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Intensive tree planting facilitates tropical forest biodiversity and biomass accumulation in Kibale National Park, Uganda


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The extensive area of degraded tropical land and the calls to conserve forest biodiversity and sequester carbon to offset climate change demonstrate the need to restore forest in the tropics. Deforested land is sometimes replanted with fast-growing trees; however, the consequences of intensive replanting on biomass accumulation or plant and animal diversity are poorly understood. The purpose of this study was to determine how intensive replanting affected tropical forest regeneration and biomass accumulation over ten years. We studied reforested sites in Kibale National Park, Uganda, that were degraded in the 1970s and replanted with five native tree species in 1995. We identified and measured the size of planted versus naturally regenerating trees, and felled and weighed matched trees outside the park to calculate region-specific allometric equations for above-ground tree biomass. The role of shrubs and grasses in facilitating or hindering the establishment of trees was evaluated by correlating observed estimates of percent cover to tree biomass. We found 39 tree species naturally regenerating in the restored area in addition to the five originally planted species. Biomass was much higher for planted (15,675 kg/ha) than naturally regenerated trees (4560 kg/ha), but naturally regenerating tree regrowth was an important element of the landscape. The establishment of tree seedlings initially appeared to be facilitated by shrubs, primarily Acanthus pubescens and the invasive Lantana camara; however, both are expected to hinder tree recruitment in the long-term. Large and small-seeded tree species were found in the replanted area, indicating that bird and mammal dispersers contributed to natural forest restoration. These results demonstrate that intensive replanting can accelerate the natural accumulation of biomass and biodiversity and facilitate the restoration of tropical forest communities. However, the long-term financial costs and ecological benefits of planting and maintaining reforested areas need to be weighed against other potential restoration strategies.Research highlights▶ Intensive tree planting produced a closed canopy regenerating forest with10 years. ▶ 39 naturally regenerating tree species were found in the replanted forest. ▶ Shrubs, particularly Lantana camara, threaten the future success of the regeneration.
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Forest Ecology and Management 261 (2011) 703–709
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Intensive tree planting facilitates tropical forest biodiversity and biomass
accumulation in Kibale National Park, Uganda
Patrick A. Omejaa,b, Colin A. Chapmanb,c,d,, Joseph Obuaa, Jeremiah S. Lwangab, Aerin L. Jacobe,
Frederick Wanyamaf, Richard Mugenyif
aFaculty of Forestry and Nature Conservation, Makerere University, P.O. Box 7062, Kampala, Uganda
bMakerere University Biological Field Station, P.O. Box 967, Fort Portal, Uganda
cMcGill School of Environment, 855 Sherbrooke St. West, McGill University, Montreal, Canada H3A 2T7
dWildlife Conservation Society, 2300 Southern Boulevard, Bronx, NY 10460, USA
eDepartment of Biology, McGill University, 1205 Docteur Penfield, Montreal, Canada H3A 1B1
fUganda Wildlife Authority, P.O. Box 3530, Kampala, Uganda
article info
Article history:
Received 19 September 2010
Received in revised form
24 November 2010
Accepted 26 November 2010
Available online 24 December 2010
Anthropogenic disturbance
Biomass accumulation
Carbon offset
Tree planting
Lantana camara
Acanthus pubescens
The extensive area of degraded tropical land and the calls to conserve forest biodiversity and sequester
carbon to offset climate change demonstrate the need to restore forest in the tropics. Deforested land
is sometimes replanted with fast-growing trees; however, the consequences of intensive replanting on
biomass accumulation or plant and animal diversity are poorly understood. The purpose of this study was
to determine how intensive replanting affected tropical forest regeneration and biomass accumulation
over ten years. We studied reforested sites in Kibale National Park, Uganda, that were degraded in the
1970s and replanted with five native tree species in 1995. We identified and measured the size of planted
versus naturally regenerating trees, and felled and weighed matched trees outside the park to calculate
region-specific allometric equations for above-ground tree biomass. The role of shrubs and grasses in
facilitating or hindering the establishment of trees was evaluated by correlating observed estimates of
percent cover to tree biomass. We found 39 tree species naturally regenerating in the restored area in
addition to the five originally planted species. Biomass was much higher for planted (15,675 kg/ha) than
naturally regenerated trees (4560 kg/ha), but naturally regenerating tree regrowth was an important ele-
ment of the landscape. The establishment of tree seedlings initially appeared to be facilitated by shrubs,
primarily Acanthus pubescens and the invasive Lantana camara; however, both are expected to hinder
tree recruitment in the long-term. Large and small-seeded tree species were found in the replanted
area, indicating that bird and mammal dispersers contributed to natural forest restoration. These results
demonstrate that intensive replanting can accelerate the natural accumulation of biomass and biodiver-
sity and facilitate the restoration of tropical forest communities. However, the long-term financial costs
and ecological benefits of planting and maintaining reforested areas need to be weighed against other
potential restoration strategies.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
Between 2000 and 2005, the world lost 7.3 million ha (or
200 km2) of forest per day (FAO, 2005). This figure does not
include vast areas of forest that are degraded by selective logging
or fire, both of which affect huge areas (Chapman et al., 2006).
This rapid rate of degradation is caused by a number of socio-
economic and political factors, partially due to large increases in
human population in most tropical countries (Brown and Pearce,
Corresponding author at: 855 Sherbrooke St. West, McGill University, Montreal,
Quebec, Canada H3A 2T7. Tel.: +1 514 398 1242.
E-mail address: (C.A. Chapman).
1994; Myers, 2002; Wright and Muller-Landau, 2006; Jacob et al.,
2008). In many regions, widespread commercial logging of tropical
forests provides access to previously remote areas and promotes
policies for agricultural expansion. For example, in the 1970s the
governments of Brazil (Steininger, 2000), Indonesia (Lawrence,
2005), and Uganda (Hamilton, 1984; Struhsaker, 1997) adopted
agricultural reforms to expand productive areas. They provided tax
incentives to encourage migration from densely populated regions
to forested areas that could be converted to agriculture. Unfortu-
nately, many of these formerly forested regions rapidly lost soil
fertility; the subsequent decline in crop yield forced settlers to
abandon recently cleared land (Brown and Lugo, 1994; Dobson
et al., 1997). As a result, it is estimated that there are 350 millionha
deforested and another 500 million ha degraded secondary and
0378-1127/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
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704 P.A. Omeja et al. / Forest Ecology and Management 261 (2011) 703–709
primary tropical forests; many of these areas have since been aban-
doned (ITTO, 2002; Lamb et al., 2005). The current scale of tropical
deforestation and the large areas of degraded and abandoned lands
underscore the need for intervention to restore biodiversity and the
ecological functions, processes, and goods and services previously
provided by these lands (de Groot et al., 2002; Boyd and Banzhaf,
In many cases, natural succession can cause forest to return to
deforested areas within a reasonable time frame (i.e., years to a
few decades) (Reiners et al., 1994); however, succession can also
occur at a very slow rate (Brown and Lugo, 1994; Chapman and
Chapman, 1999) and be considered arrested if it does not proceed
within a reasonable time frame (Aide et al., 1996; Shono et al.,
2007). Instances of arrested succession from both anthropogenic
and natural causes have been reported throughout the tropics,
including Brazil (Nepstad et al., 1991), Colombia (Aide and Cavelier,
1994), Panama (Brokaw, 1983), Singapore (Corlett, 1991), Sri Lanka
(Ashton et al., 1997), and Uganda (Chapman and Chapman, 1999;
Chapman et al., 1999). Arrested succession may reflect a lack of tree
seeds or resprouts, high seed or seedling mortality (Nepstad et al.,
1996; Ashton et al., 1997), inhospitable abiotic and biotic site con-
ditions (e.g., a lack of mycorrhizae or limited soil nutrients; Janos,
1980; Uhl et al., 1988; Corlett, 1991; Lwanga, 2003; Lawes and
Chapman, 2005), or competitive dominance of herbs and shrubs
(Denslow et al., 1991; Duncan and Chapman, 1999; George and
Bazzaz, 1999a,b; Duncan and Chapman, 2003b).
