RESEARCH COMMUNICATIONS
Comparing structure and composition
of coniferous forests in Subansiri
district, Arunachal Pradesh
M. D. Behera , S. P. S. Kushwaha†,#, P. S. Roy†,
S. Srivastava†, T. P. Singh† and R. C. Dubey*
†
Forestry and Ecology Division, Indian Institute of Remote Sensing,
Dehra Dun 248 001, India
*Botany and Microbiology Department, Gurukul Kangri University,
Hardwar 249 404, India
Structure and composition of a semi-natural coniferous forest (subtropical pine; 30-year-old Pinus
plantation) was compared with natural coniferous
forest (temperate/subalpine conifers) to judge the
ecological significance. The study revealed that the
plantation in the subtropical region could not attain
the climax phase in the succession ladder, even after
30 years. The total number of species, genera and
families observed for temperate/subalpine coniferous
forests was found to be higher than that for subtropical pine forest. It was noticed that only few tree
species were dominant in both the forest types.
Rosaceae was found to be the most speciose family
occurring in both the forest types. Both temperate/
subalpine coniferous and subtropical pine forest
accommodated one endemic species each, i.e. Magnolia
rabianiana and Saurauia grifithii, respectively. The
arrangement of population structure to low girth sizeclasses for subtropical pine forest may be ascribed to
low adaptability to local climate. Phyto-sociological
studies revealed that the subtropical forest was less
complex from the ecological structure and composition
point of view in comparison to the temperate/
subalpine coniferous forests.
FOREST structure and composition are strongly correlated
with environmental factors, such as climate and topography1–3. A new species, when introduced into an allien
environment, usually takes some time to adapt to the new
habitat. If the new habitat becomes suitable to the introduced species, then the species flourishes and eventually
passes through the processes of ecological succession to
finally attain the climax stage. Studying the composition
and diversity of such species and its habitat and comparing with similar habitat types, perhaps becomes the
yardstick to judge the level of adaptation to the environment and the ecological significance.
Quantitative inventories of forest flora have been
mainly concentrated on the species-rich tropical forests4,5
although species-poor forests have also been recognized6.
Species-poor or low-diversity forests may be defined as
those in which 50–80% of the canopy trees are represented by only one tree species7. Conservation and management of such forests require understanding of the compo#
For correspondence. (e-mail: [email protected])
70
sition of particular forests in relation to other similar
forests8. Recent quantitative plant diversity inventories
include the Eastern and Western Ghats of the Indian
penunsula5,8. Similar studies are lacking from forests of
the Arunachal Himalaya, which forms an important
segment of the Eastern Himalaya.
Coniferous forests are very important from both ecological and economic viewpoint, as most of the conifers
are used for timber, fuelwood, resins and other purposes.
Subansiri region of Arunachal Pradesh has many natural
coniferous forests distributed at higher elevations. At
places, the conifers have been over-exploited, especially
in the vicinity of human habitations. Most of the places
still remain least disturbed either due to steepness
of terrain or remoteness9. Behera10 has classified and
mapped the forest vegetation types of Subansiri district at
1 : 250 000 scale using IRS-1C LISS-III satellite images.
He has classified the coniferous forests into two categories based on the spectral characteristics, i.e. subtropical pine and temperate/subalpine coniferous forests11. The
satellite-derived temperate/subalpine coniferous forests
correspond to 12/C3a – East Himalayan mixed coniferous
forests and 14/C2 – East Himalayan sub-alpine birch/fir
forests of Champion and Seth12. Similarly, subtropical
pine forest corresponds to 9/C2 – Assam sub-tropical pine
forests of Champion and Seth12. Presumably, Champion
and Seth based their classification on the study of pine
forests in Shillong plateau of Meghalaya, where pure
Pinus kesiya formations occur13. But in Subansiri district
of Arunachal Pradesh, this forest type is quite dissimilar
in its species composition and occurrence. P. kesiya and
few other species like P. patula, and P. roxburghii were
introduced from Shillong plateau thirty years ago and
planted in Yachuli–Hapoli belt. It extends in the subtropical region between 1000 m to 1800 m elevations. P.
kesiya has proved exceedingly well for afforestation of
jhum fallows and forms pure stands of tall trees, but largescale insect attack was prevalent, making it difficult
to manage the plantation13. They have poor species
diversity14. This paper compares and contrasts plant
species diversity and compositional characteristics of the
30-year-old semi-natural pine forest with that of the
natural coniferous forests occurring in one of the Indian
hotspot regions.
