Z. Woldu, M.A. Mohammed Saleem Agriculture, Ecosystems and Environment 79 2000 43–52 45
was run for two complete years, August 1996–July 1997 and August 1997–July 1998. The plant species
and other data for each replicate of the week were entered in access database. Relevant information was
extracted using the structured query language.
2.3. Grazing experiments To study the influence of grazing on the grass-
land vegetation, six sites with varying slopes ranging from 0–8 were selected to represent the area where
the livestock of the community grazed. Each site had 10 m × 10 m plots where a grazing was totally pre-
cluded NOG, b moderately grazed MDG — 1.8 Tropical Livestock Unit Month — TLUMha and c
very heavily grazed VHVG — 4.2 TLUMha see also Mwendera et al., 1997. The NOG and MDG
plots were enclosed by barbed wire fences and there was no fencing around VHVG plots. The door of the
fence around MDG was opened for 3 days in a week for the free grazing livestock of the farming commu-
nity. Grazing took place during all days of the week in VHVG. Data on species composition, per cent cover
of three most dominant species and bare ground were collected at 30 days interval from the second week of
September to the second week of December. This pe- riod is shortly after the summer rain season when plant
growth rate is maximal and most plants bear inflo- rescence. During the long dry period January–May
and the summer rain period June–September most species in VHVG and some in MDG and NOG are not
identifiable. Data were collected for three consecutive years from 1995–1997.
Only the list of species in NOG and VHVG were considered for the present article. The result which
includes MDG will be communicated in another pub- lication.
2.4. Data analysis The weekly manure-seedling data from the five
replicates were pooled for each month and a data matrix was constructed for each year with the species
in the rows and months on the columns. The species composition of the manure M was compared with
data on the grazing experiment plots using chi square χ
2
. The relative occurrences of the four important grassland families were calculated for each year of
Fig. 1. Monthly average rainfall in Ghinchi Research Station, Ethiopia in 1996 and 1997.
the grazing experiment and manure seed bank data. The relative composition of the annual and peren-
nial species in each experiment was also calculated. Rainfall data of 1996 and 1997 was obtained from
Ethiopian Agricultural Research Meteorological Ser- vices and the monthly average rainfall of the 2 years
were plotted Fig. 1.
Principal Components Analysis PCA was per- formed using Syntax to find the influence of time on
the species composition of the manure seed bank. The PCA is an ordination technique which involves
extracting the same number of axes of variations as in the rows or columns of the input data matrix
in decreasing order of importance. Scatter diagram scattergram of the two axes showing the highest
variations provides a two dimensional display of the underlying pattern in the original data matrix see
Orloci, 1978.
3. Results and discussion
3.1. Species in manure seed bank and grazing experiment
Table 1 gives the occurrence of the species in the manure seed bank during the 12 months of the year in
