Vol.2, No.4, 443-450 (2011)
doi:10.4236/as.2011.24057
C
opyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Agricultural Scienc es
Chemical properties of wild coffee forest soils in
Ethiopia and management implications
Taye Kufa
Ethiopian Institute of Agricultural Research, Jimma Research Center, Jimma, Ethiopia;
Received 7 September 2011; revised 19 October 2011; accepted 27 October 2011.
ABSTRACT
The study aims at determining the status of soil
chemical fertility in four wild coffee forests of
southeast ern and southw estern Eth iopia. Acc ord-
ingly, soil samples were collected from surface
and subsurface depths at three sites w ithin each
forest and analy zed for soil chemical properties.
The results depicted that the soils at the four
coffee forests did not reveal significant varia-
tions for most parameters, except Mg, CEC and
C:N ratio. Significant variations w ere determined
between the surface and sub-surface soils of
the four studied forests, partly indicating the
impacts of anthropogenic factors on vegetation
cover and soil fertility status along profile depth.
At Harenn a, surfa ce so il had si gnifica ntly hi gher
total nitrogen and organic matter than sub-surface
soil. The decline in available phosphorus with
soil depth was also significant at the Harenna
and Yayu forests. Most soil results were com-
parable and showed inter- an d in tra -fo rest varia-
tions, demonstrating the contributions of vege-
tation cover and climate gradients. The study
revealed the declined soil quality parameters
with increased depth, demonstrating the vul-
nerability of forest soils to human-induced dis-
turbances of natural habitats and land degrada-
tion, coupled with climate changes. Overall, the
results underline the need for a multi-site forest
conservation and promote productivity of high
quality coffee standards. This demands urgent
supports for implementing community-oriented
management and incentive options towards main-
taining environmental sustainability and coffee
genetic resources for global benefits.
Keywords: Carbon Sequestration; Coffee Forest
Environments; Profile Depth; Soil Fertility; Wild
Coffee Genetic Resourc es
1. INTRODUCTION
The montane rainforest areas in Ethiopia are the only
known center of origin and genetic diversity for the
highland arabica coffee (Coffea arabica L). In its origi-
nal forest habitat, arabica coffee occurs in the multi-
strata of forest ecosystems and thus it is a shade-loving
plant. Since time immemorial, coffee has been grown in
the humid montane rainforests of southwestern Ethiopia
[1,2]. As to its adaptation, coffee grows in wide ecology
and it does not appear to have very specific soil re-
quirements. In fact, it performs just as well in the clay-
silcaceous soils of granite as it does on soils of volcanic
origin with diverse characteristics or even on alluvial
soils [3,4]. Water-logging can reduce yield by a substan-
tial amount and kill trees if it is prolonged. Texture and
depth of the soil are, therefore, extremely important fac-
tors. Coffee tree is capable of extending its root system
considerably. It requires an effective depth of greater
than 150 cm. This characteristic enables it to exploit a
considerable volume of land and to thus offset a relative
lack of fertility. Highly suitable areas had high soil or-
ganic matter (SOM > 3%) content. With regard to soil
pH, a slightly acid soil is preferred. The best conditions
are between pH 5.3 and 6.5. However, there are also
highly productive coffee plantations on soils that are
nearly neutral (pH = 7.0) [1,4]. Nitrogen is the most im-
portant single element affecting the growth of roots.
However, shoots lack nitrate reductase and thus cannot
utilize nitrate. Phosphorus is an important element in
shoot growth and leaf initiation. Thus, when shoot
growth is more needed than root growth, phosphatic
fertilizers should be applied to encourage faster growth
of suckers [3,5].
In Ethiopia, the natural coffee forest areas, which have
conserved the sustainable ecology and Coffea arabica
gene pools, are now seriously threatened by several fac-
tors. These include, among others, increasing population
pressure, expansion of farmlands, forest land-use con-
flicts, priority for other food and cash crops and other
socio-economic factors [6-9]. There are still natural cof-

T. Kufa / Agricultural Sciences 2 (2011) 443-450
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444
fee forests in southwest and southeast Ethiopia with rich
biodiversity including the wild Coffea arabica popula-
tions. The major coffee production systems include for-
est, semi-forest, garden and plantations. The forest eco-
system, which includes coffee forest and semi-coffee
forest production systems, occupies nearly 33% of land
used for coffee production and contributes 25% of na-
tional coffee production. In this regard, the importance
of rainforest conservation can be viewed against the
background of man-made destruction or change in about
60% of the Ethiopian forests during the last thirty years.