The study area lies between 26°55′–28°42′N latitude
and 92°41′–94°37′E longitude (Figure 1). It occupies an
area of approx. 20,000 km2, inhabited by 2,06,064 people15.
District Subansiri, which falls in the Eastern Himalayan
biogeographic zone, owes its high floral and faunal
diversity to its strategic location – at the junction of three
biogeographic realms, viz. the Palaeoarctic, the IndoMalayan and the Indo-Chinese. According to the biogeographic classification, the area resides in Himalaya – East
Himalaya biogeographic region16. Numerous streams and
rivers dissect the topography of the area. Average annual
rainfall is generally heavy (3000 mm annually). TempeCURRENT SCIENCE, VOL. 82, NO. 1, 10 JANUARY 2002
RESEARCH COMMUNICATIONS
rature ranges from a minimum of 5°C in winter to a
maximum of 38°C in summer at foothills and plains,
whereas it varies from below freezing point to 25°C at
higher reaches (Figure 2). The people of this area have
kept themselves closer to nature due to lack of communication with their counterparts elsewhere17.
Temperate and subalpine coniferous forests occur
between 2800 and 4000 m altitudes beyond temperate
broad-leaved evergreen forests. They experience heavy
snowfall during winter months. The lower limit of such
forests is dominated by mixed coniferous types, which
include species of Abies, Pinus, Taxus, etc. whereas the
upper limit predominantly comprises Abies, Juniperus,
Larix, Picea, Tsuga and Taxus species (Figure 3). Subtropical pine forests occur between 1000 and 1800 m in
subtropical regions of the district. These forests are
mainly represented by species Pinus in association with
species like Alnus nepalensis and Rhus javanica (Figure
4), shrubby and herbaceous vegetation, viz., Desmodium
sp., Indigofera sp., Rubus sp., etc. Because of recurrent
fires during winter season, epiphytes and other undergrowths are less in this forest14.
Probability proportionate stratified random sampling
method was adopted for field survey using various sizes
of quadrats for various growth and life forms18. For
sampling various strata of vegetation, nested quadrat
sampling method was followed. A 20 m × 20 m plot for
trees (of ≥ 15 cm cbh) and a 5 m × 5 m nested plot in the
same quadrat were laid for shrub layers (shrubs/saplings
of ≥ 5 cm cbh) (Figure 5). For herb layer (herbs/seedlings) four 1 m × 1 m plots were laid, of which three were
laid at the three out of four corners and one randomly
inside the 20 m × 20 m plot. The epiphytes, creepers,
climbers and other lianas and their host plants were also
noted (if present, by counting their numbers) in order to
take into account all the above ground floral components.
The species–area curve was plotted for each forest type.
Specimens were identified by referring to the herbarium
collection at Forest Research Institute, Dehra Dun, Botanical Survey of India, Shillong and State Forest Research
Institute, Itanagar. Some specimens were also named with
assistance from local villagers and after local names were
agreed upon, specimens were cross-referenced with
available literature19–26. Stem-size class for most abundantly occurring tree species was estimated in both the
forest types based on their cbh measurements. Relative
frequency, relative density, relative dominance and importance value index (IVI) were calculated following
N
INDIA
Upper Subansiri
0E
28
28°N
Eastern
Himalaya
280E
28°N
Lower Subansiri
Itanagar
Western
Ghats
Figure 3.
Subalpine coniferous forest near Nyapin.
Figure 1. Location of the study area (Subansiri district, Arunachal
Pradesh)33.
600
min. temp 0C
rainfall(mm)
max. temp 0C
400
30
20
200
10
0
0
J
Figure 2.
F
M
A
M
J J
A
S
O
N
D
Ombothermic graph showing rainfall and temperature9.
CURRENT SCIENCE, VOL. 82, NO. 1, 10 JANUARY 2002
Figure 4.
Subtropical pine forest near Yachuli.
71
RESEARCH COMMUNICATIONS
Mishra27. Stem-size classes were estimated based on their
cbh measurements seen in Table 1.
