




































In ternationa l
Scholars
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African Journal of Environmental Economics and Management ISSN 2375-0707 Vol. 7 (7), pp. 001-010, July, 
2019. Available online at www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 
 
 

 

Full Length Research Paper 

 

Effect of biotic and abiotic factors on composition 
and foraging intensity of subterranean termites 

 
Swidiq Mugerwa1,2*, Moses Nyangito1, Denis Mpairwe3 and John Nderitu1

 
 

1
Department of LARMAT, P. O. Box 30197, University of Nairobi, Kenya. 

2
National Livestock Resources Research Institute, P. O. Box 96, Tororo, Uganda. 

3
Department of Animal Science, Makerere University, P. O. Box 7062, Kampala, Uganda. 

 
Accepted 07 March, 2019 

 
Elucidating the influence of ecological factors on composition and foraging intensity of subterranean termites 
is critical in development of sustainable termite management strategies. Our aim was therefore to analyze the 
effect of selected biotic and abiotic factors on composition and foraging intensity of termites. We used 
principal component and canonical correspondence analysis to select appropriate factors and to model 
relationships respectively. MACROTERMES species occurred in sites where the quantity of litter was generally 
above the mean. However, MACROTERMES HERUS (Rambur) and MACROTERMES spp.4 occurred in sites where the 
litter quantity was below the mean. TRINERVITERMES OECONOMOUS (Tragardh) and ODONTOREMES spp.1 were noted to 
occur in the direction of increasing quantity of biomass. Generally, most species occurred in sites where soil 
pH was above or slightly below the mean (4.8). Majority of the species were also noted to occur in sites where 

bulk density was below or slightly above the mean (1.55 g/cm
3
). Highest bait consumption (95%) occurred 

within a range of 55 to 60% basal cover beyond which the amount of bait consumed reduced. Litter and 
biomass quantity, pH and bulk density were noted as the most influential environmental variables determining 
composition of termites while basal cover was the major determinant of foraging intensity. 
 
Key words: Rangelands, Macrotermes, rangelands, vegetation, litter, biomass, basal-cover. 

 
INTRODUCTION 

 
Determinants of the structure and activity of subterranean 
termites at a large-scale are well known: climate, soil 
type, land use management practices and landscape 
structure are among the most influential factors (Dauber 
et al., 2003, 2005). At smaller scales, however, there is 
less agreement about the biotic and abiotic factors that 
drive variability in composition and activity of macro-fauna 
including subterranean termites (Lavelle and Spain, 
2001). Mitchell (2002) reported that the amount of 
available litter (both leaf and wood) was a major 
determinant of foraging intensity on vegetation by 
generalist feeders such as members of the genera 
Macrotermes and Odontotermes. He further noted that in 
sites with limited litter resources, termites resorted to  
 
 
 
*Corresponding author. E-mail: swidiqk@yahoo.com. Tel: 
+256782660295. 

 
 
 

 
standing biomass and consumed more than 60% of the 
standing crop. Mathieu et al. (2009) and Attignon et al. 
(2005) also reported that high encounters of Macrotermes 
species (mainly fungus growers) were associated with sites 
with high litter biomass and low soil water content. Curry 
(1994) observed the survival and activity of macro-fauna on 
various sites to be influenced by the micro-climate and the 
quality of food in the various sites. Micro-climate is very 
important since the body temperature of soil macro-fauna 
varies with external temperature (thermo-conformers) and 
the range tolerated by many species is narrow (Geiger and 

Aron, 2003). Geiger and Aron (2003) further noted that soil 
macro-fauna including subterranean termites need to 
maintain body water content within fairly narrow limits, 
which creates a dependence on soil water. This implied 
that the structure, survival and activity of subterranean 
termites would be enhanced on sites with acceptable 
levels of soil water content. Martison et al. (2008) 
reported that soil macro-fauna organisms are also 



 
 
 

 

sensitive to the nutrient content of their food because 
they need to maintain their internal chemical 
concentrations and the balance between the different 
nutrients of their body within a strict range. To this effect, 
elements of food quality such as phosphorus (McGlynn 
and Salina, 2007), nitrogen (Waren and Zou, 2002) and 

Ca
2+

 (Reich et al., 2005) content, can become a limiting 

factor to composition, survival and activity including 
foraging intensity of subterranean termites. Mathieu et al. 
(2009) also reported that the composition and activity of 
subterranean termites was influenced by presence of 
basal vegetation with more diversity in areas covered with 
grass tufts than on bare ground.  