46 Z. Woldu, M.A. Mohammed Saleem Agriculture, Ecosystems and Environment 79 2000 43–52
Table 1 List of species in manure seed bank M, no grazing plots NOG
and very heavily grazed VHVG
a
Species Manure
NOG VHVG
Abutilon sp. 1
Acacia abyssinica 1
Ajuga remota 1
Alchemilla fischeri 1
1 Amaranthus hybridus
1 1
1 Anagalis arvensis
1 Andropogon abyssinicus
1 Arthraxon lancifolius
1 1
Bidens biternata 1
1 Bidens pilosa
1 1
Bothriochloa insculpta 1
Brachiaria semiundulata 1
Brassica nepus 1
1 Carduus chamaecephalus
1 1
Carum carvi 1
1 Centaurium tenuiflorum
1 Cerastium octandrum
1 Chenopodium album
1 Chenopodium ambrosoides
1 Chloris pycnothrix
1 Cineraria abyssinica
1 1
Cirsium vulgare 1
Coleus punctatus 1
1 Commelina africana
1 1
1 Commelina bengalensis
1 Commelina subulata
1 Conyza tigreensis
1 Corchorus trilocularis
1 Corrigiola litoralis
1 Corrigiola sp.
1 Crassocephalum rubens
1 Crepis carbonaria
1 Crotalaria spinosa
1 Cynodon dactylon
1 1
1 Cynoglossum coeruleum
1 1
Cyperus rigidifolius 1
1 1
Cyperus teneriffae 1
1 Datura stramonium
1 Dichrocephala integrifolia
1 1
1 Digitaria rivae
1 1
1 Dischoriste radicans
1 1
Echinochloa colona 1
1 Eleusine floccifolia
1 1
1 Eragrostis botryodes
1 1
Eragrostis tef 1
Eragrostis tenuifolia 1
1 1
Eriochloa meyeriana 1
Euphorbia petitiana 1
Evolvulus alisinoides 1
1 1
Falkia oblonga 1
1 1
Fimbristylis complanata 1
1 Galinsoga parviflora
1 1
1 Galium spurium
1 Table 1 Continued.
Species Manure
NOG VHVG
Geranium arabicum 1
Gnaphalium luteo-album 1
1 1
Guizotia abyssinica 1
Guizotia scabra 1
1 1
Haplociadum abyssinicum 1
Hibiscus sp. 1
1 Hibiscus tridentata
1 Hibiscus trionum
1 1
Hygrophila auriculata 1
1 1
Hyparrhenia arrhenobasis 1
1 Hyparrhenia filipendula
1 Hyparrhenia hirta
1 1
Hyparrhenia rufa 1
Hyparrhenia sp. 1
Indigofera sp. 1
1 Kohautia coccinia
1 1
Kyllinga appendiculata 1
Lactuca inermis 1
Laggera pterodonta 1
Lathyrus sativus 1
Lens culinaris 1
Leucas marticinensis 1
1 Lolium perenne
1 Lotus corniculatus
1 1
1 Medicago polymorpha
1 1
1 Oxygonum sinuatum
1 Panicum sp.
1 1
1 Pennisetum clandestinum
1 1
1 Pennisetum divisum
1 1
1 Pennisetum riparium
1 1
Pennisetum villosum 1
1 Persicaria nepalensis
1 1
1 Phalaris paradoxa
1 1
1 Phyllanthus rotundifolius
1 1
1 Plantago lanceolata
1 1
1 Poa annua
1 Poa leptoclada
1 Polygala sp.
1 1
Rumex nepalensis 1
1 1
Scirpus inclinatus 1
1 Scleria clathrata
1 1
Scleria hispidior 1
Scorpiurus muricatus 1
1 1
Sesbania sesban 1
Setaria verticillata 1
1 1
Sida rhombifolia 1
Snowdenia polystachya 1
1 1
Solanum nigrum 1
1 1
Sonchus sp. 1
Sorghum bicolor 1
Sphaeranthus suaveolens 1
1 1
Spilanthus mauritiana 1
1 1
Sporobolus africanus 1
1 1
Tagetes minuta 1
Thesium radicans 1
Z. Woldu, M.A. Mohammed Saleem Agriculture, Ecosystems and Environment 79 2000 43–52 47
Table 1 Continued. Species
Manure NOG
VHVG Trifolium abyssinicum
1 1
Trifolium acaule 1
Trifolium burchellianum 1
Trifolium cryptopodium 1
Trifolium johnstonii 1
Trifolium lanceolatum 1
Trifolium multinerve 1
Trifolium rueppellianum 1
Trifolium schimperi 1
1 1
Trifolium semipilosum 1
1 1
Trifolium simense 1
Trifolium steudneri 1
1 1
Trifolium tembense 1
1 1
Triticum aestivum 1
Uebelinia abyssinica 1
1 Verbascum sinaticum
1 Verbena officinalis
1 1
1 Veronica abyssinica
1 1
1 Veronica anagallis-aquatica
1 Vigna oblongifolia
1 Xanthium spinosum
1 Zea mays
1
a
0 stands for absence and 1 stands for presence.
1996 and 1997, and the occurrence of species in the NOG and VHVG from 1995 to 1997.
