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
|
N°
|
Scientific Name
|
Nbre ind
|
Circ.
|
DBH
|
BA m2/ha
|
RD (%)
|
RDo (%)
|
N°
|
Scientific name
|
Nbre ind
|
Circ.
|
DBH
|
BA m2/ha
|
RD (%)
|
RDo (%)
|
|
1
|
Lepidotrichilia volkensi
|
301
|
9663
|
3019,7
|
715,8
|
24,2
|
46,081
|
29
|
Ekebergia capensis
|
3
|
210
|
65,625
|
0,3381
|
0,24
|
0,0218
|
|
2
|
Xymalos monospora
|
306
|
8813
|
2754,1
|
595,41
|
24,6
|
38,331
|
30
|
Albizia adianthifolia
|
1
|
200
|
62,5
|
0,3066
|
0,08
|
0,0197
|
|
3
|
Afrocrania volkensii
|
43
|
2745
|
857,81
|
57,764
|
3,45
|
37,186
|
31
|
Inconnue 2
|
3
|
150
|
46,875
|
0,1725
|
0,24
|
0,0111
|
|
4
|
Alangium chinense
|
56
|
2163
|
675,94
|
35,866
|
4,49
|
23,089
|
32
|
Rhamnus prinoides
|
8
|
142
|
44,375
|
0,1546
|
0,64
|
0,01
|
|
5
|
Olea hochtetteri
|
17
|
2117
|
661,56
|
34,357
|
1,36
|
22,118
|
33
|
Psychotrya mahoni
|
8
|
138
|
43,125
|
0,146
|
0,64
|
0,0094
|
|
6
|
Prunus africana
|
20
|
1701
|
531,56
|
22,181
|
1,61
|
14,279
|
34
|
Clematis sinensis
|
7
|
133
|
41,563
|
0,1356
|
0,56
|
0,0087
|
|
7
|
Allophylus kivuensis
|
60
|
1700
|
531,25
|
22,155
|
4,82
|
14,263
|
35
|
Markhamia lutea
|
6
|
130
|
40,625
|
0,1296
|
0,48
|
0,008
|
|
8
|
Maytenus arguta
|
62
|
1227
|
383,44
|
11,541
|
4,98
|
0,743
|
36
|
Dombeya goetzenii
|
4
|
114
|
35,625
|
0,0996
|
0,32
|
0,0064
|
|
9
|
Bersama abyssinica ssp. paullinioides
|
13
|
1193
|
372,81
|
10,911
|
1,04
|
0,7024
|
37
|
Ritchiea albertsii
|
3
|
82
|
25,625
|
0,0515
|
0,24
|
0,0033
|
|
10
|
Ehretia cymosa
|
22
|
1156
|
361,25
|
10,244
|
1,77
|
0,6595
|
38
|
Mimulopsis solmsii
|
6
|
76
|
23,75
|
0,0443
|
0,48
|
0,0029
|
|
11
|
Croton macrostachyus
|
8
|
845
|
264,06
|
54,737
|
0,64
|
0,3524
|
39
|
Mezoneuron angolense
|
5
|
67
|
20,938
|
0,0344
|
0,4
|
0,0022
|
|
12
|
Maesa lanceolata
|
17
|
765
|
239,06
|
44,863
|
1,36
|
0,2888
|
40
|
Adenia rumicifolia
|
4
|
58
|
18,125
|
0,0258
|
0,32
|
0,0017
|
|
13
|
Gouania longispicata
|
38
|
744
|
232,5
|
42,434
|
3,05
|
0,2732
|
41
|
Lindackeria sp.
