Forest Ecology and Management xxx (2014) xxx–xxx
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Forest Ecology and Management
journal homepage: www.elsevier.com/locate/foreco
Use and cultivation of plants that yield products other than timber from
South Asian tropical forests, and their potential in forest restoration
M.S. Ashton a,⇑, I.A.U.N. Gunatilleke b, C.V.S. Gunatilleke b, K. Tennakoon c, P.S. Ashton d
a
School of Forestry and Environmental Studies, Yale University, United States
Department of Botany, University of Peradeniya, Sri Lanka
c
Department of Biology, University of Brunei Darussalam, Brunei
d
Department of Organismic and Evolutionary Biology, Harvard University, United States
b
a r t i c l e
i n f o
Article history:
Available online xxxx
Keywords:
India
Mixed dipterocarp
Evergreen
Deciduous
Sri Lanka
Western Ghats
a b s t r a c t
Rural communities have traditionally valued forests for a diversity of products and services, with timber
serving a minor role. No-where has this diversity been greater than in tropical South Asia, and in particular south India and Sri Lanka. As economies advance towards full development and populations become
increasingly urbanized, forests become increasingly valued for their services. National development generally occurs at differing rates in different regions, with rural forest dependent communities falling
behind and pockets of poverty long remaining. The demand for ‘non-timber forest products’ (NTFPs)
therefore changes from subsistence to monetary based values. Overall, though, forests have suffered an
unprecedented decline with development in the tropics, especially in Asia. This necessitates restoration
which takes account of the enrichment of economy, wellbeing and culture which forest products provide.
Methods for such restoration, and the fundamental principles upon which these must rest, are presented
for species yielding NTFP’s. In this paper we first review the history of NTFP species use within south
India and Sri Lanka. Second we provide a description of the broad regional characterizations of the forest
formations within this region in relation to their affiliated patterns of NTFP use and exploitation. We consider seven guilds as a way to categorize NTFP’s into autecological groups for application in restoration
silviculture, and use it as a framework to suggest restoration protocols for South Asian forests. We use
examples of scenarios based on experimental studies of NTFP’s in reforestation trials which take account
of different social values and land tenures. We conclude with a call for further research.
Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction
Beyond the deserts, it is considered on ecological grounds that
tropical Asia, like South America, was continuously covered with
closed forest before the advent of humankind (Cerling et al.,
1997; Bond et al., 2005). Unlike Africa, these two tropical regions
lack the rich browsing fauna which reduces so much of the deciduous woodlands of seasonal Africa to orchard savanna or even
grasslands (Bond et al., 2003, 2005). In tropical Asia, only where
great rivers gush out of the Himalaya to extensive floodplains do
grasslands exist. But the use of fire by Asia’s human ancestors
has been dated to 1.8 million years ago, and hominid-induced fire
must surely have modified tropical Asia’s deciduous forests at least
since then (Bond et al., 2003, 2005).
⇑ Corresponding author. Address: 360 Prospect St., Yale University, New Haven
CT 06511, United States. Tel.: +1 203 432 9835; fax: +1 203 432 3809.
E-mail address: mark.ashton@yale.edu (M.S. Ashton).
Tropical south Asia has had the good fortune to retain traditions
of forest use of unique diversity and complexity. These traditions
survived remarkably intact through the many invasions of peoples
from the temperate north. Such invasions have in fact enriched forest use and tree agriculture. While the Dravidian cultures of South
India retained sophisticated traditions of plant use, the Indo-Arians, the Mughals and the European colonists brought fruit species
(Kosambi, 1975). These introductions became incorporated into
‘tree gardens’, diverse mixtures of trees that provide fruit, medicines and spices, which now characterize the more humid parts
of the region (Diamond, 2002).
Tree gardens have always remained a separate entity from the
natural forest whose uses also achieve an unequalled complexity.
Minority peoples in India and the rural poor in Sri Lanka are now
mostly confined to the un-irrigable lands of the hills, where the
remaining natural forest exists. These peoples conserve in their
traditions the specific knowledge of local conditions and habitats,
as a continuum of accretion since people first colonized these
http://dx.doi.org/10.1016/j.foreco.2014.02.030
0378-1127/Ó 2014 Elsevier B.V. All rights reserved.
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
2
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
forests. The introduction of irrigation technology, perhaps through
the dry warm temperate period of the Indus culture 4-2000 YBP,
provided the agricultural wealth and an ease of communication
that led to the first urban civilizations (Kosambi, 1975; Maloney,
1992). These in turn fostered the great indigenous religions, Hinduism, Jainism and Buddhism, and a documented pharmacopeia,
Ayurveda, that remains the foundation of medical tradition today,
in complement to the western ‘scientific’ tradition (Kosambi,
1975). The increased communication also led to homogenization
of knowledge and the spread of a more uniform tradition fostered
by lively regional trade in medicinals. Most of these species continued to be harvested from their indigenous forest habitats (Fox,
1995; Mahapatra and Mitchell, 1997).
But the last century has brought challenges to this progress.
Although minorities and other poor rural communities have continued to depend largely on their individual place-specific, and
more general Ayurvedic knowledge and resources, increases of
both rural and urban populations continues to foster increasing demand of NTFP’s (Chomnitz and Kumari, 1998; Bhakat and Pandit,
2003). Few current studies have critically examined whether and
to what extent demand can be met by natural populations. At
the same time, exploitative harvesting of some species for wider
markets is leading to threatened extinctions. This has been increasingly reported in the case of herbs from Himalayan alpine grasslands (Olsen, 1998; Adhikari et al., 2004); but even some
commoner tree species such as eaglewood (Aquilaria species notably A. krassna) in East Asia are being threatened (Chakrabarty et al.,
1994; Soehartono and Newton, 2001). It is both surprising and
worrying how few useful indigenous forest species have been
brought into cultivation; and how little experimental work has
been done on their silviculture. Research on restoration of degraded forests and wastelands has started to include species that
yield products other than timber. The principles and optimal methodologies for such restoration will be presented.
In this paper we first provide a review of history of NTFP species
use within the tropical region of southern India and Sri Lanka. Second we provide a description of the broad regional characterizations of the forest formations within the region in relation to
their affiliated patterns of NTFP use and exploitation. Third we describe the seven main functional and ecological categories (guilds)
of NTFP’s and provide ten economically important examples. We
consider the seven guilds as a way to categorize NTFP’s into autecological groups for application in restoration silviculture. We
use it here as a framework in our proposed restoration protocols
for South Asian tropical forests for different social and economic
objectives. We conclude with recommendations for further research and summarize present challenges of NTFP use.
2. A rich and complex history
People cannot survive without a ready supply of carbohydrates.
Plant sources in the tropics, doubtlessly also present in ancient
time as indicated by surviving nomadic cultures, include palm
trunk cores, yams (Dioscorea, Ipomaea and Colocasia), grass and
other seeds (Morrison, 2007; Zohari et al., 2012). Although the
starch yielding Metroxylon and Eugeissona palms yield important
sources of starch in the wet tropics of East Asia, neither exists
now in tropical South Asia (Ruddle, 1979), while cereal grasses
and the prevailing yam genus there, Dioscorea, are most abundant
in dry regions (Mahapatra and Tewari,2005; Zohari et al., 2012).
Humans arrived in sufficient numbers in South Asia perhaps
100 thousand years ago as the last north temperate ice age was
beginning to increase in intensity. During this cooling period, the
southwest Indian monsoon abated, probably for prolonged periods
(e.g. Wang et al., 2001). Much of the land was likely desert, but
there would also have been significant seasonal precipitation to
support deciduous forest, well provided with game and sufficiently
rich in carbohydrate sources to support nomadic tribes. Lowland
evergreen forests would have retreated to those foothill valleys
which continued to receive orographic rainfall. Evidence is accumulating, nevertheless, that humans were surviving in such forest
refuges both in the Western Ghats and in SW Sri Lanka, where rock
shelters provided escape from rain and predators (Perera et al.,
2011). Remains of carbohydrate sources have not survived, but a
Sri Lankan site yielded shells of Canarium nuts, sure evidence that
the surrounding forest was rain forest (Coronel, 1996). Dioscorea,
the major carbohydrate source for Peninsular Malaysian forest
negritos, would surely also have been important to South Asian
forest dwellers, while the possibility of an early discovery of flour
production would have permitted storage of carbohydrate from
seasonal tree seeds such as Vateria, and even the supra-annually
yielding beraliya (Shorea section Doona) in SW Sri Lanka (Gunatilleke et al., 1993). Such plant foods require cooking, so fuelwood,
along with hafts for cutting implements, digging sticks and other
tools would have been among early harvested NTFPs, as well as
medicinals which would surely have been gathered by ancestral
hominids (Morrison, 2007).