The number of species per year in the grazing ex- periment ranged between 50 and 59 while it ranged
between 62 and 64 in the manure experiment Table 2. The number of families in the grazing areas ranged
between 16 and 21 while it ranged between 17 and 22 in the manure experiment when the data of each year
Table 2 Proportion of the four important plant families in the grazing area and in the manure during the study period at Ghinchi in the Ethiopian
highlands over 3 years Grazing areas
Manure 1995
1996 1997
6 1996
1997 6
Species 50
59 50
94 62
64 86
Families 16
21 17
28 18
22 24
1 Poaceae 32
Poaceae 24 Poaceae 34
Fabaceae 26 Poaceae 23
2 Fabaceae 14
Asteraceae 20 Asteraceae 20
Poaceae 23 Fabaceae 20
3 Asteraceae 12
Fabaceae 11 Fabaceae 8
Asteraceae 13 Asteraceae 13
4 Cyperaceae 12
Cyperaceae 10 Cyperaceae 6
Cyperaceae 5 Cyperaceae 5
Total 70
65 66
67 61
are considered separately. The number of species in- creased to 94 and 79; and the number of families in-
creased to 28 and 24 in the grazing areas and manure seed bank, respectively, when the data of the whole
period were pooled together. The grazing experiments and the manure seed bank had 37 species 14 families
in common. The manure seed bank species included six annual food crop species.
The relative importance of the four major grass- land families in Ghinchi grazing area corresponded to
the pattern in the grassland communities in the east African highlands in general, and in Ethiopia, in par-
ticular Woldu, 1986. Members of the Poaceae were the highest, followed by those of Asteraceae, Fabaceae
and Cyperaceae in that order. In the manure seed bank, however, Poaceae and Fabaceae were equal in impor-
tance and were higher than the other two families. The percentage of Asteraceae was higher and the percent-
age of Cyperaceae was lower than in the grassland communities. The number of species, families and the
relative importance are presented in Table 2.
The chi-square analysis showed that the composi- tion of species in the M versus NOG, M versus VHVG
and NOG versus VHVG are significantly different χ
2
= 6.13, 5.48 and 25.65, respectively, significant at
p = 0.01. The species unique to M, NOG and VHVG and those common to the three treatments are given
in Table 3. The results indicate that the species com- position of the manure seed bank mostly resembled
the species composition of VHVG and less to those of NOG. The relatively higher resemblance between
M and VHVG may suggest that the areas where the livestock grazed were identical to VHVG.
48 Z. Woldu, M.A. Mohammed Saleem Agriculture, Ecosystems and Environment 79 2000 43–52
Table 3 Species unique to manure seed bank M, no grazing NOG, very heavily grazed VHVG and those common to the three treatments
M–NOG–VHVG Species occurring
Species occuring Species occurring
Species occuring in manure, only in manure
only in NOG only in VHVG
NOG and VHVG Abutilon sp.
Anagalis arvensis Ajuga remota
Amaranthus hybridus Acacia abyssinica
Andropogon abyssinicus Bothriochloa insculpta
Commelina africana Chenopodium album
Cirsium vulgare Brachiaria
Cynodon dactylon Chenopodium
Corchorus trilocularis semiundulata
Cyperus rigidifolius ambrosoides
Eriochloa nubica Centaurium
Dichrocephala integrifolia Commelina bengalensis
Hyparrhenia filipendula tenuiflorum
Digitaria rivae Conyza tigreensis
Hyparrhenia rufa Cerastium octandrum
Eleusine floccifolia Corrigiola litoralis
Kyllinga appendiculata Chloris pycnothrix
Eragrostis tenuifolia Corrigiola sp.
Lactuca inermis Commelina subulata
Evolvulus alisinoides Crassocephalum rubens
Laggera pterodonta Crepis carbonaria
Falkia oblonga Eragrostis tef
Lolium perenne Crotalaria spinosa
Galinsoga parviflora Euphorbia petitiana
Oxygonum sinuatum Datura stramonium
Gnaphalium luteo-album Galium spurium
Scleria hispidior Hibiscus tridentata
Guizotia scabra Geranium arabicum
Trifolium johnstonii Hyparrhenia sp.