Seed limitation often inhibits the recovery of tropical forest tree
biodiversity when deforested areas are large or far from intact (i.e.,
non-degraded) forest. The majority of tropical tree species have
animal-dispersed fruits (Howe and Smallwood, 1982; Chapman,
1995), but many frugivores avoid deforested areas (DaSilva et al.,
1996; Zanne and Chapman, 2001), especially mammals (Chapman
and Chapman, 1999). Wind-dispersed seeds may arrive at defor-
ested sites in high numbers; however, since they are small-seeded,
the harsh micro-site conditions associated with abandoned lands
often limit the establishment of these seedlings. For example, Ingle
(2003) found that the stem density of vertebrate-dispersed species
outnumbered wind-dispersed species in montane forests of the
Philippines, although 15 times more wind-dispersed seeds arrived
in these degraded areas. Furthermore, seed dispersal limitation can
be severe for large-seeded tree species because in many systems the
predominant seed dispersal agents in abandoned areas are small
birds and bats that typically only carry small seeds (Nepstad et
al., 1996; Duncan and Chapman, 1999). These limitations can be
reduced when remnant trees (Guevara et al., 1986) and shrubs
(Vieira et al., 1994; Holl, 2002) are present because they attract
large seed dispersers and facilitate forest regeneration under their
canopies. In some deforested areas grasses invade before primary
successional tree species establish. High grass biomass can increase
the likelihood and intensity of fire, further arresting natural for-
est restoration (Nepstad et al., 1990; Lwanga, 2003). In previously
forested systems, fire can also impoverish soils, reduce seedling
growth (Aide et al., 1996), and impede forest recovery (Buschbacher
et al., 1988).
The Uganda Wildlife Authority (UWA) and Face the Future (for-
merly the Forests Absorbing Carbon Emissions (FACE) Foundation),
hereafter UWA–FACE, have a collaborative reforestation program
in Kibale. This intensive program was designed to facilitate the
rapid restoration of woody vegetation in a large area of the park
that was illegally encroached by agriculturalists who cleared forest
and grassland areas to plant crops (Chapman and Lambert, 2000;
Struhsaker, 2003). The primary objectives of our study were to
(1) quantify species richness of naturally regenerating (i.e., non-
planted) trees in Kibale National Park, Uganda, and (2) compare
the biomass accumulation of planted versus naturally regenerating
trees in sites replanted by UWA–FACE.
Fig. 1. The location of Kibale National Park within Uganda and the location of the all
restoration compartments planted to date (light grey) and the study compartments
(dark grey) within Kibale.
2. Methods
2.1. Study area and UWA–FACE field activities and costs
This study was conducted between May 2005 and May 2006
in the southern section of Kibale National Park, Uganda (Fig. 1).
The park (795 km2) is located in western Uganda (0.13–0.41N
and 30.19–30.32E) near the foothills of the Ruwenzori Moun-
tains (Chapman and Lambert, 2000; Struhsaker, 1997). Kibale is a
mid-altitude, moist-evergreen forest that receives 1697 mm of rain
annually (1990–2009). Although there are some early successional
species in the park (e.g., Albizia grandibracteata,Polysciasfulva,
Trema orientalis;Zanne and Chapman, 2005), Kibale is notable for
its lack of aggressive colonizers typical of other tropical regions
(e.g., Musanga spp., Cecropia spp.). Within the park, there is a
gradual decrease in elevation from north to south, which corre-
sponds to an increase in temperature, decrease in rainfall, and
changes in forest composition (Struhsaker, 1997). In the south,
the un-encroached forest is dominated by Cynometra alexandri
and its affiliated species; however, there are also areas of mixed
forest along riverine strips and even Acacia woodland to the far
In 1994, UWA–FACE started a reforestation program to estab-
lish carbon offsets on degraded land in Kibale, with tree planting
commencing in 1995. The project is based in the southern part of
Kibale in an area which was illegally occupied by agriculturalists in
the 1970s until their eviction in 1992 (van Orsdol, 1986; Baranga,
1991). Agricultural encroachment adversely affected approxi-
mately 120 km2(15% of the total area of Kibale), mainly leading to
forest destruction and grassland clearing (Chapman and Lambert,
2000). After the eviction, grassland areas became dominated by ele-
phant grass (Pennisetum purpureum) because frequent fires set by
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P.A. Omeja et al. / Forest Ecology and Management 261 (2011) 703–709 705
poachers or that spread into the park from neighboring subsistence
farms prevented natural forest regeneration (Struhsaker, 2003).
For the first phase of the replanting program (Phase 1:
1994–1997), the majority of seedlings were raised from seeds or
collected from the wild (wildings). A limited number of species
survived transplantation into the restoration areas, which were
typically dominated by the grass P. purpureum. As a result, future
replanting phases concentrated on planting Albizia spp., Bridelia
micrantha,Sapium ellipticum,Celtis durandii, and Warbugia ugan-
densis seedlings. The species were collected from the forest floor
in areas that were not affected by agricultural encroachment (one
person can collect up to 180 wildings per hour), transferred to a
nursery, watered, and kept in plastic covered chambers with high
humidity for four weeks until a new root system formed. Special
care was taken during collection and acclimatization in the nurs-
ery to ensure the roots healed before wildings were planted in the
restoration areas. Vegetative propagation by cuttings accounted
for 5% of the trees planted. Cuttings were directly set to root in
7cm×21 cm poly-bags containing a 1:1 mixture of forest topsoil
and sand.
Preparing the site for planting involved clearing the elephant
grass along a series of 2-m wide paths spaced in a 5 m ×5 m grid,
and digging a small pit every 5 m along the paths for the seedling;
thus, 400 tree seedlings were planted per hectare. The replanted
area was divided into a series of well mapped compartments to
facilitate monitoring. The size and placement of the compartments
were done by UWA–FACE and were based on convenience (e.g.,
the edge of the road formed the compartment border). A total of
16.35 km2were replanted in eight compartments during Phase 1
(Fig. 1). After planting, the seedlings were monitored and weeded
two to three times a year to protect them from fire and to limit
competition, primarily from grasses. Fire breaks were cut between
compartments and UWA–FACE staff fought fires and maintained
access roads to protect the planted areas. The total cost for these
activities was approximately US$120,000 per km2(UWA–FACE,
2.2. Sampling design
The eight study compartments were mapped using GPS units at
the time of planting and the corners marked with trenches. We
used maps from UWA–FACE to identify the compartments and
individual trees that were planted during Phase I. We randomly
established ten 10 m ×50m plots in each compartment using ran-
domly generated locations and directions. If a plot extended beyond
the edge of the compartment, it was re-oriented to 180oppo-
site the original direction. We identified each seedling, sapling,
and mature tree in the plot and measured their height, diame-
ter at breast height (DBH), and diameter at ground height (DGH).
Diameter at breast height is a commonly used metric that allows
comparisons with other studies; diameter at ground height allowed
us to evaluate small stems and was used in our allometric analysis
to estimate biomass. It was easy to separate planted from naturally
regenerating individuals as the seedlings were originally planted
in straight lines at set intervals.