Species evenness (Margalef28 and Menhinick29), dominance (Simpson30) and diversity (Shannon–Weaver31)
indices were calculated following Hill32. Forest type-wise
data were entered in Excel (Microsoft Excel 97, version
4.0 on Windows95 operating system in a Pentium PC)
spreadsheets. STATECOL (Ecological Statistics), a software package was used to calculate various species
richness and evenness indices32.
The species–area curve plotted for temperate/subalpine
coniferous forest followed the same trend, with gradual
increase in the number of species with area initially up to
0.28 ha; and then it appeared to be asymptote for all
species. However the curve drawn for subtropical pine
forests became asymptote at 0.16 ha (Figure 6).
Table 1.
Estimation of stem-size class
Stem-size
class
Range of cbh
(in cm)
A
B
C
D
E
15–30
30–60
60–90
90–120
120
1m
20m
5m
1m
1m
5m
20m
1m
Figure 5.
50
Sample design of nested quadrat9.
con
stp
40
Cumulative
number of species
30
20
10
0
0.04
0.2
Area in ha
Figure 6.
72
Species–area curve.
0.32
0.36
Table 2.
Sl.
No.
Species and their corresponding families in the study area
Plant species
Family
A. Temperate/subalpine conifers
1 Abies densa Griff.
2 Ainsliaea sp.
3 Alnus nepalensis D.Don
4 Alpinia sp.
5 Anaphalis sp.
6 Berberis macrosepala Hk.f. and Thomson
7 Berberis wallichiana DC.
8 Psychotria curviflora Wall.
8 Coriaria nepalensis Wall.
9 Crassocephalum crepidioides (Benth.) Moore
10 Cyathea spinulosa Wallich ex Hk.f.
11 Cymbopogon intermedius D.Don
12 Elscholtzia blanda Benth.
13 Gaultheria fragratissima Wallich.
14 Gnaphalium luteo-album L.
15 Hemiphragma heterophyllum Wall.
15 Hemiphragma sp.
16 Indigofera linifolia (L.f.) Retz.
17 Inula cappa (Buch.-Ham. ex D.Don) DC.
18 Lycopodium sp.
19 Myrsine semiserrata Wall.
20 Oenothera rosea L.
21 Pinus wallichiana A.B. Jack.
22 Pleioblastus callosa
23 Polypodium sp.
24 Potentilla polyphylla Wall. ex Lehm.
25 Pyrus griffithii Decne.
26 Quercus lanata Sm.
27 Quercus sp.
28 Rhododendron anthopogon D.Don
29 Rhododendron hodgsonii Hk.f.
30 Rhododendron lanatum Hook.f.
31 Rhododendron setosum D.Don
32 Rubus gigantiflorus Hara
33 Rubus pentagona Wall. ex Focke
34 Rubus sp.
35 Rungia parviflora Nees
36 Saccharum spontaneum L.
37 Skimmia anquetilia Taylor and Airyshaw
38 Strobilanthes sp.
39 Taxus wallichiana Zucc.
40 Tsuga dumosa D.Don
Pinaceae
Asteraceae
Betulaceae
Zingiberaceae
Asteraceae
Berberidaceae
Berberidaceae
Rubiaceae
Coriariaceae
Asteraceae
Cyatheaceae
Poaceae
Lamiaceae
Ericaceae
Asteraceae
Scrophulariaceae
Scrophulariaceae
Fabaceae
Asteraceae
Lycopodiaceae
Myrsinaceae
Onagraceae
Pinaceae
Poaceae
Polypodiaceae
Rosaceae
Rosaceae
Fagaceae
Fagaceae
Ericaceae
Ericaceae
Ericaceae
Ericaceae
Rosaceae
Rosaceae
Rosaceae
Acanthaceae
Poaceae
Rutaceae
Acanthaceae
Taxaceae
Pinaceae
B. Subtropical pine
1 Alnus nepalensis D.Don
2 Anacardium sp.
3 Barleria sp.
4 Berberis wallichiana DC.
5 Clerodendrum bracteatum Wallich
6 Clerodendrum sp.
7 Cyathea sp.
8 Desmodium tilliaefolium (D.Don) G.Don
9 Dysoxylum gobara (Buch.-Ham.) Merr.
10 Elaeocarpus lanceaefolius Roxb.
11 Indigofera linifolia (L.f.) Retz.
12 Litsea glutinosa (Lour.) Robinson
13 Maesa indica (Roxb.) A.DC.
14 Neolitsea spinulosa (Wallich) ex Hk.f.
15 Pinus kesiya Royle ex Gord.
16 Rubus acuminatus Sm.
17 Rubus ellipticus Sm.
18 Rubus kurzii Balak.
19 Rubus lasiocarpus Sm.