In the rangelands of Nakasongola District in Uganda, 
vegetation is typically dominated by large herb turfs of the 
genera Hyparrhenia and Brachiaria, which clearly 
alternate with bare ground and shrubs. The vegetation 
cover is highly variable, from dense to completely bare 
ground leading to heterogeneous habitats with varying 
biotic and abiotic factors. The composition and foraging 
intensity of subterranean termites seem to be driven by 
the site-specific biotic and abiotic properties occurring on 
the different vegetation patches. On some patches, the 
termite assemblage structure is dominated by 
Macrotermes species while Cubitermes species dominate 
on other patches. Further, the population and foraging 
intensity of subterranean termites also varies from one 
site to another with most of the patches experiencing 
extra-ordinarily high foraging intensity of termites 
resulting into denudation of basal vegetation, forage 
scarcity and eventually poor livestock performance. 
Typical foraging is characterized by subterranean 
galleries leading to surface foraging holes from which 
termites emerge to remove dead grass and grass litter 
under cover of constructed soil sheeting. Termite foraging 
is particularly obvious during the dry season when bare 

rangeland can have up to 55 foraging holes per m
2
 

(Cowie and Wood, 1989). During such times the 
combined grazing effect of livestock and termites is to 
virtually denude considerable tracts of grassland, 
exposing soils to erosion by both wind and water 
(Mitchell, 2000).  

Recognizing the impact of biotic and abiotic factors on 
composition and foraging intensity of subterranean 
termites in savanna ecosystems, development of 
sustainable termite management strategies in the termite 
infested rangelands of Nakasongola requires adequate 
knowledge of the site-specific influence of biotic and 
abiotic factors on the composition and foraging intensity 
of termites. This will ensure that management of 
rangeland ecosystems aim at provision of the necessary 
ecological resources and conditions to overcome the 
detrimental impact of subterranean termites on rangeland 
vegetation. However, such information is still poorly 
documented. In particular, we lack information on the 

 
 
 
 

 

biotic and abiotic factors that enhance foraging intensity 
of subterranean termites as well as the ecological factors 
that are responsible for the variation in termite 
assemblage structure across various rangeland sites.  

Our aim was thus to analyze the effect of biotic (tree 
canopy cover, number of woody species, biomass and 
basal cover) and abiotic (soil moisture, soil temperature, 
bulk density, soil pH, litter quantity and soil organic 
matter) on the composition and foraging intensity of 
subterranean termites on the grazing lands in semi-arid 
Nakasongola. We examined two hypotheses: (1) the 
composition of subterranean termites will not vary among 
sites with different biotic and abiotic factors and (2) the 
percentage of baits consumed by subterranean termites 
(foraging intensity) will not vary among sites with different 
biotic and abiotic factors. 
 
 
MATERIALS AND METHODS 
 
Description of the study area 
 
The study was conducted on one savanna site, locally referred to 
as Kamukama Ranch. The site is located in Nakasongola District 
(55°140’ N, 32° 50’ E) of Uganda (Figure 1). The mean daily 
maximum temperature in the district is 30°C. Rainfall range 
between 500 to 1000 mm per annum and there are two rain 
seasons. The main rain season occurs from March-April to June-
July while the second rain season follows from August to October-
November. A long dry season occurs from December to February 
while a short spell comes around July-August.  

The vegetation on the study site mainly comprised of three 
vegetation cover types depending on the extent of anthropogenic 
activities/disturbance on specific ranch sites. The three vegetation 
cover types included dense vegetation cover (>50% basal cover), 
sparse vegetation cover (25 to 50% basal cover) and bare ground 
(<25% basal cover). The vegetation cover types are majorly a 
product of intricate interactions between climatic conditions and 
anthropogenic activities such as overgrazing, indiscriminate tree 
cutting and bush burning among others. The dense vegetation 
cover category on the study site mainly comprised of Tarrena 
graveolens and Acacia species forming 62 and 3% of the total 

woody canopy cover and woody density of 575, 125 trees ha
-1

 
respectively. The herbaceous vegetation was dominated by 
Brachiaria species contributing 88% of the basal cover. The sparse 
vegetation cover category was dominated by Cynodon dactylon and 
Loudetia kagerensis forming 67 and 12% of the species cover. 
Scattered woody species on the sparse vegetation cover were also 
dominated by T. graveolens, forming 34% of the woody canopy 
cover. The bare ground category mainly comprised of highly 
scattered Harrisonia abyssinica and T. graveolens forming less than 
0.5% canopy cover each. The number of mounds ranged from 33 to 

525 with an average of 227 mounds ha
-1

. The soil is generally 
moderately acidic with the pH ranging between 4 and 5.5. The soil 
organic matter (%), nitrogen (%), available phosphorus (ppm) and 
potassium (cmoles/kg) were 1.3, 0.1, 4.2 and 0.23 respectively. The 
soils generally belonged to the soil textural class of sandy loam. 