The date of arrival of cereal cultivation is unclear. The cereals
were, likely rice and millet varieties that would have been introduced from the north and east more than 10 thousand years BP
(Zohari et al., 2012). The main practice of cultivation would have
been swidden; that is to say by slashing forest patches, burning
the dried slash which releases nutrients, and cultivation until
weeds overtake the capacity to control, then abandonment to natural regeneration (Dove, 1983; Rangarajan, 1999). This would have
resulted in the first major change in human dependency on the forest. Here artificial canopy gaps would have been made for the first
time, increasing the relative area of successional stages in the forest. These gaps would have been small, having little effect on seed
dispersal for regeneration; and occupied for short enough periods
in wet climates to have limited impact on soil surface conditions.
The most abundant, and therefore many of the most used, NTFPs
are successional light demanders, and would have increased as a
consequence of swidden. The initiation of cultivation would also
have fundamentally changed the role of men and women in food
gathering. Whereas mixed bands, or men alone, would have foraged over the long distances formerly necessary to gather sufficient harvests of carbohydrate and many other NTFPs, Swidden,
following initial preparation by men, permitted cultivation which
women came to dominate. Women, who may always, as now, have
been responsible for woody litter fuel collection, also came to dominate the collection of many other accessible NTFPs growing in
nearby successional stands (Dove, 1983).
The arrival of irrigation, perhaps 3000 year BP, led for the first
time to permanent forest clearance (Kosambi, 1975; Maloney,
1992). This resulted in the retreat of NTFP species to non-irrigable
upland forest, much of which continued under swidden as populations expanded; to the fertile riparian fringes where woodland has
traditionally been retained as flood defense; and to the deciduous
forests of regions too dry for all but local irrigation, and where
many NTFP’s continued in intensive use and in abundance. Irrigation also produced the excess of food, notably cereals, and facilitation of communication and trade through road building, which
provided the means for the first cities, city states, and regional ruling hierarchies. Land tenure became settled and enshrined in tradition or law (Rangarajan, 1999; Sarker, 2011). That resulted, at some
time following the loss of the fertile lowlands to irrigation, and the
need for ready access to uncommon or long-lived NTFP’s, to the
origin of the woody ‘tree gardens’ for which the moister regions
of South Asia are so celebrated (Hochegger, 1998; Illukpitiya and
Yanagida, 2010).
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
Evidence from current plant distributions and the stone reliefs
in Borubudor, Java, and elsewhere, suggest that south Asians
migrating eastward during classical times accomplished the astonishing feat of transporting living seedlings, of NTFP-yielding indigenous forest tree species lacking seed dormancy, to East Asian
communities who still cultivate them: Syzygium, Artocarpus heterophyllus and Mangifera indica fruit trees, Cassia fistula with elegant
blossoms, Terminalia arjuna for feeding the Tussar silkmoth caterpillar (Hutterer, 1983; Ashton, 1999). And bananas, rambutans
(Nephelium spp.), mangosteen (Garcinia mangostana) and durian
(Durio zebithinus) came the other way (Hui-Lin, 1970; Hutterer,
1983). Whereas major trade in NTFP’s in the East Asian tropics
has developed with China over somewhat more than a millennium
(Lauffer, 1919; Kosambi, 1975), international trade with South
Asian nations, which included forest yielding spices (cinnamon,
pepper) has also been long established with Europe and the Middle
East (Crone, 2004). Starting during the Roman Empire c. 2 millenia
ago, and growing thereafter with the Middle East, trade in spices
again grew with the arrival of European colonial powers: in South
Asia, the Portuguese, then Dutch and British (Kosambi, 1975). The
Portuguese brought species that yield NTFP’s from tropical American forests for domestic use, and these uses have become incorporated into S. Asian culture: Many, including papaya (Carica papaya),
soursop (Annona spp.) and caimito (Chrysophyllum cainito) have become intrinsic members of South Asian tree gardens; and what
must food have been like there without chili? But the Dutch and
British established botanical gardens throughout the tropics for
the purpose of exchanging commercially useful plants, including
those yielding NTFP, worldwide, with the ultimate objective of
large scale plantation of those that proved profitable in international markets (Brockway, 1979; McCracken, 1997). The introduction of tea (Camellia sinensis), coffee (Coffea arabica, Coffea
canephora), and Hevea rubber, trees indigenous to evergreen forests in their places of origin, have changed the evergreen forest
landscapes of tropical South Asia on a massive scale (Brockway,
1979). It may seem extraordinary that not one of these commercial
introductions, even in its original form unimproved by selection,
has invaded native forests; this reflects the fine level of their niche
specificity to their source communities. Their large scale commercial plantations have weaned populations from traditional forest
products in favor of products in international markets, and have
doubtless resulted in extinctions (Dove and Kammen, 1997).
Now, no South Asian community is independent of wider markets.
The Dravidian cultures of the south retained sophisticated traditions of plant use, such as of the sugar palm Borassus fabellifer
for which an ancient sutra describes eight hundred uses (Fox,
1977; Cassou and Depommier, 2002), and groves of useful forest
plants such as the Soppina Betta betle palm groves which originally
served as a source of fuelwood, fodder and leaf litter for manure
and agriculture cultivation (Mani, 1985; Nayak et al., 2000). But
the tree garden has always remained a separate entity from the
natural forest whose uses also achieved an unequalled complexity.
Minorities, now mostly confined to the more remote lands of the
hills, conserve in their traditions the specific knowledge of local
conditions and habitats (Bhat et al., 2001; Davidar et al., 2008).
3. Characterization of forest formations, patterns of NTFP use
and forest exploitation
The tropical forests in south India (comprising the states of Kerala, Karnataka, Tamil Nadu and Andhra Pradesh) and Sri Lanka are
broadly correlated with the nature and degree of seasonality in
rainfall, ranging from mixed dipterocarp forests of the southwest
region and much of the Central mountain range of Sri Lanka, which
lack a dry season, to the thorn woodland of the dry east and central
3
on the Deccan and northwest and southeast of Sri Lanka, where
there are at least eight dry months (Fig. 1). A secondary axis of forest differentiation is correlated with elevation, in which there are
gradual changes in mean annual and seasonal temperatures along
with rainfall and, most specifically zones of cloud and fog, up the
mountains within the region, many of which ascend above
2000 m. The forests can be conveniently categorized, in relation
to their prevailing NTFP’s into seven regional formations modified
after Champion and Seth (1968); Gunatilleke and Ashton (1987)
and Ashton (1995, 2003). The seven categories are: 1. mixed dipterocarp forest; 2. seasonal evergreen dipterocarp forest; 3. semievergreen forest; 4. moist deciduous forest; 5. dry deciduous forest; 6. thorn woodland; and 7. tropical lower montane (some upper
montane) forest. The species yielding the most important commercial non-timber forest products within each of these forest formations and their regions have been summarized (Table 1) and
described in more detail by their distribution, ecology, use and cultivation (see Appendix I).
The lowland, including lower hill forests are confined below
750 m. There is then a gradual ecotone to 1200 m, above which
the montane forests are confined. The mixed dipterocarp forest exists as a refuge, of c.10,000 km2 in southwest Sri Lanka, and is an
appendage to the main part of the forest formation which dominates the lowlands of Sunda Land, 2000 km to the east. Mean annual rainfall may reach 5000 mm and is never below 2500 mm.
This kind of forest comprises both lowland and hill dipterocarp
associations and is species diverse, well stratified, and dominated
by high statured trees (30–45 m) in the genera Dipterocarpus, Mesua, Cullenia and Shorea.
Seasonal evergreen dipterocarp forest (both lowland and hill)
dominates the western foothills of the Western Ghats from Cape
Comorin north to Shimoga (Fig. 1). Receiving the brunt of the rains
as the southwest monsoon is forced up the slopes of the Ghats, annual rainfall can exceed 8 m, though there is also an annual dry
season of 2–4 months, increasing from the south. They are shorter
and less clearly stratified than the mixed-dipterocarp forest formation, except in sheltered coves (Subramanyam and Nayar, 1974).
