JEE
ISSN: 2288-1220
https://doi.org/10.5141/jee.22.015
RESEARCH
Journal of Ecology and Environment (2022) 46:11
Population structure and regeneration of
Zanthoxylum armatum DC. in Salyan, Nepal
Nirmala Phuyal1,2* , Pramod Kumar Jha1 , Pankaj Prasad Raturi3
and Sangeeta Rajbhandary1
1
Central Department of Botany, Tribhuvan University, Kathmandu 44600, Nepal
Forest Research and Training Center, Ministry of Forests and Environment, Kathmandu 44600, Nepal
3
Ashok Medicinal and Aromatic Plants Center, Dabur Nepal Pvt. Ltd., Kavre 45210, Nepal
2
ARTICLE INFO
Received February 7, 2022
Revised March 22, 2022
Accepted March 23, 2022
Published on April 18, 2022
*Corresponding author
Nirmala Phuyal
E-mail nirmalaphuyal@gmail.com
Background: Zanthoxylum armatum is one of the 30 prioritized medicinal plants for
economic development of Nepal with a high trade value. Understanding the ecology of
individual species is important for conservation and cultivation purposes. However, relation of ecological factors on the distribution and populations of Z. armatum in Nepal remain unknown. To address this knowledge gap, an attempt has been made to study the
population structure, distribution, and regeneration potentiality of Z. armatum. Vegetation
sampling was conducted at six different localities of Salyan district along the elevation
range of 1,000 m to 2,000 m.
Results: Altogether 50 plant species belonging to 44 genera under 34 families were
found to be associated with Z. armatum. Significantly higher species richness was found
at Rim (1,400–1,700 m) and Chhatreshwori (1,800–2,000 m) and lower at Kupinde (1,600–
1,800 m). The highest population density of Z. armatum was at Kupinde (1,600–1,800 m)
with a total of 1,100 individuals/ha. and the lowest at Chhatreshwori (1,800–2,000 m) with
740 individuals/ha. Based on the A/F value (Whitford index), it can be said that Z. armatum has random distribution in the study area. The plants were categorized into seedlings,
saplings and adults based on plant height and the status of natural regeneration category
determined. The regeneration potentiality of Z. armatum in the study area was fair with
the average seedlings and saplings densities of 150 and 100 individuals/ha. Respectively.
A Shannon–Weinner index mean value of 2.8 was obtained suggesting high species diversity in the study area.
Conclusions: The natural distribution and regeneration of Z. armatum is being affected
in the recent years due to anthropogenic disturbances. Increasing market demand and
unsustainable harvesting procedures are posing serious threat to Z. armatum. Thus, effective conservation and management initiatives are most important for conserving the
natural population of Z. armatum in the study area.
Keywords: density, distribution, ecology, population, species diversity, regeneration
Introduction
Zanthoxylum armatum DC. (Rutaceae), commonly
called Timur in Nepali (English: Nepal pepper or prickly
ash), is an aromatic large shrub up to 6 m high. It is one of
the 30 prioritized medicinal plants for economic development (DPR 2006). It is found in hot valleys of subtropical
to temperate Himalayas (Kashmir to Bhutan), north-east
India and Pakistan, Laos, Myanmar, Thailand, China,
Bangladesh, Bhutan, Japan, North & South Korea, North
Vietnam, Taiwan, Lesser Sunda Islands, Philippines, Malaya peninsula and Sumatra (Nair and Nayar 1997). In Nepal, it is distributed from west to east at an elevation range
of 1,000 m to 2,500 m in open places or in forest undergrowth (DPR 2007). The plant grows well in open pastures,
wastelands and secondary scrub forests with adequate
rainfall. Moist areas with deep soils exposed to sun and degraded slopes, shrub lands, natural forests and wastelands
are the suitable habitat for Z. armatum (Phuyal et al. 2019).
Z. armatum (Fig. 1) has been used extensively in traditional indigenous medicinal practices in Nepal by different
ethnic communities. Several ethnobotanical studies have
documented the various ethno-medicinal uses in different
types of ailments. The different parts of the plants: leaves,
fruits, stem, bark, seeds have been used as carminative, antipyretic, appetizer, stomachic, toothache, dyspepsia (Kala
Copyright © The Ecological Society of Korea in collaboration with The Korean Society of Limnology
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Phuyal et al.
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Journal of Ecology and Environment (2022)46:11
MAPs including Z. armatum . So, understanding of ecology and biology of these valuable plants is very crucial for
agro-technology development and commercial cultivation,
which ensures the steady supply of raw materials without
hampering their natural population. No study has been
conducted previously regarding ecological status including
the population, distribution, frequency, abundance, and
regeneration status of Z. armatum from Nepal. The present
study, therefore, aims to find the ecological status of Z. armatum in Salyan district regarding its distribution, density, frequency, abundance, diversity, and regeneration potentiality.
Materials and Methods
Fig. 1 Zanthoxylum armatum.
2005; Manandhar, 2002; Singh et al. 2016). This plant species is not only used for pharmaceutical purposes, but also
used in the flavoring and fragrance industries (Phuyal et
al. 2020). Based on its varied industrial uses, its demand is
constantly increasing both in domestic and international
markets. Increased market demands, devious modes of
collection and insufficient technical knowledge and proper
skills of harvest and postharvest techniques have posed serious threats to the native populations attributing to a
sharp decline of the species in the wild, due to which the
regeneration of this species is adversely affected (Phuyal et
al. 2019).
The National Conservation Strategy (1988), Master Plan
for the Forestry Sector (1988), Industrial Enterprises Act
(GoN 1992), Forest Act (GoN 1993) and Regulations (GoN
1995), Herbs and Non-Timber Forest Products Development Policy (DPR 2004) have emphasized on the subsequent development and commercialization of the Non-timber Forest Products including Medicinal and Aromatic
Plants (MAPs) for uplifting the livelihood of the rural
communities through sustainable and wise use of these
valuable resources. Trade Policy in Nepal (GoN 2009) has
also prioritized Z. armatum as an important commodity
for export.