 

Sampling and classification of termite species 
 
The standardized sampling protocol developed by Jones and 
Eggleton (2000) was used to sample termites. The protocol 



  

  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Figure 1. Map of Uganda showing the location of Nakasongola District. 

 

 

involved lying belt transects of 100 m length by 2 m width, divided 
into 20 contiguous sections of 5 × 2 m. Each section was sampled 
by two trained people for 30 min (a total of one hour of sampling per 
section). In each section the following microhabitats were searched: 
12 samples of surface soil (each about 12 × 12 cm, to 10 cm 
depth); accumulations of litter and humus at the base of woody 
plants, the inside of tree stumps, dead logs, branches and twigs; 
the soil within and beneath very rotten logs; subterranean nests, 
mounds, carton sheeting and run ways on vegetation, and arboreal 
nests up to a height of 2 m above ground level. Workers and 
soldiers (if present) from every termite population encountered were 
sampled and the samples were preserved in 80% ethanol. The belt 
transect provides a measure of relative abundance of termites 
based on the number of encounters with each species in the 
transect. An encounter was defined as the presence of a species in 
one section. The vegetation of the study site was blocked in to three 
vegetation categories based on the quantity of vegetation covering 
the ground. The three categories included dense (> 50% basal 
cover), sparse (25 to 50% basal cover) and bare ground (< 25% 
basal cover). Two replicate belt transects were run in each of the 
three vegetation categories between December and January, the 
period when termite activity and subsequent destruction of 
vegetation by termites is reported to be severe (Nakasongola 
District State of Environmental Report, 2004). Sampling for termite 
species was conducted in 2010 and 2011. Taxonomic identification 
for collected samples was done at family, sub-family, genus using 
standard determination keys by Webb (1961) and where possible to 
species’ level using existing records of termite species in 

 
 

 
Nakasongola rangelands by Sekamatte (2001). 

 

Sampling for biotic and abiotic variables 

 
Several environmental variables were recorded between 2010 and 
2011 to assess their influence on termite assemblages. 
Measurements were made during the main rainy (March-April/June-
July) and the dry season (December to February). The soil water 

content (percent gH2Og
-1

 oven-dry soil) was measured from four 
surface soil samples (2 to 10 cm) taken from sections 3, 8, 13 and 
18 of every belt transect (Attignon et al., 2005). The same samples 

were analyzed for bulk density (g/cm
3
), soil pH and soil organic 

matter (%) according to methods described by Anderson and 
Ingram (1993). Soil temperature (°C) was determined by randomly 
inserting thermometers in the soil at any two locations in each of the 
four sections (3, 8, 13 and 18). The same sections were also 
sampled for herbaceous biomass quantity and litter quantity (both 
wood and leaf litter). The number of functional/live termite mounds 
per section was also quantified. Because the size of the sections 
was no sufficient to quantify canopy cover (Kent and Coker, 1992), 
three plots of 50 by 50 m were established in every vegetation 
category to enable estimation of tree/woody species density and 
woody canopy cover. Herbaceous biomass quantity was estimated 

by randomly placing two quadrats (1 m
2
) in each of the four 

sections. The above ground herbaceous vegetation within each 1 

m
2
 quadrat was cut at ground level, put in plastic bags and weighed 

as described by L.’tMannetje (1978). To quantify the amount of litter 



 
 
 

 
Table 1. Cumulative variability explained by five factors and factor loadings of vegetation variables.  

 
 Vegetation variables F1 F2 F3 F4 F5 

 Eigenvalue 3.287 0.852 0.457 0.256 0.148 

 Variability (%) 65.75 17.03 9.14 5.12 2.96 

 Cummulative (%) 65.75 82.78 91.92 97.04 100 

 Factor loadings      
 Biomass quantity 0.88 -0.35 -0.16 0.04 0.29 

 Litter quantity 0.84 -0.03 0.47 -0.28 -0.01 

 No. of woody species 0.61 0.73 -0.28 -0.15 0.03 

 Woody canopy cover 0.87 0.24 0.2 0.39 -0.06 

 Basal cover 0.84 -0.38 -0.30 -0.06 -0.25 
 
 
 
 

available, two quadrats (1 m
2
) were placed randomly in each of the 

four sections and all available dead plant material enclosed by the 
quadrat was collected, oven dried and weighed. The woody canopy 
cover and the number of woody species for each plot were 
estimated according to methods described by Kent and Coker 
(1992). 