Though generically similar, their communities lack some important endemic tree genera, differ substantially at species level and
are one quarter less rich. Both forest formations are now restricted
to government forest timber reserves and parks since most has
been converted to rubber, tea, coffee, rain-fed rice, coconut and
small holder tree gardens. Many of these lands outside of forest reserves and government lands are held privately by small-holders
or commercial estates. Much of the private land as well as some
government land has been abandoned and reverted to grass and
fern (see Ashton et al., 2014). The most commercialized non-timber forest products (NTFP’s) exploited from the remaining native
forest in these two forest formations comprise medicinals (such
as Coscinium fenstratum), cane (Calamus spp.) for artisanal work,
resins for incense and fragrance (e.g. Gyrinops walla), and sugar
from forest palms (Caryota urens) (Narendran, 2001; Senaratne
et al., 2003; Gopalakrishnan et al., 2005; Murthy et al., 2005)
(Fig. 2). In India, tribal peoples and farmers are much poorer than
the rural small-holders in Sri Lanka, and more heavily depend on a
host of subsistence NTFP crops that include litter for manure and
fuel wood for cooking (Mani, 1985; Jacob and Alles, 1987).
The moist deciduous and semi-evergreen forest formations differ in the obvious character of evergreenness that indicates rarity
of crown fires. Fire promotes the moist deciduous characteristic,
because all but a few evergreen species are fire sensitive even to
ground fires as seedlings, whereas most deciduous species even recover from crown fires by epicormic shoots. However, the two formations are often intimately integrated within the same landscape
with semi-evergreen occupying soils and landforms that are more
fire resistant (e.g. riparian areas, flood plains), and lands with lower
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
4
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
Tropical South Asia
se
se
dd
ARABIAN
SEA
Andhra Pradesh
ts
m
se Karnataka
Goa
Key to Forest Formaons
mdf – mixed dipterocarp forest
edf - dipterocarp forest
se - semi-evergreen forest
md - moist deciduous forest
dd - dry deciduous forest
ts – thorn scrub
m - montane tropical forest
* Shiroma
m
edf
md
Tamil Nadu
Kerala
100 N Lat.
dd
md
dd se
se
Cape Comorin
SRI LANKA
se
ts
m
INDIAN OCEAN
mdf
ts
Fig. 1. Regional forest types of South India and Sri Lanka depicting original extents of 1. Tropical wet evergreen forest (comprising lowland and hill rain forests); 2. Tropical
semi-evergreen (monsoonal) and moist deciduous forest; 3. Tropical dry deciduous forest and woodland; 4. Tropical thorn scrub; 5. Tropical lower and upper montane
forests. Current intact forests that now remain are shaded within each zone.
Table 1
Summary of properties of exemplar non-timber forest producing genera for tropical South Asia.
NTFP
Properties
Habit
Phenology
Habitat
Succession
Range
Use
Economy
Conservation
Vateria
Gyrinops
Caryota
Calamus
Elettaria
Coscinium
Diospyros
Santalum
T
E
C
C
LE
MNS
DL
N/E
T
E
U
C
SE
S
I
V
W
E
C
S
W
BMN
S
V
W
E
C
S
W
BCEMN
R
V
H
E
U
C
LE
MFS
DRI
V
V
E
G
P
SE
MC
SR
N
T
D
D
SC
W
MN
S
N
HT
D
D
SC
W
MS
I
V
Key: Habit: tree (T), vine (V), woody monocot (W), herb (H); phenology: evergreen (E), deciduous (D), hemiparasitic (H); habitat: gap (G) evergreen forest canopy (C),
understorey (U); deciduous forest (D); successional role: pioneer (P), stem exclusion (S), later succession (C); range: local endemic (LE), South Asian endemic (SE), Asian wide
(W); Uses: construction (B), cordage (C), furniture etc. (E), medicinal (M), food, drink, stimulant (N), flavoring (F), scent, cosmetic (S); economy: domestic (D), local market (L),
state (S), region (R), international (I); conservation status: not threatened (N), vulnerable (V), threatened (T), endangered (E).
frequency and intensity of human-induced fire. The moist deciduous forests primarily occur along the lowland western coastal plain
of Kerala, before and adjacent to the slopes of Ghats that promote
higher rainfall and the seasonal evergreen-diptercarp forest. Moist
deciduous formations (with some semi-evergreen) are also extensively found on the eastern foothills of the Western Ghats in Karnataka, and in the north-east peninsula mostly comprising
Andhra Pradesh and Orissa. In these regions dry seasons can extend up to six months of the year; annual rainfall is generally less
than 2000 mm. The moist deciduous forest that does remain includes teak (Tectona grandis) down the western coastal plain (Kerala) and Sal (Shorea robusta) in the north-east (Andhra Pradesh,
Karnataka). Sal is managed both as plantations and as native
forests for timber (Champion and Seth 1968). The native forests
of Sal are also characterized by Terminalia and Lagerstroemia species and are the forests richest in bamboo, especially Bambusa
and Dendrocalamus, which play a diverse and important part in
rural economies. Other NTFP’s include fruit trees (Mangifera spp.,
– Mango; Aegle marmelos- wood apple), plants of medicinal value
including gingers and amla (Phyllanthus emblica), food plants for
tussar silk moth (T. arjuna), a host of plants for the lac insect,
and trees of importance to both Bhuddist and Hindu religions (Ficus religiosa, Butea monosperma) (Sequiera and Bezkorowajnyj,
1998; Hegde and Enters, 2000; Sharma et al. 2006).
A distinct semi-evergreen forest is also represented along the
south-east coastal hills of Tamil Nadu and most of northeastern
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
5
Fig. 2. A series of photographs depicting NTFP’s in the mixed dipterocarp forest region of southwest Sri Lanka: (A) Rattan (Calamus thwaitsi) growing along the forest edge; (B)
Cardamom (Elettaria cardamomum var. Major) growing in an old skid road of selectively logged forest; El (C) tapping the inflorescence of kitul palm (Caryota urens) for sugar;
(D) Juggery sugar from kitul palm syrup
Sri Lanka, that Champion called dry evergreen forest. This forest,
dominated by evergreen species, is notophyllous. These regions receive some dry season rain from the north-east monsoon. In Sri
Lanka much of this forest remains as ancient second growth post
land abandonment from civilization collapse in the 1314th centuries (De Silva, 1981). Several such forests there are now wildlife
parks and reserves. This forest formation is characterized by Chloroxylon swietenia, Drypetes sepiaria, and the genera Diospyros, Ficus,
Lagerstroemia, and Terminalia. The NTFP’s utilized in this forest are
largely the same as those listed for the moist deciduous formation
(Shankar et al., 1998; Narendran, 2001). In India very little of this
forest remains but that which does has been degraded, sometimes
to grassland savanna by livestock owned by local communities.
The tropical dry deciduous forest formation occurs from the
foot of the Western Ghats on the eastern (leeward) side where
and rainfall is very seasonal, only amounting to between 900 and
1300 mm per year and with 6–9 month dry season. Most are subject to frequent ground fires, which can develop into crown fires in
moister climates, particularly where the exotic shrub Lantana camara dominates the understorey. This forest formation is widely
reduced to waste land by overgrazing and lopping in northern peninsular India but is still widespread in the south; in many regions
what forest remains comprise small relics that resemble savanna
woodlands or are protected as sacred groves around Hindu temples
(see Bhagwat et al., 2014). It is generally open-canopied; and includes tree genera such as Diospyros, Anogeissus latifolia, Vitex,
and various legumes such as Dalbergia lanceolaria and, more locally, Hardwickia binata. Second growth forests of this formation
have a rich history of use with many well-known NTFP’s of medicinal use (P. emblica), and wrappers for local bidi cigarettes (Diospyros melanoxylon) (Chopra, 1993; Sequiera and Bezkorowajnyj,
1998; Hegde and Enters, 2000). It hardly exists in Sri Lanka, where
its climate is restricted to the north-west.
