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Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 24-36

Floristic Composition of Home-garden Systems in Dumbara (Knuckles)

Conservation Area with an emphasis on Endemic Species

D. M. A. J. Dissanayake and P. L. Hettiarachchi
*

Faculty of Applied Sciences, Rajarata University of Sri Lanka

Date Received: 24-11-2012 Date Accepted: 18-02-2013

Abstract

Home gardens are multistoried ecosystems and are important not only for in-situ biodiversity

conservation, but also as valuable food sources, fodder, medicine and spices. The main objective of

this study was to make decisions about the variations of home garden composition and to identify the

endemic species. Fifty five home gardens were studied in northern flank from January to April 2012.

Two large (10x10m
2
) and four small (1x1m

2
) quadrates were studied in each home garden. Individuals

≥ 1.5 m height and ≥ 1 cm DBH were measured to calculate IVI. Species identification was done on

site and further at the National Herbarium, Peradeniya. Total of 1335 individual woody-perennials and

4603 herbs were found in 11,000 m
2

of study area. One hundred and fifty two woody-perennial species

(19 endemic, 44 naturalized exotics, 37 cultivated and 52 timber) under 54 families and 56 herb

species (46 medicinal) belonging to 33 families were recorded. Euphorbiaceae was the dominant

family with 15 species, followed by Fabaceae (11 species), Anacardiaceae (10 species), Rutaceae (10

species), Myrtaceae (7 species), Rubiaceae (6 species), Arecaceae (6 species), Moraceae (5 species),

Sapindaceae (4 species) and Zingiberaceae (4 species). Highest number of plant families (43) was

recorded in Pitawala, while the lowest number of plant families was recorded in Polommana (24).

Based on the Importance Value Index (IVI), the species to pay highest priority for conservation were

selected. According to Shannon diversity values for different villages, Rathninda is the most stable and

less disturbed, whereas Polommana is the most unstable and highly disturbed village. There were five

endemic Anacardiaceae species (Campnosperma zeylanicum, Mangifera zeylanica, Semecarpus

coriaceae, Semecarpus nigro-viridis, Semecarpus walkeri). Twelve percent of the studied population

were interested in timber trees such as Tectona grandis, Melia azedarach, Swietenia macrophylla and

Chloroxylon swietenia. Twelve percent of the studied population preferred fruit trees while 5% were

interested in some medicinal plants. Preference of this nature indicates that in the future, the plant

diversity in these home gardens is likely to decline considerably. This might even lead to the

extinction of rare, endemic plant species. Therefore, people in northern flank encouraged to

incorporate multipurpose endemic plants and plants with less IVI values in their home gardens in

order to maintain high diversity and to conserve endemic and relatively rare plants while gaining

substantial income through their home gardens.

Keywords: Northern Flank, Home gardens, Conservation, Woody-perennials, Endemic species

1. Introduction

Tropical home gardens are generally regarded as sustainable production systems (Abdoellah et

al. 2001). A home garden is a clearly bounded piece of land cultivated with a diverse mixture of

annual and perennial crops, and on which a house is built (Karyono, 1990). The major function of

home gardens especially in rural areas, are subsistence production and income generation

(Soemarwoto and Conway, 1992). Because of the high biodiversity existing in home gardens, a wide

spectrum of multiple-use products can be generated with relatively low labour, cash or other inputs

(Christanty, 1990).

*Correspondence: phlakshmi@yahoo.com
Tel: +94712448139, +94771238980
ISSN 2235-9370 Print / ISSN 2235-9362 Online ©2013 University of Sri Jayewardenepura

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 27-39

In times or seasons of scarcity, home gardens with their diverse products available year-round,

contribute to food security. They also fulfil many social, cultural and ecological functions (Abdoellah

et al., 2001). The multi-layered, forest-like vegetation structure of home gardens contributes

substantially to the sustainability of this production system. Among others, this structure can protect

the soil from erosion, offers a habitat to wild plants and animals, promotes a favourable microclimate

and makes efficient use of light, water and other resources (Christanty et al., 1986). Because of their

large crop species and varietal diversity, home gardens are regarded as an ideal production system for

in situ conservation of genetic resources (Watson and Eyzaguirre, 2002). However garden diversity

varies according to ecological or socio-economic factors or characteristics of gardens or gardeners

(Christanty et al., 1986).

Home gardens particularly preserve much of the cultural history, as they are the sites where

many useful plant species have been subjected to intense management regimes over extended periods.