We established small (1 m ×1 m) subplots every 5 m next to
the path used for planting. We estimated the percentage cover of
shrubs, dominant grasses, and average vegetation height (cm) and
identified plants using well recognized plant keys (Polhill, 1952;
Kingston, 1967; Hamilton, 1991; Katende et al., 1995; Lwanga,
Species richness and density data were log transformed
prior to analysis. We estimated species diversity using the
Shannon–Wiener index (Krebs, 1989) and evaluated the effects
of grass and shrub cover on species richness, biomass, and tree
height using a regression analysis. We selected and measured
trees in forested land adjacent to the park to provide a site-
specific estimate of dry tree biomass. We chose nine species
commonly found in regenerating areas: Albizia grandibracteata,
Bridelia micrantha,Celtis africana,Celtis durandii,Clausena spp.,
Maesa lanceolata,Funtumia latifolia,Milletia dura, and Trema ori-
entalis. Individuals of similar sizes to regenerating trees (both
planted and naturally regenerating stems) in the replanted area
were selected (i.e., DBH = 1.1–10.0 cm and DGH = 1.6–11.0 cm; dry
weight = 0.25–10 kg; total n = 200 stems), and we measured their
DBH and DGH. We felled the trees at ground level, removed the
branches, and measured the total dry weight of stems and leaves.
We cut the tree stems into small sections and air dried them until a
constant mass was attained. The dry biomass of trees in the planted
areas was predicted by the allometric equation log DGH (r2= 0.653,
n= 200, y= 2.053x+ 2.056).
We measured the seed size of tree species found naturally regen-
erating in the plots to evaluate the relative role of birds and large
mammals in moving seeds into the restoration areas. We mea-
sured the longest axis of 20 seeds from six adult trees in the
adjacent undisturbed forest. Based on the observations of the for-
aging activity of birds and mammals (Chapman, unpublished data),
we estimated the largest seed typically dispersed by birds in this
community to be Olea capensis (mean length = 1.39 cm) (exclud-
ing black and white casqued hornbills, Bycanister subcylindrucus).
Seeds larger than 1.39 cm were assumed to be mammal dispersed.
Smaller seeds could be dispersed by either mammals or birds,
since mammals often disperse both small-and large-seeded species
(Wrangham et al., 1994).
3. Results
The mean predicted biomass of planted trees in the eight
compartments was 15,657 kg/ha (range: 4120 kg/ha (n= 76) to
26,916 kg/ha (n= 244); Table 1), while the mean biomass of the
naturally regenerating trees was 4560 kg/ha (range: 1126 kg/ha
(n= 30) to 11,470kg/ha (n= 162); Table 1). In general, the naturally
regenerating trees represented 22.5% of the total biomass in the
restoration area.
A total of 39 tree species established themselves naturally in
the compartments in the ten years since replanting (Table 2). The
restoration program introduced only one tree species that did not
regenerate naturally in the area (Sapium ellipticum), although this
species is commonly found in the neighboring forest. Determin-
ing what proportion of the species in the adjacent forest these
39 species represent is difficult: many species in Kibale are rare
and would require extensive sampling to identify, and the forest
composition changes along a north–south gradient in elevation
and rainfall. However, species/area curves from our previous sam-
pling suggest that the number of new species found decreases after
sampling approximately 2 ha of scattered plots. Sampling 8.6 ha
throughout the park resulted in the identification of 74 species
(Chapman et al., 1997). This suggests that approximately half the
species in the adjacent forest were also present in restoration
Tree species diversity and evenness varied among plots: species
diversity was highest in compartments 109 (2.36) and 114 (2.32),
while evenness was highest in compartment 109 (0.45), followed
equally by 101, 103 and 113 (all 0.38; Table 3). Compartment 109
had 23 tree species and the individuals were distributed relatively
equally among these species. The contribution of the tree planting
to species diversity was negligible (Table 3).
Acanthus pubescens and Lantana camara were the dominant
shrubs in all compartments. We did not find a relationship
between the percentage cover of shrubs and grasses in the
subplots and the biomass of naturally established or planted
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Table 1
Above ground biomass (kg/ha) and stem densities (per ha) of woody tree species, and percentage coverage of grass and shrubs in the study compartments, Kibale National
Park, Uganda.
Compartment Planted Natural regrowth
Grass Shrub Biomass NNo. of spp. Biomass NNo of spp.
101 27 27 9620 152 5 1154 30 7
102 26 36 20,786 234 5 1126 42 8
103 31 37 15,114 318 5 7318 148 14
107 40 27 4,120 152 5 2496 72 8
108 30 34 14,126 430 5 2626 66 8
109 30 37 12,440 248 5 5060 246 19
113 24 37 22,276 448 5 11,470 162 18
114 37 28 26,916 488 5 5230 134 21
Total 125,398 36,480
Mean 15,675 4560
Standard deviation 7362 3534
Table 2
Tree species, mean seed length (where available) and frequencies for the study compartments Kibale National Park, Uganda. Tree species are arranged according to their
frequency of occurrence. Trees marked with an asterisk are considered to be mammal dispersed.
Tree species Mean seed length (cm) Not planted Planted Total
Bridelia micrantha 0.74 2 173 175
Warbugia ugandensis 0.99 1 57 58
Sapium ellipticum 0.57 0 55 55
Albizia grandibracteata 0.77 4 16 20
Harrisonia abyssinica 0.39 10 0 10
Allophyllus rubifolius 0.64 9 0 9
Combretum molle 808
Acacia spp. 0.68 7 0 7
*Mimusops bagshawei 1.65 8 0 8
Tabernaemontana holstii 1.06 7 0 7
Grewia occidentalis 0.75 7 0 7
*Erythrina abyssinica 1.83 7 0 7
Cassia spectabilis 0.83 6 0 6
Ficus capensis 0.10 6 0 6
Gardenia lanciloba 505
Rauvolfia vomitoria 1.27 4 0 4
Prunus africana 0.87 2 0 2
Markhamia lutea 1.17 4 0 4
Croton macrostachyus 0.82 0 4 4
Diospyros abyssinica 0.75 3 0 3
Antidesma spp. 303
Spathodea campanulata 1.00 3 0 3
Funtumia latifolia 0.29 3 0 3
Celtis durandii 0.50 0 2 2
*Chrysophyllum albidum 2.10 2 0 2
Olea capensis 1.38 1 0 1
Uvariopsis congensis 1.24 1 0 1
Mangifera indica 101
Carissa edulis 101
*Pseudospondias microcarpa 1.47 1 0 1
Maesa lanceolata 0.32 1 0 1
Kigelia africana 1.16 1 0 1
Persea americana 001
Apodytesdimidiate 0.47 1 0 1
Coffea eugenioides 0.93 1 0 1
Psidium guajava 0.49 1 0 1
Eudenia spp. 0.97 1 0 1
Dovyalis microcarpa 0.90 1 0 1
Dasylepis eggeling 0.73 1 0 1
Blighia unijugata 1.19 1 0 1
119 305 425
Table 3
Species richness, Shannon diversity index, and evenness of woody tree species naturally growing in the eight study compartments, Kibale National Park, Uganda.
Compartment All species Natural regrowth
NDiversity Index Evenness Diversity Index Evenness N
101 180 1.71 0.38 1.71 0.63 15
102 276 1.24 0.25 1.04 0.64 21
103 233 2.09 0.38 2.13 0.49 74
107 224 1.71 0.36 1.71 0.48 36
108 248 1.38 0.25 1.71 0.49 33
109 247 2.49 0.45 2.36 0.49 23
113 305 2.16 0.38 2.22 0.55 81
114 311 2.00 0.35 0.25 0.20 67
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trees. However, after combining the planted and the naturally
established trees, the percentage of shrub cover was positively
correlated to tree biomass (r2= 0.207, p= 0.026), while there was
a negative correlation between tree biomass and percentage
grass (r2=0.081, p= 0.018). However, the amount of variation
in tree biomass explained by either of these relationships was
The largest seed that birds in Kibale have been observed
to disperse is Olea capensis, which has an average seed length
of 1.39 cm (Chapman, unpublished data; Table 2). Mimusops
bagshawei,Chrysophyllum albidum,Pseudospondias microcarpa, and
Erythrina abyssinica were found in the compartments and their seed
sizes are longer than 1.39 cm; therefore it is likely that these species
were dispersed into the area by mammals (E. abyssinica is thought
to be a mimetic seed, one that is brightly colored but without any
pulp, so it does not provide any nutritional reward for dispersal).
