11. REVIEW OF LITERATURE

REVIEW OF LITERATURE

Success~on IS one of the most Important directional forces drlvlng vegetation (Horn

1974). Change In specles composition and processes, of communities over time is known

as ecolog~cal succession (Van der Maarel 1996; S~ngh el al. 2006). Most of the work on

successron concentrates on vegetat~onal development. There are three main types of

sucesslons dependrng on the h~story and lnrt~al cond~t~ons of the landscape. Succession

occurring on newly exposed substrate IS called pnmary successlon. as on volcanic

depos~ts. dune sand. and mud flats. Land that has been d~sturbed by eventirecumng

events l ~ k e fire, floods, humcanes, agnculture and pasture use, has topsoil, and exist~ng

sources for regeneration In the form of seed banks or tree stumps, and the vegetational

development on r t 1s called secondary successlon. Secular succession concerns long-term

vcgetat~onal changes to changes In cl~mate covering thousands of years. (Clernents 1916;

Van der Maarel 1996)

Success~on IS an old concept proposed nearly a century ago, but has seen lncreaslng

volumes of l~terature produced on the subject, attesting to 11s Importance in the current

scenano of land degradat~on. The subject has seen many theones, models and field

studres debat~ng d~fferent polnts of view, and therr ~mplicat~ons for central for restoration

ecology and b~od~vers~ty conservation.

It is now agreed that most of the succession seen 1s sequential, w~th one set of species

being replaced by that of another which is usually longer lived, with herbaceous species

being replaced by woody species (McCook 1994). This IS though by no means the only

pathway possible, with cyclic successlon and autosuccess~onidemographic being other

possibilit~es (Huston & Smlth 1987; Ylh et al. 1999; Platt & Connell 2003).

Clements (1916) was the first to suggest the concept of change in vegetation. According

to hlm the process of 'nudation' or formation of a bare area, was followed by 'migration

of specles', whlch lead to 'ecesls' or establ~shrnent of the spectes. The establ~shed species

produced a 'reaction' by altenng the habitat (eg casting shade, improving soil fertility) in

whlch they occurred, malung II more sultable for other life-forms, but detrimental to their

own existence as they could not compete w~th the new amvals. Th~s produced a

sequential replacement of specles, wlth the propagules of the later stages arriving at the

disturbed sue by 'relay flonstlcs'. He considered this pattern of succession more

appl~cable for pnmary successlon but not secondary successlon which could have a

exlstlng seed bank or root-stock for regeneration. The succession produced progressive

stab~l~zatlon leading to a slngle endpoint, a cllmax he defined by an assoclatlon of trees

that was slmllar to an 'super-orgasm'. An lmportant finding ln tus study that species

lnteractlon are facultative amel~oratlng so11 and mtcro-habltat and habitat conditions for

subsequent I~fe-forms was largely Ignored till the md-e~ghties when the role of posltive

interactions began regaining focus In ecological research (Bertness & Callaway 1994;

Bruno et al. 2003 ) as an Important process to be considered during succession and wlth

practical application In rcstoratlon of degraded landscapes (Castro 2002, 2004; Gomez et

el. 2004; Brooker et al. 2008).

Clements' concept of a 'super-organ~sm' was strongly refuted by Gleason (1926), who

considered that communit~es were ~ndiv~dualistic. This concept was camled further by

Egler's (1954) concept of 'Initial florist~c compostt~on' where the d~fferent growth rates

of species, that all occur from the lnlt~ation of success~on determines successlon, w~thout

leadlng to a slngle climax. Wllson eral. (1992) polnted out that there have been two

interpretat~ons of t h ~ s concept by researches through the years. In one Interpretation, that

they call 'complete lnltlal flonstlcs', propagules of all the specles needed for successlon

are w~despread and so available at every site In an area that experiences d~sturbance, as

ascnbed to by Connell & Slatyer (1977), Whittaker (1989). Whitmore (1989) and many

others. The other 1s called the 'pre-emptlve lnltlal floristics', where the specles that are

present ~ n ~ t ~ a l l y , dominate success~on and Influence ~ t s course by pre-ernptlng other

specles. According to thls lnterpretatlon, a d~fferent set of ~ m t ~ a l specles may be present

on other sltes. The two d~ffenng ~nterpretatlons have Important lmpl~cat~ons for land

management

Pickett et al. (2001) studylng successlon In the Buell successlon found that woody specles

appeared early In successlon. but were not able to establish successfully. Therefore

'volleys of ~nvaslon' by the same specles were necessary before the later successional

species could establ~sh In a site.

Besides the timrng of the propagules' arrival at the site, the I~fe-h~story traits of the

species were also wns~dered ~mportant to explain the sequence of species normally seen.

Different strategies, of life expectancy. slze, dispersal, growth and survival of specits

adapted to different polnts In succession were considered by Dmry & Nisbct (1973).

Gnme (1974) described three l ~ f e history strategies based on a comb~nat~on of two factors

stress and dlsturbance at different levels. Ruderals found in areas w~th low stress

(resource availab~l~ty) and htgh disturbance are usually herbs; stress tolerants occumng in

hlgh stress and low dlsturbance, are usually herbs, shrubs and trees; and competitors

found In places w~th low stress and low dlsturbance, are usually shrubs and trees.

Gleason (1926), Egler (1954), Dmry and Nlsbet (1973) did not consider interactions

between plants In thelr theories Tllman (1985) proposed the resource-ration hypothes~s

that cons~dered competltlon for resources and tradwffs in life-h~story traits in plants to

deal w~th resources. If these resources are inversely proportion as nltrogen availability

and light lntenslty are, then sequentlal replacement of species occurs. wthout sayng how

the resources change.