Through many years, farmers have cultivated and selected the plant species they desired, and in this

way, home gardens are reservoirs of current and potential resources as well as a crucial site of

selection and domestication of some plant species (Hawks, 1983)

Plant composition in home gardens is possibly influenced by factors like: access to water, economic

activities of owners and availability of labour, traditional social organization, modernization processes

and economic development (Rico-Grey et al., 1990). Using multivariate statistical techniques,

researchers have found that floristic composition of home gardens was relatively similar within

villages, but varied among regions.

The home gardeners are perpetual experimenters, and they are constantly trying and testing

new species, varieties and management over the centuries they have selected specific species and

manipulated their physical and ecological locations, planting for maximising space and production.

From the ground layer to upper canopy, the gradient of light and humidity determine different niches

that species exploit according to their own requirements (Fernandes and Nair, 1986). Therefore study

of these parameters gives an idea of the temporal and spatial positioning of plants, species interaction

and mixed species silviculture that are pertinent for designing multistate agro forestry and for the

management of its productivity (Gillespie et al., 1993).

Dumbara range is very important in terms of its hydrological wealth as the catchment of Sri

Lanka’s longest river, the Mahaweli. The range is endowed with many different forest types. A total of

1033 flowering plants belonging to 141 families have been recorded from the diversified vegetation

types in Dumbara. Among them, 255 (25%) are tree species, while the balance consists of shrubs or

herbs , Of the total number of flowering plant species documented in Dumbara, 15% are endemic to

Sri Lanka, while about 3% are nationally threatened. Although the Dumbara area covers less than

0.5% of the land in the country, it contains almost one third of the island’s flowering plant species

(Diversity of woody plants in the Dumbara forest, Environment Management Division - Forest

department, 2005).

Home gardens similar to natural forests are found around the homesteads of Dumbara area. A

well-developed multi-storey home garden generally includes a canopy (20 m), sub canopy (10 m) and

shrub/ herb layer. Home gardens are also important faunal habitats that provide animals with feeding

and nesting grounds. There are around 80 villages in and around the Dumbara forest region which

form a unique bio cultural landscape. Even in this sophisticated era, life in these villages exhibit the

simple harmonious co-existence of man and nature.

Information on the studies carried out in home garden in the northern flank of Dumbara is

scares. This study was carried out in some peripheral villages of the Northern Flank of Dumbara home

gardens to examine component interactions and productivity in the home gardens. Information on only

two related studies namely “Conservation implications of home garden agro-forestry systems”, and

“Livelihood Development” carried out by DGAPIK Abeywardana, (University of Peradeniya) in 2008

is available. However, those only provide information on 3 villages; Kalugala, Kosdanda and

Udailluka in Dumbara South-Eastern Flank. Hence, this study is important to compare the results of

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 24-36

above two Flanks and to make decisions about the variations of home garden composition in

Dumbara. This study was designed to accomplish following objectives;

• To identify floristic composition of home garden systems in some peripheral villages of

Dumbara (Knuckles) Conservation Area.

• To identify the endemics, naturalized exotics and timber trees in the study area

• To identify plant species and highly disturbed villages for conservation

2. Methodology

2.1 Study area

Dumbara conservation forest nestles within the Dumbara Mountain Range – Sri Lanka’s misty

mountains. Located at latitudes 70 5’N and longitudes 810’ E and covering 180 km
2
, its situated at the

boundary of the wet and dry zones. The study area of the research lies in several peripheral villages of

the Knuckles Conservation area, located in Matale district. Geographical coordinates are 7° 17' to 7°

40' North and 80° 43' to 80° 55' East. This covers areas including human habitations, well wooded

home gardens, Paddy fields and forest patches. The study area is situated within the wet zone of Sri

Lanka.

Figure 1: Detailed map of the study site

To conduct the study, six villages (Pitawala, Polommana, Atanwala, Rathninda, Mahala

Kotuwa and Illukkumbura) from the northern flank (within Matale District) of Dumbara Conservation

Area were selected in January 2012 considering some factors such as elevation and distance from the

existing natural or semi-natural forests. Five (5) home gardens from Polommana village (because there

were only five homes) and ten (10) home gardens from other 5 villages were selected. To study the

structure and composition of the home garden vegetation, the following methods were applied:

a.) Woody vegetation: Two large (10 m x10 m) quadrates were studied from each home garden

selected. All the individuals above 1.5 m height and above 1 cm DBH were identified into species

level, counted and recorded the number of individuals, DBH and height were measured. To quantify

and compare the species dominance within home gardens in each village, Density, Frequency,

Dominance, basal area and Importance Value Index (IVI) were calculated for the species.

b.) Herbaceous (ground layer) vegetation: Two small (1 m x1 m) quadrates were studied from each

large quadrate selected (Four quadrates for each home garden). All individuals were identified into

their species level, counted and recorded.