 

Estimation of foraging intensity 

 
The effect of biotic and abiotic factors on foraging intensity was 
estimated using dried Hyparrhenia rufa grass baits as described by 
and Nash et al. (1999) and Pearce (1997). We selected H. rufa 
because the grass is reported to be among the most susceptible 
grass species in the area and is thus readily consumed by 
subterranean termites. Four litter bags (18 ×15 cm) of mesh size 4 
mm, containing the same quantity of dried H. rufa grass were 
randomly placed on the surface in each of the four sections (3, 8, 
13 and 18) of every belt transect. The bags were surrounded by 
three big stones to hold them in position or to prevent livestock and 
run-off from displacing them. The bags were removed after two 
weeks and were replaced twice in every season. After collection of 
baits, gallery carton and soil were carefully removed from all baits. 
The cleaned baits were oven dried at 60°C for 72 to 96 h and the 
dry weight recorded. The percentage of bait consumed (PC) was 

estimated as PC = ((Wi-Wf )/ Wi)*100 were Wi is initial weight of 

grass bait before consumption by termites, Wf is final weight after 
consumption by termites. The percentage of bait consumed by 
termites was used as a proxy for determination of foraging intensity. 

 

Data analysis 

 
In order to establish the effect of environmental variables on 
composition of termite species, we subjected the biotic and abiotic 
factors to principal component analysis (PCA) to obtain non-
correlated factors which were linear combinations of the initial 
variables (Jolliffe, 2002). Based on the eigenvalues and the 
variability explained by each factor, a few factors were selected. 
The vegetation and soil variables were analyzed separately in PCA 
and the selected variables for vegetation and soil were subjected to 
canonical correspondence analysis (CCA) in XLSTAT (2011). We 
opted for factors that accounted for at least 90% of the cumulative 
variability. PCA (Pearson type; correlation biplot) of vegetation 
variables led to selection of three factors which accounted for 92% 
of the cumulative variability. PCA (Pearson type; correlation biplot) 

 
 
 

 
of soil variables led to selection of four factors that accounted for 
98% of the cumulative variability. The selected factors were then 
used to model relationships in CCA (ter Braak and Verdonschot, 
1995) by extracting synthetic environmental gradients from the 
ecological data set as well as to develop ordination biplots. In order 
to establish the effect of environmental variables on foraging 
intensity (percentage of baits consumed), we also subjected the 
biotic and abiotic factors to (PCA) to obtain non-correlated factors 
which were linear combinations of the initial variables (Jolliffe, 
2002). Based on the eigenvalues and the variability explained by 
each factor, a few factors were selected. The selected factors were 
subjected to non-linear regression to clearly model the relationship. 
 

 

RESULTS 

 
Effect of environmental variables on composition of 
subterranean termites 

 

Principal component analysis on vegetation variables 
indicated that the first three factors explained 92% of the 
cumulative variability (Table 1). Biomass quantity (BQ), 
number of wood species (NWS) and litter quantity (LQ) 
were strongly correlated with factors one (r = 0.88), two (r  
= 0.73) and three (r = 0.5) respectively. Biomass quantity, 
number of wood species and litter quantity also loaded 
highest on F1, F2 and F3 respectively. The factor loading 
for BQ, LQ and NWS was 0.88, 0.73 and 0.47 on F1, F2 
and F3 respectively. The three vegetation variables were 
thus selected for inclusion in canonical correspondence 
analysis to establish the effect of the factors on 
composition of termite species. On the other hand, 
principal component analysis on soil variables showed 
that the first four factors explained 98% of the cumulative 
variability (Table 2). Soil water content (SWC), pH, bulk 
density (BD) and soil organic matter (SOM) were highly 
correlated with factors one (r = 0.86), two (r = 0.69), three 
(r = 0.69) and four (0.38) respectively. SWC, pH, BD and 
SOM also loaded highest on F1, F2, F3 and F4 
respectively. The factor loading for SWC, pH, BD and 
SOM was 0.86, 0.69, 0.69 and 0.38 on F1, F2, F3 and F4 



  
 
 

 
Table 2. Cumulative variability explained by five factors and factor loadings of soil variables.  