Huston & Sm~th (1987) too proposed a competltlon model for resources but based on

~nd~v~duals. They made no aprrorr assumption of correlation of I~fe-h~story strategies to

d~fferent polnts tn successlon, and took into account that many resources have been

proved to be ~nversely correlated In them ava~lab~lity. They stated that when plants are

adapted to explo~t one set of conditions (resource availability or environmental

conditions) and cannot compete In other cond~tions, plants have inversely correlated traits

and this produces sequentla1 replacement. Divergent, convergent, cycllc and suppressive

succession arc possible with different combination of life-history tram Their model

without explicitly stating it, considers that the change in conditions is brought about by

the plants themselves, thus explalnlng the change in envrronmental condltlons and

species sequence seen usually In successlon.

Horn (1974) described successlon as a plant- by-plant replacement process based on I~fe-

history traits of slze, age, growth rate of establishment and shade tolerance, without

considenng specles Interaction. Plcken (1976) expressed the same Idea genetically,

stating that ~t 1s lmportant to malntain the tram that allow ~t occupy a point In the

contlnnum of condlt~ons that charactenze succession but also have some vanabll~ty to

survlve In new condltlons

Connell and Slayer (1977) cons~dered the role of Interactions as central to the process of

successlon and proposed three different possibilities facilltat~on, Inhibition and tolerance

and their model has been the most lnfluentlal since Clements' concept (1916). Many

researchers now try to determlne the pathway that predominates a landscape before

recommending appropnate management practices for forestry or restoration (Kobayasht

2004). Walker and Chapln (1987) though conslder that forces cannot be segregated Into

three pans, and that more than one interaction maybe Important In any succession, with

facil~tat~on more Important In the lnltial phases and cornpetltlon more widespread later.

They considered blologlcal Interactions important to determlne not the outcome but the

rate of succession.

Rejmanek and Leps (1996) found that a particular assoclatlon could also change from

negative to neutral to negatlve again. Brooker and Kikividse (2008) stress the need to

differentlate between the lntenslty of competltlon, which 1s ~ t s absolute Impact, and

importance, whlch 11s vimpact relatrve to its environment. So even ~f competition or

negatlve lnteractlons are detected it is necessary to determine ~ t s Importance.

Greig-Sm~th (1952) Interpreted the 'super-organism' concept of Clements (1916) as

impllng "direct Interactions between Individuals both of the same species and d~fferent

spec~es" and studled palrwlse Interaction to deteremine ~f the Interactions were more in

the cl~max. He found that the secondary forest had more posltive lnteractlons w~th the

least In the prlmary forest. Focusing on species Interactlons, many stud~es have tned to

quant~fy the ~nteractlons, and study the trend in change of the typeislgn (pos~tive or

negat~ve) through succession.

Gre~g-Sm~th (1952) proposed the p~oneer-buildmg-mature phases for Interactlons.

According to t h ~ s hypothesis. dunng the pioneer stage there IS small scale heterogeneity

and the d~spers~on of spec~es IS random. In the burldlng phase, due to reproduct~on,

grouplng of plants occurs, so there are more number of Interactlons found. In tlme these

patches grow and coalesce, so the d~stnbut~on of indiv~duals IS random again. Grelg-

Srnlth (1952) formulated thls hypothes~s based on a study of chronosequence of tropical

forests. The recovering forest aged 15 years had the most number of interaction the

younger forests less, wlth the pristine forest having the least number of mteractlons- all of

which were positive.

Myster and Pickett (1992) formulated three hypotheses of which two are based on the

findlngs by Bauaz (1979) and Parish and Bazzaz (1982) of competltlon in early stages

of succession and the prevalence of broad n~ches for early successional species and

specialized ntches for the later successional specles. ( I ) There should be more

Interacttons and increase In intens~ty of lnteracttons with time and (2) there is more

competltlon among annuals and b l e ~ u a l s compared to perennials. (3) Abundant native

specles are ~nvolved In more Interactions compared to exotics, slnce abundant species

may be funct~onally domlnant and Interacting (Crawley 1986).

Testlng these hypotheses In the old field Buell success~on In USA, Myster and Plcken

(1992) found no proof for the first hypothesis, as the number of lnteractlons decreased

over 18 years. There was proof for the second hypothes~s, as there were more interactions

between annual and blemuals than among perenn~als and there were relatively more

poslt~ve lnteractlons than negative ~nteractions. It was the exotlcs that were more

abundant and lnvolved m more lnteractlons; In the later seres when the natlve species

~ncreased In abundance they were together m more Interacttons.

T~lman (1990) considered herblvory as an environmental factor on par with nutrient and

light availability, that determines trade-offs In competitive ability In plants that can

influence the course of succession. Interspec~fic assoclatlons withln plant communities

are a result of aggregated populat~ons, whlch result as a product of reproduction

(vegetatively), symbios~s/positive or m~cro-hab~tat heterogeneity like soil, topography,

light ctc. (Smith 1954). Comparing painvise interactions she found that the number of

interactions were decreased by grazing, as grazing pressures eliminate more favourable

mlcro-sltes and make the habitat more uniform, w~th a subsequent break down in

Interacttons.

S~milanly G~tay & Wilson (1995) found that grazing Increases heterogeneity at (0.1 m x

O.lm) scale, that is the average size of b~te of herbivores, but decreases heterogeneity at

larger scales. Studyng associations In landscapes - aged 1-28 years- protected from fire

and grazlng, they found that the lnteractlon panem followed the p~oneer-buildmg -mature

phases of Greig-Sm~th (1952). as a result affecting community structure.

Posit~ve lnteractlons In particular, as an Important ecolog~cal process in stable and

successional communltles are lncreas~ngly documented, in contrast to early ecological

schools of thought which concentrated on compehtlon and consumer processes to expla~n

the regulat~on of populations and communltles (Bemess & Leonard 1997; Stachowicz

2001; Brooker et al. 2008).

Posit~ve lnteractlons can create new habitats, In wh~ch many small scale positive or

negatrve tnteractions can occur (Jones 1997; Bruno et al. 2003), by ameliorat~on of stress.