20 Sarcospermum arboreum Benth
21 Saurauia roxburghii Wallich
22 Smilax aspera L.
23 Urena lobata L.
Betulaceae
Anacardiaceae
Acanthaceae
Berberidaceae
Verbenaceae
Verbenaceae
Cyatheaceae
Fabaceae
Meliaceae
Elaeocarpaceae
Fabaceae
Lauraceae
Myrsinaceae
Lauraceae
Pinaceae
Rosaceae
Rosaceae
Rosaceae
Rosaceae
Sapotaceae
Saurauiaceae
Liliaceae
Malvaceae
CURRENT SCIENCE, VOL. 82, NO. 1, 10 JANUARY 2002
RESEARCH COMMUNICATIONS
In case of temperate/subalpine coniferous forest, a total
of 40 species were encountered that belong to 22 families
and 32 genera, of which 10 are only tree (≥ 15 cm cbh)
species (Tables 2 and 3). Asteraceae, Ericaceae and
Rosaceae were the most speciose families (with five
species), Pinaceae and Poaceae (with three species)
wherein 13 families were represented by one species each.
Taxonomically, Asteraceae was the most diverse family
(with five genera), Pinaceae, Poaceae and Rosaceae (with
three genera) and Acanthaceae, Berberidaceae and Ericaceae (with two genera) whereas 15 families were
Table 3.
Sl. No.
Family-wise contribution to genera and species
Family
Genera
Species
A. Temperate/subalpine conifers
1
Acanthaceae
2
Asteraceae
3
Berberidaceae
4
Betulaceae
5
Coriariaceae
6
Cyatheaceae
7
Ericaceae
8
Fabaceae
9
Fagaceae
10
Lamiaceae
11
Lycopodiaceae
12
Myrsinaceae
13
Onagraceae
14
Pinaceae
15
Poaceae
16
Polypodiaceae
17
Rosaceae
18
Rubiaceae
19
Rutaceae
20
Scrophulariaceae
21
Taxaceae
22
Zingiberaceae
2
5
2
1
1
1
2
1
1
1
1
1
1
3
3
1
3
1
1
1
1
1
2
5
2
1
1
1
5
1
2
1
1
1
1
3
3
1
5
1
1
2
1
1
B. Subtropical pine
1
Acanthaceae
2
Anacardiaceae
3
Asteraceae
4
Berberidaceae
5
Betulaceae
6
Cyatheaceae
7
Elaeocarpaceae
8
Fabaceae
9
Lauraceae
10
Liliaceae
11
Malvaceae
12
Meliaceae
13
Myrsinaceae
14
Pinaceae
15
Rosaceae
16
Sapotaceae
17
Saurauiaceae
18
Verbenaceae
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
4
1
1
2
Table 4.
represented by only one genus. Whereas, in case of
subtropical pine forest, a total of only 23 species were
encountered that belong to 18 families and 19 genera, of
which 4 are only tree (≥ 15 cm cbh) species (Tables 2
and 3). Taxonomically, well-represented families include
Rosaceae (with four species), Lauraceae and Verbenaceae
(two species each) whereas 15 families had a single
species. Seventeen families were represented by only a
single genus, except Lauraceae (with two genera). The
average mean tree basal area calculated for temperate/
subalpine coniferous forest was found to be comparable
with subtropical pine forest (Table 4). The proportion
of genera to species, families to species and families
to genera was observed to be higher in case of temperate/subalpine coniferous forests than the other types
(Table 4).
Population distributions of tree species were computed
according to five girth classes (Table 5). It was observed
that tree species were distributed in all the girth classes in
case of temperate/subalpine forest, but in case of subtropical forest, they fell only within the lower three
classes, viz. A, B and C. For temperate/subalpine coniferous forests, the graph showing the number of tree
species initially increased for the girth class A (31) and B
(40) and then decreased for C, D and E, whereas for
subtropical pine forests the graph increased abruptly for
the two lower girth classes and decreased for class C
(Figure 7).