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 27-39

3.2 Identification of plant species

Onsite identification was done for the common species using the expert and indigenous

knowledge. They were identified up to species level using the checklist. Determination of other

species was done with the help of National Herbarium, Peradeniya.

Structured and informal interviews were conducted when necessary (depending on the literacy

level of the household). Additionally, the traditional practices and rituals related to forest-home garden

activities and use of indigenous knowledge on wellbeing of the system were taken into surveying.

2.3 Data Analysis

1. Shannon-Weiner index: Species diversity of the plants recorded in quadrates was analyzed with the

use of Shannon-Weiner index.

H = -∑i=1 (pi) (log pi)

H= Shannon- Weiner index

S= Number of Species

Pi = Population of total sample belonging to the i
th

Species

2. Density, frequency and dominance were calculated for IVI (Importance Value Index)

3. Bio-Diversity professional version 2.0 was used to analyse distribution, Simpson Diversity index

and Margalef Diversity index.

3.4. Data Analyzing Techniques

Abundance

Relative Frequency =
Number of sample plots with a sighting of a species

Total number of sample plots ×100

Relative Density =
!"#$% &' ()*(+(*!,-. &' , ./$0($.

!"#$% &' .,"/-$ /-&1. 2(13 , .(431()4 &' , ./$0($. × Sample plot area
∑7 89:;<= >? @AB@C@B9DEF >? D FG<H@<F 89:;<= >? FD:GE< GE>IF J@IK D F@LKI@AL >? D FG<H@<FM

×100

Relative Abundance = Relative Frequency + Relative Density

Importance Value Index (IVI)

A measure often used to describe and compare the species dominance of the plots is the

Importance Value Index of Cottam and Curtis (1956). The IVI for a species is calculated as the sum of

its relative dominance, its relative frequency and its relative density. Certain points have to be

acknowledged, to understand the arguments the IVI is providing. Also some species may be dominant

in one site but do not occur in the other sites. Therefore their local dominance is not displayed in the

overall statistics. Still, the IVI is giving a figure with the overall importance of a species.

Relative Frequency 2 =
Number of individuals of a species

Total number of Species ×100

Relative Dominance 2 =
Total basal area of a species
Total basal area for all species ×100

Relative Density 2 =
Number of individuals of a species
Total number of individuals × 100

IVI = Relative Frequency 2 + Relative Dominance 2 + Relative Density 2

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 24-36

3. Results and Discussion

A total of 1335 trees and 4603 herbs were recorded in 11000 m
2
(1.1 ha) in six peripheral

villages (55 home gardens) in Dumbara region. Hundred and fifty two plant species (19 Endemic

species, 44 Naturalized exotics, 37 species - only under cultivation and 52 timber species) under 54

families and 56 herb species (46 Medicinal) belonging to 33 families were recorded.

Euphorbiaceae was the dominant family having 15 species, followed by Fabaceae (11 species),

Anacardiaceae (10 species), Rutaceae (10 species), Myrtaceae (7 species), Rubiaceae (6 species),

Arecaceae (6 species), Moraceae (5 species), Sapindaceae (4 species) and Zingiberaceae (4 species).

The remaining families contained 1 to 3 species.

Anacardiaceae, Arecaceae, Cariaceae, Commelinaceae, Euphorbiaceae, Fabaceae, Lauraceae,

Meliaceae, Moraceae, Moringaceae, Musaceae, Rubiaceae, Rutaceae, Sabiaceae, Sapindaceae and

Sterculiaceae were present in all villages. Highest number of plant families (43) was recorded in

Pitawala, while the lowest number of plant families was recorded in Polommana (Table 1).

Asteraceae, Boraginaceae, Ebanaceae, Malvaceae, Punicaceae, Theaceae and Thymelaceae were only

recorded in Rathninda sites. Plant species in Debrageaceae, Lecythidaceae and Melastomataceae were

recorded only in Pitawala home gardens.

