J. Mt. Sci. (2008) 5: 257–264 DOI 10.1007/s11629-008-0078-z
Population Ecology of the Endangered Himalayan Yew in Khokhan Wildlife Sanctuary of North Western Himalaya for Conservation Management Shreekar Pant1 and S.S. Samant2* 1 Centre for Biodiversity Studies, School of Biosciences & Biotechnology, Baba Ghulam Shah Badshah University, Rajouri, J&K, India 2 G.B. Pant Institute of Himalayan Environment & Development, Himachal Unit, Mohal-Kullu- 175 126, Himachal Pradesh, India *Corresponding author, E-mail:
[email protected];
[email protected]; Phone: +91-1902-225329 Ext. 21 (o); Mobile: +91-9816316318; Fax: +91-1902-226347
Abstract: The Himalayan Yew (Taxus baccata subsp. wallichiana) is an endangered native high value medicinal plant of the Himalayan Region. The several medicinal properties of the bark and leaves of this species have increased its risk of extinction due to pressures for utilization. It is also subjected to harvest for fuelwood. The species does not regenerate well from seed and that is another risk factor. The objective of this research was to investigate the population ecology of the species as a foundation for its conservation. Six forest communities in the Khokhan Wildlife Sanctuary where the species is present were sampled. The abundance of the species, impacts of harvesting and its current regeneration patterns indicate that it may soon be extirpated from the Sanctuary. A plan for conserving the remaining sub-populations is presented. It could provide a template for conservation in other locations where the species is at risk. Key Words: Anthropogenic Pressure; Conservation Management; Himalayan Yew; Khokhan Wildlife Sanctuary; Regeneration
Received: 21 March 2008 Accepted: 30 June 2008
Introduction Taxus baccata L. subsp. wallichiana (Zucc.) Pilger (Himalayan Yew), locally known as ‘Rakhal’ in various parts of the Himalaya is an endangered native species (Samant et al. 1998, Samant 1999). It is the only member of Taxus found in India. Globally, Taxus is found in North America, East Asia and Europe. Taxus baccata (English Yew); T. brevifolia (English Yew); T. canadensis (Canada yew); T. cuspidata (Japanese Yew) and T. floridana (Florida Yew) are the prominent species. In India, it is distributed in the temperate and subalpine zones of the Himalayan region between 1800-3300 m amsl (Singh and Singh 1992, Samant 1993). However, the population is very small throughout the IHR due to high anthropogenic pressure. Generally, Himalayan Yew is a slow growing species found as an understory species in several forest communities of the Indian Himalayan Region (IHR). It is closely associated with Abies pindrow, Quercus semecarpifolia, Q. floribunda, Q. leucotrichophora, Betula utilis, Acer caesium, Pinus wallichiana, Rhododendron arboreum and Betula alnoides (Singh and Singh 1992, Dhar et al. 1997, Samant et al. 2002, Joshi
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2002, Pant 2005). Globally, the yew is primarily valued for the medicinal properties of taxol, but the Himalayan Yew has several other medicinal uses as well. Taxol was first extracted from the bark of the Taxus brevifolia (English Yew) (Anonymous 1976). Its anti-cancerous properties were first reported in 1964 (Appendino 1993). After identification of taxol’s potential for treating cancer, the genus gained global notoriety. In India, the conservation community became concerned that increased utilization of Himalayan Yew as a source of taxol would increase its endangerment. Himalayan Yew is also a source of the drug Zarnab, which is frequently used in the Unani System of Medicine. The extract derived from the bark and leaves is used to cure bronchitis, asthma and poisonous insect bites and is also used as aphrodisiac. A paste made from the extract is applied externally to cure headache. In the remote areas of the Himalaya, local inhabitants collect the bark for making a traditional tea for treatment of coughs and colds (Purohit et al. 2001). Aside from its medicinal uses, yew wood has value as an extremely hard and durable wood product. In East-Anglia and India, yew wood has been used for making furniture, for woodcarving and also for fuel. Because of its many beneficial uses, Himalayan Yew has been exploited to the brink of extinction. Its habitats have also been degraded by deforestation and human land uses (Samant et al. 2001). The effects of over-utilization and habitat degradation are exacerbated by the species’ relative intolerance to fire and drought and poor regeneration. Himalayan Yew has very thin bark as compared to some other yew species, making it susceptible to fire. It regenerates poorly from seed. After seeds fall in September ~ October, they remain dormant for nearly eighteen months. If seedlings successfully germinate, they grow quite slowly (Shukla et al. 1994, Nandi et al. 1994, Rikhari et al. 1998). The objectives of this research were: i) to assess the status of Himalayan Yew in the Khokhan Wildlife Sanctuary; ii) to identify factors responsible for depletion of the population; and iii) to develop a strategy for conservation of the species in the Sanctuary.