The driest climate with woody vegetation cover supports tropical thorn woodland formation, extensive on the Deccan Plateau
and south-western Rajasthan and adjacent Andhra (Champion
and Seth 1968), and in the northwestern and southeastern corners
of Sri Lanka. These comprise low statured open trees such as Acacia
spp., Capparis spp., and Euphorbia spp. with sparse grass appearing
during the rainy season. This forest formation experiences a long
dry season, exceeding 9 months, with variable rainfall averaging
400–900 mm per annum. In Sri Lanka such forests comprise mostly
wildlife refuges. In India much of the land is tribal and community
owned and degraded because of poor control, weak regulation and
absence of consistent management practices. Some of the NTFP’s
exploited from the remaining forest comprise trees that produce
fragrant woods with medicinal properties and resins (Santalum album, Pterocarpus santalinus) (Ambasta, 1986; Anon., undated,).
Lower (and upper) montane forests are evergreen notophyll or
microphyll forests that are restricted to elevations over 900 m:
on both slopes of the Western Ghats, a few valleys in the north
of the Eastern Ghats, and the Central, Rakwana and Knuckles
Ranges of Sri Lanka. Rainfall typically exceeds 3000 mm per year,
with short dry seasons lasting from January–March though dry
periods may intervene over more of the year towards the north
of the Ghats. Again, much of this forest in Sri Lanka has been converted to tea, and extensive forest remaining is now in parks. In India conversion has been to coffee and livestock pastures towards
the north and on the drier eastern slopes of the Western Ghats.
In addition Sri Lanka has extensive areas of dark histosols, rich in
organic matter, which have been converted within the last thirty
years to vegetable production for consumption in nearby cities.
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
6
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
Much of the forest that has not been cleared has been cut for fuelwood for heat and cooking by these market garden farmers, and by
tea estate workers. Extensive areas of forest that remain have been
cleared of the understorey to cultivate the spice cardamom (Ellettaria cardamomum). This is particularly the case for the Knuckles
and Rakwana ranges of Sri Lanka, and primarily in Kerala and Karnataka in the Western Ghats (Anon., undated; Ambasta, 1986;
Dhakal et al., 2012).
mode of dispersal and germination (see Table 2). We believe our
framework to be general enough for use across all tropical forest
regions, but it is most applicable to tropical South Asia. Toward
that end we provide some well recognized (native and exotic)
South Asian NTFP species for easier understanding as guild examples in this section (see Table 3 for natives).
4. Functional and ecological categories of NTFP’s
Those plant species that yield NTFP’s that establish very early
after a disturbance and flourish in the open before canopy closure
from the next young stand of regenerating trees would be considered ‘‘pioneers of stand initiation’’ (e.g. gap phase; Whitmore,
1990). We identify two NTFP guilds within this stage of stand
development: 1. Pioneers that are shade-intolerant, fast-growing
herbaceous monocots, woody shrubs or herbaceous vines that
spread quickly through vegetative means but originally regenerated either from the soil seed bank (e.g. Clidemia hirta; Rubus
spp., blackberries) or from their dispersal as seed rain by small
birds and bats (e.g. Malpighia spp., acerola; Piper spp., pepper)
(Guild 1); and 2. those that are fast growing, shade-intolerant pioneer trees, that form a spreading crown (Guild 2). In the more ever
wet forest formations (mixed dipterocarp, seasonal evergreen dipterocarp and montane) Guild 2 species are generally large-leaved
with umbrella-shaped crowns, that are superficial-rooted and
weak in structure (e.g. Erythrinia spp; Macaranga spp., Trema
spp.,); but are very effective at usurping canopy growing space
and nutrients that would be leached post disturbance if such species were not present (Whitmore, 1990). In the more seasonal
moist and dry deciduous forest formations the species in this guild
dramatically reduce their leaf size and arrangement to produce a
more diffuse leaf canopy that is often deciduous (e.g. Gliricidia sepium, Albizia spp.). Some species in Guild 2 also fix nitrogen – a nutrient that is usually deficient after a severe soil disturbance.
In terms of categorizing their uses based upon their ecology,
NTFP’s in Guild 1 often produce multitudes of small fruits
that are high in sugar, and/or large roots and fruits that are important sources of carbohydrate (Solanum spp., potatoes; Manihot
To develop silvicultural guidelines for species that yield nontimber forest products, it is first important to develop a system
of identifying and then categorizing autecological traits that species have in common. This provides a systematic protocol for identifying the most promising species or species group for a given
silvicultural treatment (Smith et al., 1997). It has been well defined
for trees where differences in their shade and drought tolerance,
their successional status, together with their mode of dispersal
and germination provide a framework for regeneration methods
and post-establishment treatments. As far as we are aware this
has yet to be done for NTFP’s, probably because they comprise an
eclectic mix of growth habits ranging from ground-story herbs,
to vines to canopy trees (Ticktin, 2004). We present a simple
framework here restricted to both woody dicots and monocots
(mostly woody). Firstly, we have identified three phases of stand
development that we think important for characterizing an NTFP’s
successional status: (1) Stand initiation; (2). Stem exclusion; and
(3). Understorey re-initiation/old growth (after Oliver and Larson,
1996). Secondly we divide species that yield non-timber forest
products into seven functional groups (guilds) based upon their
growth habit, and stage of reproductive maturity (successional status) in relation to phase of stand development (Table 2; Fig. 3). By
characterizing plants that yield NTFP’s by these two major attributes, there is enough of a structural framework to identify some
common ecological themes among NTFP species that can provide
the basis for devising silvicultural methods of regeneration and
treatment (see Section 5). Within these guilds we describe their
4.1. The seven guilds
Table 2
Functional groups of plant species producing non-timber forest products as defined by their successional status (after phase of stand development – Oliver and Larson, 1996) and
by their growth habit in the wild. Examples of well known NTFP’s throughout the tropics are provided along with their uses.
Phase of stand
development
Growth habit
Autecological characteristics
Examples
NTFP uses
Initiation
1. Shrub-like
herbs, vines,
and shrubs
2. Small trees
Pioneers, shade intolerant, often clonal or from buried seed banks
Croton spp. Manioc,
Banana
Carbohydrate food
sources in fruits and roots
Pioneers, shade-intolerant, light-seeded, small bird or bat dispersed;
large-leaved in evergreen forests, small-leaved in deciduous forests;
water-use inefficient, fan or umbrella-shaped wide crowns, low wood
density, spreading, sometimes clonal
Pioneers and early successional, shade intolerant, fast-growing,
columnar, becoming small-crowned, tall
Albizia spp. Inga spp.,
Gliricidia spp., Macaranga
spp., Trema spp.
Nurse trees in mixed
cropping systems, nfixing, shade providers
Rubber
Nuts, fruits, latex and
Betel nut palm light
constriction timber
Spice
Utility wood
Medicinals, cordage, fiber,
medicinal, lac
Stem exclusion
3. Fast-growing
trees
4. Vines
Understorey
re-initiation
5. Understorey
shrubs and
small trees
6. Subcanopy
trees
7. Canopy trees
Shade-intolerant to shade tolerant, pioneers, requiring support from
trees in stem exclusion; fruits dispersed by small birds, bats and
mammals
Shade-tolerant, slow-growing, late-successional often clonal sprouting
and spreading, planar branches, with chemicals for protection; reliance
on advance regeneration
Shade-tolerant, slow-growing, late-successional, deep-crowned, with
chemicals and resins for protection; reliance on advance regeneration
Shade-tolerant, slow-growing, late successional, tall, large spreading
shallow to deep crowns, with chemicals and resins for protection,
reliance on advance regeneration
Cloves
Pinus spp.,
Rattan, Grape Butea
superba
Cacao, Coffee, tea
Medicinals, beverages,
spices
Gyrinops, Mangosteen
Fruits, incense, sugars
Dipterocarps Durian
Large carbohydrate fruits
resins, incense
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and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
7
Fig. 3. A graphical depiction of the successional position of each of the seven guilds over successional time.
esculenta, manioc). Species in Guild 2, because of their growth morphology, comprise almost all the nurse and shade trees used in
agroforestry systems. Many are now widely planted in the wetter
regions (Ashton and Ducey, 1999).