 
Soil variables F1 F2 F3 F4 F5 

Eigenvalue 2.692 1.001 0.763 0.443 0.100 

Variability (%) 53.85 20.029 15.255 8.861 2.005 

Cummulative (%) 53.85 73.879 89.134 97.995 100.00 

Factor loadings      
Soil temperature -0.78 0.31 0.39 0.34 0.15 

Soil water content 0.86 -0.25 -0.30 0.25 0.20 

pH 0.63 0.69 0.13 -0.33 0.10 

Soil organic matter 0.83 0.35 0.16 0.38 -0.16 

Bulk density 0.51 -0.5 0.69 -0.11 0.02 
 
 

 

respectively. Four soil variables were selected for 
inclusion in canonical correspondence analysis to 
establish the effect of the variables on composition of 
termite species.  

Since the origin (0, 0) of any environmental variable on 
the ordination biplot represents the mean of that 
particular variable, Macrotermes species are generally 
considered to have occurred in sites where the quantity of 
litter was above the mean (Figure 2). However, 
Macrotermes herus and Macrotermes spp.4 occurred in 

sites where litter quantity was below the mean (778 kgha
-

1
). Pseudocanthotermes species, Cubitermes spp.3 and 

1 also occurred in sites where the amount of litter was 
lower than the average litter quantity. By projecting 
species points on the line of litter quantity, it was 
indicated that Macrotermes spp.2 had the highest  
weighted average for litter quantity while 
Pseudocanthotermes species seemed to occur in sites 
where the litter quantity was extremely below the 
average. It was further noted that although Macrotermes 
species occurred in sites where amount of litter was 
above the mean, the species disappeared in sites where 
litter quantity was greatly above the mean. Trinervitermes 
oeconomous and Odontoremes species were noted to 
occur in the direction of increasing quantity of biomass 
and once the line of biomass quantity is extended beyond 
the displayed maximum point, T. oeconomous and 
Odontoremes spp.1 would have the highest weighted 
average than all the displayed species. The point for 
number of woody species (NWS) occurred at the origin of 
both litter quantity and biomass quantity and was 
associated with species which occurred in sites where the 
quantity of litter and biomass was around the mean.  

Projection of soil variables on the axes showed that pH 
was more correlated with axis 1 while BD was more 
correlated with axis 2 than other variables (Figure 3). 
Generally, most species occurred in sites where soil pH 
was above or slightly below the mean (4.8). It was noted 
that the majority of Macrotermes species and 
Odontotermes species occurred in sites where the pH 

 
 

 

was slightly above or below the mean. The species 
(Macrotermes and Odontotermes) were noted to 
disappear in the direction of increasing pH. Most of the 
species occurred in sites where bulk density was below 

and slightly above the mean (1.55 g/cm
3
). The diversity of 

species was noted to decline in the direction of increasing 
bulk density. It was also noted that Macrotermes spp.1, 
Odontotermes spp.1, Microtermes species and 
Pseudocanthotermes species were the only members of 
the sub-family Macrotermitinae that occurred in sites 
were bulk density was below average. Most members of 
the sub-family Macrotermitinae occurred in sites where 
bulk density was slightly above the mean and finally 
disappeared in sites with high bulk density. Only 
Ancistrotermes species and Cubitermes spp.3 were 
noted to occur in sites with high values of bulk density. 
 

 

Effect of environmental variables on foraging 
intensity of subterranean termites 

 

Principal component analysis on environmental variables 
led to selection of four principal components (factors) that 
contributed 96% of the cumulative variability (Table 3). 
Based on the loading of various environmental variables 
on the selected factors, four variables were selected to 
explain the effect of the variables on foraging intensity of 
subterranean termites. The selected variables included 
basal cover (BC), number of mounds (NM), litter quantity 
(LQ) and woody canopy cover (WCC). BC and NM 
loaded highest on F1 (0.99) and F2 (0.799) while WCC 
and LQ loaded highest on F3 (0.641) and F4 (0.45) 
respectively. Pearson correlation tests showed significant 
(p>0.05) correlations between BC and the other three 
selected variables. BC was positively correlated with NM 
(r=0.65, p=0.001), WWC (r=0.7, p<0.0001) and LQ 
(r=0.83, p<0.0001). Based on results from principal 
component analysis and Pearson correlation tests, only 
one variable (BC) was selected to explain the variability in 
foraging intensity since the remaining variables were 



  
 
 

 

2 
 
 
 

1.5 
 

 

1 
 

 

0.5 

%
) 

 
 

F2
(4

2.
37

 

0  
 

 

 

 

-0.5 
 

 

-1 

 
 
 
 

 

MICROTERMES SPECIES 
ANCISTROTERMES 

 
SPECIES 

 
 