Stress according to Stachow~cz (2001) is any exuinis~c condition that effects an

indiv~duals s u ~ ~ v a l or fitness, and can be physiological (example temperature, salinity,

drought conditions), phys~cal (e.g effects of wind, waves, currents) or biotic (competition,

predation, disease). Any organism that d~rectly or ~ndirectly Improves the environment

for individuals of its own species or other species is a habitat modifier. Jones (1997)

called the process ecosystem engineering and the species responsible for it as ecosystem

engineers. Many habitat modifiers whlch are the basis, on which entlre communit~es are

built, were called foundat~on species by Daylon (1975). Jones (1994, 1997) identified two

types of ecosystem engineers -autogenic and allogenic. He defined them as follows-

-autogenlc physlcal engineers directly transform the environment via endogenous

processes (e.g. tree growth, development) that alter the structwe of the engineer and the

engineer remains part of the engineered environment.

-allogen~c physlcal engineers change the envtronment by transfomlng hvlng or

nonllvlng materials from one phys~cal stage to another, and the engineer is not

necessarily part of the permanent physical ecosystem structure (eg. beavers).

The benefits accrulng from assoctatlon w~th habltat modlfiersl ecosystem engmeers can

vary. For intra-specific and inter-specific ~ndiv~duals thls may be defense agalnst

common predators or ameliorat~on of stress by virtue of their density or creation of

favourable m~cro-cllmates for ngeneratlon. The seedling and juvenlle stages are the most

vulnerable stages In a plant's life-hlstory, so favourable temperature, soil moishlre and

fertility conditions, protection against predators provided by adults can increase the rate

of survival and establishment of even conspec~fics, out welghing costs of even intense

competition (Bemess & Yeh 1994; Bruno 2000). Groups of indiv~duals could withstand

physiological stress better than sol~tary indiv~duals m conspeclfics of Iva ,frtescens, a

marsh elder. The scadlings of the elder were able to survive under adult can-specifics,

since the shade of the adult reduced evaporation and thus resultant soil salinity as

opposed to bare patches (Bertness & Yeh 1984). Positive interactions among con-

specifics have helped in maintainrng the upper inter-tidal limit of mussels (Bertness &

Leonard 1997).

The idea that facilitatron can benefit other species though promoted by the early

ecologists has been garnering ev~dence only recently and its implicat~ons for the

comrnunlty structure and functlonrng are greater than intra-speclfic facil~tations

Stachowicz (2001). There can be more than one inter-specific habitat modifer or

ecosystem engineer, whose effects may be small, and be practically indrscemrble or

slgnlficant enough to create new habitats (Jones et al. 1994; Jones et al. 1997). The

multiple eco-system engrneers sometimes interact together to enhance or degrade a

habitat (Brarser et al. 2008). S ~ m ~ l a r to rntra-spec~fic facilitation, inter-specific facllltation

too occurs by providing refuge from predators, nutrient transfer, trophic facilitation and

protection from competition.

Protectron from predation results. when plants in manne and terrestrial envimnrnents

suffer less herbrvory and Increase fitness by growing with species unpalatable to the

herbwore (Atsan & Dowd 1976). Insects l ~ v e on plants that have chemical defenses

(Bemays & Graham 1988). Troph~c facilitation can occur through many specific plant-

animal mutalisms like pollination and seed dispersal. When the plants are keystone

species like figs, a breakdown of the fig-figwasp mutualism can have Important

ecosystem level consequences (Hanison 2000). Nutrient acquisition in plants occurs in

stressful conditions by classic symbiotic associatrons like nitrogen-fixing bacteria in

nodules of legumes and due to the presence of endolecto myconhizal fungi (Stachowicz

2001). In fact some of these mycorrhizal fungi are the reason for the mono-dominance of

certain trees species, affecting the community structure of a forest.

Ants associated with Acacia spp, protects the trees from herbivory and other competing

plants and In return is provlded food and domictie by the plants (Janzen 1966). Posrtive

species-~nteractions have several Important consequences. They can Increase or decrease

species diversity in a place. Olne,ya lesora that acts as nurse plant has a greater number of

species growing In ~ t s shade than In bare areas of the Sonoran desert (Suzan et al. 1996).

On the other hand two ecosystem engineers, the white-tailed deer (Odocoileus

virginranus) and the lnvaslve plant Japanese stllt grass (Microstegium vimineum), Interact

to completely alter the structure and composltion of the subcanopy wlthln northern

dec~duous forests In USA, thereby decreas~ng the number of bird specles that were

dependant on the mid-canopy for nesting sites and food (Balser et al. 2008).

So though the effect of fac~lltatron on a local scale can either decrease or Increase

d~verslty, on a larger scale by increasing spatlal heterogene~ty, positive Interactions

Invariably Increase divers~ty at the landscape level and further at the ecosystem level tw

(Jones et al. 1997; Wright & Jones 2007). Since the effect that ecosystem engineers have

on the physical space in whlch other species live and these direct effects can last longer

than the llfetime of the organism - engineenng can in essence outlive the engineer

(Hastings et al. 2007). Thus ecosystem engneering/facilitation can enhance species

richness and composltion stability over time to change patterns of species dominance

(Badano a al. 2006).

There are variations In the strength of facilitation, which increases spatially, with thermal

stress, predator pressure and lower lat~tudes (Bertness & Leonard 1997; Stachowlzc

2000) and temporally, Increases In dner years (Gdmez-Apancro et al. 2004). When stress

decreases and benefits from posltlve Interactions decrease, competltlon becomes more

Important, so mutual~sm and competition are a continnum of interactions (Bronstein

1994; Stachowtzc 2001). However Mlchalet (2006), show that both negative and posltlve

interactions can occur at the same tlme, w~th the net effect being posltlve In tlmes of

stress. Vanous factors l~ke age of beneficiary or land facilitator and the presence of above

ground or below ground competltlon between the two can result in fitness loss for ecther

(M~chalet 2007).