Table 1: Number of plant families in each study site

Village No. of Plant Families

Pitawala 43

Polommana 24

Atanwala 26

Rathninda 42

Mahala Kotuwa 34

Illukkumbura 31

3.1. Endemic plants, naturalized exotics and timber trees in the study area

Among the 152 plant species, 19 were endemics (12.5 %). There were 5 endemic plant species;

Campnosperma zeylanicum, Mangifera zeylanica, Semecarpus coriaceae, Semecarpus nigro-viridis,

Semecarpus walkeri in Family Anacardiaceae. Other endemic species were Callophyllum

trapezifolium, Garcinia quaesita (Clusiaceae); Diptocarpus zeylanicus, Shorea hulanidda

(Dipterocarpaceae); Agrostistachys hookeri, Phyllanthus myrtifolius (Euphorbiaceae); Aidia gardneri,

Diplospera erythrospora (Rubiaceae); Strobilanthes anceps (Acanthaceae); Canarium zeylanicum

(Burseraceae); Diospyros oppositifolia (Ebanaceae); Scolopia crassipes (Flacourtiaceae) and

Pandanus ceylanicus (Pandanaceae).

Out of the forty four naturalized exotics (28.9%) found, 5 species name;ly Codiaeum

variegatum, Jatropha curcas, Manihot esculenta, Phyllanthus acidus and Ricinus communis were in

family Euphorbiaceae. There were 4 from each Fabaceae and Rutaceae. Several other families

contained 1 to 3 naturalized exotics. These species are utilized by the home gardeners for various

purposes such as fruit, timber, medicine and as fence trees.

Thirty seven species (23.0%) out of which 5 species were in family Rutaceae were found only

under cultivation in these six villages. Fifty two species (34.2%) recorded are used for timber

purposes. They are in Combretaceae and Sapindaceae. The major threat is that most endemic plant

species such as Campnosperma ceylanicum, Mangifera zeylanica, Garcinia quaesita, Diptocarpus

zeylanicus, Shorea hulanidda, Diospyros oppositifolia and Gardonia speciosa are fell for timber.

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 27-39

3.2. Comparison of endemic species, naturalized exotics and trees only under cultivation in each

village

Most of the endemic species (17), naturalized exotic species (44), species found only under

cultivation (33) were recorded in Rathninda when comparing with other villages. The lowest number

of Endemics (6) was recorded in Atanwala (Figure 2). The number of plant families and the number of

plant species recorded in Polommana were comparatively low. This may be because there were only 5

home gardens for the entire village. Other families had left this village in 10 to 15 years ago due to

poor access to the home and lack of various other facilities. Therefore, those home gardens (without

the home) are now added to the forest boundary and controlled by the forest department. Highest

number of plant species was recorded in Rathninda while the lowest number of plant species in

Polommana (Figure 2).

Figure 2: Number of plant species, endemic, naturalized exotic and timber plant species in studied

villages

3.3. DBH Variations of plants in study sites

All villages are rich with the plants in lowest DBH range (1-50 cm). Individuals in this range in

all villages, are more than twice in number, to the 50-100 cm DBH range (Figure3). Plants in 151-200

cm DBH range were not observed in Polommana and Atanwala (Figure.3). This may be due to the fact

that villagers have used the trees with higher DBH for their timber purposes. Moreover, it should be

noted that the DBH also vary depending on the plant species.

Highest number of plant individuals (9 individuals) in both 101-150 cm DBH and 151-200 cm

DBH (7 individuals) was recorded in Pitawala. There were more than two hundred plant individuals in

Rathninda and Mahala kotuwa belonging to 1-50 cm DBH range (Figure 3).

3.4. Height Variation of the plant individuals in the study area

Most of the plants in studied villages were less than 10 m in height. There were 21 individuals

in 11-15 m range in Pitawala. Individuals taller than 15m were not observed in Polommana and

Rathninda (Figure 4).

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Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 24-36

Figure 3: Number of individual plants in each DBH class in all village

3.5. Density

The total tree density of Pitawala, Polommana, Atanwala, Rathninda, Mahalakotuwa and

Illukkumbura were 1195, 870, 1160, 1310, 1410 and 1240 ha
-1

respectively. Species were classified

into 5 density classes, E to A; where species that belongs to class E have lowest density while those in

A have highest density. The intermediates were also assigned accordingly. Species that belonged to

density class E need more attention with respect to conservation.