For temperate/subalpine coniferous forests, Pinus wallichiana was observed to be the most important species
having highest IVI value (99.14, 33.05%), of which
relative dominance contributed to 48.53 followed by
relative density of 26.61 and relative frequency of 24.00
(Table 6). Only three species (P. wallichiana 99.14
(33%), Tsuga dumosa 68.5 (23%) and Abies densa 41.89
(14%) contributed to 70% of the total IVI, which was
contributed by a single family, i.e. Pinaceae (Table 6).
Thirty per cent of the rest was attributed by 7 species.
Whereas, the subtropical pine forest was most prominently dominated by species of Pinus kesiya (IVI =
166.42, 55.4%) in which relative density contributes to
93.06 (31%) followed by relative frequency of 40 (13.3%)
and relative dominance of 33.36 (11.1%) (Table 5). The
three tree species contribute to relative density total of
only 7, whereas P. kesiya contributes to 93, indicating
absolutely high density.
Margalef’s index for species richness showed a higher
value (43.21) for temperate/subalpine coniferous forest,
but for subtropical pine forest, the value was com-
Forest type-wise mean basal area (m2/ha) and ratio of species, genus and family
Forest type
Temperate/subalpine conifers
Subtropical pine
Mean basal area
Genus: species
Family: species
Family: genus
0.034
0.029
1.25
1.21
1.82
1.28
1.45
1.06
CURRENT SCIENCE, VOL. 82, NO. 1, 10 JANUARY 2002
73
RESEARCH COMMUNICATIONS
Table 5.
Sl. No.
Population distribution of tree species
Species
A. Temperate/subalpine conifers
1
Abies densa Griff.
2
Chasalia curviflora Wallich.
3
Hemiphragma heterophyllum Wall.
4
Myrsine semiserrata Wall
5
Pinus wallichiana A.B. Jack.
6
Quercus lanata Sm.
7
Rhododendron anthopogon D.Don
8
Rhododendron hodgsonii Hk.f.
9
Taxus wallichiana Zucc.
10
Tsuga dumosa D.Don
B. Subtropical pine
1
Pinus kesiya Royle ex Gord.
2
Litsea glutinosa (Lour.) Robinson
3
Alnus nepalensis D.Don
4
Elaeocarpus lanceaefolius Roxb.
paratively low (Table 7). But the Menhinick’s index
showed a comparative value for both the forest types
(Table 7). Simpson’s index was higher (0.78) for subtropical pine forest in comparison to its counterpart,
indicating that few species were dominant in that forest
type (Table 7). Shannon–Weaver index of species
diversity was higher for temperate/subalpine forest
(5.82) in comparison to subtropical pine forest (3.25)
(Table 7).
The coniferous forests present in the Subansiri district
of Arunachal Pradesh showed distinct characteristics. The
temperate/subalpine forests enjoy the climax stage, being
natural types. But, the Pinus plantation in the subtropical
region could not attain the climax phase in the succession
ladder even after 30 years, which was revealed from the
study. We have noticed that P. kesiya species flourished
well, whereas the introduced Pine species like P. patula,
and P. roxburghii were not observed in the study plots.
The number of species, genera and families present in
subtropical forest was less than found those in temperate/
subalpine forest (Tables 2 and 3). This was also reflected
from the species–area curve, wherein the graph for
subtropical pine forest became asymptote earlier than the
temperate/subalpine forest (Figure 6). Though Rosaceae
was found to have occurred with highest number of genus
and species in both the forest types, they were represented
only by herbaceous flora. It was noticed that only few tree
species were dominant in both the forest types. But
diversity of both the forests was greatly attributed to the
presence of shrubs and herbs9. Higher genera to species,
families to species and families to genera ratio was
observed for temperate/subtropical forests (Table 4).
Temperate/subalpine forests had higher mean tree basal
area, indicating the presence of larger amount of standing
biomass with respect to the subtropical pine forest (Table 5).