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1
Study Area
This study was conducted during 2004 ~ 2005 in the Khokhan Wildlife Sanctuary (KhWLS) located in the Kullu district in North West Himalaya. The Khokhan Wildlife Sanctuary is rich in biodiversity and covers part of the Mohal Khad Watershed in Kullu Valley. It encompasses 19.35 km2 and was created under the Punjab Birds and Wild Animals Protection Act for the conservation of biodiversity. Altitude ranges between 1,600 ~ 3,000 m amsl and the area supports diverse habitats, species and communities of the subtropical, temperate and sub-alpine zones. Local inhabitants are dependent on the vegetation for meeting their domestic needs.
2 Materials and methods 2.1 Identification and selection of sites and habitats The sites representing Taxus baccata subsp. wallichiana were selected along transacts between 1,600 ~ 2,400m amsl. Observations on altitude, aspect, slope and habitat were recorded. Sites were distinguished on the basis of whether or not they were associated with a watercourse or not. 2.2 Field procedures and analysis Field surveys were conducted during 2004 ~ 2005 within the selected sites in the KhWLS. Data on over story trees were collected in 50 × 50 m plots. Seedlings and saplings were sampled in 10 randomly placed 10 × 10 m sub-plots. Standard ecological methods were used to collect the data (Curtis and McIntosh 1950, Grieg-Smith 1957, Misra 1968, Kersaw 1973, Muller-Dombois and Ellenberg 1974, Dhar et al. 1997, Joshi and Samant 2004, Samant and Joshi 2004). For trees, total basal area and Importance Value Index (IVI) were calculated. IVI was calculated as the sum of relative frequency, relative density and relative basal area. The abundance data from different sites were pooled to get community averages in terms of density, total basal area and IVI. Communities were named based on the IVI. For sites where a single species contributed
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50 percent or more of the total IVI it was considered to be a single species-dominated community. Observations were made on factors responsible for depletion of Himalayan yew within the plots. Local residents knowledgeable about utilization were interviewed to supplement field observations.
3 Results and Discussion Sixty-five sites were sampled. Of those,
Himalayan Yew was only found in six. The physical and vegetation characteristics of the six sites where the species was found are presented in table 1. It was found in both riparian and upland site with topographic slopes ranging from 10 ~ 600. In all, 17 different forest communities were sampled. Of those, Himalayan Yew was found as an associate in communities dominated by Abies pindrow, Abies pindrow-Cedrus deodara mixed; Cedrus deodara, Picea smithiana, Quercus floribunda, and Quercus semecarpifolia (Table 1).
Table 1 Site characteristics and occurrence of Taxus baccata subsp. wallichiana in Khokhan Wildlife Sanctuary of the North Western Himalaya Site
Altitude (m)
Habitat
Slope ( 0)
1
2,380
SM
10
2
2,220
SM
35
3
2,320
R
60
4
1,800
SM
35
Picea smithiana
Abies pindrow, Prunus cornuta, Quercus leucotrichophora, Quercus floribunda
5
1,790
SM
35
Quercus floribunda
Pinus wallichiana, Quercus leucotrichophora
6
2,340
SM
15
Quercus semecarpifolia
Quercus floribunda, Persea odoratissima, Aesculus indica, Juglans regia
Community type
Abies pindrow
Abies pindrow-Cedrus deodara mixed
Cedrus deodara
Other Associates
Persea odoratissima, Picea smithiana, Quercus floribunda, Taxus baccata subsp. wallichiana
Taxus baccata subsp. wallichiana, Quercus floribunda, Picea smithiana, Aesculus indica Abies pindrow, Cornus macrophylla, Pinus wallichiana
Abbreviations used: SM=Shady Moist; and R=Riverine
3.1
Regeneration patterns of Himalayan Yew
Data on Himalayan Yew regeneration within the communities where it occurred are presented (Figure 1 ~ 6). Yew seedlings and saplings were in relatively low abundance as compared to the other associated species of the communities. Yew seedlings were not found in Abies pindrow-Cedrus deodara mixed, Abies pindrow and Quercus semecarpifolia communities. Neither seedlings nor saplings were recorded in the Quercus
semecarpifolia community. The low abundance of yew as compared to other associated species indicates either a competitive disadvantage as compared other species, selective exploitation, poor regeneration from seed or all three affects. Given this trend, the species may soon be extirpated from the Sanctuary. Similar findings have been reported from studies in the Uttarakhand Himalaya (Dhar et al. 1997, Rikhari et al. 2000, Samant et al. 2002, Joshi 2002, and Pant 2005). The Total Basal Area and Importance Value
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Index of the Himalayan Yew and other associate species have been presented in table 2. These values indicate that the values recorded for the Himalayan Yew are relatively less compared to the
other associate species. This may be due to the favorable climatic conditions for the growth and development of the associate species.