Kigelia africana seedlings (average seed length =1.16cm) were also
found in the restoration areas; these seeds were likely dispersed
by elephants or large primates (probably baboons or chimpanzees)
since the seeds are embedded in a large fruit with a hard rind (aver-
age 60 cm long) (Katende et al., 1995). Seeds smaller than 1.39 cm
probably do not place a size constraint on the disperser and can be
dispersed by both mammals and birds.
4. Discussion
The results of this research have five contributions, they: (1)
demonstrate that the replanting program was successful at accu-
mulating biomass of planted trees, (2) show that native trees
naturally establish under planted trees, quickly creating a reason-
ably rich tree species assemblage, (3) quantify the financial costs
of enrichment planting, which is considered relative to poten-
tial costs of other strategies, such as fire exclusion, (4) consider
the role of grasses and shrubs, particularly the invasive Lan-
tana camera, in forest regeneration, and (5) provide evidence that
large and small-seeded tree species were found in the replanted
area, indicating that bird and mammal dispersers were likely
using regenerating forest habitat and contributing to natural forest
First, we demonstrate that the active restoration of the degraded
lands in Kibale was relatively successful as indicated by the pre-
dicted biomass the planted trees accumulated approximately 10
years after planting. Success should be measured (i) relative to
the goals of the program, which in this case was to accumu-
late biomass, and (ii) relative to other methods, of which there
have been many that have been evaluated in Kibale or elsewhere
(Chapman and Chapman, 1999; Chapman et al., 2002; Martinez-
Garza and Howe, 2007; Vieira et al., 2009). If agricultural land
in the Kibale region is abandoned and left to recover without
intervention, it will take a very long time for a closed canopy tree-
dominated community to regenerate, even if it is close to seed
sources (Chapman and Chapman, 1999). Chapman and Chapman
(1999) studied such an area and found that it took four years for
trees >5 m tall to reach a biomass of 8.9 kg/ha; even 17 years later
these areas are still dominated by shrubs and grasses (unpublished
data). However, excluding fire from degraded, regenerating agri-
cultural land increases the rate of reforestation (Lwanga, 2003) and
fire can be excluded over large areas at relatively low cost (Omeja,
unpublished data). Some researchers have advocated using timber
plantations, typically with non-native species, as a means to eco-
nomically reforest areas (Lugo, 1997; Parrotta et al., 1997; Lamb,
1998), since native forests can regenerate underneath the planta-
tions or following timber harvest, and timber sales can help pay
for restoration efforts. In Kibale, this management strategy was
successful for reforesting areas, despite the considerable damage
caused by initial and poorly planned timber extraction (Chapman
and Chapman, 1996; Duncan and Chapman, 2003a; Omeja et al.,
2009). This use of this plantation strategy of reforestation in
Kibale included all functional groups (pioneers, later-seral species
and wind and animal dispersed); however, animal dispersed tree
species will rarely be found if the plantation is not near native forest
(Zanne and Chapman, 2001).
Second, we documented that many tree species will natu-
rally establish under planted trees, creating a reasonably rich tree
species assemblage within a period of time that is reasonable for
management. The natural establishment of a diverse tree commu-
nity with accumulating biomass (almost 1/4 of the total biomass)
suggests that these initially species-poor areas (i.e., five planted tree
species) will quickly and naturally become richer and accumulate
woody tree biomass. One of the most important contributions of
programs such as the UWA–FACE restoration project is the rapid
rate of biomass accumulation of woody trees that sequester carbon
(Holl and Howarth, 2000; UWA–FACE, 2005; Coomes et al., 2008).
The fact that the diverse community of naturally regenerating
trees within these restoration areas has also quickly accumulated
biomass suggests that such programs may contribute to the rela-
tively rapid restoration of biodiversity. Furthermore, observations
of animal occurrence in the replanted areas suggest that biodiver-
sity of both plants and animals is rapidly recovering (Jacob and
Chapman, unpublished data).
Third, this research raises the question of when the ecological
gains of enrichment planting are worth the considerable financial
costs. Replanting of a mixture of early and late successional tree
species has been recommended to restore diversity more rapidly
than removing disturbance and waiting for natural regeneration
to occur (Yirdaw, 2001). However, the potential application of
enrichment planting to facilitate biodiversity restoration is based
on the premise that heightened seedling recruitment will lead to
greatly enhanced regeneration of mature trees, which are worth the
additional investment that replanting programs require (Plumptre,
1995; Chapman and Chapman, 1996). Even though planted trees
have a high probability of establishing and growing, especially
when planting is timed to optimize survival rates (Duncan and
Chapman, 2003a), enrichment planting generally involves costly
nursery maintenance and field labor. For example, while enrich-
ment planting depends on the density of the trees planted, forest
restoration is estimated to cost $250,000 US per km2on bauxite-
mined land in the Amazon (Parrotta and Knowles, 1999). It cost
$120,000 US per km2to conduct the enrichment planting and
establish and maintain the fire breaks that we evaluated in Kibale
(UWA–FACE, 2005). Given the relative success of the restoration
management in Kibale, we suggest that fire exclusion be evalu-
ated in more depth as a restoration strategy, given its relatively low
cost and ease of protecting an area (see also Lwanga, 2003). To the
credit of the UWA–FACE program, they established and maintain
an extensive network of fire breaks to protect the planted areas.
Anecdotal evidence suggests that this action has helped to protect
as yet unplanted areas that are passively regenerating. These areas,
plus others studied by Lwanga (2003), have been protected from
fire for <1 to 30 years; together they create a series of natural
experiments to evaluate the role of fire prevention in tropical forest
Fourth, the positive relationship we found between the com-
bined biomass of planted naturally establishing tree species and
the percentage of plots covered by shrubs concurs with results
from other tropical forests (Vieira et al., 1994; Aide et al., 1995;
Holl, 2002). This suggests that shrubs, in this case primarily L.
camara which forms 95% of the shrub layer, initially facilitates
woody tree species establishment. Shrubs have been found to lower
temperatures, increase soil moisture (Bertness and Callaway, 1994;
Callaway and Walker, 1997), and buffer seedlings from harsh envi-
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708 P.A. Omeja et al. / Forest Ecology and Management 261 (2011) 703–709
ronmental condition, such as heat from the sun (DaSilva et al.,
1996; Nepstad et al., 1996). These shrubs may also be beneficial in
that they deter fire (Lwanga, 2003) and reduce browsing (Sharam
et al., 2009). Generally, tropical areas with well-established ever-
green undergrowth tend to be less susceptible to fire damage than
areas with an accumulation of dry grasses (Parrotta, 1992; Lugo
et al., 1993; Parrotta, 1993). Exposed grassy sites, on the other hand,
have negative effects on site microclimate, with more pronounced
temperature fluctuations and differences in humidity and water
availability (Bazzaz, 1991) that are extremely stressful for plants
(Loik and Holl, 1999). Furthermore, grass-dominated areas are very
prone to fire in the dry season and successive fires severely curtail
forest succession.