The Importance of stress In determlnlng plant-plant relationsh~ps has been established

and evidence of fac~l~tat~ve effects between plants tended to come from severe

environments, such as deserts, arctlc or alplne tundra systems, or salt marshes. Increased

env~mnmental severity appeared to Increase either the potentla1 for, or strength of,

positive interactions, relative to negatlve interact~ons, thus shfting the observable net

interactions toward facil~tatton In extreme envlmnments (Callaway & Walker 1997;

Gdmez-Aparicio et al. 2004; Cav~eres et al. 2006).

The stress gradient hypothesis (SGH) based on the model of Bertness and Callaway

(1994) which includes both stress and consumer pressure as forces pmmotlng facilitation

exmints pancrns across gradients. Studies conducted along various stress gradients to

test thls model found confllctlng evldence for the SGH model. Choler et al. (2001) found

that increas~ng altitude was associated wlth lncreaslng frequency of facilitative

Interactions. They also found that facllitatlon depended on specres identity and facilitated

specles were common at the extreme ends of their env~ronmental tolerance and led to

range expanslon. Along the andity gradient (Gomn-Apanc~o et al. 2004, Agular & Sala

1999) found nurse plants ameliorated water stress, but Tielborger and Kadmon (2000)

found that wlth Increasing ramfall, the lnteractlons changed from negatlve to neutral, and

then to beneficlal In desert herbs facilitated by shrubs. However, Maestre et al. (2006)

found In a meta-analysis that there was no Increase in elther negatlve or posltlve

lnteractlons between plants in arid and semiarid environments.

The Importance of posltive lnteractlons has now been accepted and there- are many

attempts to Integrate ~t Into vanous general concepts to explaln population, community

and landscape level ecology. Bruno et al. (2003) have proposed a revlslon of the niche

theory. posltlve density dependence at high population densities, relatlonshlp between

specles dlverslty and community lnvlslbillty and role of competltlve dominants. The

expanslon of nlche is based on the model proposed by Hacker and Games (1997). where

the reallzed nlche is expanded by facllltat~on, which is itself a modification of the

intermediate d~stwbance hypothes~s (Sousa 1979). This model can in fact explain

Increase in diversity by facilitation wlth Increasing disturbance from medium to severe.

Michalet et al. (2006) further developed these ideas, suggeshng that facilitation promotes

diversity at medium to high environmental severity by expanding the range of stress-

intolerant competitive specles into harsh physical conditions.

Since facilitation has been recognized as an important stmcturing force In natural plant

commun~ties, 11 is be~ng recommended for developing vegetation restoratlon tools,

part~cularly in severe and h~ghly disturbed envmmments. Many ecosystem

engineersifac~litators have s~gn~ficant effects on Important ecosystem processes of

management concern-hydrology, nutrient cycling and retentlon, erosion and sed~ment

retention, for examplewh~le at the same time creatlng habitat for other specles that also

Influence b~ogeochem~cal processes vla nutrient uptake, conversion, and release (van

Breemen & Flnz~ 1998). 'F~nally, humans are often responsible for the loss or

~ntroduction of such englneenng specles, with the potentla1 for large secondary

consequences' (Coleman & W~lliams 2002). So there is cons~derable potential for

applyng the ecosystem englneenng concept in management. Ecosystem enpneers can be

Important tn controlling local m~croclimate and could therefore be ~nfluential In

maintatn~ng refuges for other species, even In the face of climate change (Cavieres et al.

2002). There are many studles reporting strong fac~l~tat~ve effects dunng restoratlon In

high mountaln environments (Aens et al. 2007). and M e d ~ t e m e a n regions (Gomez-

Apanc~o et al. 2004) and trop~cal ram-forests (Parrona et al. 1997).

Ident~fyng the facil~tator or ecosystem englneer that are of dtsproportionately important,

so that it can be managed to asslst in proactive management IS necessary (Hobbs et al.

2006). But predicting apnor wh~ch specles will be important as physical engineers is

difficult (Jones et al. 1997). Research and management should be gu~ded by strategically

identifying key knowledge gaps, and use precious and llnle available resources to

maintam single species that could ensure ecosystem conservation (Brooker et al. 2008).

Most of the studies regarding plant -plant positive mteractions, focus on 'nurse plant'

benefits found In condltlons of high stress. These nurse plants, create '~slands of fertility'

(Schleslnger & Pilmanls 1998; Agular & Sala 1999). found etther tn patches or bands

leading to so-called tlger or leopard vegetation (Aguiar & Sala 1999) reflectmg the

redistnbut~on of resources and progagules. These patches of vegetation have been the

focus of study for a long tlme (Kershaw & Looney 1985), including the role of nurse

plants (Shreve 193 1).

Nurse-plants are have recorded in deserts (Suzan et al. 1996), alptne regions (Cavieres

2006). salt marshes (Bertness & Yeh 1994). tnter-tidal regions (Bermess & Leonard

1997; Stachowlcz 2001; Bruno 2001), Medlterrenean regtons (Gomez-Aparicio et al.

2004) Many studles have found that the specles nchness under or around these nurse

plants 1s stgnlticantly h~gher than that found In bare areas. There are even reports of

them fac~lttating lnvaslves in Andes (Cavleres 2008).

Successful recruitment 1s crucial for the establishment and maintenance of population

levels of any species (Bertness & Yeh 1994), and nurse plants provtde optimum

conditions for germination, seedllng emergence and establishment by creating spatial

heterogeneity in an otherwise harsh environment. In any given case the collection of

factors or any slngle of these factors that make nurse plants, facilitators can differ

(Stachowicz 2000; Bruno 2001; Gomez-Apanc~o et al. 2005a, 2005b).

