed, signs of human activity were seen in the Mwaro ecological corridor. However, the majority of these activities are noted in the first half of the

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line transect, that is to say, near the foot of Mount Mashahi (Figure 13). We did not notice these types of signs at the highest altitudes. Over 80% of signs of human illegal activities consist of trails, most of which are actively used for poaching. The remaining signs are cuts of shrubs with machetes. We noted a strong pressure on natural resources of plant origin at the limit in the park near the Kibumba ranger outpost for finding tutors used in the fields of climbing beans. A more spectacular case was the removal of plastic labels three weeks after their fixations on 8 individuals of the species Maytenus arguta at the distance of 1250 m on the transect. Another interesting case is the cutting of the trees of the type of Olea hochstetteri used to manufacture wheel of a type of traditional wooden bicycle known locally as the "Chukudu" and utilized for transporting food products and charcoals. Olea hochstetteri is also highly prized for the quality of charcoals it produces; this exposes the species to potential threats.

4.5. Flora of interest to the Mountain Gorilla

We have reported throughout this study that 40 species of plants are eaten by gorillas. Species widely distributed over the transect were: Basella alba, Desmodium rependum, Discopodium penninervium, Impatiens burtonii, Impatiens purpureo-violacea, Mimulopsis solmsii, Urera hypselodendron, Tacazze apiculata, Thalictrum rhynchocarpum and Vernonia auriculifera. Note also that the herbaceous plant species consumed by mountain gorilla were present in more or less stable composition along the line transect excluding the following: Begonia meyerijabannis (segment 6), Carduus nyasanus var nyasanus (segment 5), Ensete Ventricusum (segment 4), Lactuca sp. (segment 6), Lobelia giberroa (segment 7), Rudia cordifolia (segment 2) and Vernonia adolfi-fridoricii (segment 7). These are indeed specific to particular segments and are therefore the less widely distributed on the line transect. These species are those which respond to the rule of altitudinal distribution and were found in specific ranges of altitude.

Figure 30 compares the species eaten by gorillas in the whole herbaceous flora in the Mwaro corridor.

The highest elevations are specifically the most diverse in herbaceous species. Accordingly, species eaten by gorillas follow the same trend. Thus, it seems that the presence of more species eaten by gorillas at higher altitude may explain why the mountain gorillas prefer high altitudes as their ecological niche where they may find most of their foods and at the same time avoid food competition with other primates present in high density at lower altitudes.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

Number of species

40

20

60

50

30

10

0

Segl

ot herbacées

Herbaceous species Esp. Consommées

Species eaten by Gorillas

Seg2

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ype segme

Segments

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Figure 30. Distribution of herbaceous species eaten by mountain gorilla in different segments

4.6. Comparison of plant species consumed by gorillas according to different sites

Another study of plant species of interest to the gorillas is the one carried out in Kahuzi-Biega National Park (Yamagiwa et al., 2004). It brings together 236 items from 116 species identified as food for gorillas inhabiting the montane forest of Kahuzi-Biega National park. Of these species, 44 are consumed for their fruits, 5 for their seeds, 80 for their leaves, 1 as a young plant, 9 for their flowers, 6 for their the roots, 32 for their barks, 2 unidentified dead wood and 6 for their stems.

Comparing our results with those of Yamagiwa et al. (2004), the most species reported as gorilla food in the Mwaro corridor were also reported in Kahuzi-Biega. To name just a few: Discopodium penninervium, Basella alba, Urera hypselodendron and Ensete ventricosum among others. There is also a large number of species in Mwaro not reported as consumed by the gorillas in Virunga National Park, while reported as eaten in Kahuzi-Biega National Park. It is for example: Schefflera goetzenii and Jasminum abyssinicum

A similar study carried out in Bwindi Impenatrable National Park in Uganda (Ganas et al., 2004) compared the species eaten by mountain gorillas following an altitudinal gradient, putting more emphasis on the differentiation of gorilla feeding behaviour according to the consumed parts of the plant. According to this study, there is a very marked difference between the plant parts eaten by gorilla with altitude.