Presently, observations and the correlation that we found sug-
gest that the shrub layer in Kibale appears to be initially helping
the regenerating trees acclimatize and form the dominant canopy;
however, studies have shown that there may be a shift in the
direction of this interaction over the long-term (Callaway, 1997).
In the future, the shrub layer, particularly that of the dense L.
camara shrubs, may not be conducive to a diverse regenerating
plant community as it may suppress seedlings from reaching forest
canopy layer (Zalucki et al., 2007). Introduced L. camara has been
reported to have harmful effects on ecosystems in other regions.
For example, Lantana sp. was ranked as the most significant weed of
non-agricultural areas in south-east Queensland, Australia (Zalucki
et al., 2007). In Kenya, the replacement of native pastures by L.
camara is threatening the habitat of the sable antelope (Hippo-
tragus niger), and acts as a safe haven for disease transmitting
tsetse-flies and a detrimental force to forest and ecosystem regen-
eration (Zalucki et al., 2007). The impenetrable thickets formed by L.
camara are also concerning because they restrict the movement of
even highly mobile animals, such as elephants (Loxodonta africana)
and baboons (Papio anubis), which likely reduces seed dispersal.
The balance between the advantages that establishing seedlings
receive from altered microclimate around L. camara versus the dis-
advantages of reduced seed input and potential long-term inhibited
growth remains unknown. Thus, if L. camara continues to form a
dense shrub layer then the regeneration pathway to forest recov-
ery may be diverted to an arrested successional state. This suggests
that there is a pressing need to investigate the long-term role
of L. camara in forest restoration and experimentation involving
removal would help clarify its role.
Lastly, the size of seeds of tree species naturally regenerating in
the area reflects the presence of different dispersing animals in the
restoration area. Most fruit-eating animals only feed on a portion
of the fruits that are available in the forest. Fruit selection no doubt
depends on a variety of factors such as morphology, nutritional
value, color, and the abundance of secondary compounds. How-
ever, seed size is a key factor known to influence which frugivores
disperse different species of fruits (Herrera, 1985; Wheelwright,
1985; Fischer and Chapman, 1993). A seed cannot be moved away
from the adult tree crown if it exceeds the size of gape of a bird
(Wheelwright, 1985; Chapman et al., 2003). Given that a num-
ber of tree species have seeds too large to be dispersed by birds,
and the fact that mammals disperse both large and small seeds,
it seems probable that mammals, such as elephants and baboons,
have played an important role in the accumulation of tree species
richness in the regenerating areas of Kibale. Bridelia micrantha (bird
dispersed) and A. grandibracteata (wind and rodent dispersed) had
higher stem densities than other species, and most of these were
growing naturally. These are trees species with small seeds, long
distance dispersal capability, long persistence in the soil seed bank,
and have the ability to colonize gaps within forest canopies (Zanne
and Chapman, 2005; Omeja et al., 2009), attributes that allow rapid
colonization of disturbed areas.
5. Conclusion
The potential for restoring degraded forests in Kibale National
Park is high following intensive planting of only five tree species.
We found that 39 tree non-planted species were able to establish
and accumulate considerable biomass following the planting pro-
gram. This regeneration facilitates the recovery of other tree and
animal species of conservation concern. There are many limitations
to forest restoration, and we speculated that the major future lim-
itation at this site is the heavy presence of L. camara that may slow
the progress of current restoration efforts. A more detailed under-
standing on the role of L. camara in future restoration needs to be
This research was supported by the Canada Research Chairs
Program, Wildlife Conservation Society, Natural Science and Engi-
neering Research Council of Canada, Committee on Scientific
and Technological Cooperation of the Organization of Islamic
Conference, Islamabad, Pakistan, and International Foundation
for Science, Stockholm, Sweden. We thank the Uganda Wildlife
Authority, Uganda National Council for Science and Technology,
and Makerere University Biological Field Station for granting per-
mission to conduct this research. The field assistants of the Kibale
Fish and Monkey Projects provided very valuable help. Previous
versions of this manuscript benefited from comments by Lauren
Chapman and Mike Lawes.
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... Lwanga, 2003;Shono et al., 2007). Firebreaks are a relatively simple and cost-effective measure to prevent the spread of fire, but only if well-maintained and frequently stripped of volatile material (FAO, 2019;Omeja et al., 2011). To motivate local communities to maintain the firebreaks and help prevent the spreading of fire, the FAO (2019) proposes planting food crops in the firebreaks. ...
... To date, the most common approach is therefore to plant a number of early-successional, exotic seedlings that function as nurse plants by shading out weeds and grasses, improving soil conditions, reducing fire risk and facilitating seed dispersal and colonization by increasing forest connectivity (Griscom and Ashton, 2011;Holl et al., 2000;Lamb et al., 2005). Planting pioneer species can facilitate natural establishment of native species in the understory (Omeja et al., 2011) or the promotion of late-successional species by under-planting (Ashton et al., 2001) or seeding . ...
... The most reported disadvantage of planting seedlings is its high cost as it involves nursery management, transportation and field labour (FAO, 2020; Omeja et al., 2011). Additional expenses on weed control, mulch or fertilizer application or extensive monitoring can hereby add up quickly (Palma and Laurance, 2015). ...
Full-text available
Humid tropical forests are increasingly exposed to devastating wildfires. Major efforts are needed to prevent fire-related tipping points and to enable the effective recovery of fire-affected areas. Here, we provide a synthesis of the most common forest restoration strategies, thereby focusing on post-fire forest dynamics in the humid tropics. A variety of restoration strategies can be adopted in restoring humid tropical forests, including natural regeneration, assisted natural regeneration (i.e. fire breaks, weed control, erosion control, topsoil replacement, peatland rewetting), enrichment planting (i.e. planting nursery-raised seedlings, direct seeding) and commercial restoration (i.e. plantation forests, agroforestry). Our analysis shows that while natural regeneration can be effective under favourable ecological conditions, humid tropical forests are often ill-adapted to fire, and therefore less likely to recover unassisted after a wildfire event. Active restoration practices may be more effective, but can be costly and challenging to implement. We also identify gaps in knowledge needed for effective restoration of humid tropical forests after fire, hereby taking into account the ecosystems and socio-economic conditions in which these fires occur. We suggest to incorporate fire severity in future studies, to better understand and predict post-fire ecosystem responses. In addition, as fire poses a recurring and intensifying threat throughout the recovery process, more emphasis should be placed on post-restoration management and the prevention of fire throughout the different phases of the restoration process. Furthermore, as tropical wildfires are increasing in scale, establishing collaborative capacity and setting priorities for efficient resource allocation should become a major priority for restoration practitioners in the humid tropics. Finally, as global fire regimes are changing and expected to intensify in the context of climate change, land use and land cover change, we suggest to put continuous effort into fire monitoring and modelling to inform the development of effective restoration strategies in the long-run.
... Active restoration involved planting of native species every year from 1995 to 2010 (except in 2001) in areas (3996 ha) with limited potential for natural recovery due to presence of fewer spontaneously regenerating seedlings as a result of elephant grass competition and fires (Ssekuubwa et al., 2018). Planting sites were prepared by clearing grass along a series of 2-m-wide trails spaced in a 5 Â 5 m grid, and digging planting pits every 5 m along the trails (Omeja et al., 2011). The planting density was 400 seedlings per ha. ...
... The main species planted were Albizia spp., Bridelia micrantha, Croton macrostachyus, Shirakiopsis elliptica, Celtis gomphophylla, and Warburgia ugandensis. The planted area was divided into a series of compartments (i.e., sites) of different sizes and weeding was carried out two to three times a year (Omeja et al., 2011). The areas with a high potential for natural recovery (2593 ha) due to the presence of many spontaneously regenerating seedlings were left to undergo natural forest regrowth (Ssekuubwa et al., 2018). ...