The shade of the nurse plants regulates the soil temperature and the ambient temperature

and by reducing evaporation of soil molsture makes more water available to young plants

(Shreve 1931; Holmgren 1997). In addlt~on the evapotransplratlon of the plant are less

under shade (Franco-Nobel 1989). Soil temperature is very important to determine the

health and growth of the newly germmated radlcle, whlch can dry fast. Holmgren (1997)

found that there 1s an tnteraction of micro-cl~matlc gradients and physiological tradeoffs,

so In mesrc condlt~ons where shade 1s the detnmental factor, as water is available

everywhere In the environment. But In xenc condtt~ons marked by extreme temperature

(htgh In case of and regions) and low molsture, life In the hgh light conditions is nearly

impossible, so the plants survtve better under shade

Many stud~es have found that the photosynthet~cally actlve radiatton IS better suited to

plant germinat~on under shade than In bare areas (Vallente et al. 1991; Casal et al. 2001).

The h~gher organlc matter content under the shade of nurse plants occurs due to abiotic

processes, mainly driven by wlnd and water, include redtstnbut~on of fine soil particles,

associated mineral nutnents and litter that 1s concentrated underneath vegetated patches.

Biotic processes results fmm the action of roots, whlch absorb nutnents from the soil

under the densely vegetated patches, as well as from the so11 of the bare-soil matrix

(Aguiar & Sala 1999). The vegetated patches also manage to accumulate more

progagules due abiotic factors like wind and rain and by biotically by attracting seed

dispersers like animals and birds by providing perches for them or because they bear

fruits. (Agu~ar & Sala 1999).

Besides interactrons, vegetation climax, is one of the most Important concepts in

succession. The existence of a slngle endpolnt the climax vegetatron by Clements

(1914), for a given set of cltmat~c characteristics of a site, has been recurrently

challenged, belng replaced by the acceptance of poly-cl~max based on differences In

hab~tats glving edaph~c, topograph~c, fire, and zootlc cl~max (Slngh et al. 2006). Absolute

climax has been cons~dered an abstract concept since communrtles are repeatedly subject

to drsturbances that prevent a communtty from belng at equiltbnum (Sheil 1999). Yet the

concept of a srngle cl~max has endured cnttcism, and 1s tacttly accepted in research

(Ptckett 1976). In fact, most studies evaluate the rate of successlon, based on the

companson of sltes w~th the 'cl~max pnmary forest' as the possible endpoint, either In

terms of spectes composition or structure of forests rn degraded tropical envuonments

(Corlen 1989; Myster & Walker 1997; Zhuang & Corlen 1997; Shell 1999; Rivera et al.

2000; Lu et al. 2003; Kobayashi 2004; Lebrlja-Trejos et al. 2008). Detenn~ning the

resilience of different forest types and the recovery ttme needed for any landscape to

resemble the poss~ble climax, is a domlnattng theme In recent successional studies.

Ewel (1980) found that w p ~ c a l dry forest (TDF) successton had few sera1 stages, so

predicted more resilience, compared to humid tropics. Though there is increasing

convergence through tlme, the rate of successlon decreases in time (Myster 1984; Myster

& Pickm 1990). Resilience is influenced by the hab~tat type and the initial conditions of

the site Including the type of d~sturbance (Keever 1983; Myster & Picken 1990, 1992).

Degraded lands need more time for recovery (Uhl et a1.1988; Lugo 2002). The resilience

rates recorded In TDF have been also Influenced by methodolog~cal constraints like the

cho~ce of reference sites, and sampllng criteria used (Kennard 2002; Pena-Claros 2003;

Lebrija-Trejos et al. 2008).

The TDF succession is charactensed by a short early phase dominated by herbs and

shrubs, followed by a ploneer tree phase to be replaced by pnmary forest specles

(Lebnja-Trejos et al. 2008). They also found that domtnant pioneer species were absent

from the natural regeneration dynam~cs of the mature forest, whlch is in contrast with

most secondary successions In TRF, where species that colonlze fallows are generally the

same ones lnvolved In the gap dynamics In mature forest .

Grasses and herbs domlnate for two years In Mexrco and for e~ght years In Bollvia

(Kennard 2002) There was a recovery of specles richness, w~th maximum reached at

rmd-success~onal stages, but not the or~ginal composition (Aide 1996; Colon & Lugo

2006; Lebrija-Trejos et al. 2008). A~de et al. (1996) found spec~es divers~ty low till 10

years, then began increasing from 10- 15 years to 40 years in Puerto Rico. In another also

In Puerto Rim in 45 years specles level were similar to than In the forest (Colon & Lugo

2006). In Bolivia. Pena-Claros (2003), and Toledo and Sal~ck (2006) found that the

species richness was higher In the under slorey, than tn the upper storey.

The convergence of vegetation stmcture was faster. Aide et al. (1996) found density,

basal area and height were s~mllar to the forest in 40 years. as did (Lebrija-Trejos et al.

2008) wh~le ~t reached 70 % In the a Boliv~an forest by 25 years and 50 years (Pena-

Claros 2003) and kept increasing with age In others (Toledo & Salick 2006). Dens~ty for

trees peaked after 25 years to 14,000 trees/ ha In Puerto Rico for trees t 1 cm dbh.

Density of trees exceeded and was twice as much as forest density In Bollvta (Kennard

2002)

Basal area Increased from 5m2 I ha in 9.5 years to 40m2/ha for trees ? I cm dbh In 60

years In Pueno Rlco (A~de et a1.1996); and from 12.3 m2/ha in the 2* year to 36.3m2/ha

for trees t 1 cm dbh In 40 years (Pena-Claros 2003) and 2.9 m2/ha In 5 years to 21.6

m'lha in Bollvia (Toledo & Sal~ck 2006). Basal area was the amibute that showed the

slowest ncovery in Mex~co (Lebrija-Trejos et al. 2008).

The distnbut~on of slze <lass of trees 2 10 cm. showed maximum dens~ty In lower slze

classes < 20 cm dbh (Kennard 2002) and Rulz et al. ( 2005) found that 61% of the trees

with dbh ( 2.5 to 5 cm) and 35 % wlth he~ght (>2.5-5 m). They found a reverse J-sahped

population structure as did Sabagol (1992) In Nicaragua with 87% of tress < 30 cm dbh

and average height of 15- 30 m. In Bollvla, Kennard (2002) found cover was l~m~ted to

10-20% in 1.2.3 years but Increased to 56% In 5 years.