The second phase of stand development is defined by canopy
closure of the new regenerating stand, with intense competition
and self-thinning among competing trees (stem exclusion phase
of Oliver and Larson, 1996; the building-phase of Whitmore,
1990). The understorey is deeply shaded, and the crowns of the
stand are tightly packed and seemingly growing together. Species
that dominate the canopy of this stage of succession are ‘‘pioneers
of stem exclusion’’. Two NTFP guilds can be identified with species
that mature at this stage of stand development: (1) the trees that
embody the stem exclusion process – fast-growing, tall, columnar-stemmed, with tightly-packed crowns that are predominantly
shade-intolerant and if over-topped are quick to die (Guild 3); and
(2) the vines that depend on stem exclusion for support (Guild 4).
The pioneer trees of stem exclusion are some of the world’s most
productive timber trees for the construction industry given the
nature of their growth and stature, but they are also trees that
can efficiently produce abundant amounts of sap, latex and resin
(e.g. Alstonia spp.; Eucalyptus spp.; Castilla eleastica, Panama rubber
tree; Hevea brasiliensis Brazil rubber; Pinus spp, pine); and, given
space through thinning and cultivation, some are important producers of nuts and fruits (Spondias spp., – jobo; Syzygium spp. –
rose apple).
The other NTFP guild that dominates this stage of stand
development are vines. Vines can easily usurp this growing space
post-disturbance if the stem exclusion process is not uniform but
broken by edge and shaded by larger, older trees of the original forest (e.g. selective logging). The vines vary in their shade tolerance,
either waiting for the disturbance as advance regeneration in the
forest understorey (e.g. Calamus, cane) or originate from seed rain
(wind or small birds) after the disturbance (e.g. Vitis, grape)
(Schnitzer and Bongers, 2002). Many of these species yield cordage
and fiber (Calamus spp., Desmoncus spp.), while some species produce medicines from either the stem or from leaves and fruits (Passiflora edulis, Ziziphus oenoplia) (Ashton et al., 1997a; Parrotta,
2001). And the root tuber of Dioscorea spp. vines (yams), still
valued medicinally, were the original mainstay of hunter-gatherer
sustenance prior to agriculture within the South Asian region.
The third and last phases of stand development have been combined (‘‘understorey re-initiation’’ and ‘‘old growth’’ (mature phase
of Whitmore 1990) primarily because differences in their development do not clearly differentiate the autecology of NTFP’s. These
phases of development are later successional, where mid-successional tree species that come to dominate stem exclusion are overtopped by much taller-statured, longer-lived late-successional
species. Here, shading in the understorey becomes less homogenous as forest structure and foliage stratification becomes the most
complex, and new canopy gaps begin to form; persisting regeneration (e.g. advance regeneration) of the shade-tolerant late successional species re-establishes in the understorey, whose seed is
from the reproductively mature trees that have now ascended into
the sub-canopy and canopy. Species that mature and produce
NTFP’s at this stage of succession can be categorized into three
guilds: (1) understorey shrubs and small understorey trees that
are shade-tolerant, can often recover from damage by sprouting,
with planar branches maximizing light capture, produce small
flowers and fruits, and synthesize nasty tasting chemicals in their
leaves for protection (Guild 5); (2) taller subcanopy trees that usually have deep columnar crowns, are shade-tolerant, and produce
larger and more nutritious fruit than those in the understorey
(Guild 6); and (3). canopy trees that are long-lived, developing first
with columnar crowns which, once they attain the canopy, spread
to become conical or dome-shaped (Guild 7) (Ashton and Hall,
2011).
Understorey shrubs and small trees produce NTFP’s that comprise many medicines, beverages and spices because of the chemicals that they harbor (e.g. C. sinensis, tea; Coffea spp., coffee;
Elettaria spp., cardamom; Gyrinops spp.,; Theobroma cacao, cacao).
Similarly, late-successional sub-canopy trees produce the same
kinds of products but, because of access to more light, produce
fruits that are larger and more nutritious (e.g. A. heterophyllus,
Canarium spp., Garcinia indica (kokum), Pouteria spp.). The large
canopy trees often produce the most nutritious or carbohydrate
rich fruits because of their crown position’s access to the most
light, but many also produce incense and resins. These trees also
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8
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
Table 3
Guild categorization for some important native non-timber forest products in South Asia by evergreen and seasonal deciduous forest types.
1. Wet mixed-dipterocarp and seasonal evergreen dipterocarp forests
Initiation
1. Shrub-like herbs, vines and shrubs
2. Small trees
NTF species
Use
Colocasia spp.,
Dioscorea spp.
Elettaria cardomomum
Justicia adhatoda
Macaranga peltata
Root food (yam)
Root food (yam)
Spice
Medicinal
Wrapper
Stem exclusion
3. Fast-growing trees
4. Vines
Alstonia macrophylla
Calamus spp.,
Coscinium fenestratum
Piper betel,
Piper nigrum
Medicinal,
Cordage
Medicinal
Medicinal, masticant
Spice
Understorey initiation
5. Shrubs/small trees
6. Subcanopy trees
Agrostistachys coriacea
Caryota urens,
Garcinia gummi-gutta, G. indica
Gyrinops walla,
Semecarpus spp.,
Mangifera spp.
Shorea section Doona,
Vateria spp.,
Roof thatch
Syrup, sugar
Spice
Incense, resin, fiber
Medicinal,
Fruit food
Fruit food
Fruit food, medicinal
Barleria prionitis,
Capparis zeylanica
Carissa carandas,
Pandanus amaryllifolius
Phyllanthus emblica,
Medicinal
Medicinal
Fruit food
Cordage
Medicinal
Cassia fistula,
Cochlospermum religiosum
Butea superba
Religious
lac
Medicinal
Croton aromaticus
Butea monosperma
Erythroxylum monogynum,
Aegle marmelos,
Anogeissus latifolius
Areca catechu,
Bambusa spp.,
Borassus flabellifer,
Dendrocalamus spp.,
Diospyros melanoxylon,
Ficus religiosa
Mangifera indica
Mangifera zeylanica
Santlum album,
Terminalia arjuna,
Pterocarpus santalinus,
Medicinal
lac, religious
Medicinal
Fruit, food
Medicinal
Masticant
Cordage, furniture etc.
Sugar, syrup
Various
Wrapper, medicinal
Religious
Fruit food
Fruit food
Incense
Silk
Incense, resin
7. Canopy trees
2. Semi-evergreen, moist and dry deciduous, and thorn scrub forests
Initiation
1.Shrub-like herbs,
vines and shrubs
2. Small trees
Stem exclusion
3. Fast-growing trees
4. Vines
Understorey initiation
5. Shrubs and small trees
6. Subcanopy trees
7. Canopy trees
comprise species that produce the durable luxury timbers used for
furniture, veneers, flooring and heavy construction (e.g. Diospyros
spp., ebony; Durio zebithinus, durians; Mangifera spp., mangos)
(Whitmore, 1990; Ashton and Hall, 2011). These seven guilds can
be considered as a way to categorize NTFP’s for purposes of restoration of South Asian forests (Table 3).
5. Silvicultural treatments for restoration and reforestation
Silvicultural systems for NTFP cultivation in tropical South Asia
can be broadly categorized as those that rely upon natural regeneration and low intensity manipulations to secure natural regeneration for the desired species composition and structure without
planting; and those systems that rely upon intensive site preparation, planting and post-establishment treatment that more closely
control species composition and structure (Ashton et al., 2001a).
For use of NTFP’s in restoration and reforestation, this dichotomy
of intensive control (planting) and less intensive control (natural
regeneration) provides a means of categorizing management
approaches for a given circumstance.
5.1. Working with second growth forests
Second growth forests in tropical South Asia arise from two
kinds of human disturbance: (1) those that originate as early successional regrowth resulting from overharvesting timber; and (2)
those that were originally old pastures used for livestock or were
formerly agricultural. Those lands that were overharvested for timber are usually state or community lands (e.g. Forest Reserves).
Lands that were originally pastures are tribal or community lands
within the drier forest formations (dry and moist deciduous forest;
thorn woodland). Former agricultural lands that have reverted to
second growth are small-holder and commercial estates that originally cultivated plantation crops such as tea, rubber and coffee
within the wet forest formations (mixed dipterocarp; evergreen
dipterocarp; montane forests). In all these circumstances, when
there is already some forest structure and composition present half
the effort in NTFP species restoration has been avoided because of
either the presence of a nearby seed source within the regrowth or
because the regrowth structure provides the environmental protection needed for NTFP species establishment (see Ashton et al.,
2014; Gunaratne et al., this issue). If appropriate the most
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M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
economic approach is to work with what NTFP’s have already
established through natural regeneration. But where the forest
structure and composition is either absent or not desirable, then
the only alternative is to plant.