These observations also indicate that the temperate/subalpine forests are comparatively older and were stable than
74
A
B
C
D
E
7
2
0
4
5
7
0
4
0
2
18
0
2
3
6
2
1
0
2
6
2
0
1
0
8
0
0
0
1
10
0
0
0
0
6
0
0
0
0
5
0
0
0
1
4
0
0
0
0
1
62
23
41
7
141
4
0
1
7
0
0
0
0
0
0
0
0
0
0
0
150
stp
ste
100
50
No. of tree
species
0
A
B
Various girth classes
Figure 7.
C
D
E
Distribution of tree species across various girth classes.
subtropical pine forests. Both temperate/subalpine coniferous and subtropical pine forest accommodated one
endemic species each, i.e. Magnolia rabaniana and Saurauia griffithii, respectively33. The presence of Saurauia
griffithii in subtropical pine forest indicated that it has an
inert tendency to grow in that climatic condition. Majority
of the species found in subtropical pine forest were of
lower girth class range, indicating that the forest is a
young one. The arrangement of population structure by
girth size–class distribution and utilization of information
derived from them have generally been used by many
workers for understanding regeneration and future stability of tree species population in forest communities34–36.
The variation in population structure of different species
in both the forest types may also be ascribed to adaptability to local climate33.
The phyto-sociological analysis revealed that the single
species, P. kesiya, accounted for 65% of IVI value and
CURRENT SCIENCE, VOL. 82, NO. 1, 10 JANUARY 2002
RESEARCH COMMUNICATIONS
Table 6.
Sl.
No.
Relative
density
Relative
frequency
Relative
dominance
IVI
A. Temperate/subalpine conifers
1 Pinus wallichiana A.B. Jack.
2 Tsuga dumosa D.Don
3 Abies densa Griff
4 Quercus lanata Sm.
5 Myrsine semiserrata Wall
6 Rhododendron hodgsonii Hk.f.
7 Hemiphragma heterophyllum Wall.
8 Taxus wallichiana Zucc.
9 Chasalia curviflora Wallich.
10 Rhododendron anthopogon D.Don
26.61
22.02
24.77
8.26
7.34
3.67
2.75
1.83
1.83
0.92
24
16
8
16
4
12
8
4
4
4
48.53
30.48
9.12
1.53
6.09
0.57
1.94
1.37
0.23
0.13
99.14
68.50
41.89
25.79
17.43
16.24
12.69
7.20
6.06
5.05
B. Subtropical pine
1 Pinus kesiya Royle ex Gord.
2 Litsea glutinosa (Lour.) Robinson
3 Alnus nepalensis D.Don
4 Elaeocarpus lanceaefolius Roxb.
93.06
1.39
4.17
1.39
40
20
20
20
33.36
47.07
16.02
3.55
166.42
68.46
40.19
24.94
Table 7.
Index
Margalef
Menhinick
Simpson
Shannon–Weaver
Phyto-sociological analysis of tree species (≥ 15cm cbh)
Species
Comparison of various indices
Temperate/subalpine
conifers
Subtropical
pine
43.21
4.29
0.3
5.82
17.5
3.06
0.78
3.25
relative density of 93. This observation well-qualified the
subtropical pine forest as species-poor or low diversity
forest7. The analysis of various richness, dominance and
diversity indices had strongly supported the above fact.
Margalef’s index showed low species richness value (17.5
vs 43.21), but Menhinick’s index showed a comparative
value (3.06 vs 4.29) for subtropical pine forest with
respect to the temperate/subalpine coniferous forests.
This is because Menhinick’s index of species richness
presupposed that a kind of functional relationship existed
between the number of species and individuals present
in the community, whereas Margalef’s index considered
the conditional presence or absence of functional
relationship of species. The Simpson’s index for dominance showed a very high value for subtropical pine
forest in comparison to that of temperate/subalpine
coniferous forest. It indicates that the subtropical pine
forest is less stabilized and less active from a functional
point of view37. The low Shannon–Weaver diversity
value for subtropical pine forest also indicated that the
ecological structure is less complex37. This analysis
on coniferous forest structure, composition and species
diversity analysis will serve as baseline information for
the researchers working in that area, for further detailed
study and analysis. It is hoped that an inventory on the
CURRENT SCIENCE, VOL. 82, NO. 1, 10 JANUARY 2002
plant regeneration status will add strength to this research
work.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Schall, J. J. and Pinaka, E. R., Science, 1978, 201, 679–686.