There have been ample studies on the medicinal plants
of Nepal regarding their botany, ecology, ethnobotany,
population size, and distribution. A significant amount of
research has also been carried out in Zanthoxylum in the
Indian subcontinent. However, there have been very few
studies in Z. armatum in Nepalese context and the study
of relation of ecological factors on the distribution and
population structure in Nepal is still meager (Phuyal et al.
2019). Understanding the ecology of individual species is
important for conservation and for cultivation purposes.
Unsustainable harvesting from the wild without proper
management practices is the major threat to most of the
Field sampling
A preliminary filed survey was carried out in April 2017
to select the study site and sampling areas, gather general
information about the study species viz. Z. armatum , and
rapport building with the local people and concerned authorities. The principal visit was conducted during the
months of May 2017 and October 2018. All necessary data
and samples were collected during that period. The details
of study sites (DFRS, 2018) and map of the study area are
presented in Figure 2 and Table 1.
The study was mainly based on primary data collection.
Necessary information was collected through extensive
field observation of the area. The data was collected through
physical measurement in the field and review of relevant
literature on similar previous studies. Systematic random
sampling design was applied in which plots were selected
by a random or stratified random plan (Misra 1968). The
sampling sites were selected from six localities to cover all
the possible habitats and associated vegetation types of Z.
armatum so that a comparative study can be done based
on disturbance factors, altitudinal difference, etc.
Vegetation sampling was done along the elevation of
1,000 m to 2,000 m. In each locality, four transect lines
were set up at 30–50 m in Z. armatum available sites. In
each transect line five plots of 5 m × 5 m were laid down at
a distance of 10 m. The number of individuals of Z. armatum and other tree and shrub species (excluding grasses)
in the sample plot associated with Z. armatum were recorded.
Vegetation attributes, including frequency, density, and
richness, were recorded, along with environmental coordinates such as latitude, longitude, and elevation of each
sample plot using a global positioning system (Garmin
model 2000) (Shaheen et al. 2011a).
Phuyal et al.
Page 3 of 15
Journal of Ecology and Environment (2022)46:11
Fig. 2 Map of Nepal showing study
area and sampling sites of Zanthoxylum armatum.
Table 1 Details of sampling sites of Zanthoxylum armatum in the study area
SN
1
Municipality
Kapurkot
Total
area (ha)
Forest
area (ha)
11,875
7,542
Forest
cover (%)
63.5
2
3
4
5
6
Baghchaur
Bangad
Kupinde
Chhatreshwori
Study site
Altitude (m)
Latitude (N),
Longitude (E)
Dhanwang
1,000–1,200
28.26875, 82.30842
Kapurkot
1,200–1,400
28.2707, 82.35038
16,251
33,678
8,453
22,709
52
67.4
Rim
Baghchaur
Kupinde
1,400–1,700
1,400–1,600
1,600–1,800
28.27611, 2.36361
28.46694, 2.28139
28.41319, 82.0935
15,011
9,841
65.6
Chhatreshwori 1,800–2,000
28.38611, 2.36361
Land use/Forest type
Forest near village
settlement
Near roadside on
edges of farmyard
Mixed Quercus forest
Mixed forest
Disturbed forest due to
road construction
Moist and dense forest
Source: 1. Forest cover and land cover: DFRS (2018), 2. Field survey.
Vegetation analysis
Density (D) (plants/ha)
����� �������������� �� � ������� �� ��� ��������
Density (D) (plants/ha) =
× 10,000
Species richness
����� ����� ����� ����������� �� ��� ���� (��)
The species richness in this study was obtained by counting the number of species present in each 5 m × 5 m sam- Relative Density (RD%)
ple plot. In this study, species richness has been defined as,
������� �� ���������� �������
2
Relative as
Density
(RD%)
=
× 100
the number of species per plot and expressed
species/m
.
����� ������� �� ��� �������
Density and abundance
Abundance (A)
Both this term refers to the number of species in a com����� ����� ����������� �� � ������� �� ��� ��������
munity. Abundance of any individual species Abundance
is expressed (A) = ���� ����� �������� �� ����� ��� ������� �������
as a percentage of the total number of species present in
community and therefore it is a relative measure (Khan et Relative Abundance (RA%)
al. 2014). In sampling the abundance of species, the indi����� ����� � ���������� �������
Relative
Abundance
(RA%) =
× 100
vidual of species is counted instead
of just
nothing their
����� ����� ����������� �� ��� ������� ��������
presence or absence was done while studying the frequency
of a species.
Frequency
Density and relative density were calculated using Yadav
Occurrence of trees and shrub species within each major
et al. (1987), whereas abundance was determined based on plots of the study area were recorded to assess their distrithe formula of Kilewa and Rashid (2014).
bution pattern in Z. armatum occurring areas. Then, fre-
Phuyal et al.
quencies of these species were obtained by following formula (Yadav et al. 1987). Relative frequency is the frequency
of a species in relation to other species.
Frequency (F) (%)
uency (F) (%) =
����� �������� �� ����� �� ���������� ������� �������
����� ����� �������� �������
Relative Frequency (RF%)
uency (RF%) =
Page 4 of 15
Journal of Ecology and Environment (2022)46:11
��������� �� ���������� �������
��� �� ����������� �� ��� �������
× 100
× 100
Distribution pattern (A/F ratio)
Abundance and frequency taken together are of great
importance in determining the structure of a community.
High frequency and low abundance indicate regular distribution whereas the converse indicates contiguous distribution. The ratio of abundance to frequency (A/F) for different species was determined for eliciting the distribution
pattern. Spatial distribution of plant species was determined following Whitford index WI (Singh and Singh,
1987) as
Distribution (WI) =
Distribution
���������
���������
(A/F
(A/FRatio).
Ratio).
If value is < 0.025 = regular distribution, value lies between
0.025–0.05 = random distribution and value > 0.05 = clumped
distribution (Whitford 1949).