 

 

PROCUBITERMES 
LQ  

 

  
 

SPECIES    
 

 MACROTERMES   SPP2 
 

 MACROTERMES  SPP3 
 

 M. BELLICOSUS  
 

 NWS MACROTERMES   SPP1 
 

   
 

  ODONTOTERMES SPP2 
 

CUBITERMES SPP3 MACROTERMES SPP4 CUBITERMES SPP2  

   

CUBITERMES SPP1 
  BP  

MACROTERMES HERUS 
 

 

 

PSEUDOCANTHOTERMES 
 

SPP 
T. OECONOMOUS 

 ODONTOTERMES SPP1 
 

 

-1.5 
 

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 

 

F1 (54.04 %) 

 
Figure 2. Ordination biplot based on canonical correspondence analysis of species/vegetation matrixes displaying 17.6% the 
inertia (= weighted variance) in species’ abundances and 96% of variance in weighted averages with respect to the vegetation 
variables. The eigenvalues of axis 1 (horizontally) and axis 2 (vertically) are 0.29 and 0.23 respectively. The eigenvalue of axis 3 
(not displayed) is 0.019. 

 

 

positively correlated with the selected variable.  
Results from nonlinear regression of percentage of bait 

consumed with basal cover indicated that highest 
consumption of baits (95%) occurred within a range of 55 
to 60% basal cover (Figure 4). Below this range, bait 
consumption was noted to decrease up to 0%. Beyond 
the same range, bait consumption was observed to 
decline but did not reach 0%. Reduction in basal cover 
from 100 to 80% was noted to double bait consumption 
from 38 to 76% while basal cover reduction from 80 to 
60% caused 24% increase in bait consumption. 
 

 

DISCUSSION 

 
Effect of environmental variables on composition of 
subterranean termites 
 

Although Macrotermes species are regarded as 

 
 

 

generalist feeders (Donovan et al., 2001; Wood, 1991) 
that forage on various organic resources such as grass, 
wood, dung and plant debris, Mitcheal (2002) noted that 
the species are predominantly litter feeders and their 
diversity and density would increase in areas with 
adequate availability of food (litter) resources. Okwakol 
and Sekamatte (2007) also noted that increased 
availability of litter due to clearance of trees led to an 
increase in density and diversity of litter feeding species, 
particularly Macrotermes species in forest ecosystems in 
Uganda. These observations agree with the observed 
trend in the current study where more species occurred in 
sites where litter quantity was above the mean. The 
occurrence of more Macrotermes species in areas with 
adequate litter resources implied that availability of food 
resources was one of the key factors influencing the 
spatial variability in diversity and density of the species. 
However, the absence of the same species in sites where 
the LQ was highest (greatly above the mean) could be 



   
 
 
 
 
 
 
 
 
 
 
 
 
 

 

F
2
 (

2
4

.1
1

 %
) 

 
 
 

 
 

2   
PSEUDOCANTHOTERMES  

   
 

 TRINERVITERMES  SPECIES 
 

 
SPECIES 

 SM 
 

 PROCUBITERMES  

1 
 

 

 
SPECIES  

 

 

OM 
 

 

 
CUBITERMES SPP2  

  
 

 M.SPP1 O.SPP1 CUBITERMES  SPP1 
 

0 
  MICROTERMES SPECIES 

 

    

ODONTOTERMES SPP2 M. HERUS 
 

 M.BILLICOSUS  

 

pH M.SPP4 
 

 MACROTERMES SPP2  

   
 

-1 
MACROTEMES SPP3  

 

   
  

ANCISTROTERMES 

SPECIES BD 

-2 
 

 

-3 
CUBITERMES SPP3 

 

 

-4 
 

-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 

F1 (46.72%) 
 

 
Figure 3. Ordination biplot based on canonical correspondence analysis of species/soil matrixes displaying 24% the inertia (= 
weighted variance) in species’ abundances and 71% of variance in weighted averages with respect to the soil variables. The 
eigenvalues of axis 1 (horizontally) and axis 2 (vertically) are 0.34 and 0.18 respectively. The eigenvalue of axis 3 and 4 (not 
displayed) are 0.12 and 0.09 respectively. 

 
 
 
 
Table 3. Cumulative variability explained by ten factors and factor loadings of environmental variables.  
 