... By disaggregating data according to tree size classes (i.e., small, medium, and large trees), we reveal long-term successional patterns for restoration plantings (i.e., active restoration) and regrowth forests (i.e., passive restoration) over a 15-year and 7-year monitoring period, respectively. We found a progressive increase towards the old-growth forest in the biodiversity and structural attributes in both restoration plantings and regrowth forests which corroborates observations from previous studies in our sites (Omeja et al., 2011Wheeler et al., 2016), and supports the prediction of the gradual continuous model of succession that successional communities gradually drift, becoming similar to the ecosystem before disturbance (Suganuma & Durigan, 2015). Species richness, evenness, Shannon-Wiener diversity, and compositional similarity to the old-growth forest of small, medium, and large trees increased overtime which reiterates the role of active and passive restoration interventions in increasing the biodiversity conservation value of human-modified tropical landscapes (Gilman et al., 2016;Wheeler et al., 2016). ...
Full-text available
Several studies evaluate active (i.e., seeding/planting) and passive (i.e., protecting forest regrowth) restoration, but few studies examine successional patterns for different plant sizes. By using biodiversity and structure, we examined whether restoration communities approach old‐growth forests over time, and whether restoration success varies for different tree sizes in both active and passive interventions. We examined how initial site conditions affect active restoration. Small (dbh ≥ 5 cm), medium (≥15 cm), and large trees (≥30 cm) were measured in 2003–2017 in permanent sample plots in restoration plantings (initially 3–8 years old) and in an old‐growth forest in Kibale National Park, Uganda. Trees were also measured in regrowth forests (initially 16 years old) in 2011–2017. We collated information about site conditions from restoration reports. Biodiversity and structure increased over time towards the old‐growth forest. Restoration plantings and regrowth forests recovered diversity and structure of small and medium trees except for large trees. Forest recovery increased with proportions of remnant banana plants and shrubs, while isolation from the old‐growth forest slowed recovery. Disaggregating vegetation inventory data by tree size may be useful in achieving a holistic measure of restoration. Restorationists could prioritize sites with remnant banana plants and shrubs, and sites closer to old‐growth forests in order to achieve better results. Our article examined whether restoration communities approach reference forests over time, assessed the influence of tree size on restoration success in restoration plantings and regrowth forests, and how landscape conditions affect active restoration. We show that restoration success is faster for smaller than larger trees. Forest recovery increases with the proportion of banana plants and remnant shrubs, while isolation from the old‐growth forest slows recovery.
... This study took place in Kibale National Park (795 km 2 ), which lies in the Albertine Rift in western Uganda (00°13′-00°41′ N, 30°19′-30°32′ E; Omeja et al., 2011). The park receives a mean annual rainfall of 1,750 mm, with mean daily temperatures ranging from 15.1°C to 23.1°C. ...
... In 1971, agricultural encroachers cleared about 120 km 2 of forests south of the park (Chapman & Lambert, 2000). In 1992, encroachers abandoned the park and the formerly encroached areas became dominated by elephant grass (Cenchrus purpureus) because frequent fires set by poachers or spreading into the park from adjacent subsistence farms prevented natural regeneration (Omeja et al., 2011). ...
... In areas where natural regeneration was not feasible, active restoration was implemented through planting native species (Omeja et al., 2011). The forest under passive restoration is bordered by the oldgrowth forest to the east and actively-restored forests to the west. ...
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Aim There has been a debate about the effectiveness of passive restoration for recovering tropical forests, but few studies quantify the success of passive restoration. The aim of this study was to better understand tropical forest succession under a passive restoration scenario. We compared floristic and functional attributes of seedlings in a passively‐restored and an old‐growth forest, and assessed the effect of restoration age and distance from the old‐growth forest on seedling attributes. Location Kibale National Park, western Uganda Methods We measured seedlings in a passively‐restored and an old‐growth forest in 2011, 2014 and 2017. We determined species diversity, structure and composition and searched the literature for functional traits. We used generalized linear mixed‐effects models to compare seedling attributes between the restored and old‐growth forest and determine the influence of restoration age and distance from the old‐growth forest. Results Seedling species abundance, evenness, basal area and height were similar between the restored and old‐growth forest. Wood density and abundance of seedlings of different dispersal modes, habitat types, fruit size categories, and regeneration strategies were also similar between the restored and old‐growth forest. However, richness, diversity and composition of seedlings were different. We found a positive effect of restoration age on species abundance and abundance of non‐zoochorous, medium‐fruited, forest‐dependent, non‐pioneer light demander and shade‐tolerant species, and a negative effect on evenness, wood density, abundance of pioneers and compositional dissimilarity. Basal area of seedlings and the abundance of zoochorous and forest‐dependent species declined while compositional dissimilarity increased with distance from the old‐growth forest. Conclusions Our results provide empirical evidence on the potential of passive restoration to recover the structure and functionality of tropical forests in a relatively short period of time. We demonstrate that the effect of restoration age and distance from the old‐growth forest is not straightforward and depends on the attributes measured.
... Closely interlinked with the degradation of these forests is the establishment and fast spread of the shrub Lantana camara (Verbanacae) (Mungi et al., 2020;Pandey et al., 2020) which seem to make it even more difficult to regenerate the Himalayan Forest ecosystems (Bhatt et al., 1994;Kumar et al., 2020). Lantana camara is seen as an additional degrading agent (Mandal and Joshi, 2014;Sharma et al., 2016;Singh et al., 2014), blocker of succession (Omeja et al., 2011) and a hinderance in performing restoration activities (Raman et al., 2009). ...
... Five of the studies reported no effect on the abundance and diversity of some tree species. Three studies found a positive effect, at least for some species (Sahu and Singh, 2008;Yeates and Schooler, 2011) and one study reported all tree species (Omeja et al., 2011) studied had declined in abundance. A clear pattern that could explain these different results cannot be detected initially. ...
In pine forests of the Western Himalaya, we assessed the plant communities with a special focus on tree regeneration under different categories of Lantana camara cover. We did not find a general negative effect on the diversity and species richness but instead a trend indicating that an increase of Lantana camara cover leads to an increase in tree regeneration. Adequate tree regeneration is essential to the establishment of diverse and resilient forests in the Western Himalaya. Lantana camara is seen by some as a detrimental factor towards reaching this aim. We assessed the woody and nonwoody vegetation in three clearly distinguishable categories of Lantana camara cover (0, 40–60 and 80–100 %) each represented by 4 replicates consisting of 3 plots each. We found a significant decrease of the vegetation cover, other than Lantana camara, especially in the ground vegetation (p < 0.05). The vegetation communities of the three different categories differed in most cases significantly from each other (p < 0.02) but there was no significant difference in the Shannon-Wiener diversity and species richness between categories for the entire plant community. We found a significant increase of tree cover in the 0 to the 40–60% Lantana camara cover category which remained stable under 80–100% cover. Although the number of seedlings and saplings tended to increase with increasing Lantana camara cover, however this was insignificant. We also found a shift from light demanding to shade-tolerant tree species with increasing Lantana camara cover. Human caused forest impacts like fire and lopping decreased with increasing Lantana camara cover. We concluded that Lantana camara can aid in the establishment of a multi tree species forest if appropriate silvicultural measures are applied. The knowledge gaps regarding the factors that determine the absence and presence of tree regeneration under Lantana camara and appropriate silvicultural measures should be more carefully examined instead of applying a blanket eradication policy of Lantana camara in the forests of the Western Himalaya.