This is a serious challenge to the remaining and frag-
mented forest areas (2.6%, about 2000 km2) with wild
coffee populations [8]. Much of the remaining forested
area is located in less accessible and/or relatively less
populated areas of the south and southwest parts of the
country [7]. Management of the inherent good soil
health can enhance sustainable production of high qual-
ity products with little or no external inputs. The ever
increasing demands for forest products and forestlands
together with the growing human population are putting
intolerable pressure on the remaining forest fragments in
Ethiopia and elsewhere. Hence, the increasingly threat-
ened environmental degradation, forest natural resources
and declining soil fertility urgently call for actions be-
fore the status reach irreversible. In view of the chal-
lenges and possible impacts of climate change on envi-
ronmental sustainability, understanding the nature of
soils at each area is important for targeting effective soil
test based amendment options, while maintaining friendly
ecosystems goods and services. Therefore, the study was
carried out to determine the extent of variations in soil
chemical properties along climate gradient and profile
depth in the wild forest coffees of southeastern and
southwestern Ethiopia.
2. MATERIALS AND METHODS
2.1. The Study Area
The study areas are geographically distant and repre-
sent the climate gradients of the remaining fragmented
montane rainforests in southeast and southwest Ethiopia,
hosting the wild arabica coffee genetic resources. These
include Harenna, Bonga, Berhane-Kontir and Yayu. Ex-
cept Harenna in the southeast, the other forests are lo-
cated in the southwest Ethiopia. They are separated by
the Great East African Rift Valley, which dissects the
country into southeast and northwest highlands and rep-
resent climate gradients of Ethiopia. These forests are
fragmented and differ in area coverage (Harenna 15,000
ha, Bonga 5000 ha, Berhane-Kontir 1000 ha and Yayu
1000 ha), physical characteristics and forest vegetation
[7]. The study forests also vary in climate with rainfall
gradients following the decreasing order of Berhane-
Kontir > Yayu > Bonga > Harenna (Table 1).
2.2. Soil Sampling and Laboratory Analyses
Soil samples were collected from three sub-sites within
each montane rainforest. About 500 g soil samples were
collected from two depths: surface (0 - 20 cm) and sub-
surface (20 - 40 cm) for laboratory analyses on the major
soil physico-chemical properties. This was accomplished
between June and July 2004, the main rain season in the
southwest, but the dry season in the southeast Harenna
forest area. The soil samples were air-dried and ground
to pass through a 2 mm sieve for determination of soil
reaction (pH), cation exchange capacity (CEC), ex-
changeable bases (K, Ca, Mg), organic carbon (OC),
total nitrogen (TN) and available phosphorus (AP). The
Table 1. Characteristics of the study wild coffee forests in Ethiopia.
VARIABLE Harenna Bonga Berhane-Kontir Yayu
Wer eda/district Mena-Angetu Gimbo Sheko Yayu-Hurumu
Site code/symbol PI PII PIII PIV
Latitude (N) 6˚23' - 6˚29' 7˚17' - 7˚19' 7˚04' - 7˚07' 8˚23'
Longitude (E) 39˚44' - 39˚45' 36˚03' - 36˚13' 35˚25' - 35˚26' 35˚47'
Altitude (m a.s.l) 1420 - 1490 1520 - 1780 1040 - 1180 1400
Slope (%) 2 - 3 3 - 6 4 - 18 1 - 8
Rainfall (mm·year–1) 950 1700 2100 1900
Max temperature (˚C) 34.4 29.9 31.4 34.7
Min temperature (˚C) 10.4 8.7 13.8 7.6
Mean temperature (˚C) 22.2 18.2 20.3 19.7
Minimum RH (%) 37.9 45.0 50.8 41.8
Maximum RH (%) 84.3 95.2 85.4 98.5
Mean RH (%) 63.2 80.4 68.9 80.9
Wind speed (m·h–1) 0.93 0.64 0.43 0.35

T. Kufa / Agricultural Sciences 2 (2011) 443-450
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445445
analyses were undertaken in soil laboratory of the Inter-
national Livestock Research Institute, Ethiopia, using the
standard laboratory procedures [10,11].