Importance Value Index (IVI)
The IVI was calculated to understand the species’ share
in the community (Curtis and Cottam 1956). Species with
the highest importance value are the leading dominant
species of the specified vegetation (Shibru and Balcha
2004). This considers density, frequency, and abundance of
the species present in the community. For each species, the
relative density, relative frequency, and relative abundance
were calculated and summed. It gives the overall importance of each species in the community structure. The IVI
for all the species was calculated by adding the sum of relative values of density, frequency and abundance. It was calculated following Bhadra and Pattanayak (2016) as
Importance Value Index (IVI) = Relative Density + Relative Frequency + Relative Abundance.
Regeneration
Population structure of naturally emerged seedlings of Z.
armatum reported in each sample plot was studied. Density of all the individuals of seedlings, saplings and adult
were determined. The size classes of individuals of Z. armatum were broadly defined according to plant height.
Plant height less than 0.1 m were classified as seedlings.
Plant height ranging from 0.1 m to 1.0 m were classified as
saplings and plant height usually more than 1 m and also
bearing reproductive structures were classified as adult
(Schemske et al.1994).
Regeneration status was totally based on population size
of seedlings and saplings (Khan et al. 1987; Saha et al.
2016). Good regeneration if seedlings > saplings > adults;
fair regeneration, if seedlings > or ≤ saplings ≤ adults; poor
regeneration, if the species survives only in sapling stage,
but no seedlings (saplings may be or = adults). If a species
is present only in an adult form it is considered as not regenerating. The status of natural regeneration was determined based on the values as shown in Table 2 (Bhuyan et
al. 2003; Khumbongmayum et al. 2006).
As shown in the above table, ‘good regeneration’ is defined as the condition in which an ample or adequate
number of seedlings and saplings contribute to the mature
population, while ‘fair regeneration’ is defined as the condition in which there were a fair number of seedlings, but
the percentage of saplings was either lower than or close to
that of the mature trees. ‘Poor regeneration’ is the condition in which individuals were found at either the seedling
or sapling stage only, in greater numbers than the mature
trees. The fourth regeneration status is termed as ‘no regeneration,’ in which a species presented only at the mature
stage and did not occur in either seedling or sapling stages.
Species diversity
Diversity in species refers to the combined effect of richness and evenness in species. While richness pertains to
the number of species in each sampling unit, evenness implies to the distribution of individuals among the species.
Species richness is a biologically appropriate measure of
diversity and the total number of species in any ecological
community, landscape, or region relative to the total number of all individuals in that community.
A diversity index can reveal the structure of biological
community in terms of numerical value. It gives more information on community composition than simply species
richness. Further, it offers insights into rarity and com-
Table 2 Different regeneration status
SN
Regeneration status
Seedling (Se)
Sapling (Sa)
1
2
3
4
Good regeneration
Fair regeneration
Poor regeneration
No regeneration
Present
Present
Absent
Absent
Present
Present
Present
Absent
5
Compare to adult
Se > Sa > adults
Se > or < Sa; Sa ≤ adult
Sa > or < or = adult
Only adult
Phuyal et al.
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Journal of Ecology and Environment (2022)46:11
monness of species in a community, thereby diversity index acts as important tool for biologists in the understanding of community structure (Muthulingam and Thangavel
2012). Several indices are used to quantify the species diversity of which Simpson’s index (Simpson 1949) and
Shannon-Wiener’s index are the most commonly used.
Shannon’s diversity index (H) and Simpson’s Index (1 − D)
in terms of density for each plot were calculated using the
following indices:
tested by Analysis of Variance (ANOVA), Tukey’s test for
normal data, and non-parametric Kruskal–Wallis one-way
ANOVA, Duncan multiple comparison test for non-normal
data.
Results
Species richness
Altogether fifty plant species (trees and shrubs) belonging
to Weaver
44 genera
under 34 families were found to be associ1963)
( ×
) (Shannon and
Shannon’s diversity index (H) =
ated with Z. armatum in the study area. Rosaceae was the
(Shannon and Weaver 1963)
dominant family with seven species, followed by Fagaceae
(
)
(Simpsonwith
1949)five species and the families Berberideae, Fabaceae,
Simpson’s diversity Index (1 − D) = 1
(
)
Moraceae, Oleaceae, and Rutaceae had two species each.
(Simpson 1949)
Quercus was the largest genera with 4 species while the
genera Castanopsis and Prunus had 2 species each (Table
Where, pi = (n/N),
3).
n = density of individual species in a plot
The species richness for each plot was the number of speN = Total density of all species in a plot
cies per plot. Significantly higher species richness (p < 0.001)
ln = Natural logarithm values
was recorded at Rim (1,400–1,700 m) and Chhatreshwori
The Shannon diversity index ranges typically from 1.5 to (1,800–2,000 m) while the species richness was significantly
3.5 and rarely reaches 4.5 (Gaines et al. 1999). The Simp- lower at Kupinde (1,600–1,800 m) (Fig. 3, Tables S1–S6).
son’s Index values range from 0 to 1. The closer the value
of Simpson’s Index to 0, the more diverse the plot will be. Density
The mean population density of Z. armatum in the study
A plot with only one species would have a Simpson’s Index
value of 1. Trends are opposite to those found for Shannon area was found to be 913.33 individuals/ha. The density
Weaver values since Simpson’s Index values decrease with among the different localities did not vary significantly
increased diversity (Reich et al. 2001). In practice, the val- (Fig. 4a). Among the six localities studied, the total density
ues below 0.5 indicates a relatively even community, while of Z. armatum was maximum at Kupinde (1,100 individuhigh values are indicative of communities dominated by als/ha), followed by Baghchaur (1,020 individuals/ha), Rim
(1,000 individuals/ha), Dhanwang (840 individuals/ha),
one or a few species.
Kapurkot (780 individuals/ha) and the lowest at Chhatreshwori (740 individuals/ha). The highest relative density
Soil analysis
Soil samples were collected from the four corners and (15.45%) of Z. armatum was at Baghchaur and lowest
center of each sample plot from the depth of 5–10 cm. The (5.35%) at Chhatreshwori (Fig. 4b). It was found to be assosubsamples were mixed thoroughly, and about 100 g soil ciated with different species at different localities and altiwere collected, air dried in shade (Yadav et al. 1987), kept tudes. Mostly it was found growing in the northern and
in zipper plastic bags, properly labeled, and brought to the northeastern slopes and had least occurrence on the south
Laboratory for the analysis of pH, soil organic carbon, total and southeastern slopes.