|
2
|
57
|
17,813
|
0,0249
|
0,16
|
0,0016
|
|
14
|
Kigelia africana
|
27
|
684
|
213,75
|
35,866
|
2,17
|
0,2309
|
42
|
Urera camerounensis
|
4
|
53
|
16,563
|
0,0215
|
0,32
|
0,0014
|
|
15
|
Tabernaemontana johnstonii
|
15
|
674
|
210,63
|
34,825
|
1,2
|
0,2242
|
43
|
Inconnue
|
1
|
45
|
14,063
|
0,0155
|
0,08
|
0,001
|
|
16
|
Schrebera alata
|
5
|
538
|
168,13
|
22,189
|
0,4
|
0,1428
|
44
|
Mikaniopsis rwandensis
|
2
|
40
|
12,5
|
0,0123
|
0,16
|
0,0008
|
|
17
|
Clerodendron johnstonii
|
30
|
531
|
165,94
|
21,615
|
2,41
|
0,1392
|
45
|
Teclea nobilis
|
1
|
38
|
11,875
|
0,0111
|
0,08
|
0,0007
|
|
18
|
Erythrina mildbraedii
|
5
|
464
|
145
|
16,505
|
0,4
|
0,1063
|
46
|
Vernonia auriculifolia
|
3
|
36
|
11,25
|
0,0099
|
0,24
|
0,0006
|
|
19
|
Polyscias fulva
|
7
|
417
|
130,31
|
1,333
|
0,56
|
0,0858
|
47
|
Gallinera coffeoides
|
1
|
23
|
71,875
|
0,0041
|
0,08
|
0,0003
|
|
20
|
Ficus capensis
|
8
|
408
|
127,5
|
12,761
|
0,64
|
0,0822
|
48
|
Strombosia scheffleri
|
2
|
21
|
65,625
|
0,0034
|
0,16
|
0,0002
|
|
21
|
Oxyanthus speciosus
|
18
|
402
|
125,63
|
12,389
|
1,44
|
0,0798
|
49
|
Tricalisia anomala
|
1
|
18
|
5,625
|
0,0025
|
0,08
|
0,0002
|
|
22
|
Bridelia micrantha
|
14
|
357
|
111,56
|
0,977
|
1,12
|
0,0629
|
50
|
Ilex mitis
|
1
|
15
|
46,875
|
0,0017
|
0,08
|
0,0001
|
|
23
|
Drypetes ugandensis
|
15
|
353
|
110,31
|
0,9553
|
1,2
|
0,0615
|
51
|
Inconnue 3
|
1
|
15
|
46,875
|
0,0017
|
0,08
|
0,0001
|
|
24
|
Entandrophragma excelsum
|
15
|
257
|
80,313
|
0,5063
|
1,2
|
0,0326
|
52
|
Celtis africa
|
1
|
14
|
4,375
|
0,0015
|
0,08
|
0.0001
|
|
25
|
Toddalia asiatica
|
14
|
257
|
80,313
|
0,5063
|
1,12
|
0,0326
|
53
|
Pavetta rwandensis
|
1
|
12
|
3,75
|
0,0011
|
0,08
|
6,96
|
|
26
|
Albizia gummifera
|
15
|
240
|
75
|
0,4416
|
1,2
|
0,0284
|
54
|
Salacia erecta
|
1
|
12
|
3,75
|
0,0011
|
0,08
|
6,96
|
|
27
|
Bridelia bridelifolia
|
5
|
240
|
75
|
0,4416
|
0,4
|
0,0284
|
55
|
Inconnue 4
|
1
|
11
|
34,375
|
0,0009
|
0,08
|
0.00006
|
|
28
|
Leptonychia mildbraedii
|
9
|
226
|
70,625
|
0,3915
|
0,72
|
0,0252
|
Total
|
1246
|
|
133772
|
1553,4
|
100
|
100
|
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
|
N°
|
Species
|
Vernac. Name
|
N.Stem
|
circumf
|
DBH
|
BA
|
BA/ha
|
RD
|
RDo
|
|
1
|
Alangium chinense
|
Mupfuka
|
16
|
677
|
2,16
|
3,6491
|
36,49
|
6,4
|
3,6087
|
|
2
|
Tabernaemontana johnstonii
|
Umubarebare
|
4
|
89,5
|
0,29
|
0,0638
|
0,638
|
1,6
|
0,0631
|
|
3
|
Adenia rumicifolia
|
|
3
|
75,5
|
0,24
|
0,0454
|
0,454
|
1,2
|
0,0449
|
|
4
|
Afrocrania volkensii
|
Mujebeshi
|
12
|
690
|
2,2
|
3,7906
|
37,91
|
4,8
|
3,7486
|
|
5
|
Allophylus abyssinicus
|
Mbayu3
|
6
|
98
|
0,31
|
0,0765
|
0,765
|
2,4
|
0,0756
|
|
6
|
Cissus humbertii
|
|
2
|
40,5
|
0,13
|
0,0131
|
0,131
|
0,8
|
0,0129
|
|
7
|
Cussonia sp.