2.3. Data Anal yses
Analysis of variance in a nested design was performed
to compare the variations in soil properties among and
within the wild coffee forest areas. In this case, the soil
samples from sub-sites and profile depths were nested
under the four forests. Comparison between means was
carried out according to Tukey test at P = 0.05 whenever
the F-test declared significant differences. Moreover, the
relationships between soil variables were determined for
each area from Pearson correlations with the SAS sys-
tem for Windows-v8 (SAS Institute Inc. Cary NC, USA),
and graphs were prepared with SigmaPlot SPW9.0
(SYSTAT Software, Inc.).
3. RESULTS
Soils did not reveal significant variations for most
chemical properties, except for Mg, CEC and C:N.
However, the Berhane-Kontir soils had the highest pH
(6.23 ± 0.42), available K (1.71 ± 1.48 meq/100 g), ex-
changeable Ca (18.14 ± 8.07 meq/100 g), electrical con-
ductivity (0.12 ± 0.02) and available P (12.84 ppm) as
compared to others. On the other hand, the Yayu soils
had the lowest pH (5.39), available K (0.49 meq/100 g)
and TN (0.18%) contents. The average Ca content varied
from 9.00 to 18.14 meq/100 g in the Bonga and Berhane-
Kontir soils, respectively. Berhane-Kontir and Harenna
soils contained almost the same amount of exchangeable
Ca. The Berhane-Kontir soils had the significantly high-
est Mg (7.54 meq/100 g) as compared to the other soils,
which did not significantly differ between each other.
Significantly the lowest CEC (20.29 meq/100 g) was
determined for the Yayu soils in contrast to the highest
values (30.16 meq/100 g) in the Berhane-Kontir and
Harenna soils (29.15 meq/100 g). Similarly, the Ber-
hane-Kontir soils had higher electrical conductivity (EC)
values as compared to the other sites, with values rang-
ing between 0.09 and 0.12. Available P ranged from 0.35
to 12.84 ppm for the Bonga and Berhane-Kontir soils,
respectively, followed by Yayu (4.65 ppm) and Harenna
(0.90 ± 0.52 ppm). Conversely, the highest SOM was
found in the Harenna (4.9%) and Bonga (3.7%) soils, the
lowest at Berhane-Kontir (2.2%) and Yayu (2.6%).
Moreover, highly significant differences in C:N were
determined and the highest (12.41) and lowest (6.63)
values were obtained for the Harenna and Berhane-
Kontir soils, respectively (Table 2).
With regard to the influence of soil depth, the Harenna
soils showed significant differences in TN and SOM and
thus, C:N between the upper and lower layers. In the
upper layers, TN (0.34%) and SOM (6.42%) were higher,
while C:N (10.78) was lower than in the lower soil layer.
On the other hand, soil pH and EC were slightly increased
at the deeper profile. Accordingly, pH values ranged
between 6.04 and 6.35, which represent a slightly acidic
soil. Exchangeable bases, CEC and available P, however,
declined down the profile. The decline in available P was
significant at the Harenna and Yayu sites. On the other
hand, soils collected from the two depths at Bonga were
not statistically different for all the soil chemical pa-
rameters. However, soil sample from the surface layer
had relatively higher mean values for all the variables,
Table 2. Soil chemical properties (means ± SD) of the studied coffee forests.
Property Harenna Bonga Berhane-Kontir Yayu ANOVA
pH (H2O, 1:2.5) 6.19 ± 0.43 5.64 ± 0.72 6.23 ± 0.42 5.39 ± 0.41 Ns
K (meq/100 g) 0.51 ± 0.53 1.04 ± 0.07 1.71 ± 1.48 0.49 ± 0.31 Ns
Ca (meq/100 g) 18.10 ± 7.78 9.00 ± 0.95 18.14 ± 8.07 11.43 ± 1.44 Ns
Mg (meq/100 g) 3.21 ± 0.30b 3.35 ± 0.22b 7.54 ± 1.80a 3.21 ± 0.45b **
CEC (meq/100 g) 29.15 ± 5.85a 30.16 ± 4.81a 26.01 ± 1.53ab 20.29 ± 1.04b *
EC (1:2.5) 0.09 ± 0.05 0.09 ± 0.03 0.12 ± 0.02 0.09 ± 0.03 Ns
AP (ppm) 0.90 ± 0.52 0.35 ± 0.12 12.84 ± 8.35 4.65 ± 7.09 Ns
TN (%) 0.24 ± 0.03 0.25 ± 0.04 0.19 ± 0.07 0.18 ± 0.03 Ns
OC (%) 2.83 ± 0.83 2.14 ± 0.61 1.27 ± 0.48 1.51 ± 0.25 Ns
SOM (%) 4.87 ± 1.43 3.69 ± 1.05 2.18 ± 0.82 2.61 ± 0.44 Ns
C:N 12.41 ± 1.85a 8.55 ± 1.15b 6.63 ± 0.24b 8.54 ± 0.40b **
Ns = Not significant (P > 0.05), *P ≤ 0.05 and ** P ≤ 0.01. Means with the same letter within a row are not significantly different (Tukey test at P = 0.05).