Wright, D.H., Oikos, 1983, 41, 496–506.
Currie, D. J., Am. Nat., 1991, 137, 27–49.
Johnston, M. and Gillman, M., Biodivers. Conserv., 1995, 4, 339–
362.
Parthasarathy, N. and Sethi, P., Trop. Ecol., 1997, 38, 19–30.
Davis, T. A. W. and Richards, P. W., J. Ecol., 1934, 22, 106–155.
Connell, J. H. and Lowman, M.D., Am. Nat., 1989, 134, 88–119.
Kadavul, K. and Parthasarathy, N., Trop. Ecol., 1999, 40, 247–
260.
Behera, M. D., Srivastava, S., Kushwaha, S. P. S. and Roy, P. S.,
Curr. Sci., 2000, 78, 1008–1013.
Behera, M. D., Ph D thesis, Gurukul Kangri University, Hardwar,
2000.
Behera, M. D., Kushwaha, S. P. S. and Roy, P. S., Geocarto Int.,
2001, 16, 53–62.
Champion, H. G. and Seth, S. K., A Revised Survey of Forest
Types of India, Manager of Publications, Government of India,
New Delhi, 1968.
Benewal, B. S. and Haridasan, K., Indian For., 1992, 112, 96–101.
Kaul, R. N. and Haridasan, K., J. Econ. Tax. Bot., 1987, 9, 379–389.
Anon., Statistical Abstract of Arunachal Pradesh, Directorate of
Economics and Statistics, Government of Arunachal Pradesh,
Itanagar, 1998, pp. 11–12.
Rodgers, W. A., and Panwar, S. H., New Forest, Dehra Dun, 1988.
Pal, G. D., Bull. Bot. Surv. India 1984, 26, 26–34.
Roy, P. S., Singh, S., Dutt, C. B. S., Jeganathan, C., Jadav, R. N.
and Ravan, S. A., DOS–DBT User Manual, Indian Institute of
Remote Sensing (NRSA), Dept. of Space, Govt. of India, Dehra
Dun, India, 1999.
Hajra, P. K., Verma, D. M. and Giri, G. S. (eds), Materials for the
Flora of Arunachal Pradesh, Botanical Survey of India, Calcutta,
1996, vol. I.
Haridasan, K., For. Bull., 1996, 3, 1–74.
Haridasan, K. and Rao, R. R., Forest Flora of Meghalaya, Bisen
Singh Mahendra Pal Singh, Dehra Dun, 1985, vol. I and II.
Bentham, G. and Hooker, J. D., Genera Plantarum, London,
1962–83, 3 vols.
75
RESEARCH COMMUNICATIONS
23. Kanjilal, U. N., Das, A., Kanjilal, P. C. and De, R. N., Flora of
Assam, Government of Assam, 1939, vol. III.
24. Kanjilal, U. N., Kanjilal, P. C. and Das, A., Flora of Assam,
Government of Assam, 1938, vol. II.
25. Kanjilal, U. N., Kanjilal, P. C., Das, A. and Purkayastha, C., Flora
of Assam, Government of Assam, 1935, vol. I.
26. Kanjilal, U. N., Kanjilal, P. C., De, R. N. and Das, A., Flora of
Assam, Government of Assam, 1940, vol. IV.
27. Mishra, R., Ecology Workbook, Oxford and IBH Publishers,
Kolkata, 1968.
28. Margalef, R., Perspectives in Ecological Theory, Univ. of Chicago
Press, 1968, p. 112.
29. Menhinick, E. F., Ecology, 1964, 45, 858–862.
30. Simpson, E. H., Nature, 1949, 163–688.
31. Shannon, C. E. and Weaver, W., The Mathematical Theory of
Communication, Univ. of Urbana, Illinois, 1949, p. 117.
32. Hill, M. O., Ecology, 1973, 54, 427–432.
33. Behera, M. D., Kushwaha, S. P. S. and Roy, P. S., Biodivers.
Conserv., 2001, 10 (in press).