In lowland forest, gorillas eat more woody items and fruits than in high altitude zones. Our study conducted at high altitude showed that leaves and fruits are by far more heavily consumed by the gorilla (Table 14) despite that Elegart (2004), after examining parts eaten by gorillas in each species of plants, it is found that leaves and fruit had negligible value.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

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5. CONCLUSION

We observed that plants in the Mwaro ecological corridor are subject to an altitudinal distribution, with a less marked presence of woody species at higher altitude, the inverse of herbaceous species. The higher elevations are rich in herbaceous species eaten by gorillas, which could explain the preference of these sites by gorillas. Despite most tragic human conflicts that affected the Mikeno sector in general and particularly the Mwaro ecological corridor, the corridor could continue playing its ecological role through its rich floral and faunal species observed during our study.

The line transect and plot established in Mwaro corridor are permanent and therefore will allow us to maintain a long-term monitoring of flora and fauna in this ecosystem.

The permanent line transect and plot will also document the use of this corridor by various animal species.

The Mwaro corridor will certainly play a big role for a more deepened understading of altitudinal distribution of plant species and especially those consumed by the gorillas, taking into account species growing at the summit of Mount Mikeno that have not been explored in the field.

The presence of chimpanzees in the Mwaro corridor will provide an interesting opportunity to document possible sympatry between mountain gorillas and chimpanzees in the Virunga Massif still not elucidated until now.

From a scientific perspective, the permanent line transect and plot will facilitate the pursuit of other studies in the fields of ornithology, small mammals, entomology, reptiles and others. Students in conservation or ecology could also use this transect for data collection of their final university dissertation or postgraduate degree.

From the conservation point of view, the permanent line transect and plot will facilitate better
monitoring of the area to fight against illegal activities which are a reality for this area.

Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

6. REFENCES

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Dowsett - Lemaire, 1990. Physionomie et végétation de la forêt de Nyungwe, Rwanda. Jupille - liège, Belgique. 29p.

Elgart-B., 2004. Fracture toughness of mountain gorilla (Gorilla gorilla beringei) food plants. New york.

Fimbel, R., 2004. Sericostachys scandens. A keystone plant in Nyungwe forest of southern in Rwanda. PCFN. 11p.

Ganas, J., Robbins, M.M., Nkurunungi, J.B., Kaplin, B.A. and Mc Neilage, A., 2004. Dietary variability of mountain gorillas in Bwindi Impenetrable National Park. International Journal of Primatology. Vol. 25.

Gentry, 1982 . Patterns of neotropical plant species diversity. Evol. Biol. 15:1-84 Hamilton, 1971. A field guid to Uganda forest trees, 279 p.

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Languy, M. et De Merode, E. 2006. Virunga ; survie du premier Parc d'Afrique. Lannoo, Tielt, Belgique, 352 pp.

White, L. et Edwards, A. 2000. Conservation en forêt pluviale africaine : méthodes de recherche. Wildlife Conservation Society, New York, 444 pp. nombreuses illustrations.

Lebrun, J. et Gilbert, G., 1954. Une classification écologique des forêts du Congo. Publ. I.N.E.A.C., Sér. Sci. N° 63.

Lejoly, J. 2007. Gestion des forêts tropicales. Cours inédit. Fac. des Sciences Université du Burundi.

Owiunji, I.; Nkuutu, D; Kujirakwinja, D; Liengola, I.; Plumptre, A.; Nsanzurwimo, A.; Fawcett, K.; Gray, M. and McNeilage, A., 2004. The Biodiversity of Virunga Volcanoes. Technical Report WCS, DFGFI, ICCN, ORTPN, UWA, IGCP. 53 p and Appendix.

Robyns. 1951 et 1958. Flore du Congo - Belge et du Rwanda - Urundi (Spermaphytes), Vol II et III. INEAC, Bruxelles.

Rutagarama, E. 1999. Initiative d'implication des populations dans des microprojets de gestion du Parc National des Volcans. Rapport préliminaire d'exécution des projets. IGCP (International Gorilla Conservation Program).

Troupin, G., 1982. Flore des plantes ligneuses du Rwanda. Tervuren.747 p. Troupin, G., 1985. Flore du Rwanda.Spermatophytes Vol.III. Tervuren. 729 p. Troupin, G., 1988. Flore du Rwanda.Spermatophytes IV. Tervuren. 725 p.

Yamagiwa, J., Basabose, A.K., Kaleme, K. and Yumoto, T., 2005. Diet of grauer's gorilla in the montane forest of Kahuzi, DRC. International Journal of Primatology. Vol. 25.

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Biodiversity survey of Mwaro corridor, Altitudinal distribution of the vegetation and assessment of Gorilla food availability

7. ANNEX

Annex 1: List of species of Mwaro ecological corridor

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