T. Kufa / Agricultural Sciences 2 (2011) 443-450
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446
except CEC, which increased from 28 to 32 meq/100 g.
Similar to Bonga, the Berhane-Kontir soils did not vary
due to profile depths and with the exception of pH and
EC, the values were slightly lower for deeper soils. At
Yayu, TN and SOM were significantly (P < 0.01) re-
duced from surface to sub-surface soils. C: N was also
significantly (P < 0.05) higher in the surface (9.24) than
in the deeper soil layer (7.83) (Ta b l e 3 ). Moreover, the
results of correlations between soil chemical properties
were found to be different among the four montane
rainforests (Table 4). Nonetheless, at all study sites, total
nitrogen (TN) of the soil was strongly correlated with
soil organic matter (P ≤ 0.001). In addition, there were
direct relationships between soil organic matter (SOM)
and inorganic ions (K, Ca, Mg) at all sites, and available
K and Ca in the Harenna soils correlated significantly.
The concentration of these soluble ions in the soil varied
slightly with soil reaction (pH).
4. DISCUSSION
The results do not differ in most of the soil chemical
properties, with the exception of significant differences
in CEC, Mg and C:N ratio. This could be related to the
similarity in forest vegetation and availability of suffi-
cient soil moisture during the different seasons. Accord-
ing to the general guidelines on the interpretation of soil
analysis results [11], the soils of the four study sites had
moderate TN. Soil organic carbon was ranked as moder-
ate for the Harenna and Bonga soils, but low in Yayu and
Berhane-Kontir. This could be attributed mainly to the
differences in the rate of decomposition and carbon se-
questration capacity of the soils. Similarly, the soils
contained exchangeable bases, ranging from medium to
very high. Nonetheless, the Ca content of the Bonga
soils was found to be low, while magnesium was very
high at all the study forests, possibly demonstrating the
similar soil-forming processes in the forest ecosystems
[12,13].
The relatively high total nitrogen contents at Harenna
and Bonga could be related to the release of mineralized
nitrogen upon decomposition unlike the relatively high
organic sources, which bind nitrogen in the organic form.
This shows the relatively higher mineralization rate at
the low altitude hot-humid Berhane-Kontir sites. This
was almost equal for the Bonga and Yayu forest soils.
The least C:N ratio at Berhane-Kontir suggests the in-
fluence of high temperature and higher microbial activity.
In general, the narrow C:N ratio indicates that the soils
contained low organic matter with ultimately increased
total nitrogen. This could minimize the competition for
the inorganic nitrogen between coffee trees and soil mi-
cro organisms, as opposed to the undecomposed materi-
als, and indicates decreased decomposition of organic
materials with an increased C:N ratio, which caused a
shortage of nitrogen in the soil similar to previous find-
ings [14]. The low C:N value could also be associated
with the contribution of leguminous shade trees to in-
crease nitrogen. The high rate of decomposition of or-
ganic material and the concentrations of acid-forming
ions, production of weak acids and basic cations could
also be amongst the possible reasons for this low C:N
ratio. Similar findings were reported elsewhere [15].
Table 3. Soil chemical properties (means ± SD) as influenced by profile depth at the four natural coffee forests of Ethiopia.