Tectonic activities shape the spatial
patchiness in the distribution of global
biological diversity
Sagar Kathuria† and K. N. Ganeshaiah†,*,#
†
Biodiversity Documentation Centre, Evolutionary and Organismal
Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific
Research, Jakkur, Bangalore 560 064, India
*Department of Genetics and Plant Breeding, University of
Agricultural Sciences, GKVK, Bangalore 560 065, India
The most well-recognized pattern in the global distribution of biological diversity is that the tropics at
lower latitudes harbour relatively more species per
unit area than the temperate zones at higher latitudes1–10
and several arguments are forwarded to explain this
pattern6–8,11–13. However within the tropics, the biological diversity does not exhibit any distinctly recognizable patterns. Rather it exhibits a very patchy
distribution and we do not as yet understand the
factors and processes driving such patchiness. In this
paper, we demonstrate a strong spatial association
between tectonic activities (TA) and the areas of high
biological diversity (HBD), especially in the tropics.
We argue that TAs over long geological time periods
bring about altitude variations in their surrounding
areas, contribute to volcanic and magma mineral nutrients and bring about climatic changes, all of which
translate into habitat heterogeneity, facilitating a high
species packaging in such areas. Thus, we propose that
within the biologically-rich tropical belt, spatial
distribution of biological diversity is brought about by
the tectonic activities.
BIOLOGICAL diversity on our planet is concentrated in the
tropical belt, but our understanding of any patterns in its
#
For correspondence. (e-mail: [email protected])
76
34.
35.
36.
37.
Schmelz, D. V. and Lindsey, A. A., For. Sci., 1965, 11, 731–743.
Robertson, F. A., Vegetatio, 1978, 37, 43–51.
Pande, P. K., Trop. Ecol., 1999, 40, 51–61.
Odum, E. P., Fundamentals of Ecology, W.B. Saunders,
Philadelphia, 1963.
ACKNOWLEDGEMENTS. We thank Drs P. K. Hajra, K. Haridasan,
G. D. Pal, and Mr S. Das, for helping with identification. We also thank
Mr. Ashish Kumar of Wildlife Institute of India (WII) for his help and
support during field-data analysis. We are grateful to the constructive
criticisms given by the anonymous referee. This study was undertaken
with financial assistance from the Department of Biotechnology and
the Department of Space, Government of India in form of a research
project on Biodiversity Characterization at Landscape Level. M.D.B.
acknowledges Council of Scientific and Industrial Research, New
Delhi for the award of a senior research fellowship (No. 9/735/UC/99EMR-I).
Received 17 July 2001; revised accepted 7 October 2001
distribution within the tropics is very limited; less so of
the factors driving such patterns. It has been suggested
that the existing biologically-rich patches of the planet
could be viewed as Holocene refugia13, akin to Pleistocene refugia. Accordingly, just as certain pockets of the
planet served as refugia for biological diversity in the
Pleistocene era14–20, in the present human-dominated
world, a few areas inaccessible to human activities have
remained as less or undisturbed islands amidst an ocean of
human habitation, retaining a high level of biological
diversity. One common feature of most of these biologically-rich areas is high altitude variation associated
with habitat diversity13,21. Most of the hot spots and areas
of high biological diversity are concentrated in hilly and
mountainous ranges that harbour diverse habitats. While
the habitat diversity associated with the altitude variations
facilitates a high species package, the altitude variation
per se renders these areas relatively inaccessible, with the
net effect that they harbour high diversity13. Large-scale
altitude variations over vast areas are created mostly due
to recurring tectonic activities (TA) over long geological
periods. Thus it is likely that recurrent TA over long
geological time periods facilitates the concentration of the
biological diversity in certain areas. TA may also result in
high biodiversity in several other ways (see later in the
article). In other words, the patchy distribution of
biological diversity within the tropics might be predominantly determined by the distribution of tectonic activity
in this zone. We tested this relation by analysing the
spatial association between the global tectonic activities
and the distribution of biological diversity.
We used two data sets to represent areas of HBD:
(a) Hot spot (HS) maps13,22,23, and (b) areas of the
world with more than 1500 vascular plant species per
10,000 sq km representing high plant diversity (HPD),
from the maps prepared by Barthlott et al.24 Cologne
(scale 1 : 130,000000). The areas with 200–1500 species
CURRENT SCIENCE, VOL. 82, NO. 1, 10 JANUARY 2002