... Kibale National park has an approximately 10,000 ha restoration project area run by the Uganda Wildlife Authority (UWA) and Forests Absorbing Carbon dioxide Emission (FACE) the future foundation (Omeja et al., 2011;UWA-FACE, 2015;Wheeler et al., 2016) (Figure 1; Figure S2, Supplementary Material). In this part of the park, elevation ranges between 1,000 and 1,440 m a.s.l. ...
... Previous works in the restoration area of Kibale NP, Uganda, have reported the successful establishment of the planted trees, natural regeneration of several tree species (Omeja et al., 2011), and recovery-patterns in tree communities (Wheeler et al., 2016), fruit-feeding butterfly communities (Nyafwono, Valtonen, Nyeko, & Roininen, 2014) and bird communities (Latja, Valtonen, Malinga, & Roininen, 2016). In the future, remote sensing could be also utilized to predict recovery of diversity patterns (Khare, Latifi, & Rossi, 2019;Laliberte, Schweiger, & Legendre, 2020) or to monitor invasive species (Royimani, Mutanga, Odindi, Dube, & Matongera, 2019), such as the invasive shrub Lantana camara, across large-scale restoration areas. ...
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Restoration has now emerged as a global priority, with international initiatives such as the “UN Decade on Ecosystem Restoration (2021-2030)”. To fulfil the large-scale global restoration ambitions, an essential step is the monitoring of vegetation recovery after restoration interventions. The aim of this study was to evaluate the utility of remotely-sensed vegetation indices, Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), to monitor the progress of forest regeneration across a tropical forest restoration project area in Kibale National Park, Uganda. Using the chronosequence approach, results indicated non-linear patterns in NDVI and EVI across the first 25 years of recovery. Both NDVI and EVI increased for the first 10 years of forest regeneration. This “greening” phase could be used as the indicator of successful onset of forest recovery. In particular, the decline of elephant grass, and the consequent arrival of shrubs and trees, can be detected as an increase in NDVI. Primary forests differed from the 25-year-old regenerating forests based on the unique combination of low mean and low seasonal variation in EVI. Our results, therefore, suggest that the long-term success of forest restoration could be monitored by evaluating how closely the combination of mean, and degree of seasonal variation in EVI, resembles that observed in the primary forest. This article is protected by copyright. All rights reserved.
... Artificial planting of seedlings and natural recovery are two important approaches to restoration in open land. Plantations can accelerate forest restoration (Campoe et al., 2010;Omeja et al., 2011), improve stand condition (Lozano-Baez et al., 2019), and fast-growing tree species, such as Larix gmelinii (Rupr.) Kuzen and Coffea arabica L., may be especially useful in multi-functional plantations that take into account economic and ecological factors (Ghazoul et al., 2019;Badari et al., 2020). ...
Forests have been planted over large areas during forest restoration programs in Northeast China. An important challenge is transforming forest species structure by allowing colonization of native species in plantations, especially under the present policy of limited logging intensity and near-natural management practices. However, research on the entire process of native tree species restoration and conversion of tree species structure over time remains limited. Therefore, a multi-year field study was conducted to document native tree species restoration in plantations and different open land-cover types in Chinese temperate forests. We evaluated native tree species restoration in plantations (n = 30) and different types of natural recovery in open areas (n = 50) as controls. The first survey was conducted in 1990, with plots sampled in plantations of age 4–30 years, and repeat surveys were conducted in 1993, 2004, and 2016. We compared the importance of abiotic and biotic factors in the different survey periods using the Random Forest algorithm for restoration outcome (i.e., presence of ‘large trees’ (DBH ≥ 5 cm) of natural tree species in plantations) and the changes in plantation tree species composition during the survey periods. The aim was to test our hypothesis that abiotic and biotic factors, such as topography, habitat, and distance from nearest forest (i.e., seed source), differ in importance under different restoration periods. The results revealed that the basal area of large trees was the most important variable for native tree species restoration in plantations over the entire survey period. Abiotic factors, such as elevation and slope, differed in importance and relevance in the different recovery periods to the restoration outcomes in plantations and open areas. Increase in distance from seed source had a negative effect on natural tree species restoration in plantations and different types of open areas. Although the correlation of distance from seed source to restoration outcomes is consistent during the entire survey period, the importance of distance from seed source varied along a chronosequence. Different forest management measures require implementation. As succession progressed, the dominance of planted tree species in plantations gradually decreased. Compared with passive natural recovery, active planting of seedlings in open land not only promotes the restoration of coniferous species that no longer exist in an area owing to excessive logging, but also promotes the restoration of other native tree species.
... future forest restoration in this region. Given the limited research on tropical forest restoration in eastern Africa, as compared to Central and South America [16,20,27,31,37,55,56], the results from our study add to the handful from Uganda [11,49,57,58] and western Kenya [36] that help to identify native tree species successional pathways or potential pathways towards future restoration efforts. ...
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Natural regeneration is less expensive than tree planting, but determining what species will arrive and establish to serve as templates for tropical forest restoration remains poorly investigated in eastern Africa. This study summarises seedling recruitment under 29 isolated legacy trees (14 trees comprised of three exotic species and 15 trees comprised of seven native species) in tea plantations in the East Usambara Mountains, Tanzania. Among the findings were that pioneer recruits were very abundant whereas non-pioneers were disproportionately fewer. Importantly, 98% of all recruits were animal-dispersed. The size of legacy trees, driven mostly by the exotic Grevillea robusta , and to some extent, the native Milicia excelsa , explained abundance of recruits. The distribution of bird-dispersed recruits suggested that some bird species use all types of legacy trees equally in this fragmented landscape. In contrast, the distribution of bat-dispersed recruits provided strong evidence that seedling composition differed under native versus exotic legacy trees likely due to fruit bats showing more preference for native legacy trees. Native, as compared to exotic legacy trees, had almost two times more non-pioneer recruits, with Ficus and Milicia excelsa driving this trend. Implications of our findings regarding restoration in the tropics are numerous for the movement of native animal-dispersed tree species in fragmented and disturbed tropical forests surrounded by farmland. Isolated native trees that bear fleshy fruits can attract more frugivores, resulting not only in high recruitment under them, but depending on the dispersal mode of the legacy trees, also different suites of recruited species. When selecting tree species for plantings, to maximize visitation by different dispersal agents and to enhance seedling recruit diversity, bat-dispersed Milicia excelsa and Ficus species are recommended.
... Proximity or functional connectivity with remnant forests is important for increased seed rain and recruitment of trees in forest succession ( and Curran, 2016;de La Peña-Domene et al., 2013). At the same time, local factors such as canopy cover and understory vegetation strongly affect seed dispersal and seedling establishment and survival (Hooper et al., 2005;Omeja et al., 2011). In this sense, the canopy cover of applied nucleation can contribute to seed dispersal in the long-term. ...
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O monitoramento por meio de bons indicadores ainda é um desafio na avaliação dos resultados de restauração ecológica no Brasil. Nesse sentido, o objetivo deste trabalho é avaliar indicadores ecológicos do processo de restauração por plantio em núcleos implantados há dois e sete anos, no Rio Grande do Sul. Foram avaliadas 20 parcelas de 5 m x 5 m, em cada área, dispostas sistematicamente sob os núcleos. Todos os indivíduos arbustivo-arbóreos com altura superior a 30 cm foram contados e identificados. As espécies foram classificadas quanto à síndrome de dispersão e tolerância à sombra. Foram calculados o índice de diversidade de Shannon e a equabilidade de Pielou. A cobertura do dossel foi verificada com densiômetro esférico convexo. Análise de variância (p<0,05) foi utilizada para comparar indicadores de composição florística, estrutura e grupos funcionais entre as áreas. Modelos de regressão linear simples entre a área de ocupação dos núcleos e a riqueza e abundância da regeneração natural foram ajustados para verificar a expansão dos núcleos. Os resultados demonstraram maior riqueza, diversidade e percentual de cobertura de dossel na área com plantio em núcleos há sete anos. Houve diferença significativa para indicadores de composição, estrutura e grupos funcionais. O modelo de regressão linear simples para a área do núcleo em função do número de indivíduos foi significativo (p<0,05). Conclui-se que os núcleos implantados há sete anos estão sendo eficientes para a restauração ecológica. O período cronológico pós-implantação deve ser considerado como variável de influência na efetividade da restauração.