Seed d~spersal is one of the ~mportant llmltlng factors In recruitment of species. In dry

forests wind is the most common mode of d~spersal (Bullock 1995). In the TDEF area.

where the study 'was conducted. endo-zoochory (69.2%) and anemochory 14% are the

most Important dispersal mode (Swampathan & Parthasarathy 2005). The mode of

dispersal can d~ffer w~th hab~tat type, with presence of perches or forest edges enhanc~ng

zoochory (Janzen 1988; Parrotta 1995) In Amazonia, autochory (60%) was the dominant

dispersal mode In open herbaceous areas w~th anemochory (40.2%) and endo-zoochory

(37.8%) being dom~nant in forest shmb vegetatlon (Arbelaez & Parrado-Rosselli 2005).

Bes~des pnmary d~spersal agents llke wmd, water, gravity and animals, secondary

dispersal by another agent from the first landing site of a dispened seed can occur. Ants

have been known to remove tlny seeds from animal dropp~ngs or from under the parent

tree to the~r nests (Turner 2001). Endochory can occur passively when the fruit is eaten as

part of a larger vegetatlon part by herb~vores (Elcott et al. 2007) or act~vely when animals

eat the fmlt for the reward offered by the plant. It 1s sometimes an expendable fleshy part,

In which case the seed IS dispersed after passlng through the gut or mouth of the anlmal

or the seed itself, where the seeds are hoarded and forgotten by animals (Turner 2001).

Though endochory is Important. the Importance of different herbivores is unclear. Elcoti

et al. (2007) found that endochory IS an Important agent of local and reg~onal populat~on

dispersal and support penlstence vla metapopulatlons. Since large herbivores can travel

far they can d~sperse seeds further than small mammals and are particularly important In

successional matnx havrng profound effect on commuruty development and structure.

(Elcott et al. 2007).

With the exception of a few pantropical weed trees, the woody success~onal flora of each

major tropical area- Afnca, Asia, and Amencas is restricted to that area, though there are

ecological equ~valcnts (Ewel 1980). Kellman (1980) pred~cted a homogenous herbaceous

weed flora and nucleated successron dominated by secondary trees specres In recovenng

forests. Most of the flora of earlier seres were reported from success~onal studies around

the world.

Gwen the sub-contrnent that Indla IS, Champron and Seth (1968) have lrsted 37 forest

types based on Thornthwalte's 1948 cllmat~c types, while they have themselves Identified

162 vegetation types based on a mrxture of factors like cl~mate, edaphr, other slte

factors, and biotic Influences These forests are inclusive of sub-groups based on

degradation due to human resource use and identifiable seral stages of the vegetation and

are l~sted below

Table 1: Forest types are groups and sub-groups classified under drfferent biomes In

India.

Biomes No of Forest types

Mo~st Trop~cal forests 62

Dry Trop~cal forests 39

Dry Montane Subtropical forests 17

Montane Temperate forests 3 1

Sub-Alpine forests 6

Alpine scrub 7

There have been relatively few studies on secondary succession, in India, compared to

the vast d~vers~ty of forest types seen. Most of these stud~es have focused on the molst

foresls prevaihng In Western Ghats (George et a1.1991; Pascal 1988) or northwestern

India (Rao & Ramakr~shnan. 1987) A prevlous study of succession In the trop~cal dry

evergreen forests (TDEF) In North Arcot and South Arcol areas recorded e~ght

success~onal stages leadlng from the Arr.\tidu spp. dom~nated grass stage to the cllmax

const~tuted by Alh~ztu urnurtr- Accrciu leucophloeu communltles (Dabholkar 1962)

Degraded lands In lnd~a are considered as being sera1 In nature, having orig~nated due to

abandoned cult~vat~on or degradation of forests, result~ng In grasslands and considered as

d~scl~maxes (Mlsra 1959). Though there are few stud~es to document the effect of grazing

on specles Interactions, there are many studies that have been conducted In grasslands to

evaluate the effect of grazlng on specles d~versity, b~omass productivity. A pattern of

Increase In specles d~vers~ty and net productivity of grasslands due to moderate levels of

grazing and loss of species under heavy grazlng reglmes is reported from H~machal

Pradesh, Varanasi and tropical savannahs In Ind~a (Singh & Mlshra 1969; Swartzan &

S~ngh 1974; Pandey & Singh 1992, Sabenval 1996), and from Serengeti in Africa (Mc

Naughton, 1979, 1993; Belsky 1992) to British l~mestone grasslands (Gibson & Brown

1992). However, cont~nued grazlng can increase not only recruitment but also extinction

(Gibson & Brown 1992).

Studies comparing grazed intensities, found that there was decrease in palatable species,

up to 30 % and increased the dom~nance of only a few species In Sahel, Africa

(Heirmaux 1998): Studying vegetational composition at increas~ng distance from a water

source Sasak~ et al. (2008) found that the influence of grazlng was more on volume than

on compos~tion.

Heavy grazlng selectively favours the establlshment of short turf and creeping perenn~al

such as Allopferrs cimicina, Brachariu distachya, Digitorio longflolru In S ~ I Lanka, and

thorny specles of Acuciu, Prosopis and Zizyphus in the V~ndhyas. Grasses like

Bothrrchlou perruso, Desmostochyu sp, Digituriu sp occur with legumrnous weeds like

Cu~sru Ioro As a result of protection from fire and grazlng, In 16 years there was an

increase in tree species richness from 4 to 16 and the tree denslty Increased from 14.6-

and 3.7- fold (Jose- F r a ~ n ~ a s 1983).

Somet~mes ~t IS the herbaceous flora of the early seres that is socially and economically

Important and ma~ntalned by grazing as in the famous Valley of flowers m Bhuyunder

valley In the Nanda D e v ~ Natlonal Park In H~malayas. An ever increas~ng list of

endangered species promoted the Lnd~an government to impose a total ban on grazing in

1982. A study conducted by Na~ than~ et al. (1992) showed that there IS subsequently less

m~neral~zatlon of so11 numents and the natural course of successlon has helped the

establ~shment of a few successional woody specles, which would eventually lead to the

eltminatlon of the herbaceous species.