Among all the species, Murraya koenigii had the greatest
nitrogen, available phosphorus, and soil potassium. Soil
organic carbon was determined by following Walkley and density with 1,140 individuals/ha at Dhanwang, Berberis
Black (1934), total nitrogen (N) by Kjeldahl method (Tsuji aristata at Rim with 980 individuals/ha and Daphne bholua
and Ohnishi 2001), available phosphorous (P) by a modi- at Chhatreshwori with with 1,100 individuals/ha. Similarly
fied Olsen’s method following Gupta (2000), soil potassium Z. armatum had greatest density at Kapurkot, Baghchaur,
(Flame photometer method following Trivedy and Goel and Kupinde with total of 1,000, 1,100, and 1,020 individu1986 and pH using a digital pH meter with 1:5 soil water als/ha respectively (Tables S1–S6). The species having lowest densities were Ligustrum confusum , Tinospora sinensis
ratio (Gupta 2000).
(200 individuals/ha at Dhanwang), Ficus semicordata (260
individuals/ha at Dhanwang), Clematis sp. (200 individuStatistical analysis
All the analyses were carried out in R platform (R Core als/ha at Rim).
Team 2020). The normality (Shapiro–Wilk test) for all the
parameters were tested prior to choosing a parametric or Frequency
The mean frequency and relative frequency of Z. armanon-parametric tool to analyze. All the parameters were
8
Phuyal et al.
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Journal of Ecology and Environment (2022)46:11
Table 3 List of plant species (trees and shrubs) recorded in the study area
SN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Name of the species
Albizzia procera (Roxb.) Benth.
Adhatoda vesica Nees
Aesculus indica (Wall. ex Cambess.) Hook.
Alnus nepalensis D. Don
Bauhinia variegate L.
Benincasa hispida (Thunb.) Cogn.
Berberis aristata DC.
Castanopsis hystrix Hook. f. & Thomson ex A. DC.
Castanopsis indica (Roxb. ex Lindl.) A.DC.
Clematis sp.
Colebrookea oppositifolia Smith
Cotoneaster microphyllus Wall. ex Lindl.
Daphne bholua Buch.-Ham. ex D.Don
Ficus neriifolia Sm.
Ficus semicordata Buch.-Ham. ex Sm.
Fraxinus floribunda Wall.
Grewia optiva J.R. Drumm. ex Burret
Juglans regia L.
Pistacia integerrima Stew. ex Brand
Ligustrum confusum Decne.
Lyonia ovalifolia (Wall.) Drude
Maesa chisia Buch.-Ham.ex D. Don
Mallotus philippinensis Muell. Arg
Murraya koenigii (L.) Spreng.
Myrica esculenta Buch.-Ham. ex D. Don
Persea odoratissima (Nees) Kosterm.
Pinus roxhburghii Sarg.
Prinsepia utilis
Prunus cerasoides D.Don
Prunus persica (L.) Batsch
Pyracantha crenulata (D. Don) M. Roeme
Pyrus pashia Buch.-Ham. ex D.Don
Quercus leucotricophora A.Camus
Quercus glauca Thunb.
Quercus incana Roxb. Hort. Beng.
Quercus semecarpifolia Smith in Rees
Reinwardtia indica Dumort.
Rhododendron arboretum Sm.
Rhus javanica L.
Rubus ellipticus Sm.
Salix sp.
Sapindus mukorossi Gaertn.
Sapium insigne (Royle) Trimen
Schima wallichii Choisy
Smilax sp.
Stephania sp.
Tinospora sinensis (Lour.) Merr.
Toona ciliate M.Roem.
Viburnum erubescens Wall.
Zanthoxylum armatum DC.
tum in the study area were 70.83% and 5.61%, respectively.
The frequency at different locality and elevation did not
vary significantly (Fig. 5a) with the highest (80%) at Baghchaur (1,400–1,500 m) and lowest (60%) at Chhatreshwori
(1,800–2,000 m). The highest total relative frequency 8.02%
was at Kupinde (1,600–1,800 m) and the lowest 3.82% at
Family
Fabaceae
Acanthaceae
Sapindaceae.
Betulaceae
Fabaceae
Cucurbitaceae
Berberidaceae
Berberidaceae
Fagaceae
Ranunculaceae.
Lamiaceae
Rosaceae
Thymelaeaceae.
Moraceae
Moraceae
Oleaceae
Malvaceae
Juglandaceae
Anacardiaceae
Oleaceae
Ericaceae
Primulaceae
Euphorbiaceae
Rutaceae
Myricaceae
Lauraceae
Pinaceae
Rosaceae
Rosaceae
Rosaceae
Rosaceae
Rosaceae
Fagaceae
Fagaceae
Fagaceae
Fagaceae
Linaceae
Ericaceae
Anacardiaceae
Rosaceae
Salicaceae
Sapindaceae
Euphorbiaceae
Theaceae
Smilacaceae
Menispermaceae
Menispermaceae
Meliaceae
Adoxaceae
Rutaceae
Local name
Sirish
Asuro
Lekh pangre
Uttis
Badahar
Kubindo
Chutro
Patle katush
Daale katush
Sikari lahara
Dhusure
Khareto
Lokata
Dudhilo
khaniu
Laakuri
Bhimal
Okhar
Kakadsinghi
Kanike
Angeri
Bilaune
Sindure
Karipatta
Kaphal
Kaulo
Khote salla
Dhatelo
Paiyun
Aaru
Ghangaroo
Mayal
Sano banjh
Phalat
Thulo banjh
Khasru
Pyauli
Lali gurans
Bhaki amilo
Ainselu
Bains
Rithha
Khirro
Chilaune
Kukurdaino
Batulpate
Gurjo
Tuni
Asare
Timur
Habit
Tree
Shrub
Tree
Tree
Tree
Climber
Shrub
Tree
Tree
Climber
Shrub
Shrub
Shrub
Tree
Tree
Tree
Tree
Tree
Shrub
Shrub
Shrub
Shrub
Tree
Shrub
Tree
Tree
Tree
Shrub
Tree
Tree
Shrub
Tree
Tree
Tree
Tree
Tree
Shrub
Tree
Tree
Shrub
Tree
Tree
Tree
Tree
Climber
Climber
Climber
Tree
Tree
Shrub/Small tree
Chhatreshwori (1,800–2,000 m) as compared to its associates (Fig. 5b). The frequency and relative frequency of other associates are presented in Tables S1–S6.