Acronychia pedunculata, Adenanthera pavonina, Annona muricata, Bambusa vulgaris,

Callophyllum trapezifolium, Capparis zeylanica, Clausena dentata, Semecarpus coriaceae, Shorea

hulanidda and Terminalia bellirica in Pitawala; Azadirachta indica, Chrysophyllum lanceolatum,

Ficus benghalensis, Melia azedarach and Syzygium malaccensis in Polommana; Ardisia missionis,

Cordia aubletii, Madhuca longifolia, Mangifera zeylanica and Trema orientalis in Atanwala;

Anacardium occidentale, Campnosperma ceylanicum, Capparis zeylanica, Diospyros oppositifolia

and Terminalia chebula in Rathninda; Asystasia variabills, Berrya cordifolia, Nephelium lappaceum,

Phyllanthus acidus, Schleichera oleosa and Terminalia bellirica in Mahala Kotuwa; Azadirachta

indica, Codiaeum variegatum, Ficus benghalensis, Jatropha curcas, Munronia pinnata, Pandanus

ceylanicus, Semecarpus nigro-viridis and Terminalia arjuna in Illukkumbura were in density class E

(5-10 density ha
-1

). On the other hand abundant species in the villages were Artocarpus heterophyllus,

Coffea Arabica, Gliricidia sepium, Mangifera indica in Pitawala; Meliosma pinnata, Cocos nucifera

in Polommana; Dimocarpus longan, Gliricidia sepium in Atanwala; Pavetta indica, Gliricidia sepium

in Rathninda, Tectona grandis in Mahalakotuwa, Artocarpus heterophyllus and Mangifera indica in

Illukkumbura.

One species in Mahalakotuwa home gardens Tectona grandis belonged to frequency class A

(81-100%). However species belonging to frequency class B (61-80%) were absent in those villages.

Mangifera indica, Gliricidia sepium in Pitawala; Cocos nucifera, Meliosma pinnata, Cinnamomum

verum in Polommana; Areca catechu, Dimocarpus longan, Gliricidia sepium, Pavetta indica in

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Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 27-39

Atanwala; Pavetta indica, Gliricidia sepium, Cocos nucifera in Rathninda; Pavetta indica, Gliricidia

sepium, Dimocarpus longan, Cocos nucifera, Citrus sinensis in Mahalakotuwa; Tectona grandis,

Mangifera indica, Gliricidia sepium, Artocarpus heterophyllus in Illukkumbura belonged to frequency

class C (41-60%).

Figure 4: Number of individuals in each height class

The frequency gives an approximate indication of the homogeneity of a stand. Previous studies

have pointed out that high values in higher frequency classes (Frequency classes A and B in this case)

and low values in lower frequency classes indicate constant or similar species composition while high

values in lower frequency classes and low values in higher frequency classes on the other hand

indicate a high degree of floristic heterogeneity(give reference). In the present study, high values were

obtained in lower frequency classes whereas low values were obtained in higher frequency classes.

Therefore, according to the above interpretation, it is possible to conclude that there exists a high

degree of floristic heterogeneity in each village in the study area.

3.6 Basal Area and Dominance

Total basal areas in Pitawala, Polommana, Atanwala, Rathninda, Mahalakotuwa and

Illukkumbura were about 16226.04, 7961.07, 13189.89, 12159.55, 10255.18 and 7647.13 cm
2
ha

-1
,

respectively. The highest basal area was recorded in fewer large size individuals; DBH 162 cm

(Artocarpus heterophyllus),145 cm (Mangifera indica), 122 cm (Mangifera zeylanica) in Pitawala;

158 cm (Artocarpus heterophyllus), 149 cm (Mangifera indica) in Polommana; 158 (Ficus hispida),

132 cm (Mangifera indica) in Atanwala; 128 cm (Artocarpus heterophyllus), 105 cm (Artocarpus

nobilis) in Rathninda; 108 cm (Artocarpus heterophyllus) in Mahalakotuwa and 89 cm (Terminalia

arjuna) in Illukkumbura. The highest contribution to their total basal area was by those individual

trees that attain greater than 100 cm DBH for many species.

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Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 24-36

Basal area provides a better measure of the relative importance of the species than simple stem

count (Cain and Castro 1959, cited in Tamirat Bekele, 1994). Therefore, species with the largest

contribution in basal area can be considered as the most important woody species in the forest. High

density and high frequency indicates regular horizontal distribution in the forest. High density, low

frequency and low dominance are typical for understory species that occur in clusters. Some tree

species with low density, low frequency and low dominance are the threaten species in the area.