Previous stud~es on the early to middle stages of successlon have shown that grazing can

reduce grass cover and favour establishment of woody plants, by reduc~ng competition

from grasses and risk of fires, and improv~ng dispersal of seeds of woody species by

grazing animals (Van Auken 2000; Rogues et al. 2001).

Spec~alization of tropical plants for hab~tat and m~cro-habitats, has been used to explain

the~r co-existence and the high species d~versity in trop~cal forests (Denslow 1987;

Gentry 1988; Clark et al. 1995) and savannahs (Barot at al 1999), w~th the species

regarded as being segregated along vanous environmental mches like I~ght, soil moisture

and nutrients (Silvertown 2004). Mass-effects, whereby the species establ~sh In sltes

through input of propagules from nearby favourable habitats in the absence of self-

sustalnlng populat~ons 1s also Important In explaining species richness (Shmida & Wilson

1988).

M~crohab~tat refers to environmental condlt~ons that vary at scales less than lo3 metres,

and hab~tats refer to strong environmental dlscont~nuity, usually at larger scales according

to Svemng (1999). Regeneration n~che IS regarded as the most important mche, as

plants' sens~ t~v~ty to factors changes with age and they are most vulnerable when they are

young (Collms & Good 1986; Svenn~ng & Balslev 1999). There have therefore being

many stud~es that study regeneration n~che's Importance to explain spatial patterns, and

thelr Influence on dens~ty and population structure.

Collins and Gwd (1986) compared the hab~tats of six tree species to cons~der their

effects on the regeneration of species and found factors like light, litter depth and nearest

neighbour occumnce as important. Various other factors have been known to ~nfluence

plants, including palms. The distribution of palms too, across tropics prov~de evidence of

the influence of heterogeneity at the level of habitats (Kahn & De Castro 1985; Peres

1994). and microhabitat as seen in the Amazonian palm community (Svenning 1999),

Costa Rican palms (Clark et al. 1995) and AFrican Borassus aethropum (Barot et al.

1999).

Clark et al. (1999) found that the distribution of palms at a scale of <I Ian' were

influenced by topography and edaph~c factors. Clark et al. (1995) found twlce the denslty

of palms on the steep slopes compared to gentle or lower slpoes, wlth spatial

heterogeneity at small to large scales (0.5 to 10 m2) affecting community structure.

Similarly Svenning (2001), found SIX species of palms in the Andean forests to be

correlated wlth altitude and aspect of mountains as well as edaphlc factors.

Schwaegerle & Bazzaz (1987) studing nine populatlons of Phlox in Texas, along

environmental gradients of several factors ltke light, nutrients, competition found that

populatlons of large plants were less sensitive to change avallablllty than smaller plants.

Different~at~on In populatlons occurred due to many processes, and populations in closed

habltats are genetically different from those In open hab~tats, allocating more resources to

persistence and competition and less to production of propagules for dispersal

(Schwaegerle & Bazzaz 1987).

There IS evidence that there is heterogeneity in microsites In homogeneous habitats

(Collins & Good 1986; Palm & Dixon 1990). Resource avallabllity Like soil, moisture,

light and nitrogen varied within patches of uniform vegetation and the range of resource

spatial difference was different among resources within a single community type. This

heterogeneity in resource dlstnbution 1s reflected in the distribution of plants (Colltns &

Good 1986; Dunslow 1987).

The difference in d~stribut~on beglns wltb amval of propagules. In heterogeneous

environments seeds settle in some sltes more readily than In other sites irrespective of

whether these sites are favourable for germinat~on, growth and establishment of the

specles (Bernard & Toft 2008). Ploneers were found to regenerate better In lighter

mlcrosltes and pnmary forest specles In darker mlcrosltes (Clark et al. 1993).

Besides regeneration, environmental factors Influence other stages of plant l~ fe too, like

growth and phenology. Llght was found to be an Important factor for growth and

reproduct~on, leadlng to population level consequences. (Oyama 1990; Svenn~ng 2002).In

1 1 populatrons of the dloeclous herb Jack-~n-the pulplt, Arrsaema rr~phyllum (Araceae),

studled for two years, Doust and Cavers (1982) found that the allocation of resources

differed among the genders depending on the type of habltats they were found in. Female

plants were found In mlcrosltes that had more Ilght, so11 pH and nutrients and male plants

were found In mlcrosltes that had less I~ght, so11 pH and nutrients. The size of plants also

d~ffered, females being 3.5 welgher than males, and allocating twice as much of dry

matter to flowers than males. More male flowersiplants in harsh habitats and more of

female flowers/plants In favorable environments have been reported In dioecious

Calophyllum brasiliense (Fischer & Dos Santos 2001) and in the Egyptian Thylmelueu

hirsum (Ramadan et al. 1994). Clark et al. (1987) found that in Zarnia skinnen, a long

lived dieocious cycad, that light and plant slze affected reproductive effort, with three

episodes of flowering In the secondary forest and only two in the darker pnmary forest in

a period of six years.

In dioeclous plants, various env~ronmental gradients like nutrients (Cox 1981),

temperature and soil rnolsture content (Freeman et at. 1980; Freeman & Vitale 1985), and

light (Onyekwelu & Harper, 1979). along which sexes segregate have been rdentified

producing deviations of sex ratio from 1:l (Meagher, 1980). A male-biased sex ratio is

usually more common In dioecious plants, as found in Chamaelirium luteum a lily

(Meagher. 1981), Borassus aethropum a savannah palm (Barot et al. 1999), double

coconut (Savage & Ashton 1983; Sllvertown 1987). and the cycad Zomia sk~nneri (Clark

& Clark 1987).