5.1.1. Restoration of NTFP’s in degraded forests
In circumstances where the existing forest has been degraded
through chronic (e.g. repetitive) exploitation of products (timber
and non-timber), the most important objective is to prevent the
chronic impact, and then either do nothing and let natural processes of stand development sort out; or facilitate these processes
through release treatments that control vines, and thin and select
trees that are undergoing stem exclusion for the future forest canopy. If degradation processes are top-down, from the extraction of
canopy trees through activities like selective logging, the focus
should be on restoration of the advance regeneration of late successional canopy species in the understorey (Guild 7) (see Ashton
et al., 2001a). If degradation processes from exploitation are bottom-up, from the removal of sub-canopy trees and shrubs through
activities such as the cultivation of shade coffee, cacao or cardamom (mixed dipterocarp, seasonal evergreen dipterocarp, and
lower montane forest formations), or from over-grazing the understorey with livestock (semi-evergreen, moist and dry deciduous
forest formations) then the focus of the restoration activities
should be on regenerating and facilitating the species composition
and structure of the forest understorey (Guilds 5 and 6) (see Ashton et al., 2001a).
Non-timber forest products in South Asian second growth forests that have originated after human disturbance (particularly
top down impacts) to primary or old growth rain forests can be
prolific and diverse (De Zoysa et al., 1991). There are several reasons for this: (1) there is an existing seed source within the residual forest itself that can easily be dispersed far and wide; (2). four
of the seven NTFP species guilds (Guilds 1–4; see Tables 2 and 3)
are pioneers of either stand initiation or stem exclusion – making
many species suited to high light and open conditions; and (3)
top down impacts in particular open up the canopy and create
openings sufficient to liberate the multiple resources of light, soil
moisture and nutrition for new forest establishment (Goodale
et al., 2012). Little attention needs to be paid to planting in these
circumstances, at least for those NTFP’s that are pioneers; but to insure their full stocking release treatments may need to be done to
remove competing vegetation (Chandrashekara and Sankar, 1998).
Many studies have shown that NTFP’s can be higher in second
growth forests that have been disturbed or logged as compared
to late successional or primary forests (Ticktin, 2004). Examples
can be seen throughout the tropics. This is particularly true for
the guild comprising NTFP’s yielding vine’s of the stem exclusion
stage (Guild 4). Examples are Calamus spp. (rattan) in Indonesia
post-swidden (Siebert, 1993), and Desmoncus after land clearance
in the floodplain forests of the Amazon (Troy et al., 1997). In South
Asia Calamus spp., Dioscorea spp., and Coscinium fenestratum have
been shown to flourish in logged forests (Ashton et al., 2001b; Muthumperumal and Parthasarathy, 2013). The pioneer NTFP guilds
comprising shrubs (Barleria prionitis, Carissa carandas, Justicia
adhatoda) (Guild 1) and trees (Macaranga spp., Alstonia spp., Coclospermum religiosum, P. emblica) (Guilds 2 and 3) of stand initiation
and stem exclusion are so ubiquitous after disturbance because of
their prolific seed dispersal (small bird, bat, and wind) and opportunistic establishment that they are often the dominant species
during early succession (De Zoysa et al., 1991; Ashton et al.,
1997a). Planting is therefore unnecessary.
The NTFP species guilds that are most sensitive to species’ loss
from top-down and bottom up disturbance processes in secondary
forests are the late successional guilds of canopy, sub-canopy and
understorey trees and shrubs (Guilds 5–7). These species rely upon
9
advance regeneration for their growth post-disturbance (see Ashton et al., 2001a). The late-successional NTFP species in the mixed
dipterocarp, seasonal evergreen dipterocarp, and lower montane
forests are usually neither common nor dominant within their
respective forest formations, and if they are it is a very local phenomenon (Gunatilleke and Ashton, 1987). If the parental seed
source has been lost because of their removal in harvesting operations then the only alternative is to enrichment plant the NTFP species within the new re-growth of the young forest. This does not
necessarily hold for the more seasonal dry forest formations
(semi-evergreen, moist and dry deciduous, and thorn woodland);
some NTFP species such as Anogeissus latifolius and D. melanoxylon
can be important components of dry forest composition (Champion and Seth, 1968). Further, these and other deciduous forest
species can regenerate in degraded forest, if not entirely destroyed,
by coppice shoots from persisting rootstocks (Champion and Seth,
1968). For those late successional NTFP’s, such as the edible fruits
from canopy trees of mixed dipterocarp and seasonal evergreen
dipterocarp forest formations (e.g. Artocarpus spp., Vateria spp.),
planting needs to be done within the re-growth where there are
sizable openings (Pelissier et al., 1998). These openings need to
be maintained to allow the trees to establish and attain the forest
canopy, without being impeded by vines, fast-growing pioneers or
the residual over story (Adjers et al., 1995; Pelissier et al., 1998).
Understorey shrubs (e.g. Agrostistachys coriacea, Croton aromaticus, Elettaria cardamomum) and sub-canopy trees (e.g. Gyrinops
walla, C. urens, Garcinia gummi-gutta, Semecarpus spp., Erythroxylum monogynum) of all forest formations can be planted beneath
the canopy; but timing is critical. Planting during stand initiation
(before canopy closure) or after understorey re-initiation (canopy
break-up) is best (Pelissier et al., 1998). This needs to be followed
by release treatments that maintain the immediate growing space
around and immediately above the planted seedlings until plants
are well established (Smith et al., 1997). Planting beneath regenerating stem exclusion stage forest will likely fail because of high
understorey shade and competition for resources with a wellestablished, vigorous canopy. Because these species are shade-tolerant creating large canopy openings should not be necessary
(Gunatilleke et al., 2006). Deciduous forest formations that are
devastated (i.e moist and dry deciduous and thorn woodland) on
the contrary, may need planting and establishment of nurse trees,
especially small-leaved light shade producing legumes, to establish
the eventual late successional canopy species, although these are
universally light demanders (e.g. D. melanoxylon, Santlum album,
A. marmelos, A. latifolius).
Some additional caveats to planting late-successional NTFP species in evergreen forests include the fact that: (1). many are site restricted, and are found on particular sites and topographic
positions, meaning that species site-specific guidelines need to
be developed (e.g. A. coriacea, E. cardamomum, Semecarpus spp.,)
(Wright, 2002; Gunatilleke et al., 2006); and (2). many of the
large-fruited species dispersed by large mammals and birds exhibit
density dependence, meaning that seedlings of the same species
should not be planted together or near their parent trees because
of susceptibility to species-specific insects, disease and seed predators (e.g. C. urens, Gyrinops walla) (Ashton et al., 2001b; Wright,
2002; Ashton and Hall, 2011).
5.1.2. Restoration of NTFP’s in second growth forests originating after
agriculture abandonment
Lands in the mixed dipterocarp, seasonal evergreen dipterocarp,
and lower montane forest formations that have been long cleared
for agriculture such as for tea, rubber, and coffee, and that were
subsequently abandoned and subject to periodic burning, revert
back to grasses and ferns maintained by use of fire (see next section). However, where fires are prevented and/or sites are wet
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
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M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
enough that the forest vegetation comes back with vigor (often
riparian areas) then a species depauperate second growth forest
can develop (Kodandapani et al., 2004). Such second growth is often low-statured, and dominated by one or two large-leaved pioneers of stand initiation that have strong abilities to vegetatively
sprout and spread (Dillenia spp., Clerodendron spp., Hibiscus furcatus) to form dense thickets that excludes the recruitment and
establishment of other species. Similar findings have been reported
elsewhere in SE Asia for the mixed dipterocarp forest (Chua et al.,
2013).
In deciduous forest and woodland formations, recruitment of
the core suite of fire tolerant coppicing tree species is usually more
diverse (Champion and Seth, 1968; Sagar et al., 2003). Their
understories are more suited to colonization by other late-successional tree species that are also fire tolerant, except where exotic
invasive dense-canopies of Lantana, or the perennial Chromolaena
and Parthenium (Asteraceae) have established and must be cleared
before reforestation can begin (Sukumar et al., 1992; Hiremath and
Sundaram, 2005).