The most frequently occurring associates (with > 70% of
occurrence) at different localities were Aesculus indica, Alnus nepalensis, Bauhinia variegata, Berberis asiatica,
Phuyal et al.
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Journal of Ecology and Environment (2022)46:11
Castanopsis hystrix, Colebrookeaa oppositifolia, Daphne
bholua, Ficus nerifolia, Fraxinus floribunda, Grewia optiva, Juglans regia, Lyonia ovalifolia, Maesa chisia, Murraya
koenigii, Persea odoratissima, Pinus roxhburghii, Prinsepia utilis, Prunus cerasoides, Pyracantha crenulata, Pyrus
pashia, Quercus glauca, Q. incana, Rhododendron arbore-
um, and Sapium insigne (Tables S1–S6).
Abundance
The abundance of Z. armatum was almost similar and
did not vary significantly in all the localities of the study
area, the values ranging from 3.00 at Dhanwang and Kapurkot to 3.40 at Baghchaur and 3.44 at Kupinde (Fig. 6a).
Likewise, the highest total relative abundance (15.45%) was
at Baghchaur and the lowest (5.35%) at Chhatreshwori (Fig.
6b). Abundance of Z. armatum was highest (3.44) at
Kupinde and relative abundance was highest (15.45%) at
Baghchaur.
Importance Value Index (IVI)
Fig. 3 Species richness at different locality and elevation (m). Different letters above bars indicate statistically significant difference
between different altitudes at p < 0.001.
Based on IVI values, Z. armatum was most dominant at
Baghchaur and Kupinde and least dominant at Chhatreshwori. The highest IVI value of Z. armatum was 38.35% at
Baghchaur and the lowest value was 14.53% at Chhatreshwori (Fig. 7). Based on IVI values, Berberis asiatica (22.88)
and Daphne bholua (20.06) were the dominant species at
Kapurkot and Daphne bholua at Chhatreshwori (Tables
S1–S6). Likewise, Zanthoxylum armatum was dominant at
Baghchaur, Kupinde, Dhanwang, and Rim with the IVI
values of 38.35, 29.42, 23.09, and 21.81 respectively (Fig. 7).
Fig. 4 Density (a) and Relative density (b) of Z. armatum at different
locality and elevation.
Fig. 5 Frequency (%) (a) and relative
frequency (%) (b) of Z. armatum at
different locality and elevation.
Phuyal et al.
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Journal of Ecology and Environment (2022)46:11
Fig. 6 Abundance (a) and relative
abundance (%) (b) of Z. armatum at
different locality & elevation.
study area. There were substantial differences in the distribution of Z. armatum , likely resulting from differences in
the degree of management and disturbance as well as from
different ecological factors.
Species diversity
Fig. 7 Importance Value Index (IVI) of Zanthoxylum armatum at
different locality and elevation.
Regeneration status
Natural regeneration of Z. armatum varied at different
elevation/localities. Both seedlings and saplings at Kapurkot (1,200–1,400 m) had higher density and the lowest density was at Chhatreshwori (1,800–2,000 m). The total seedlings and saplings densities were 200 individuals/ha and
140 individuals/ha at Kapurkot and 100 individuals/ha and
60 individuals/ha at Chhatreshwori, respectively (Table 4).
Similarly, the total seedlings and saplings densities were
180 individuals/ha and 100 individuals/ha, Baghchaur
(1,400–1,600 m), 160 individuals/ha and 100 individuals/
ha at Dhanwang (1,000–1,200 m), 140 individuals/ha and
120 individuals/ha at Rim (1,400–1,700 m), and 120 individuals/ha and 80 individuals/ha at Kupide (1,600–1,800
m), respectively.
Distribution
The distribution pattern of Z. armatum in all the localities studied were almost similar. The A/F ratio of 0.04 and
0.05 (Fig. 8) in all the localities showed that Z. armatum
has random distribution in the study area. It was found
scattered in patches associated with other species. Pure
stands of Z. armatum were not evident anywhere in the
Diversity values according to the Shannon and Simpson
indices were higher at Rim and lower at Kupinde. The
mean Shannon-Weaver diversity index (H’) which measures the diversity of Z. armatum along with its associates
ranged from 2.5 to 3.08. Among the six study sites the
highest species diversity (H’ = 3.08) was recorded from Chhatreshwori whereas the lowest species diversity (H’ = 2.5)
was recorded at Kupinde. The mean Simpson’s diversity
index (1 − D) value ranged from 0.92 to 0.95 (Fig. 9).
Soil nutrient analysis showed that soil organic carbon,
soil nitrogen, and soil phosphorus were highest at Chhatreshwori than other localities (Table 5).
Discussion
Species richness
Species composition and species richness are important
indicators for assessing the biodiversity (Husch et al. 2002)
and may strongly depend and/or be influenced by the applied management practices. The listing of 50 shrub and
tree species in the area shows the forest is rich in diversity
(Table 3). This is comparable to other studies carried out in
similar forest types of Bhutan, India, and Nepal. Wangda
and Ohsawa (2006) listed 78 tree species in west central
part of Bhutan and Buffum et al. (2008) reported 39 tree
species from the eastern part of Bhutan. Sundriyal and
Sharma (1996) recorded 81 tree species in the temperate
forest in Sikkim, and Shrestha et al. (2013) recorded 31 and
37 plant species in the two sites within the elevation range
of 2,650–2,800 m asl in Nepal.
The lower number of species recorded at Baghchaur
Phuyal et al.