|
Ikirara
|
1
|
145
|
0,46
|
0,1674
|
1,674
|
0,4
|
0,1655
|
|
8
|
Dalbergia lacteal
|
|
2
|
21,5
|
0,07
|
0,0037
|
0,037
|
0,8
|
0,0036
|
|
9
|
Drypetes ugandensis
|
Murerantuku
|
6
|
258,5
|
0,82
|
0,5320
|
5,32
|
2,4
|
0,5261
|
|
10
|
Ech n°2
|
|
2
|
20,5
|
0,07
|
0,0033
|
0,033
|
0,8
|
0,0033
|
|
11
|
Ehretia cymosa
|
Ingongo
|
2
|
89,5
|
0,29
|
0,0638
|
0,638
|
0,8
|
0,0631
|
|
12
|
Entandrophragma excelsum
|
Umuyave
|
1
|
11
|
0,04
|
0,0010
|
0,01
|
0,4
|
0,0010
|
|
13
|
Erythrina mildbraedii
|
Igiko
|
3
|
176
|
0,56
|
0,2466
|
2,466
|
1,2
|
0,2439
|
|
14
|
Ficus capensis
|
|
3
|
96,5
|
0,31
|
0,0741
|
0,741
|
1,2
|
0,0733
|
|
15
|
Ficus exasperate
|
|
1
|
22,5
|
0,07
|
0,0040
|
0,04
|
0,4
|
0,0040
|
|
16
|
Ficus n°4
|
|
1
|
10
|
0,03
|
0,0008
|
0,008
|
0,4
|
0,0008
|
|
17
|
Ilex mitis
|
Umuhisi
|
1
|
36
|
0,11
|
0,0103
|
0,103
|
0,4
|
0,0102
|
|
18
|
Kigelia Africana
|
Kiberebere
|
12
|
216
|
0,69
|
0,3715
|
3,715
|
4,8
|
0,3673
|
|
19
|
Lepidotrichilia volkensi
|
Imbayu
|
42
|
1661
|
5,29
|
21,966
|
219,7
|
17
|
21,722
|
|
20
|
Macaranga neomildbraediana
|
|
1
|
64
|
0,20
|
0,0326
|
0,326
|
0,4
|
0,0322
|
|
21
|
Maytenus arguta
|
Musubi
|
28
|
579
|
1,84
|
2,6691
|
26,69
|
11
|
2,6395
|
|
22
|
Mikaniopsis rwandensis
|
|
1
|
22,5
|
0,07
|
0,0040
|
0,04
|
0,4
|
0,0040
|
|
23
|
Neoboutonia macrocalyx
|
Itshanya
|
2
|
69,5
|
0,22
|
0,0385
|
0,385
|
0,8
|
0,0380
|
|
24
|
Olea hochstetteri
|
Indobo
|
11
|
2561,5
|
8,16
|
52,2400
|
522,4
|
4,4
|
51,660
|
|
25
|
Oxyanthus speciosus
|
|
5
|
62,5
|
0,20
|
0,0311
|
0,311
|
2
|
0,0308
|
|
26
|
Polyscias fulva
|
Kyungo
|
2
|
275
|
0,88
|
0,6021
|
6,021
|
0,8
|
0,5954
|
|
27
|
Prunus Africana
|
Umumba
|
2
|
98,6
|
0,31
|
0,0774
|
0,774
|
0,8
|
0,0765
|
|
28
|
Rhamnus prinoides
|
Umunanira
|
5
|
84,5
|
0,27
|
0,0568
|
0,568
|
2.0
|
0,0562
|
|
29
|
Ritchiea albertsii
|
|
1
|
112
|
0,36
|
0,0999
|
0,999
|
0,4
|
0,0988
|
|
30
|
Toddalia asiatica
|
|
2
|
24,5
|
0,08
|
0,0048
|
0,048
|
0,8
|
0,0047
|
|
31
|
Urera camerounensis
|
Umusheshe
|
9
|
118
|
0,38
|
0,1109
|
1,109
|
3,6
|
0,1096
|
|
32
|
Urera hypselodendron
|
|
1
|
12
|
0,04
|
0,0011
|
0,011
|
0,4
|
0,0011
|
|
33
|
Xymalos monospora
|
Igihotora
|
58
|
1328,5
|
4,23
|
14,052
|
140,5
|
23
|
13,896
|
|
34
|
Liane inconnue A119
|
|
2
|
13
|
0,04
|
0,0013
|
0,013
|
0,8
|
0,0013
|
|
35
|
Liane A184
|
|
1
|
12,5
|
0,04
|
0,0012
|
0,012
|
0,4
|
0,0012
|
|
36
|
Inconnue A190
|
|
1
|
45
|
0,14
|
0,0161
|
0,161
|
0,4
|
0,0159
|
|
Total
|
|
252
|
|
|
101,12
|
1011
|
100
|
100.00
|
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
|
N°
|
Spcies
|
Vernac. name
|
N. stems
|
Circumf.