 Environmental variables F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 

 Eigenvalue 7.42 1.23 0.67 0.31 0.21 0.13 0.03 0.01 0.002 0.001 

 Variability (%) 74.2 12.3 6.6 3.1 2.1 1.3 0.3 0.1 0.02 0.01 

 Cummulative (%) 74.2 86.5 93.1 96.2 98.3 99.6 99.86 99.97 99.99 100.0 

 Factor loadings           
 BQ 0.941 0.061 -0.04 -0.11 0.109 0.286 0.053 0.016 0.002 -0.002 

 LQ 0.85 -0.10 -0.23 0.45 0.055 -0.04 0.054 -0.003 0.000 -0.003 

 BC 0.992 0.091 -0.013 -0.002 -0.009 -0.032 -0.071 0.027 0.034 -0.010 

 NWS 0.692 -0.607 0.243 -0.163 0.221 -0.123 0.039 -0.016 0.001 -0.005 

 WCC 0.723 -0.048 0.641 0.123 -0.219 0.029 0.017 0.010 -0.002 0.002 

 NM 0.583 0.791 0.031 -0.124 -0.015 -0.113 0.071 -0.030 0.005 -0.003 

 ST -0.991 0.004 0.011 -0.028 -0.008 -0.068 0.075 0.081 0.005 -0.004 

 SM 0.986 0.090 -0.059 -0.034 0.093 -0.073 -0.015 0.035 -0.001 0.025 

 SOM 0.980 0.167 -0.060 -0.050 0.005 -0.048 -0.045 0.032 -0.033 -0.013 

 BD -0.754 0.414 0.354 0.169 0.306 0.029 -0.036 0.005 -0.001 -0.0 
 
BQ: Biomass quantity, LQ: litter quantity, BC: basal cover, NWS number of woody species, WCC: woody canopy cover, NM: number of mounds, ST: 
soil temperature, SM: soil moisture, SOM: soil organic matter, BD: bulk density. 



  
 
 

 
 100           

 

 90           
 

 80           
 

C
O

N
S

U
M

E
D

 70           
 

60           
 

   % consumed= 0.23+3.4*BC-3.05E-02*BC^2, R
2
= 0.83   

 

50           
 

B
A

IT
           

 

           
 

O
F
 40           

 

           
 

%
 

30 
          

 

           
 

 20           
 

 10           
 

 0           
 

 0 10 20 30 40 50 60 70 80 90 100 
 

 

BASAL COVER (%) 

 
Figure 4. Nonlinear regression curve of basal cover and percentage of bait consumed. 

 
 

 

partly attributed to presence high densities of predators 
particularly predator ants that nest in litter. Cubitermes 
species were noted to occur in sites where litter quantity 
was below the mean and this was partly attributed to the 
fact that the species are generally soil feeders (Donovan 
et al., 2001) and can survive in areas with limited litter 
resources. Trinervitermes oeconomous is a specialized 
grass feeder while Odontotermes species have also been 
reported to consume significant amounts of herbaceous 
vegetation. This could be a possible explanation of the 
occurrence of the species in sites with high biomass 
production as the sites could avail the species with 
adequate feed resources.  

The significant positive correlation between pH and soil 
organic matter meant that sites with low soil pH had low 
soil organic matter which limited availability of nutrients 
for plant establishment and this could have limited 
availability of adequate food resources for survival and 
activity of most termite species. Further, limited 
availability of soil organic matter meant that termites 
lacked the necessary nutrients to sustain their nutrition 
requirements. In this regard, Martison et al. (2008) also 

 
 
 

 
reported that soil macro-fauna organisms are sensitive to 
the nutrient content of their food because they need to 
maintain their internal chemical concentrations and the 
balance between the different nutrients of their body 
within a strict range. To this effect, elements of food 
quality such as phosphorus (McGlynn and Salina, 2007), 

nitrogen (Waren and Zou, 2002) and Ca
2+

 (Reich et al., 
2005) content, can become a limiting factor to 
composition, survival and activity including foraging 
intensity of subterranean termites.  

Trampling by grazing animals causes soil compaction, 
reduction of permeability, organic carbon, and nutrients, 
and restrict plant growth (Yates et al., 2000), reducing the 
input of organic matter into the soil and resources 
available to decomposers (Chapin et al.,2002). 
Eventually, the soil faunal diversity and density is likely to 
decrease in highly compacted areas. This explains the 
limited occurrence of termites in sites where the bulk 
density was greatly above the mean. The results have 
also indicated that members of the sub-family 
Macrotermitinae, the dominant sub-family on grazing 
lands in semi-arid Nakasongola, are sensitive to changes 



 
 
 

 

in bulk density and their activity and survival could be 
influenced by interventions that alter soil bulk density. 
Since the species are associated with destruction of 
herbaceous vegetation in termite infested rangelands, 
management decisions aimed at reducing bulk density 
below the average value reported in the current study 
would possibly check their activity and eventually reduce 
their destructive effect on herbaceous vegetation. 
However, more scientific investigations are necessary to 
determine the most appropriate level of bulk density that 
ensures optimum biomass production for livestock 
nutrition but also mitigating the destructive effect of 
subterranean termites on vegetation. 
 