Exchangeable base (meq/100 g)
Site /depth
(cm)
TN
(%)
SOM
(%)
pH
(H2O, 1:2.5)
EC
(1:2.5) K Ca Mg
CEC
(meq/100 g)
Available P
(ppm) C:N
Harenna * * Ns Ns Ns Ns Ns Ns *** *
0 - 20 0.34 ± 0.06a 6.42 ± 1.99a6.04 ± 0.42 0.07 ± 0.050.84 ± 0.8722.24 ± 9.583.29 ± 0.5833.53 ± 8.35 1.50 ± 1.14a 10.78 ± 1.58b
20 - 40 0.17 ± 0.03b 3.32 ± 0.92b6.35 ± 0.46 0.11 ± 0.060.18 ± 0.1913.97 ± 6.133.12 ± 0.0524.76 ± 3.32 0.30 ± 0.13b 14.05 ± 2.16a
Bonga Ns Ns Ns Ns Ns Ns Ns Ns Ns Ns
0 - 20 0.30 ± 0.07 4.53 ± 1.475.77 ± 0.81 0.10 ± 0.031.11 ± 0.2110.14 ± 2.503.47 ± 0.7328.10 ± 5.45 0.50 ± 0.28 8.73 ± 0.81
20 - 40 0.20 ± 0.02 2.85 ± 0.655.51 ± 0.64 0.08 ± 0.050.96 ± 0.347.85 ± 3.283.22 ± 0.5532.21 ± 6.92 0.20 ± 0.05 8.36 ± 1.49
B-Kontir Ns Ns Ns Ns Ns Ns Ns Ns Ns Ns
0 - 20 0.24 ± 0.10 2.88 ± 1.076.17 ± 0.56 0.12 ± 0.022.11 ± 2.0722.60 ± 9.918.14 ± 2.3424.09 ± 4.50 14.77 ± 7.38 7.05 ± 0.45
20 - 40 0.14 ± 0.05 1.48 ± 0.616.28 ± 0.40 0.12 ± 0.031.30 ± 0.9214.03 ± 9.066.94 ± 2.3127.93 ± 5.56 10.91 ± 9.37 6.20 ± 0.31
Yayu ** *** Ns Ns Ns * Ns Ns *** *
0 - 20 0.21 ± 0.02a 3.36 ± 0.47a5.54 ± 0.20 0.08 ± 0.020.70 ± 0.4513.04 ± 2.06a3.50 ± 0.3023.25 ± 2.28 8.90 ± 14.13a 9.24 ± 0.50a
20 - 40 0.14 ± 0.03b 1.85 ± 0.41b5.23 ± 0.62 0.09 ± 0.030.27 ± 0.179.82 ± 0.81b2.91 ± 0.6017.41 ± 1.97 0.40 ± 0.23b 7.83 ± 0.31b
Ns = Not significant (P > 0.05), *P ≤ 0.05, **P ≤ 0.01 and ***P ≤ 0.001. Means with the same letter within a column are not significantly different according to
Tukey grouping at P = 0.05. Abbreviations: TN = total nitrogen, SOM = organic matter, EC = electrical conductivity, CEC = cation exchange capacity, C:N =
carbon to nitrogen ratio.

T. Kufa / Agricultural Sciences 2 (2011) 443-450
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447447
Table 4. Correlation matrix values between soil chemical properties at each coffee forest of Ethiopia.
Location Variable TN SOM pH EC K Ca Mg CEC AvP
SOM 0.93**
pH –0.22 0.002
EC –0.07 0.22 0.84*
K 0.78 0.93** 0.16 0.42
Ca 0.77 0.94** 0.31 0.52 0.95**
Mg 0.46 0.60 0.46 0.47 0.79 0.70
CEC 0.84* 0.97** 0.01 0.28 0.96** 0.95** 0.61
AvP 0.86* 0.93** –0.09 0.20 0.96** 0.86* 0.71 0.93**
Harenna
C:N –0.55 –0.22 0.54 0.60 0.00 0.08 0.05 –0.03 –0.24
SOM 0.97**
pH 0.71 0.84*
EC 0.11 0.15 0.04
K 0.22 0.18 –0.10 0.38
Ca 0.36 0.22 –0.20 –0.090.80
Mg 0.12 0.03 –0.25 –0.100.86* 0.90*
CEC –0.70 –0.66 –0.59 0.61 0.28 –0.15 0.03
AvP 0.81 0.76 0.45 –0.060.62 0.75 0.66 –0.56
Bonga
C:N 0.51 0.69 0.90* 0.23 –0.04 –0.34 –0.23 –0.32 0.32
SOM 0.99**
pH –0.31 –0.37
EC 0.22 0.14 0.78
K 0.80 0.72 0.20 0.66
Ca 0.86* 0.87* –0.67 –0.180.50
Mg 0.80 0.78 –0.62 –0.120.53 0.97**
CEC 0.02 –0.05 –0.51 –0.420.04 0.32 0.48
AvP –0.44 –0.36 –0.24 –0.77–0.71 –0.21 –0.28 0.04
B-Kontir
C:N 0.36 0.48 –0.21 –0.18–0.103 0.35 0.15 –0.64 0.29
SOM 0.99**
pH –0.04 0.02
EC 0.07 0.03 –0.93**
K 0.55 0.60 0.28 –0.43
Ca 0.57 0.60 0.53 –0.660.90*
Mg 0.71 0.68 –0.18 0.37 –0.02 0.11
CEC 0.80 0.76 0.12 –0.140.33 0.57 0.71
AvP 0.40 0.47 0.20 –0.310.94** 0.80 0.01 0.16
Yayu
C:N 0.97** 0.99** 0.07 –0.040.71 0.69 0.61 0.71 0.60
Correlations are significant at *P ≤ 0.05 and **P ≤ 0.01 (2-tailed).