|
DBH
|
BA
|
BA/ha
|
RD
|
RDo
|
|
1
|
Afrocrania volkensii
|
Mujebeshi
|
23
|
1102
|
3,51
|
9,671
|
96,7
|
12,4
|
32,55
|
|
2
|
Agauria salicifolia
|
|
3
|
350,5
|
1,116
|
0,978
|
9,78
|
1,62
|
3,293
|
|
3
|
Alangium chinense
|
Mupfuka
|
2
|
107
|
0,3408
|
0,091
|
0,91
|
1,08
|
0,307
|
|
4
|
Bersama abyssinica ssp, paullinioides
|
Umukaka
|
6
|
233,5
|
0,7436
|
0,434
|
4,34
|
3,24
|
1,461
|
|
5
|
Celtis africana
|
Ingenge
|
1
|
17,5
|
0,0557
|
0,002
|
0,02
|
0,54
|
0,008
|
|
6
|
Croton macrostachyus
|
Murangara
|
1
|
37,5
|
0,1194
|
0,011
|
0,11
|
0,54
|
0,038
|
|
7
|
Dombeya goetzeni
|
Umukore
|
1
|
22
|
0,0701
|
0,004
|
0,04
|
0,54
|
0,013
|
|
8
|
Drypetes ugandensis
|
Murerantuku
|
1
|
14
|
0,0446
|
0,002
|
0,02
|
0,54
|
0,005
|
|
9
|
Ehretia cymosa
|
Ingongo
|
1
|
17,5
|
0,0557
|
0,002
|
0,02
|
0,54
|
0,008
|
|
10
|
Entandrophragma excelsum
|
Umuyave
|
1
|
17,5
|
0,0557
|
0,002
|
0,02
|
0,54
|
0,008
|
|
11
|
Ficus exasperate
|
|
1
|
11,5
|
0,0366
|
0,001
|
0,01
|
0,54
|
0,004
|
|
12
|
Gouania longispicata
|
Umusheshe
|
15
|
455
|
1,449
|
1,648
|
16,5
|
8,11
|
5,549
|
|
13
|
Kigelia africana
|
Kiberebere
|
3
|
53
|
0,1688
|
0,022
|
0,22
|
1,62
|
0,075
|
|
14
|
Lepidotrichilia volkensi
|
Imbayu
|
49
|
1195
|
3,806
|
11,37
|
114
|
26,5
|
38,28
|
|
15
|
Liane A350
|
|
1
|
18
|
0,0573
|
0,003
|
0,03
|
0,54
|
0,009
|
|
16
|
Maesa lanceolata
|
Muhanga
|
5
|
194,5
|
0,6194
|
0,301
|
3,01
|
2,7
|
1,014
|
|
17
|
Maytenus arguta
|
Musubi
|
24
|
585,5
|
1,865
|
2,73
|
27,3
|
13
|
9,189
|
|
18
|
Mezoneuron angolense
|
|
2
|
25,5
|
0,0812
|
0,005
|
0,05
|
1,08
|
0,017
|
|
19
|
Neoboutonia macrocalyx
|
Itshanya
|
7
|
140,5
|
0,4475
|
0,157
|
1,57
|
3,78
|
0,529
|
|
20
|
Nuxia congesta
|
|
1
|
110
|
0,3503
|
0,096
|
0,96
|
0,54
|
0,324
|
|
21
|
Olea hochstetteri
|
Indobo
|
2
|
139,5
|
0,4443
|
0,155
|
1,55
|
1,08
|
0,522
|
|
22
|
Pittosporum sp.