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Journal of Ecology and Environment (2022)46:11
Table 4 Seedling, sapling and adult total density of Z. armatum at different locality
SN
1
2
3
4
5
6
Samplig sites
Dhanwang (1,000–1,200 m)
Kapurkot (1,200–1,400 m)
Rim (1,400–1,700 m)
Bagchaur (1,400–1,600 m)
Kupinde (1,600–1,800 m)
Chhatreshwori (1,800–2,000 m)
Average
Fig. 8 Distribution pattern (abundance/frequency ratio, A/F ratio)
of Zanthoxylum armatum at different locality and elevation.
Density (pl/ha)
Seedling
Sapling
Adult
160
200
140
180
120
100
150
100
140
120
100
80
60
100
840
780
1,000
1,020
1,100
740
913.33
Fig. 9 Simson’s diversity index and Shannon–Weaver index for
Z. armatum and its associates.
Density
(1,400–1,600 m) and Kupinde (1,600–1,800 m) (Fig. 3) is
because of the the nearby settlement and agriculture zones
as compared to the other sites. Bhuyan et al. (2003) reported only 16 species in highly disturbed site as compared to
47 species in the least disturbed site in the eastern part of
India. Sunil et al. (2011) observed 34 tree species in the low
disturbed sites against tree species of 14 in the highly disturbed sites in the southern part of India. The lowest was
found in plantation forests, with only 9 species in Nepal
(Webb and Sah 2003). All these studies attribute the differences in the results to the degree of disturbances caused by
anthropogenic activities.
There is generally a linear relationship between vegetation attributes like species richness, diversity, and ecological factors like altitude, aspect, and distance of the site
from disturbance stimuli (Schuster and Diekmann 2005).
A monotonic decline in the number of species with increasing elevation has often been considered a general pattern (Brown 1988; Stevens 1992). Inverse correlation between altitude and species richness in Himalayan alpines
have also been established in several studies (Kala and
Mathur 2002; Panthi et al. 2007; Vetaas 2000). However,
the present study did not follow the similar pattern; maximum number of species was recorded at 1,400–1,700 m
and 1,800–2,000 m. The high species richness may be attributed to less anthropogenic activities, higher soil moisture and greater topographic variations in habitat conditions.
Several factors as lower elevation, moist habitat, resource
availability, disturbance levels, moderate fragmentation together with climatic variability, fluctuations to resources
and dispersal limitation may inf luence the population
structure (Shaheen et al. 2011a). The variation in the densities along the elevation gradient at different localities might
be the result of the variations in the soil nutrients and other abiotic as well as climatic factors. A study in Indonesia
showed that fully opened habitat with full sun exposure
during daytime may not be the suitable habitat for the natural population of Zanthoxylum acanthopodium (Junaedi
and Nurlaeni 2019).
Abundance and IVI
The density and frequency values of Z. armatum were
also high at Baghchaur and Kupinde. Nkoa et al. (2015)
stated that the abundance is related to number (density) or
frequency. The higher density and frequency might have
influenced the abundance positively in this study also. The
IVI depicts the importance of the species in terms of its
dominance and ecological success (Misra 1968). The change
in IVI among the study sites can be attributed to the change
in species composition and degree of disturbance and altitude (Saravanan et al. 2019).
Regeneration status
The average seedlings and saplings densities of Z. arma-
Phuyal et al.
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Journal of Ecology and Environment (2022)46:11
Table 5 Variation on soil chemical properties at different locality and elevation
SN
1
2
3
4
5
6
Locality
Dhanwang (1,000–2,000)
Kapurkot (1,200–1,400)
Baghchaur (1,400–1,600)
Rim (1,400–1,700)
Kupinde (1,600–1,800)
Chhatreshwori (1,800–2,000)
SOC (%)
N (%)
P (ppm)
3.09 ± 0.12
3.07 ± 0.07
2.73 ± 0.08
3.53 ± 0.16
2.58 ± 0.09
4.87 ± 0.04
0.36 ± 0.05
0.31 ± 0.04
0.29 ± 0.10
0.49 ± 0.08
0.30 ± 0.15
0.61 ± 0.03
31.11 ± 1.73
35.11 ± 2.57
30.91 ± 1.29
41.65 ± 0.92
21.03 ± 3.48
57.85 ± 1.83
K (ppm)
135.89 ± 1.43
212.27 ± 8.39
138.67 ± 3.46
428.34 ± 15.22
121.28 ± 1.92
346.84 ± 10.36
pH
6.23 ± 0.03
5.51 ± 0.07
5.75 ± 0.14
5.33 ± 0.15
5.4 ± 0.09
5.73 ± 0.1
Values are presented as mean ± standard error.
SOC, soil organic carbon; N, nitrogen; P, phosphorous.
tum in the study area were 150 individuals/ha and 100 individuals/ha. A study by Rawat and Chandhok (2009) reported saplings and seedlings layer densities ranging from
90 to 410 individuals/ha and 50 to 510 individuals/ha, respectively. In another study, the seedling and sapling layer
density ranged from 340 to 1190 individuals/ha. for seedlings and 340 to 920 individuals/ha for saplings (Saha et al.
2016). The densities of seedlings and saplings in the present
study did not show any specific pattern for elevation gradient. However, a study by Gairola et al. (2008) for different
high altitude Himalayan forests showed maximum seedling density throughout the altitudinal strata suggesting
that the slope and aspect favor regeneration of tree species.
Similarly, significant difference was observed between top
hill and bottom hill positions, with the highest amount of
regeneration in the bottom and lowest amount of regeneration in the top hill (Nur et al. 2016).
Regeneration status of any species is determined by the
number of saplings and seedlings (Dhar et al. 1997; Singh
and Singh 1992). The seedlings and saplings densities of Z.
armatum were comparatively very lower than the adult
densities in the study area. One reason for this kind of pattern might be due to the prematurely harvesting of the
fruits before even falling off of the seeds on the ground.
This severely hinders the natural seed bank stock and thus
affecting the seedling and sapling density. According to the
regeneration status table (Table 4), it can be said that the
regeneration status of Z. armatum in the study area is fair.