 

Effect of environmental variables on foraging 
intensity of subterranean termite 

 

The significant positive correlation between basal cover 
and litter quantity meant that sites with high proportion of 
basal cover also had high quantities of litter. This implied 
that such sites had adequate food resources for both 
generalist termite feeders (members of sub-family 
Macrotermitinae) and the specialized grass feeders 
(Trinervitermes species). This could have resulted to the 
low response of termites to supplementary food sources 
in form of baits. The observed increase in bait 
consumption due to a decline in basal cover from 100% 
implied that feed availability was limiting and hence  
termites responded greatly to provision of 
additional/alternative food resources in form of baits. 
However, this trend occurred up to a certain point (55 to 
60%) beyond which the proportion of bait consumed 
started to decline. As basal cover continues to decline, 
the land becomes bare leading to high rates of run-off, 
erosion, and eventually loss of soil organic matter. The 
bare surfaces are also associated with low soil water 
content due to reduced water infiltration and high soil 
temperature which limit the survival and populations of 
termites. Eventually, the consumption of baits decreased 
as the land became bare not because the termites had 
plenty of food resources to forage on but because there 
were limited populations of termites to feed on the baits. 
The findings of the study suggested that availability of 
adequate food resources (litter and standing biomass) is 
critical in determining the foraging intensity of 
subterranean termites on organic resources. This implied 
that the foraging intensity of subterranean termites on 
alternative food resources would be high in sites with 
inadequate conventional food resources. No wonder, 
foraging intensity of termite on rangeland vegetation was 
reported to be highest on degraded patches with sparse 
vegetation cover and limited availability plant biomass 
and litter. The results of the study are consistent with 
findings of Wood (1991) who noted that destructive effect 
of termites on rangeland vegetation was more severe on 

  
  

 
 

 

overgrazed land with limited net primary productivity and 
litter availability. 
 

 

Conclusion 

 

In sum, the composition and foraging intensity of 
subterranean termites on grazing lands in semi-arid 
Nakasongola was influenced by certain biotic and abiotic 
factors. Litter and biomass quantity were noted as the 
most influential vegetation variables while soil pH and 
bulk density were noted as the most influential soil 
variables driving the variability in composition of 
subterranean termites. Increasing litter quantity was 
noted to favor occurrence of Macrotermes species to a 
certain level beyond which the species disappear. 
Recognizing the fact that Macrotermes species are 
reported as the major pests to vegetation on grazing 
lands in Nakasongola, interventions that enhance 
accumulation of litter beyond the level for their optimum 
occurrence would reduce their destructive effect on 
vegetation. It was further observed that basal cover was 
the main determinant of foraging intensity of termites on 
dried H. rufa grass. The foraging intensity was noted to 
decrease with increase in basal cover suggesting that 
management decisions for rangeland vegetation need to 
focus on maintaining adequate basal cover if termite 
damage on vegetation is to be reduced.  

The termite species in the Nakasongola ecosystem are 
predominantly litter feeders but can forage on 
herbaceous biomass in absence of adequate litter 
sources to cause significant denudation of rangeland 
vegetation. Ecologically sustainable management of 
these species requires rangeland managers to sustain 
the ecological integrity of termite infested ecosystems 
through undertaking appropriate ecosystem management 
techniques that maintain an ecological equilibrium 
between termites and other ecosystem components to  
prevent competition for ecological resources. 
Anthropogenic activities that degrade ecosystems such 
as overgrazing and indiscriminate tree cutting need to be 
checked. It is also important to sustain adequate 
availability of organic materials (such as litter) and 
herbaceous vegetation cover to avail termites with 
adequate food resources to prevent them from damaging 
vegetation. However, further research in the field need to 
focus on development of thresholds for litter (both 
quantity and quality) and amount of vegetation cover 
beyond which termites become destructive. 
 

 

ACKNOWLEDGEMENT 

 

The study was partially funded by the Regional 
Universities Forum for Capacity building in Agriculture 
(RUFORUM) and the National Livestock Resources 



 
 
 

 

Research Institute (NaLIRRI) in Uganda. 
 

 
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