Hygrophila auriculata Guizotia abyssinica
Thesium radicans Lotus corniculatus
Haplociadum abyssinicum Xanthium spinosum
Medicago polymorpha Lathyrus sativus
Panicum sp. Lens culinaris
Pennisetum clandestinum Poa annua
Pennisetum divisum Poa leptoclada
Persicaria nepalensis Sesbania sesban
Phalaris paradoxa Sida rhombifolia
Phyllanthus rotundifolius Sonchus sp.
Plantago lanceolata Sorghum bicolor
Rumex nepalensis Tagetes minuta
Scorpiurus muricatus Trifolium acaule
Setaria verticillata Trifolium burchellianum
Snowdenia polystachya Trifolium cryptopodium
Solanum nigrum Trifolium lanceolatum
Sphaeranthus suaveolens Trifolium multinerve
Spilanthus mauritiana Trifolium rueppellianum
Sporobolus africanus Trifolium simense
Trifolium schimperi Triticum aestivum
Trifolium semipilosum Verbascum sinaticum
Trifolium steudneri Veronica anagallis-
Trifolium tembense aquatica
Verbena officinalis Vigna oblongifolia
Veronica abyssinica Zea mays
3.2. Proportion of life-forms The pattern of occurrence of annuals and perennials
in M clearly follows the pattern of the rainfall Figs. 1, 2A and B. Although the Ethiopian highland is known
for its bimodal rainfall Gamachu, 1977, the rainfall pattern of Ghinchi in 1996 and 1997 was unimodal.
Comparison of the rainfall of the 1996 and 1997 shows that the rainfall in 1996 was evenly distributed while
that of the 1997 was concentrated mainly between July and September and had a long dry period. This seems
to have a bearing on the composition of annuals and perennials. The evenly distributed rainfall in 1996 ap-
pears to have encouraged the continuous availability and production of seeds from annuals hence their dom-
inance in the manure seed bank 69 while the rela- tively more arid climate and high torrential rainfall in
the summer of 1997 had discouraged annuals 57
Z. Woldu, M.A. Mohammed Saleem Agriculture, Ecosystems and Environment 79 2000 43–52 49
Fig. 2. Annuals and perennials in the species composition of the manure seed bank in A 1996; B 1997.
but encouraged the persistence of perennials through out the year. The composition of annuals in M was
63, while that of the grassland NOG, and VHVG pooled together was 41. Seventy eight percent of
the species unique to M were annuals, while the pro- portions of annuals unique to NOG and VHVG were
28 only. The proportion of annuals in the species
Fig. 3. Proportion of annuals and perennials in the species unique to manure seed bank M, no grazing NOG, very heav-
ily grazed VHVG and those common to the three treatments M–NOG–VHVG
common to M, NOG and VHVG was 40.5 Fig. 3. The list of species is given in Table 3.
3.3. Temporal patterns of occurrence The seasonal pattern in the samples indicates that
the seeds of perennials attain dominance at the peak of the rainfall July–September while the seeds of the
annuals were dominant during the rest of the year. The PCA of M in 1996 showed three distinct
clusters whereas that of 1997 showed four diffused clusters Fig. 4A and B. The relatively higher annual
precipitation and the more even distribution of the rainfall in 1996 may have provided more uniform cli-
matic conditions during most part of the year hence the less number of clusters. It is interesting to note
that each month clustered with the month preceding or succeeding indicated that the clusters also follow
the seasonal pattern. The life-form of the species in the clusters corresponds to the average precipitation
of the months. The number of annuals was higher than the perennials in those clusters where the aver-
age rainfall was higher Fig. 5A and B. The general pattern of the clusters suggests that the species in the
50 Z. Woldu, M.A. Mohammed Saleem Agriculture, Ecosystems and Environment 79 2000 43–52
Fig. 4. Scattergram of the months by data from the manure seed bank M showing their relationship to each other as influenced by the species composition of the manure seed bank in A 1996; B 1997.
Z. Woldu, M.A. Mohammed Saleem Agriculture, Ecosystems and Environment 79 2000 43–52 51
Fig. 5. Annuals and perennials in the ordination cluster of A 1996; B 1997. The letters in the scattergram correspond to months.
grazing areas matured at different times of the year and therefore had diverse phenological history.
4. Implications