However, among the six localities, Kapurkot had comparatively better regeneration status than other sites and Chhatreshwori had lower regeneration potential.
Natural regeneration is a key process for the continued
existence of a species in a community. The three major
components of successful regeneration are the ability of
species to initiate new seedlings, their survival and growth
(Saikia and Khan 2013). Presence of sufficient number of
seedlings, saplings and young trees in a given population
indicates successful regeneration (Saxena and Singh 1984),
which is frequently influenced by the biotic interactions
and anthropogenic disturbances. The future composition
of the forests depends on the potential regenerative status
of tree species within a forest stand in space and time (Henle et al. 2004). Generally, regeneration of a species is usual-
ly affected by anthropogenic and natural factors. Seed germination rate in Z. armatum is very low (Phuyal et al.
2018) and hindered by the presence of hard seed coat; the
seeds undergo a strong dormancy and may take few
months to years for germination (Chadha 1976). Furthermore, the solitary seeds in the fruit also limit the quantities
of seed (Singh and Rawat 2017) and lower the rate of germination. Because of the high demand of Z. armatum , its
commercial cultivation in the study area is escalating
during the last few years. There is also a high demand of
plantlets but the supply is minimum due to lack of nurseries. District Forest and Plant Resources offices at Salyan
provided free plantlets to the interested farmers, still the
supply is inadequate to meet the demand. This has put a
high pressure on the naturally regenerating seedling and
saplings in the natural forests as the villagers uproot the
seedlings and saplings from the forest to plant them in
their farmland, which greatly alters the regeneration status
of Z. armatum naturally. Furthermore, the fruits are prematurely harvested from the wild, probably affecting the
seedbank of Z. armatum , leading to lower production of
seedlings.
Regeneration of any species is confined to a peculiar
range of habitat conditions and the extent of those conditions is a major determinant of its geographic distribution
(Grubb 1977) and the presence of saplings under the canopies of adult trees also indicates the future composition of
a community (Pokhriyal et al. 2010). The natural regeneration of Z. armatum is adversely affected by physiological
dormancy and high emptiness nature of seeds as a result
the seed germination is extremely rare in wild.
The reason behind less density, frequency, abundance
and regeneration at Chhatreshwori might be due to the
overexploitation by the local people as they collect bigger
trees for their own consumption and extra income.
Distribution
It was apparent that the natural distribution of this valuable species has been shrinking in the recent years due to
anthropogenic disturbances, as a similar trend for other
Himalayan medicinal plants as well (Vashistha et al. 2006).
Increasing market demand and unsustainable harvesting
are posing serious threat to the natural population of Z.
Phuyal et al.
Journal of Ecology and Environment (2022)46:11
armatum . It is one of the many other medicinal plants that
is collected with high preference for market as well as local
use (Kunwar et al. 2015).
Anthropogenic disturbances mainly harvesting from the
wild without proper care and uprooting of the seedlings
and saplings for transplanting them in farmyard were
found to be the major cause affecting the natural distribution of Z. armatum in the study area. Being a thorny plant,
disturbance from grazing was however not apparent for
the species as for many other medicinal plants.
There was a huge discrimination in the harvesting pattern and collection of Z. armatum in the study area.
During field visit at the fruiting season, it was a very common scene that the plants in farmers’ farmyard were overloaded with ripe fruits while those in the wild were harvested prematurely. Plants in the farmyard were considered
private and those in the forest were public so whoever saw
them first would harvest haphazardly. Though the farmers
were aware of the enormous economic benefits of the species, there seems to be a lack of awareness towards the conservation and sustainable harvesting of the species from
the wild.
Species diversity
The mean average species diversity (Shannon index, H)
value of 2.8 recorded in the present study is comparable to
the results of similar investigations in different Himalayan
regions: 1.53–2.88 in the western Himalayas (Gaur and
Joshi 2006; Samant et al. 1998), 2.39–4.63 in the Gharwal
Himalayas (Nautiyal et al. 1999), 2.5–3.10 in the trans-Himalayan alpines of Nepal (Panthi et al. 2007) and 3.13 in
the alpine pastures of Kashmir, Pakistan (Shaheen et al.
2011).
The higher value of the diversity indices is an obvious
indication of high species diversity and abundance
(Adekunle et al. 2013). This diversity index is comparable
to that found in the tropical forest of Eastern Ghats ranging between 3.76–3.96 (Naidu and Kumar 2016). Forests
with Shannon index greater than 2 are considered as medium to highly diverse in terms of species (Giliba et al. 2011).
Thus from the findings of this study it can be said that the
study area falls in the category of forests with high diversity.
The differences of diversity between different localities
and altitudes of the study area could be because of variations in the soil type, rainfall trends, anthropogenic action,
land use change, and so forth. Lowest diversity noted in
Kupinde could be explained by the fact that the forest is
totally degraded due to road construction and land slides.
Road networks increase resource extraction and encroachment into the forest leading to a reduction in biodiversity
(Hitimana et al. 2004; Sundriyal and Sharma 1996). Higher
species diversity and species richness at Chhatreshwori
could be because of relatively high soil nutrients. Several
studies have established a direct relationship between soil
Page 11 of 15
nutrients and species diversity. Grime (1973), Tilman and
Pacala (1993) demonstrated that soil fertility has a considerable impact on species diversity. Similarly, Loreau et al.
(2001) also suggested that species diversity is usually related to soil fertility. The forest was comparatively dense and
moist at Chhatreshwori. Moisture is also one of the important determinants of species richness and composition
(Vetaas 2000). Soil organic matter, nutrients and moisture
plays an important role in the vegetation composition of
any area (Tang 1990).
There have been ample studies on the population size
and distribution of other medicinal plants in Nepal. But no
study has been conducted previously on the population,
distribution, frequency, and abundance of this species so
no comparable data is available from Nepal. However, a
study from India recorded a low population size of Z. armatum from the villages of Chamoli district of Uttarakhand, India; the average density was 368.2 individuals/ha.