There were also remarkable differences in the CEC of
the soils, the highest and lowest being from the Bonga
and Yayu soils, respectively. This is in line with the par-
ticle distribution of these soil types, i.e., higher sand
content in Yayu than in Bonga soils. Moreover, such
differences in CEC could also be attributed to differ-
ences in the humification and generation of pH-de-
pendent adsorptive sites on the organic exchange com-
plex. In this regard, several studies [12,13,16] pointed
out similar findings in coffee soils of Ethiopia. These
authors have associated soil fertility status with rainfall
and temperature gradients, and soil biochemical proc-
esses. Consequently, soils of high rainfall areas are
highly leached and weathered with low pH, poor satura-
tion of cation exchange complex, low total exchangeable
bases, low concentrations of available phosphorus and
total nitrogen. The present results for soil CEC and
available phosphorus were not consistent with the rain-
fall gradient, as the soil samples were taken under moist
forest covers at relatively shallow soil depths. The high

T. Kufa / Agricultural Sciences 2 (2011) 443-450
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448
soil available phosphorus in the Berkane-Kontir soil as
compared to the others might come mainly from de-
composition of organic sources. Available P followed the
order of Bonga, Berhane-Kontir, Yayu and Harenna for-
est soils. The level of P at the Berhane-Kontir and other
forests is medium to low, respectively, according to the
standards [17]. This indicates the specific ability of each
soil type in fixing P. The highest SOM was found in the
Harenna and Bonga soils in contrast to the lowest SOM
at Berhane-Kontir and Yayu. At all sites, SOM was
higher than the range reported in forest soils [15]. The
relatively low available P in the Bonga soils could be
related to the capacity of the soil for fixing P due to the
high concentration of Aluminium (Al) and iron (Fe) in
the soil. As a result, several reports [4,13,18] also de-
scribed the limited availability of P in most coffee soils,
underlining the adaptation and low requirement of coffee
plants to P.
The higher TN and exchangeable bases in the upper
soils could partly illustrate the contribution of shading
and soil cover to reduce leaching and improve the nutri-
ent retention capacity of forest soils. The ratio of C:N
provides an indication of the type of organic matter pre-
sent in the soil and, in particular, the degree of humifica-
tion [2]. The C:N values of 12 and less than 10 indicate
good and impoverished (low organic matter content)
soils, respectively. However, the low C:N values ob-
tained at all forest sites except Harenna, demonstrate the
high concentration of TN in the soil, possibly from de-
composition of organic matter and/or nitrogen fixation.
This again could be associated to the climatic gradients
between the southeast and southwest montane rainforests.
Other authors [19,20] pointed out that the potential nu-
trient carrying capacity of the soil is determined by the
nature and the amounts of organic colloids present in the
soil.
The more humid the environment, the greater is the
proportion of recalcitrant organic matter. Moreover, clay
particles physically protect recent organic addition to
soils and form stable organo-mineral complexes with the
humus fraction [11]. In soils low in clay and receiving
small amount of annual precipitation, less soil organic
carbon is lost, because the capacity of the original soil
system to sequester carbon is reduced due to ready soil
aeration and the reduced physical protection of organic
matter by clay. The maximum available phosphorus at
Berhane-Kontir indicates its high fixation capacity. The
significant decline down the soil depth at Berhane-Kon-
tir and Yayu suggests that SOM and exchangeable bases
mitigate the fixation problem. The same findings on soil
P have been reported for the other coffee soils [4,18].