There are several remedies that incorporate NTFP’s into these
monodominant vegetation thickets. All need a heavy hand in
removing existing vegetation (either manually or with a bull dozer), that then piles and burns the slash. This opens up the growing
space to either allow natural regeneration to establish site generalist and opportunistic pioneers (Guilds 1–4); or to promote a planting and cleaning regime for late-successional understorey,
subcanopy and canopy NTFP trees (Guilds 5–7) similar to those
suggested in the preceding section (Sagar et al., 2003).
5.2. Reforesting open lands
Open land generally means lands that were formerly forest,
were cleared for plantation agriculture (tea, rubber, coffee), and
because of poor markets, degraded soils, or insecure tenure the
lands have subsequently been abandoned yet have not regenerated
into secondary forest. Such lands, in the mixed dipterocarp and
seasonal evergreen dipterocarp forest formation regions of South
Asia usually revert to grasslands (Imperata cylindrica) or fernlands
(Dicranopteris linearis) that are maintained by fire (Cohen et al.,
1996). In the moist and dry deciduous forest formations the invasive shrubs L. camara, Chomolaena odorata and Parthenium hysterophorus can dominate particularly on the degraded soils of
wastelands (Kodandapani et al., 2004; Kohli et al., 2006). In circumstances like these, where little to no residual forest cover exists, establishing NTFP species within a new forest can be
approached in two ways. The first approach is to establish a firetolerant, fast-growing, often exotic, pioneer tree plantation (pioneer trees of stem exclusion – Guild 3), that can shade out the invasive grass, fern or shrub, facilitating natural regeneration of NTFP’s
(Guilds 1–4) or allowing for NTFP species under plantings (Guilds
4–7) (see Ashton et al., 2014).
The second approach is to establish NTFP species plantings together with planted or seeded pioneers of initiation and stem
exclusion (Guilds 1–4). This approach simulates a successional
agricultural system such as an indigenous swidden system. It requires intensive maintenance and careful control at the early
stages of development to weed out and maintain the growing
space for the planted NTFP seedlings within the pioneers, which given their nature can be very effective at crowding out competition.
Selecting the right pioneers is therefore critical. As the successional
processes of the new forest progress the intensity of maintenance
and control treatments declines to almost nothing.
5.2.1. Sequential reforestation
In some circumstances it would make sense to plant surrogate,
usually exotic species, categorized as pioneers of stem exclusion, as
an initial nurse crop on waste lands (Guild 3). These trees often
have the ability to usurp the growing space away from grasses,
shrubs and ferns (which are themselves often exotic), after which,
given some period of time, the plantation understorey becomes
conducive to the establishment of other native tree species. However, it was never consciously considered until foresters and
researchers observed the recruitment of second growth rain forest
in plantation understories of certain species (Parrotta et al., 1997).
Studies conducted within the mixed-dipterocarp forest formation at the Sinharaja Man and the Biosphere (MAB) Reserve in
southwest Sri Lanka have demonstrated that reforestation with
fast-growing fire tolerant Pinus caribaea is a useful way for controlling and extirpating crown fire and invasive species in wet climates, and facilitating the recruitment of native species through
natural regeneration after plantation canopy closure (Shibayama
et al., 2006; Tomimura et al., 2012; see Ashton et al., 2014); and
through enrichment planting (Ashton et al., 1997b; Ashton et al.,
1998). This work is supported elsewhere by other studies where
similar understorey recruitment of native species was reported
for Acacia mangium (Otsamo, 2000; Norisada et al., 2005); Eucalyptus (Parrotta et al., 1997; Kanowski et al., 2005); and T. grandis
(Koonkhunthod et al., 2007). However, studies have also suggested
that rain forest regeneration can fail beneath plantations because
of inability to prevent fire (Kanowski et al., 2005; Shibayama
et al., 2006); allelopathy from the exudates of the plantation trees
themselves (e.g. teak – Healey and Gara, 2003; Eucalyptus – Lamb,
1998); and deep shade created by the plantation canopy (e.g. A.
mangium – Otsamo, 2000). It therefore means that careful selection
of the plantation tree species for the circumstance at hand is critical for NTFP restoration.
Research at Sinharaja, in a wet aseasonal climate, demonstrated
that P. caribaea, a tree that shows no ability to naturalize in this
forest, has the capacity to increase surface soil organic matter
and water-holding capacity in the absence of ground fire, and promote diffuse understorey light of high quality and partial shade;
both environmental phenomena conducive to regeneration
recruitment (Ashton et al., 1997b). Our studies there recorded
the spontaneous establishment of a number of important NTFP’s
of all seven guilds (though mostly the pioneer Guilds 1–4) beneath
pine including the vine Calamus thwaitesii, the understorey latesuccessional trees Cinnamomum zeylanicum and Chaetocarpus castanocarpus; the subcanopy palm C. urens; and the canopy tree Canarium zeylanicum (Shibayama et al., 2006; Tomimura et al., 2012). To
secure higher stocking and control of NTFP’s supplemental plantings can be done. This may be the only alternative if there is no
nearby seed source from adjacent rain forest (Tomimura et al.,
2012). NTFP vine’s C. thwaitesii and C. fenestratum (Guild 4) establish well along the edges of canopy openings created within the
pine (Ashton et al., 2014). Planted seedlings of C. urens (Guild 6)
do best within the center of canopy openings of pine; and understorey trees and shrubs like E. cardamomum (Guild 5) do well beneath the pine canopy and along the edges of openings (see
Ashton et al., 2014). Plantings of most late-successional canopy
tree species (e.g. Vateria spp., Guild 7) showed greatest increment
growth in both diameter and height within those moderate sized
canopy openings where three rows of pine had been removed
(Ashton et al., 1997b; Ashton et al., 1998). As with planting regimes
within second growth forest (see preceding section) consideration
must be given to whether the species of choice is site restricted or
exhibits negative density dependence.
All of the results to date on facilitating natural and planted
regeneration that yield NTFP’s have been in the wetter forest formations. For the semi-evergreen and the seasonally moist and
dry deciduous forest formations, the idea of incorporating plant
species that produce NTFP into plantations needs to be tested. As
far as we are aware no trials have been conducted as of yet but
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
obvious plantation tree species to test are teak (T. grandis), Eucalyptus spp. and sal (S. robusta). Both teak and Eucalyptus spp. have
been shown to both facilitate and suppress natural regeneration
establishment elsewhere, so clearly, this needs further
examination.
5.2.2. Simultaneous reforestation through successional agriculture
The use of tree plantations to facilitate NTFP’s is a novel idea
that can be used on lands that require low investments and relatively low monetary rewards. However, there are plenty of open
lands where people are willing to invest labor and money for higher rewards. In such investments direct reforestation and restoration toward the use of successional agroforestry systems (e.g.
swidden systems) whereby agricultural food and commercial
annuals can be inter-planted with NTFP trees and shrubs that over
a period of years usurp the growing space first to pioneer shrubs
and trees of stand initiation (Guilds 1 and 2), then to pioneers of
stem exclusion (Guilds 3 and 4) and subsequently to understorey,
subcanopy and canopy late-successional NTFP trees (Guilds 5–7).
This plantation design would resemble a traditional stratified
indigenous tree garden, so familiar within the region (see Ashton
and Ducey, 1999 for details) (Fig. 4). Conceptually, such a system
may be a modern day swidden but, instead of a focus on subsistence crops, focus should be on commercial NTFP’s for today’s global and regional economies. NTFP’s are sequentially yielded over
successional time, eventually ending in a simplified but stratified,
second growth rain forest. The finances of similar systems have
been evaluated in comparison to the intensive commercial production of tea and income calculated is equivalent or higher (Ashton
et al., 2001b). The problems lie in the degree of sophistication
needed to practice such plantings successfully.
Currently, we write this based on only a few experimental studies done by us (Ashton et al., unpublished data). We are not aware
of any work that has demonstrated this through planting trials and
careful experimentation and publication; though clearly such ideas
have been descriptively recorded by researchers observing some of
the original indigenous subsistence swidden systems of the region
such as chena (Sri Lanka) and jum systems (western Himalaya)
(Spenser, 1966; Ramakrishnan, 1992; Arunachalam and Arunacha-
11
lam, 2002); and we suspect many current day reforestation/restoration plantings may have developed similar plantings but without
publishable records. The only well documented adoption of swidden cultivation techniques in modern day tree plantation systems
is the taungya system of Burma (Nair, 1984), adopted over
100 years ago!