3.7 Importance Value Index

To analyse IVI, all species encountered in all villages were grouped into five IVI classes based

on their total IVI values. Those species, which receive lowest IVI value, were grouped into the fifth

IVI class whereas those species with highest IVI value were put under the first IVI class. Those

species, which were grouped in the fifth IVI class needs highest consideration for conservation while

those grouped in the first IVI class, need monitoring and management.

Based on the IVI output, the following species accorded the highest priority for conservation

efforts: Osbeckia aspera (1.02), Acronychia pedunculata (1.12), Murraya exotica (1.16), Bambusa

vulgaris(1.20), Clausena dentata(1.25)in Pitawala; Phyllanthus indicus (2.66), Manihot esculenta

(2.66), Bambusa vulgaris (2.84), Annona glabra(3.05), Moringa oleifera(3.14) in Polommana;

Alstonia scholaris (1.07), Citrus grandis (1.21), Melia azedarach(1.29), Cordia monocica (1.42),

Syzygium assimile (1.42) in Atanwala. Hibiscus rosa-sinensis (0.86), Phyllanthus reticulates (0.87),

Manihot esculenta(0.90), Melia azedarach(0.93) in Rathninda; Solanum violaceum Ortega (0.95),

Phyllanthus emblica (0.97), Phyllanthus acidus (0.99), Citrus reticulate (1.02), Bambusa vulgaris

(1.05) in Mahala Kotuwa; Pandanus ceylanicus (1.11), Anacardium occidentale (1.18), Phyllanthus

emblica (1.25), Codiaeum variegatum (1.72), Flacourtia indica (1.72) in Illukkumbura.

The importance value index is imperative to compare the ecological significance of species

(Lamprecht, 1989). It indicates the extent of dominance of a species in the structure of a forest stand

(Curtis and McIntosh, 1951). It is stated that species with the greatest importance value are the leading

dominants of the forest.

3.8 Diversity Indices

If Shannon diversity index value lies between 1.5 and 3.5, it is considered as a less disturbed

habitat. When this index value reaches 3.5, the habitat is more stable. According to the Shannon

diversity values of these study sites; Rathninda (1.85) is the most stable less disturbed habitat when

compared with the others. Polommana (1.51) seemed to be the most disturbed and unstable habitat

(Table 2).

The increased value for Margalef diversity indicates the high Biodiversity. This is a

comparative measure with other sites. In this case Pitawala (16.069) has the highest diversity while

Polommana (8.733) has the lowest (Table 2). If Simpson Biodiversity index is less than 0.5; species

are more equitable. Here all the values are around 1.0, and hence species are heterogeneous.

3.9 Composition of herbs in the study area

Fabaceae was the leading family for herbs including seven plant species. Asteraceae and

Poaceae contained four species in each, in Rubiaceae there were 3 species. Remaining families

contained 1 to 2 species (Appendix I). Lamiaceae is the dominating plant family in the study area

counting 797 individuals. Nevertheless there were only two species in this family, Ocimum

tenuiflorum and Plectranthus zatarhendi (Appendix I). In number; 2588 plant individuals were found

in Pitawala (56.22% of total individuals); all the recorded families except Anacardiaceae and

Menispermaceae were present in Pitawala (93.93%).

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 27-39

Table 2: Diversity indices for plant species (excluding herbs) in all study sites

Village
No. of

species

No. of

individu

als

Margalef

Diversity

Menhink

Diversity

Shannon

diversity

Brillouin

Diversity
Evenness

Base

10
Base 2

Base

Simpson

Diversity

Inverse

Simpson

dominance

Shannon

Diversity

Pitawala 25 578 3.774 1.04 1.26 4.18 1.22 4.05 0.972 0.591 0.901

Polom-

mana 23 318 3.818 1.29 1.19 3.94 1.13 3.74 0.956 0.487 0.87

Atanwala 21 381 3.365 1.08 1.04 3.31 1 3.31 0.896 0.312 0.789

Rathninda 31 560 4.741 1.31 1.33 4.41 1.28 4.24 0.971 0.518 0.889

Mahala

Kotuwa 29 427 4.623 1.40 1.32 4.4 1.27 4.21 0.979 0.618 0.905

Illuk-

kumbura 22 356 3.575 1.17 1.2 3.99 1.15 3.82 0.965 0.559 0.895

A Shannon index for any of the village does not lie between the ranges of 1.5 - 3.5. So,

herbaceous layer in each study site is disturbed and less stable. Margalef diversity value is higher in

Rathninda village (4.741), followed by Mahalakotuwa (4.623). Less diversity of the herb species in

ground layer is shown in Atanwala. Simpson diversity values in all villages are more than 0.5. As

such, species in all villages are heterogeneous (Table 3).