Due to low population size, it has been placed in the International Union for Conservation of Nature (IUCN) vulnerable category (Kala 2010). The same study also recorded
Berberis aristata, Ficus, Grewia optiva, Pyrus pashia, Pyracantha crenulata, Quercus, etc. as the major associates of
Z. armatum (Tables S1–S6).
The market price of the fruits is very good so the extensive demand of this species has put an enormous pressure
on the natural population. Though the farmers have already started commercial cultivation of Z. armatum , the
collection from wild has not yet decreased. Since the fruits
are difficult to harvest because of the thorns, destructive
harvesting without taking proper care is a common practice, creating a tremendous pressure on its existing populations in the wild. Similar scenario also prevails in Uttarakhand, India where harvesting of the entire plant before
setting even flowers along with the profuse invasion from
woody weeds such as Lantana has negatively impacted the
natural distribution of Z. armatum (Kala 2010). Threats to
Z. armatum from invasive species was however not evident
in the present study. Since the plant is thorny and aromatic, grazing by livestock is not a threat to the natural population of Z. armatum , instead it also provides shelter and
protection to its associated species in the natural habitats
by preventing from livestock grazing and browsing (Kala
2010).
Z. armatum has been prioritized by the government of
Nepal as one of the important medicinal plants for economic development with a high emphasis on cultivation
and agro-technology development (DPR 2006). Owing to
its great economic potential, the Karnali Provincial government, which includes Salyan, has announced a Zanthoxylum Year Program in the province’s hilly districts
and all the three levels of government: federal, provincial,
and local, have prioritized Z. armatum farming. The federal government also announced to celebrate fiscal year
Phuyal et al.
Page 12 of 15
Journal of Ecology and Environment (2022)46:11
2019–2020 as the year of Z. armatum plantation. The market price of the fruits is also very good so the extensive demand of this species has put an enormous pressure on the
natural population. Though the farmers have already started commercial cultivation, the collection from wild has not
yet decreased.
Diversity and distribution patterns of species are greatly
affected by various factors, including area, latitude, precipitation, and temperature (Zhang et al. 2011). The large scale
pattern in species distribution and physiognomy is also
governed by the climate. Climate can be characterized by
different variables which mainly determines the distribution pattern of species distribution in any area (Bakkenes
et al. 2002).
Overall, due to the increase in population size and the
overexploitation of forests, change of land use among other
factors; negative impacts can result on the forest ecology
including reduction of plant stock, disruption of regeneration, and loss of nutrients in harvested materials (Murkherjee and Chaturvedi 2017). Other factors that may affect the sustainability of plants are collection of premature
plants, grazing, and soil erosion. Therefore, deliberate efforts should be taken by all stakeholders to ensure that
these plants are used in a sustainable way.
Supplementary Information
Supplementary information accompanies this paper at
https://doi.org/10.1186/jee.22.015
Table S1. Population density (in ha), frequency, abundance, and distribution of Z. armatum and its major associates at Dhanwang (1000–1200 m). Table S2. Population
density (in ha), frequency, abundance, and distribution of
Z. armatum and its major associates. Table S3. Population
density (in ha), frequency, abundance, and distribution of
Z. armatum and its major associates. Table S4. Population
density (in ha), frequency, abundance, and distribution of
Z. armatum and its major associates at Baghchaur (1400–
1600 m asl). Table S5. Population density (in ha), frequency, abundance, and distribution of Z. armatum and its major associates at Kupinde (1600–1800 m asl). Table S6.
Population density (in ha), frequency, abundance, and distribution of Z. armatum and its major associates at Chhatreshwori (1800–2000 m asl).
Abbreviations
NTFPs: Non-timber Forest Products
MAPs: Medicinal and Aromatic Plants
RD: Relative Density
RF: Relative Frequency
RA: Relative Abundance
Conclusions
Species composition, density, distribution and regeneration status can be considered important factors to judge
the status of a forest. Z. armatum was found to be distributed randomly in Salyan district and the lower number of
seedlings and saplings indicates a fair regeneration pattern.
Although the dependency on natural forests for the collection of berries is gradually being replaced by cultivation in
private land in the recent years, unsustainable harvesting
and collection of saplings from the wild has not been
stopped completely. Anthropogenic disturbances including
premature harvesting and digging up of saplings was
found to severely affect the natural distribution and regeneration in the study area. Increasing market demand and
unsustainable harvesting procedures are posing serious
threat to the natural population of Z. armatum . Thus, effective conservation and management initiatives are most
important for conserving the wild genetic diversity of Z.
armatum in the study area. Establishment of high-tech
nurseries and free distribution of saplings to the farmers
could possibly reduce the pressure on natural population
and also uplift the economic status of the marginalized
and poor communities. Assessment of diversity and regeneration status of species is important for their sustainable
utilization, management, and conservation. Therefore, a
systematic management plan is required for the conservation and sustainable utilization of this valuable species.
IVI: Importance Value Index
SOC: Soil organic carbon
Acknowledgements
We are thankful to Mr. Krishna Pun from District Plant Resources
Office, Salyan for his help during the field work. Special thanks to
Prof. Dr. Ram Kailash Prasad Yadav, Head, Central Department of
Botany, Tribhuvan University for his encouragement.
Authors’ contributions
PKJ and SR conceptualized and supervised the research. NP collected and analyzed the data and wrote the manuscript. PKJ, PPR, and SR
critically commented and approved the final version of the manuscript.
The authors read and approved the final version of the manuscript.
Funding
This study was supported by the Dabur Nepal CSR Fellowship (Late
Sri Ashok Chand Burman) 01/2016’.
Availability of data and materials
All data involved in this study are available from the corresponding
authors upon request.
Ethics approval and consent to participate
Not applicable
Consent for publication
Not applicable
Phuyal et al.
Page 13 of 15
Journal of Ecology and Environment (2022)46:11
Competing interests
Northwest Research Station; 1999.
The authors declare that they have no competing interests.
Gairola S, Rawal RS, Todaria NP. Forest vegetation patterns along an altitudinal gradientin sub-alpine zone of west Himalaya, India. Afr J
Plant Sci. 2008;2(6):42-8.
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