10000
Trees Saplings Seedlings
Density (Ind ha -1 )
1000
100
10
1 TD
TB
CD
AC
AP
CA
CM
ID
JR
PO
PS
PW PA Species
PC
QF
QL
RA
RJ
BA
PD
QS
RW
AI
Figure 1 Contribution of Taxus baccata subsp. wallichiana in different layers of Abies pindrow community
10000
Trees Saplings Seedlings
Density (Ind ha -1 )
1000
100
10
1 TD
TB
AP
AI
CD
PS
QS Species
RW
UW
FM
PD
PO
RA
Figure 2 Contribution of Taxus baccata subsp. wallichiana in different layers of Abies pindrow-Cedrus deodara mixed community 10000
Trees Saplings Seedlings
Density (Ind ha -1 )
1000
100
10
1 TD
TB
CD
AI
ID
JR
PD
PO Species
PS
POC
PC
QF
BA
PW
QL
Figure 3 Contribution of Taxus baccata subsp. wallichiana in different layers of Cedrus deodara community
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1000
Trees Saplings
Density (Ind ha -1 )
Seedlings 100
10
1 TD
TB
AP
CD
FM
ID
PS
PW
POC
PC
QF
QL
Species
Figure 4 Contribution of Taxus baccata subsp. wallichiana in different layers of Picea smithiana community Trees
10000
Saplings Seedlings
-1
Density (Ind ha )
1000
100
10
1 TD
TB
CD
PO
PS
PW
QF
QG
QL
RA
AI
Species
Figure 5 Contribution of Taxus baccata subsp. wallichiana in different layers of Quercus floribunda community Trees
1000
Saplings Seedlings -1
Density (Ind ha )
100
10
1 TD
TB
AP
AI
PD
ID
JR
PO
PS
QF
QS
PC
RA
Species
Figure 6 Contribution of Taxus baccata subsp. wallichiana in different layers of Quercus semecarpifolia community
Abbreviations used: TD=Total density; TB=Taxus baccata subsp. wallichiana; AP=Abies pindrow; AC=Acer cappadocicum; CD=Cedrus deodara; CM= Cornus macrophylla; ID= Ilex dipyrena; JR=Juglans regia; PO=Persea odoratissima; PS=Picea smithiana; PW=Pinus wallichiana; CA=Celtis australis; PCe=Prunus cerasoides; PC=Prunus cornuta; QF=Quercus floribunda; QL=Quercus leucotrichophora; RA=Rhododendron arboreum; RS=Rhus javanica; BA=Betula alnoides; PD=Persea duthiei; QS=Quercus semecarpifolia; RW=Rhus wallichii; AI=Aesculus indica; UW=Ulmus wallichiana; FM=Fraxinus micrantha; POC=Populus ciliata; and QG=Quercus glauca
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Table 2 Community wise Total Basal Area (Ind m-2) and Importance Value Index in Khokhan Wildlife Sanctuary of the North Western Himalaya Community types Species
Total Basal Area 1
2
Importance Value Index
3
4
5
Abies pindrow
65.87 99.09
-
6.44
-
Acer cappadocicum
0.01
-
-
-
Aesculus indica
-
-
5.88 0.98
-
Cedrus deodara
0.01 38.99 21.39 4.81
Celtis australis
0.96
-
-
-
-
-
Ilex dipyrana
2.71
Juglans regia Persea duthiei
Fraxinus micrantha
Persea odoratissima
1
2
0.51 206.75124.29 -
5.90
-
3
4
5
6
-
49.69
-
4.58
-
-
-
-
0.50 0.80 27.04 17.98 6.89 0.11
-
-
-
-
-
-
-
0.82
-
-
-
-
-
-
1.46 0.30
-
0.44 30.68
2.79
-
1.08
-
-
-
-
0.16
-
-
29.34
-
1.03
-
9.16 27.52 2.96 44.64 2.67
Pinus wallichiana
4.08
-
-
-
3.00 2.44
0.60 0.12
-
-
-
20.69
-
-
-
13.01 13.67
-
5.65
1.86 26.31
-
11.83
-
-
15.16
0.01
-
10.59
-
-
4.59
-
28.68
-
-
35.85 6.25
1.12 40.71 34.40 39.70 168.28 18.58 5.89 -
16.31
-
-
33.56 27.36
-
-
-
-
-
6.80
5.90
-
-
-
-
15.89
-
-
-
-
-
-
-
-
-
4.09
-
Prunus cornuta
3.81
-
0.91 8.55
14.58
-
16.76 29.23
Quercus floribunda
7.04
-
0.52 5.90 22.44 1.07 42.93
-
32.66 40.72 150.25 4.56
-
-
-
0.16
-
-
-
0.11
-
-
Rhododendron arboreum
0.15
-
-
Rhus javanica
0.60
-
Rhus wallichii
-
6.09
Quercus leucotrichophora Quercus semecarpifolia
Taxus baccata subsp. wallichiana Ulmus wallichiana
-
42.76 20.40
Prunus cerasoides
Quercus glauca
-
-
4.58 75.51 200.88 30.16 23.52
0.11 0.65 47.37
Picea smithiana
Populus ciliata
6
-
1.36
-
-
-
-
-
15.65
-
6.23 5.46
-
5.92
-
-
31.03 25.65
-
-
17.52
-
6.48
-
-
-
100.25
-
0.50
-
6.25
-
-
-
4.49
-
-
-
-
-
5.89
-
-
-
-
-
-
-
-
-
-
16.75
-
-
-
-
11.98 6.72 0.45 0.77 1.76 0.16 54.53 29.73 14.43 16.50 11.15 5.89 -