|
|
1
|
22
|
0,0701
|
0,004
|
0,04
|
0,54
|
0,013
|
|
23
|
Polyscias fulva
|
Kyungo
|
2
|
130
|
0,414
|
0,135
|
1,35
|
1,08
|
0,453
|
|
24
|
Prunus africana
|
Umumba
|
5
|
210
|
0,6688
|
0,351
|
3,51
|
2,7
|
1,182
|
|
25
|
Psychotrya mahoni
|
|
1
|
12
|
0,0382
|
0,001
|
0,01
|
0,54
|
0,004
|
|
26
|
Rhamnus prinoides
|
Umunanira
|
2
|
24
|
0,0764
|
0,005
|
0,05
|
1,08
|
0,015
|
|
27
|
Schefflera myriantha
|
|
1
|
21
|
0,0669
|
0,004
|
0,04
|
0,54
|
0,012
|
|
28
|
Schrebera alata
|
|
4
|
298
|
0,949
|
0,707
|
7,07
|
2,16
|
2,38
|
|
29
|
Toddalia asiatica
|
|
1
|
12,5
|
0,0398
|
0,001
|
0,01
|
0,54
|
0,004
|
|
30
|
Urera hypselodendron
|
|
1
|
19
|
0,0605
|
0,003
|
0,03
|
0,54
|
0,01
|
|
31
|
Xymalos monospora
|
Igihotora
|
17
|
319
|
1,016
|
0,81
|
8,1
|
9,19
|
2,728
|
|
Total
|
|
185
|
|
|
29,71
|
297
|
100
|
100
|
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
Page 31
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
|
N°
|
Species
|
Vernac. name
|
N.stems
|
Circumf.
|
DBH
|
BA
|
BA/ha
|
RD
|
RDo
|
|
1
|
Alangium chinense
|
Mupfuka
|
2
|
91
|
0,29
|
0,066
|
0,659
|
6,25
|
1,676
|
|
2
|
Croton macrostachyus
|
Murangara
|
3
|
38
|
0,121
|
0,011
|
0,115
|
9,38
|
0,292
|
|
3
|
Drypetes ugandensis
|
Murerantuku
|
1
|
16,5
|
0,053
|
0,002
|
0,022
|
3,13
|
0,055
|
|
4
|
Lepidotrichilia volkensi
|
Imbayu
|
5
|
358
|
1,14
|
1,02
|
10,2
|
15,6
|
25,94
|
|
5
|
Neoboutonia macrocalyx
|
Itshanya
|
19
|
596
|
1,898
|
2,828
|
28,28
|
59,4
|
71,88
|
|
6
|
Urera hypselodendron
|
Umuse
|
2
|
28
|
0,089
|
0,006
|
0,062
|
6,25
|
0,159
|
|
Total
|
|
32
|
|
|
3,934
|
39,34
|
100
|
100
|
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
|
N°
|
Species
|
Vernac.name
|
N. stems
|
Circumf.
|
DBH
|
BA
|
BA/ha
|
RD
|
RDo
|
|
1
|
Alangium chinense
|
Mupfuka
|
5
|
302
|
0,9618
|
0,7262
|
7,26172
|
11,9
|
7,7609
|
|
2
|
Allophylus abyssinicus
|
|
1
|
110
|
0,3503
|
0,0963
|
0,96327
|
2,38
|
1,0296
|
|
3
|
Dombeya goetzeni
|
Umukore
|
3
|
349
|
1,111
|
0,9689
|
9,68942
|
7,14
|
10,365
|
|
4
|
Lepidotrichilia volkensi
|
Imbayu
|
3
|
109,5
|
0,3487
|
0,0954
|
0,95449
|
7,14
|
1,0203
|
|
5
|
Maesa lanceolata
|
Umuhanga
|
4
|
376
|
1,197
|
1,1248
|
11,2476
|
9,52
|
12,03
|
|
6
|
Neoboutonia macrocalyx
|
Itshanya
|
25
|
892,5
|
2,842
|
6,3404
|
63,4042
|
59,5
|
67,782
|
|
7
|
Urera hypselodendron
|
Umuse
|
1
|
12
|
0,0382
|
0,0011
|
0,01147
|
2,38
|
0,0123
|
|
Total
|
|
42
|
|
|
9,3532
|
93,5321
|
100
|
100
|
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
|
N°
|
Species
|
Vernac.name
|
N.stems
|
circumf
|
DBH
|
BA
|
BA/ha
|
RD
|
RDo
|
|
1
|
Afrocrania volkensii
|
Mujebeshi
|
3
|
152