Collection management techniques used in map and geography libraries to describe and provide access to materials ensure researchers can engage with collections as viable sources of research data. Many practitioners create frameworks to market these collections as potential sources of data, whether used alone or alongside other research data. These frameworks bear similarities to the FAIR data movement, where data producers are encouraged to make their data Findable, Accessible, Interoperable, and Reusable. I frame the historical landscape photograph collections of the American Geographical Society Library and the United States Geological Survey Library as FAIR research data, offering the potential to engage with trends, concerns, or concepts being explored by geographers. When highlighting the FAIRness of these collections, we have an opportunity to better understand how they may be used as standalone sources of data, as well as alongside other FAIR data sources in scientific research. As another FAIR data source, I use the DataONE Data Catalog to contextualize these photographs alongside present-day datasets from fieldwork in similar landscapes. I encourage map and geography libraries to understand how the FAIRness of their collections enable unique research opportunities, leveraging the momentum surrounding FAIR research data in open science/open research communities.
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An increasing amount of information is being collected on the ecological and socio-economic value of goods and services provided by natural and semi-natural ecosystems. However, much of this information appears scattered throughout a disciplinary academic literature, unpublished government agency reports, and across the World Wide Web. In addition, data on ecosystem goods and services often appears at incompatible scales of analysis and is classified differently by different authors. In order to make comparative ecological economic analysis possible, a standardized framework for the comprehensive assessment of ecosystem functions, goods and services is needed. In response to this challenge, this paper presents a conceptual framework and typology for describing, classifying and valuing ecosystem functions, goods and services in a clear and consistent manner. In the following analysis, a classification is given for the fullest possible range of 23 ecosystem functions that provide a much larger number of goods and services. In the second part of the paper, a checklist and matrix is provided, linking these ecosystem functions to the main ecological, socio–cultural and economic valuation methods.
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Forest plantations established on degraded sites can accelerate natural succession through their effects on vegetation structure, microclimate, and soils. Spatial and temporal patterns of secondary forest species regeneration were studied in permanent quadrats in Albizia lebbek plantation plots and control areas at a degraded coastal pasture in Puerto Rico. Approximately 6.7 years after plantation establishment, a total of 22 tree and shrub species were found in the plantation plots, compared with only one species (Albizia lebbek) found in the control plots. The majority of tree species in the plantation have seeds that are dispersed by either birds or bats, suggesting that the plantation canopy plays a key role in the regeneration process by providing roosting habitat for seed-dispersing animals. Spatial variations in plantation understory seedling populations were found to be associated with both distance from probable parent trees and understory light intensity. These results indicate profound differences between the plantation and adjacent control plots with respect to their provision of regeneration habitat for secondary forest species, and suggest several factors that should be considered in the design of “foster ecosystems” for the rehabilitation of severely degraded tropical forests.
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Selective logging operations harvest trees above fixed diameter limits and therefore remove the trees which are likely to provide seed for the forest regeneration. A study in the Budongo Forest in W Uganda showed that the % of trees fruiting at different diameters varies between species. For the mahoganies, Khaya and Entandrophragma, fruit production occurs at larger diameters than many other species. For these species the amount of fruit produced in areas of the forest exploited for timber is considerably less than in unlogged forest. The implications for forest management are discussed. -from Author
The author summarizes 20 years of research in the Kibale forest in Uganda. The main body of the book demonstrates the adverse effects of logging on community structure and other aspects of forest ecology. The author provides evidence that future logging must be done at far lower intensities than is currently the norm, if intact ecosystems are to be maintained. Detailed recommendations for harvest plans compatible with the conservation of biodiversity and ecological integrity are outlined. Struhsaker addresses the underlying causes of tropical deforestation and concludes that although there are numerous proximate factors, the ultimate causes are rapidly increasing human populations and rates of consumption per capita. Comparisons with relevant studies elsewhere in the tropics are drawn and specific recommendations to address the problems are offered.
We investigated the role of the fern understory of closed-canopy forests as an ecological filter shaping the density, species composition, size structure, and spatial distribution of the seedling bank. In New England deciduous forests we tested the hypothesis that the understory stratum is a selective filter that differentially influences growth and survival of tree-seedling species by comparing performance of Acer rubrum, Betula alleghaniensis, and Quercus rubra seedlings in plots where the fern understory was undisturbed, partially removed, or completely removed. We related seedling growth and survival to microenvironmental characteristics of experimental plots in order to further explore mechanisms responsible for the filtering capacity of the fern understory. The presence of a fern understory reduced growth and survival of all seedling species, but the magnitude of the effect differed among species. Mortality resulting from resource limitation in Quercus below the fern understory was balanced by mortality resulting from insect herbivory in fern-free areas. Relative biomass growth rates of all species were negatively influenced by the presence of fern cover, whereas relative height growth rates of Acer and Quercus were uniformly low and insensitive to the presence of fern cover. Growth and survival rates indicate that only Quercus seedlings can emerge from the fern stratum in the absence of understory or overstory canopy disturbance. A trade-off between persistence in low light and maximum growth in understory light levels was observed among species. The relative growth rate of Betula in terms of biomass and height was more responsive to light levels than were relative growth rates of Acer or Quercus, and the growth rate of Betula was higher than that of Acer and Quercus in all light levels. However, survival of Betula below the fern stratum was lower than survival of Acer and Quercus. The fern understory has the capacity to selectively filter tree seedlings as they grow up through it because seedling species respond differentially to the presence of fern cover. The selective filtering of tree seedlings by the fern understory results in a seedling spatial structure that reflects the spatial heterogeneity of the fern stratum. The seedling pool below the fern stratum has a lower seedling density and different species composition and size structure than the seedling pool in fern-free areas.
The Kibale Forest Corridor Game Reserve lies between the Queen Elizabeth National Park (QENP) and Kibale Forest Reserve in Uganda. The Game Corridor was gazetted in 1926 to allow for the free movement of animals. Since the early 1970s forest resources have been depleted rapidly and encroachers have moved into the Game Corridor and settled. At the same time elephant Loxodonta africana numbers went from 3000 in 1973 to 500 in 1989 in the QENP. The Kibale Game Corridor should be retained as a conservation area and the trend of encroachment should be reserved. -from Author
Ranching and logging operations are transforming the moist tropical forests of an eastern Amazonian landscape into a mosaic of pastures and regrowth forests. The new ecosystems of this region are agriculturally unproductive, biologically impoverished, and far more flammable than the mature forests they replace. In the absence of fire, the forest regrows on abandoned sites, accumulating biomass and species at a rate that is inversely related to the intensity of use prior to abandonment. Forest regrows slowest on those rare abandoned pastures that were once scraped with bulldozers. The grass- and shrub-dominated old fields that form on some of these sites resist forest regrowth because of numerous barriers to tree establishment and growth. Knowledge of these barriers provides a basis for developing inexpensive techniques to restore agricultural productivity in old fields by implanting tree-based agricultural systems or to restore forest regenerative capacity in old fields by establishing trees that attract seed-carrying animals and ameliorate harsh environmental conditions. These restoration techniques will be needed over large areas of Amazonia if current attempts to reform degraded pastures fail. -from Authors