6.78
-
-
-
-
-
20.94
-
-
-
-
Abbreviations used: 1=Abies pindrow; 2= Abies pindrow-Cedrus deodara mixed; 3= Cedrus deodara; 4= Picea smithiana; 5= Quercus floribunda; and 6=Quercus semecarpifolia
3.2 Stand Structure of Yew The size class distribution of yew that were recorded in the plots (based on CBH) reinforced the observations of limited regeneration. Over 42 percent of the yew trees were larger than 90 cm in circumference. Nearly 18 percent were from 71 ~ 90 cm; almost 11 percent were from 51 ~ 70 cm; and almost 30 percent were from 30.1 ~ 50 cm.
260 262
The saplings and seedlings were relatively very less in number. 3.3 Anthropogenic pressures The leaves and bark of Taxus are extracted for domestic consumption and trade. The extraction of bark can cause mortality through girdling.
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collected from the largest trees (> 60 percent are affected) but all size classes are subjected to the practice (40 percent of trees 71 ~ 90 cm; 50 percent of trees 51 ~ 70 cm; 53 percent of trees 30.1 ~ 50 cm) (Figure 7). Considering the yew’s natural limitations e.g., susceptibility to fire, poor regeneration potential and utilization significantly increases its risk of extirpation from the Sanctuary.
Total Individuals
Bark Removal
Leaf Felling
Lopping
28
14
21 14
7
7 0
0 >90
71-90
51-70
No. of Affected Individuals
Total Individuals
Collection of wood for fuel by the Gujjars and inhabitants of the peripheral villages causes damage, increases susceptibility to disease and likewise contributes to mortality. The information gathered during this study indicated that 50 percent of the surviving yew trees have been affected by bark removal and the remainder are subject to lopping and felling for fuel. Most bark is
31.4-50
Size Class
Figure 7 Size class distribution of Taxus baccata subsp. wallichiana in Khokhan Wildlife Sanctuary of the North Western Himalaya
4 Conclusion It is estimated that half of the estimated 13.6 million species on the earth may become extinct by the year 2050 unless appropriate measures are taken save them (Puspangadan and Nair 2001). Taxus is one of the endangered species of the Indian Himalayan Region (Samant et al. 1998, Samant and Pal 2003, Ved et al. 2003). Although the present study was limited to one location, its findings indicate that there is an urgent need to develop an appropriate conservation strategy for this species. Some principles upon which such a plan could be developed follow. (1) The population of Himalayan Yew throughout the Indian Himalayan Region should be inventoried using standard ecological methods. (2) A monitoring plan should be developed and implemented to determine trends in existing populations. (3) Sustainable methods of bark and leaf extraction should be developed and disseminated to local inhabitants.
(4) Further, research should be done on the regeneration of this species, both vegetative and by seed. An effort should be made to enlist the aid of local residents in propagating the species. (5) In-situ conservation of the species should be promoted. Seedlings developed from seeds and cuttings should be transplanted to appropriate locations in the Sanctuary and their growth and survival should be monitored.
Acknowledgements Authors are thankful to Dr. U. Dhar, Director, G.B. Pant Institute of Himalayan Environment & Development, Kosi-Katarmal, Almora for encouragement & providing necessary facilities. Mr. K.D. Thakur is acknowledged for his help in the field survey. Authors greatly acknowledge Dr. Richard Harris for editing the manuscript, and two anonymous reviewers for their valuable comments.
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