Table 3. Diversity indices for herbaceous layer in each study site

3.10 Villagers’ income through their home garden products

People in Polommana receive higher income through their home garden because they have no

other option to increase their economy other than cultivating crops. Though they are far away from

accessible facilities they grow crops in large areas to have their income. There was no statistically

significant relationship between the level of economy and the composition of plant species in the

home garden (chi-square = 13.308
a
, p = 0.102).

3.11 Expected other plants

Preference of villagers regarding what to grow in their home gardens varies from family to

family. Most prefer Cocos nucifera (57%) due to increasing price of coconut. Twenty four percent of

people expressed an interest in growing timber trees as Tectona grandis, Melia azedarach, Swietenia

macrophylla and Chloroxylon swietenia. Twelve percent preferred fruit trees, 5% requested for

medicinal plants such as Azadirachta indica, Munronia pinnat and Cannabis sativa. These

expectations indicate that in the near future, only few plant species will be grown in these home

Village
No. of

species

No. of

individuals

Margalef

Diversity

Menhink

Diversity

Shannon

diversity
Evenness

Base 10
Base

Simpson

Diversity

Inverse

Simpson

dominance

Shannon

Diversity

Pitawala 89 239 16.069 5.757 1.79 5.93 0.988 0.366 0.916

Polommana 40 87 8.733 4.288 1.51 5 0.987 0.516 0.94

Atanwala 72 230 13.056 4.748 1.71 5.69 0.988 0.443 0.922

Rathninda 97 259 17.276 6.027 1.85 6.13 0.992 0.439 0.929

Mahala Kotuwa 76 272 13.379 4.608 1.71 5.69 0.988 0.45 0.911

Illuk-kumbura 64 248 11.427 4.064 1.66 5.52 0.987 0.475 0.92

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 24-36

gardens (Figure 5). Consequently, the biodiversity will be greatly reduced and might even lead to the

extinction of rare, endangered species.

3.12 Plant diseases and home garden management

Plant diseases such as fungal attacks in bark, insect attacks in coconut bark, Iron deficiencies,

harms of vegetable caterpillar, insect damages in leaves and parasitic plants were observed in home

gardens. Plant management can be different in each home garden and the amount of planting in a

garden is often difficult to evaluate. Plant management in home gardens was categorized into three

main groups: cultivated, protected or spared.

1. When plants are said to be cultivated, they are sown or planted by the owner.

2. Plants are categorised as protected or encouraged when they are transplanted from other zones

outside the garden or when they grow spontaneously in the garden. The owner decides to protect or

encourage the plant, for example, by supporting it or attaching the plant to a solid structure, or by

putting stones around the plant.

3. Spared plants are plants that spontaneously grow in the garden and are not removed. Either the

farmer knows that the plant does not harm any other plant in the garden, or that it has a specific use.

Also trees for shade or the edible species are spared. These plants belonged to the original

vegetation before the farmers settled in and were not removed when the house was built or when

the home garden was established.

3.13 Villagers’ attitudes and contribution towards the Biodiversity Conservation through their Home

garden

Seventy two percent of people in all villages knew that by improving the plant composition in

their home garden, they can contribute to protect the biodiversity. They were aware of the fact that the

richness of plant composition in home garden will lead to the improvement of human beings as well as

the protection of the Dumbara forest. However the important thing to be pointed out is that 23% of

people didn’t know that they can conserve biodiversity through the home gardens. So to have a better

world in the future, for their children and for future generations, they should be encouraged to

conserve biodiversity in their home. Another point is that if the biodiversity is maintained at a high

level, species extinction will be low. This will benefit everyone.

The majority of the people were aware that the conservation can be done not only in the forests

but also in their home gardens. To conserve the biodiversity, women have started to plant various wild

varieties of crops in their home gardens. Women can be encouraged to grow a variety of species to

obtain cut flowers. They can make an income out of it.