5.3. Social and economic goals
Different socio-economic circumstances in forest ecological and
socio-economic conditions dictate which of a number of approaches in forest restoration with NTFP’s can be taken. When
the degraded forest or wasteland is owned by the government,
the planting of NTFP species is a reforestation incentive toward
promoting the co-management of land with a local community.
The ultimate government goal may be for park restoration, buffer
zone protection of nature reserves, watershed stabilization, or continued commercial timber production; but the use of NTFP’s is a
method of involving the community in forest restoration for protection. Approaches to achieve these goals are likely low input,
and low-intensity, utilizing nearby native forests as a seed source
for open lands and working with degraded native forests wherever
possible (as suggested above).
Approaches and opportunities for private landowners and commercial estates would be different, with incentives to more clearly
control forest structure and composition, with the expectation of
increasing income and species yield from NTFP’s as well as timber
for households (small private landowners) or the regional market
(large private landowners and estates). Options here are to plant
either through enrichment within second growth forests or to
reforest open land through plantation systems. Much of the extensive open land is either state or municipal owned. The opportunity
exists for lease arrangements with the state to incentivize private
investment in reforestation.
Clearly, there are many other variations in social goals and tenure regimes but we provide two general examples for government
and private approaches that can utilize the different restoration
models that we have described above.
Fig. 4. A series of photographs depicting the successional and growth habit changes of a mixed species plantation over a ten year period. The photographic time series is for
an experimental planting on. (A) Alang-alang (Imperata cylindrica) grassland in the Hantana highlands, Sri Lanka. (B). Pioneers of initiation (Gliricidia sepium) were planted as
live stakes with a site treatment establishing a nitrogen-fixing groundcover to secure open growing space. (C). Pioneers of stem exclusion (Alstonia macrophylla) and latesuccessional canopy trees (Michelia champaca) and understorey shrubs (Elettaria cardamomum) were planted one year later beneath the Gliricidia sepium. (D) Ten years later
Alstonia macrophylla dominates the stem exclusion stage of the plantation with Michelia champaca asecending into the canopy. (Ashton et al., unpublished data).
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
12
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
6. Management implications
6.1. Further research
In anticipation of a more prosperous future, and of a resurgent
rural economy with a renaissance of rural quality of life, researchers have been experimenting with different approaches to restore
value to degraded forests for rural communities, and to the plantations of exotic timber species that had, in effect, deprived them of
their traditional forest heritage. In particular, much more research
is needed to further examine and test techniques of cultivating
NTFP’s in both native forests and their plantation analogs. Some
areas of focus should be:
1. Rigorous controlled experimental trials in South Asia’s semievergreen, moist and dry deciduous forests, currently so
degraded by overexploitation especially by domestic cattle,
must be the future priority. So far, this work has focused on
the mixed dipterocarp and seasonal evergreen dipterocarp forest formations. Restriction of cattle to fenced pastures during
the wet monsoon will be essential if hay production and
thereby increased cattle health and carrying capacity, but also
tree regeneration, is to be achieved. As has been the experience
in the temperate west, and also in Rajasthan and elsewhere in
India, this may only be achieved by establishing land tenure
rights to individuals and families.
2. The development of growth and product yield estimates for a
range of NTFP’s in relation to variations in soil and climate
3. The testing and development of enrichment planting guidelines
for late-successional NTFP’s in second growth forests of all
formations.
4. Documentation of recruitment of NTFP’s beneath tree plantations within all forest regions,; and subsequent under planting
and canopy opening trials of late-successional NTFP’s within
such plantations.
6.2. Concluding remarks: The present challenge
The ideal economic transition from traditional to market economies is expressed in a Kuznets Curve (Fig. 5). It is the poorest
communities now that depend most on NTFP’s (Chomnitz and Kumari, 1998; Baghel and Gupta, 2002; Adhikari et al., 2004; Belcher
and Kusters, 2004). Chronic poverty ensues when these communities grow beyond the carrying capacity of their environment and
methods of cultivation known to them, while NTFP’s become
exploited beyond their capacity to yield (Tacconi, 2007); and when
family holdings become divided below food sufficiency, Such poverty can be overcome, either by the appearance of alternative
sources of income such as work in the city or for government; or
in part by reinvesting the profits derived from trade in the traditional resource – forest products in the present case – with the
aim of increasing its productivity (Chopra, 1993; Nair, 1984; Mohd
Shawahid and Awang Noor, 1999; Saxena, 2003). In either case,
development, manifested in the opening of the traditional forest
resource to the wider market, initially draws its value down as it
is exploited. But reinvestment can, by wise management actually
raise the value of the resource – the forest as well as crop species
– beyond former levels, thereby increasing the prosperity of those
dependent on it. If this returning profit is invested in the people
themselves, in their health and in particular their education (Saxena, 2003), they come, as in ancient times, to revalue the forest resource more for other qualities, notably services including the
forest’s capacity to moderate water supply and local weather, later
through its enhancement of the quality of life through its beauty,
tranquility, and later still its conservation of our local and global
natural heritage reflected in spiritual values, over products more
valued in the past. But demand for those traditionally valued products – protein as game, medicinals, cordage – may still persist albeit in a different way, for recreation, heritage, or in a persisting
niche market, spurred by the continuing respect, reliance on –
and proven success – of the Ayurvedic medical and philosophical
tradition (Saxena, 2003; Olsen and Helles, 2009). The forest, in part
because it is now so much smaller in area and has therefore itself
become a sort of rarity, gains a value in the successfully developed
economy vastly greater than it ever had. Such is the case of forest
resources and their value in Germany and in Japan, among the
leading developed economies.
Overexploitation eventually decreases supply. This should lead
to increased value and prices in an undistorted economy. But many
of those rural populations that endure persisting poverty will then
be less able to afford forest goods upon which they continue to depend. Often, suppliers to the market among the rural poor lose
what profit they can make to middle-men, who may keep them
in debt slavery by loans with unrealistic repayment rates. Meanwhile, overharvesting sustains undervaluation until extinction
approaches.
These problems are exacerbated by the fact that different regions and communities within every country are at different stages
in the development curve. Urban regions especially, generally at a
more advanced stage, exert unsustainable demands on the resources of communities as yet unable to protect their own interests, thereby increasing economic inequalities. Motivation can
Fig. 5. A graphic depiction of a Kuznets curve illustrating environmental degradation in relation to stage of economic development (Modified after Panayotou, 1993).
Please cite this article in press as: Ashton, M.S., et al. Use and cultivation of plants that yield products other than timber from South Asian tropical forests,
and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030
M.S. Ashton et al. / Forest Ecology and Management xxx (2014) xxx–xxx
only be reinvigorated by restoring a sense of ownership. Legislation is essential to ensure that all communities have the opportunity to follow the Kuznets curve (Fig. 5) to a satisfactory modern
economy. When the forest has become most degraded, and is often
least valued, those products and services that remain are exploited
to extinction unless the motivation is reversed, protection afforded, and restoration achieved. Lest we forget, species extinction
is irreversible.
Acknowledgements
We would like to thank the MacArthur Foundation, USAID PSTC,
Norwegian Aid and our respective Universities (Peradeniya, Yale
and Harvard) for funding and infrastructure support. We also
acknowledge the help received from numerous technicians (M.A.
Gunadasa, T.M.N. Tennakoon, B.W. Gunasoma) and graduate
students (Sunil Gamage, Chisato Tomimura, Tomohiro Shibayama,
Andrew Cohen, R.M.C.S. Ratnayake, Bandulla Senerath, Chandrakumara Artigalle). We are indebted to Prof. Kamal Bawa who was
associated with the USAID PSTC grant and for guiding us during
the NTFP species pollination biology project at Sinharaja and the
National Resources, Energy and Science Authority, Sri Lanka for
administrative support of the local components of the grants.
Appendix A. Supplementary material
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.foreco.
2014.02.030.
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and their potential in forest restoration. Forest Ecol. Manage. (2014), http://dx.doi.org/10.1016/j.foreco.2014.02.030