|
0,4841
|
0,183967
|
1,8397
|
6,67
|
1,27
|
|
2
|
Dombeya goetzeni
|
Umukore
|
11
|
309
|
0,9841
|
0,760235
|
7,6024
|
24,4
|
5,23
|
|
3
|
Galliniera coffeoides
|
Kibonobono
|
4
|
182
|
0,5796
|
0,26371
|
2,6371
|
8,89
|
1,82
|
|
4
|
Neoboutonia macrocalyx
|
Itshanya
|
25
|
1293
|
4,118
|
13,31197
|
133,12
|
55,6
|
91,6
|
|
5
|
Oxyanthus speciosus
|
Umuhanamambo
|
2
|
33
|
0,1051
|
0,008671
|
0,0867
|
4,44
|
0,06
|
|
Total
|
|
45
|
|
|
14,52855
|
145,29
|
100
|
100
|
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
Page 34
Table 11: species DBH = 10 cm segment 6 of the 7 Km line transect
in Mwaro corridor
|
N°
|
Espèces
|
Vernac. name
|
N. stems
|
Circonf
|
DBH
|
BA
|
BA/ha
|
RD
|
RDo
|
|
1
|
Afrocrania volkensii
|
Mujebeshi
|
6
|
306
|
0,9745
|
0,75
|
7,45475
|
10
|
2,2646
|
|
2
|
Galliniera coffeoides
|
Kibonobono
|
3
|
40
|
0,1274
|
0,01
|
0,12741
|
5
|
0,0387
|
|
3
|
Hagenia abyssinica
|
Umugeshi
|
17
|
1622
|
5,166
|
20,9
|
209,497
|
28,3
|
63,629
|
|
4
|
Hypericum revolutum
|
Mushunguru
|
8
|
482
|
1,535
|
1,85
|
18,4964
|
13,3
|
5,6189
|
|
5
|
Maesa lanceolata
|
Umuhanga
|
6
|
89
|
0,2834
|
0,06
|
0,63048
|
10
|
0,1916
|
|
6
|
Neoboutonia macrocalyx
|
Itshanya
|
17
|
1080
|
3,439
|
9,28
|
92,8398
|
28,3
|
28,21
|
|
7
|
Senecio mannii
|
Mutagara
|
3
|
44
|
0,1401
|
0,02
|
0,15408
|
5
|
0,0468
|
|
Total
|
|
60
|
|
|
32,9
|
329,2
|
100
|
100
|
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
|
N°
|
Species
|
Vernac.name
|
N.stems
|
circumf
|
DBH
|
BA
|
BA/ha
|
RD
|
RDo
|
|
1
|
Hypericum revolutum
|
Mushunguru
|
14
|
1104
|
3,514
|
9,693
|
96,93
|
32,6
|
41,57
|
|
2
|
Prunus africana
|
Umwumba
|
5
|
516
|
1,643
|
2,119
|
21,19
|
11,6
|
9,089
|
|
3
|
Hagenia abyssinica
|
Umugeshi
|
8
|
988,5
|
3,148
|
7,779
|
77,79
|
18,6
|
33,36
|
|
4
|
Afrocrania volkensii
|
Mujebeshi
|
12
|
661,5
|
2,107
|
3,485
|
34,85
|
27,9
|
14,94
|
|
5
|
Esp. Inconnue
|
|
4
|
175
|
0,557
|
0,244
|
2,438
|
9,3
|
1,046
|
|
Total
|
43
|
|
|
23,32
|
233,2
|
100
|
100
|
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
|
0-50
|
50-100
|
100-150
|
150-200
|
200-250
|
250-300
|
300-350
|
350-400
|
400-450
|
450-500
|
Distance (m)
|
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
|
Indices
|
Segm1
|
Segm2
|
Segm3
|
Segm4
|
Segm5
|
Segm6
|
Segm7
|
|
Shannon H
|
2,746
|
2,471
|
1,276
|
1,646
|
1,447
|
1,756
|
1,319
|
|
Simpson 1-D
|
0,8918
|
0,857
|
0,6055
|
0,7889
|
0,7013
|
0,7922
|
0,7179
|
|
Equitability E
|
0,7663
|
0,7264
|
0,7124
|
0,9186
|
0,8078
|
0,9023
|
0,9513
|
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.
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