Figure 5. Preference of home gardeners for various categories of plants

Dissanayake & Hettiarachchi /Journal of Tropical Forestry and Environment Vol. 3, No. 01 (2013) 27-39

People of the bordering villages are well aware of the importance of the Dumbara forest. So,

they inform relevant authorities if a stranger tries to enter into the forest. They don’t complain about

the people that go to get medicine and poles to make utensils. According to females of the bordering

villages, they do not cut down trees or kill animals, not only in the forest but also in their home

gardens. Educating people, mainly the younger generation about the importance of the biodiversity

and the Dumbara is done mainly by the females/mothers. They fulfil the task by giving the traditional

knowledge and the cultural values to the future generations.

The isolation of the region, its frontier character, and the rapid changes that are occurring, in

terms of population growth, legal state of land, and political boundaries, make socio-economic data

scares and unreliable. The clandestine nature of many activities in the area and the uncertain legality

of others make it difficult to get honest responses from local people or government officials about

local activities.

Biodiversity loss of the Dumbara forest is resulting due to at least two proximate causes: the

habitat loss and the extraction of flora and fauna. The direct or indirect cause for the habitat

fragmentation in the Dumbara forest was clearing for agriculture in the past. Poverty is prominent in

the bordering villages of Dumbara forest.

Cash is earned by selling agricultural products which provides the main source of income for

the bordering villagers and from day labour. Agriculture, in the study area remains small-scale as a

result of ecological limitations such as shortage of water during the year and unpredicted weather

patterns as well as economical limitations such as lack of proper market value. Due to the increasing

population, encroachment can be seen. Hunting is another threat to the biodiversity of Dumbara forest.

Hunting is carried out by man in the farm plots to protect their crops from wild boars and spotted deer.

Even though the hunting is illegal these people have no other option.

According to gathered information giant-squirrels have become a menace to the people of the

bordering villages. This species destroy the crops of the home gardens. This is a great economic loss

but still a solution has not been provided by the government.

4. Conclusions

Home gardens in Dumbara Conservation area comprises with high number of endemic species,

timber species, and naturalized exotics with cultivated crops. People in these peripheral villages have

no proper idea as how to attain plant conservation through the home gardens. Awareness programs can

direct villagers to obtain the maximum benefit of the home garden rather than going into the forest for

extractable products. Traditional knowledge of the fringe villagers should also be conserved.

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Appendix I:

Total number of trees/ shrubs belonging to different families in each village

Plant Family Pitawala Polommana Atanwala Ratninda
Mahala

kotuwa
Illukkumbura

ACANTHACEAE 8 0 0 0 0 4

ALOACEAE 46 5 5 6 17 0

AMARANTHACEAE 136 42 8 0 21 24

ANACARDIACEAE 0 3 0 0 0 0

APIACEAE 270 46 52 62 27 31

ARACEAE 0 0 0 5 0 0

ASPARAGACEAE 83 8 0 24 0 23

ASTERACEAE 174 23 9 8 31 18

BROMELIACEAE 3 0 0 0 0 0

CANNACEAE 15 0 0 5 2 4

COMMELINACEAE 3 0 0 0 3 0

CONVOLVULACEAE 33 2 0 31 0 0

CRASSULACEAE 3 0 0 0 0 3

CUCURBITACEAE 73 12 7 13 5 12

EUPHORBIACEAE 14 0 0 0 1 13

FABACEAE 198 20 19 22 59 37

LAMIACEAE 431 47 122 98 37 62

MALVACEAE 142 7 17 35 23 24

MELASTOMATACEAE 3 3 00 0 0 0

MELIACEAE 23 0 4 7 5 0

MENISPERMACEAE 0 0 3 2 0 0

PANDANACEAE 71 4 19 8 11 13

PHTOSPORACEA E 23 0 0 13 10 0

PLUMBAGINACEAE 12 0 0 9 3 0

POACEAE 169 26 25 32 46 14

RUBIACEAE 79 0 0 55 2 12

RUTACEAE 134 26 21 17 21 13

SAPINDACEAE 162 20 7 42 29 31

SMILACACEAE 4 0 0 4 0 0

SOLANACEAE 2 0 0 0 0 0

TILLIACEAE 2 0 0 0 2 0

TRAPACEAE 47 6 6 14 3 3

ZINGIBERACEAE 225 18 57 48 42 15