Despite the physical characteristics of the land and the
high rainfall patterns of the study sites, the inherent fer-
tility of the soil and thus quality of the land is main-
tained primarily due to the vegetation cover. The analy-
sis indicates that some soil attributes were noted to de-
cline with soil depth, suggesting the risks associated
with soil degradation. Therefore, assessment and man-
agement of SOM is important based on the recognition
that organic matter plays a role in the supply of major
and minor plant nutrients, improvement of physical and
chemical constraint, through reduced leaching, and fixa-
tion losses, as a storage for plant nutrients and a buffer-
ing against adverse conditions [13]. The bulk of coffee
soils in Ethiopia are classified as Nitosols, which are
highly weathered and originated from volcanic rocks
that require application of fertilizers for coffee cultiva-
tion under reduced shade environments. These soils are
deep and well drained and have medium to high contents
of most of the essential elements, except nitrogen and
phosphors [4,13]. Altogether, soils of the study areas can
be classified as Humic Nitosols, which occurs in areas
with high precipitation, mainly under natural vegetation
in the lowlands and in the highlands [21].
Forests play a pivotal role in maintaining ideal soil
properties and hence fauna and flora of the forest eco-
system. To this end, our present results provide high-
lights the roles of less forest disturbances in maintaining
high quality soils and coffee diversity in the natural cof-
fee forests of southeastern and southwestern Ethiopia. In
the semi-forest coffee production system, the level of
human interventions is minimal merely to systematically
remove the dense shading and undergrowth weeds,
largely to facilitate coffee harvesting [22]. The wild cof-
fee forest soils were characterized by ideal chemical
fertility status with high soil organic matter and major
plant nutrients. This may be attributed to the high litter
fall mainly from indigenous upper canopy shade trees.
The results corroborate with other authors [9,23,24] who
reported the adverse impacts of deforestation on coffee
ecology and natural gene pools. The declining soil fertil-
ity across locations and profile demonstrated the need
for site-specific forest management for enhanced organic
coffee production and benefit from the premium interna-
tional coffee prices [25]. Hence, exerting efforts to con-
serve the fragmented forest areas is thus parts and parcel
of making sound land use planning with full local com-
munity participations and fair benefit sharing to improve
the livelihoods of the rural poor. This demands strong
international collaborations and participation of the local
communities [26].
5. CONCLUSIONS AND MANAGEMENT
IMPLICATIONS
The study show inter- and intra-forest variations in
soil characteristics of the montane rainforests, possibly

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449449
due to the effects of forest management, vegetation
composition, site variables, parent materials and climate
gradients presented in Table 1. Moreover, significant
variations were detected between soil profile depths for
most soil properties could demonstrate the possible ad-
verse impacts of human induced soil erosion from culti-
vated lands. The present findings underline the contribu-
tions of vegetation cover in building up high quality soil
fertility status and preventing run-off on steep slopes.
Hence, the opened up plots should deserve special atten-
tion of rehabilitation works of future management inter-
ventions.
The declining soil fertility across locations and profile
demonstrated the need for site-specific forest manage-
ment. However, studies on seasonal variations in dy-
namics of carbon sequestration, nitrogen sources and
mineralization processes call for further works. To ex-
haust the present findings and use soil properties as geo-
graphical indicators, more transects within and around
each study remain to be assessed over seasons and
across locations. To ensure traceable specialty coffees,
there is a need for comprehensive works on the relation-
ships between quality attributes and environmental as
well as soil factors. This study would also provide prac-
tical implications for cost-effective environmental sus-
tainability and utilization of the remnant forest land-
scapes, maximum biodiversity and functioning ecosys-
tem services for global benefits. As to what extent forest
management levels, composition of plant species, parent
materials, soil microorganism and biochemical process
can dictate soil fertility status are among the focussed
areas that deserve attentions. The friendly coffee forest
environments are highly vulnerable to climate change
patterns and thus also require especial mitigation and
adaptation strategies. Moreover, in view of the ever in-
creasing population pressure, the trade-offs between
agricultural productivity, quality, biodiversity, and eco-
system goods and services call for strong collaborations
between the national and international actors to ensure
sustainability components (environmental, economical
and social) for the well being of the global population in
general and Ethiopian people in particular.
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