Among all factors light emerges as the singe most important factor that affects

distribution, density and population structure 'Tree species can In fact be arranged along

a continuum of adaptlve response to the avallab~l~ty and durat~on of incident radiation

(Denslow 1987). Light IS necessary for regeneration, establishment and growth of

seedlings (Denslow 1987; Clark et al. 1987, 1993; Svenning 2002), for growth of the

plant and reproductive activ~ty (Oyama 1990; Chazdon 1986; Svenning 2002).

The differential needs of resources and therefore choice of hab~tats and microhabitats by

plants is one of the major dnv~ng force that can explain the density, dispersion and

population structure of species (Alvarez-Buylla 1994; Barot et al. 1999). The reverse J

structure that populations usually show, though, is more a consequence of density

dependant mortality in the youngest ontogeny, than spatial heterogeneity (Van Valen

1975; Pinard 1993; Silva Matos et al. 1999; Souza & Martin 2002). In some palms the

seedlings were found w ~ t h adults as in friarleu deltoidae ( Svenning & Balslev 1999) but

many studies also report seedlings belng found away from the parents In palms such as

the Brazilian acaulescent palm AIruleu humifis (Souza & Martln 2002), and Eulerpe

edults (Silva Matos & Watklnson 1998) The Influence of spatial heterogeneity influences

all the ontogenlc stages, as demonstrated In Allalea hum11i.y (Souza & Martin 2002),

where fire was the lnfluenclng factor, whlle Barot et al (1999) found that the clumped

dlsperslon of all the ontogenlc stages In the Afncan Borossus uethiopurn was due to

nutnent nch patches In a savannah

There are however relatively few ecolog~cal stud~es of palms, w ~ t h most studies deallng

with taxonomic or econom~c botany of the family (Borchsenlus et al. 1998) even though

Arecaceae is one of the most useful group of plants dlsuibuted In the troplcs and parts of

subtroplcs, conslstlng of 201 genera and 2650 species (Mabberley 2000). Palms are

economically important as they Include major plantat~on specles like oil palm, coconut

and date palm. However, most palm products are non-commercial, being part and parcel

of dally llfe in ~ r a l areas worldwide, used predomtnantly for food, thatch, handicrafts,

construction and med~clne (Basu & Chakravany 1994; Borchsenius et al. 1998).

Most of the degraded lands or 'wastelands', as they are commonly called, serve as

common property resources (CPR) in Indio. owlng to then degradation. they do not offer

high returns to their usen. hence only the rural poor and lntermed~ary households use

them for fodder 'and fuel wood. Such 'wastelands' contribute to employment, asset

accumulat~on and to 14-23 per cent of the Income. especially for the rural poor (Jodha

1989). Patterns of use vary w~th gender, wlth the women belng recorded as the

predom~nant resource users in Himachal Pradesh (Berkes et al. 1998).

'Wastelands' In lndla are est~mated at 6385 million hectares, accounting for 20.17% of

the total land area (328.73 million hectares), according to the Natlonal Wastelands

Inventory Project, undertaken by Natlonal Remote Senslng Agency (2000). There are 13

categones of wastelands, of whlch degraded forests makeup 4.44% and grazlng lands

0.82% , degraded land under plantation0.18 %, land with or wlthout scrub 6.13%, gullled

and ravenous land 0.65% of the total Indian land mass. Of the total deslgned wastelands,

50% are non-forest areas.

The land ownership is private fallow land, v~llageiRevenue land or forests. The negatlve

Image of the 'wastelands' has ensured that it has long been a target for various

development schemes by the Central and State governments. The nation w d e Soclal

forestry programme Instead of supplying fodder and fuel for the local people was

diverted for commercial and lndustnal use (Slngh 1985). The Comprehensive Wasteland

Development Project In Tam11 Nadu initiated in 2002-2003 seeks to lease a hundred

thousand hectares of community lands to corporates, besides pnvate wastelands, without

llsting benefits for the local people (Sarvanan & Mahapatra 2003). Among the latest

threat to the local population's access to 'wastelands' for usufruct benefits is the proposal

to use I I million hectares of 'wastelands' (7 per cent of the cultivable area in the country)

for monocultures of Jatropha by 2012 to supply biofuels, to meet India's aim to achieve

20 per cent blend of bio-diesel by 2010 (Mishra & Awasthi 2006). The long-term

requirement to keep carbon in storage ln forestry projects requtred to be ma~nta~ned for

Clean Development Mechanism (CAD) under the Kyoto Protocol to mitigate cltmate

change, if implemented in Ind~a, can also conflict wtth the short-term needs of the poor, ~f

the energy and other biomass needs from the CPR are not addressed and the benefits of

carbon sequestration IS not channelled to the mral poor, lead~ng to tensions and eroston of

benefits (Gundimeda 2004). '

So t t IS necessary to tncorporate social sclence research wtth ecological research for

successful landscape restoratlon (Sabagol 1992, Sanchez- Azofe~fa et al. 2005) Parch et

al (2001) recommend uslng spontaneous successlon for ecolog~cal restoratron, a

relat~vely new field, keeping tn m~nd the alms of project restoratlon of cltmax vs

reclamat~on for soc~ally acceptable condtt~on or product~ve use, and evaluation of site

env~ronmental cond~ttons before dec~dlng whether spontaneous successton 1s an

appropnate way to ach~eve the alms. T h ~ s should be supported by pred~cttng successional

development, suggesting possible lnterventlon (cultural practices or species introduction)

at appropriate junctures of success~on and monitoring of results.

There are mtxed reports of the effect of dtfferent kinds of management. The choice of an

appropnate overstorey species in plantation is critical as the can 'catalyize' successlon by

influencing subsequent patterns of colonization. Nineteen specles of secondary tree

species were found established under Casuarina equiseirijoha, Eucalyptt~s robusfa and

Leucaena leucocephala, while there was no regeneration in bare unplanted areas (Parona

1998). George et al. (1991) too found that after 15 years the understorey in a Eucalyphcs

plantation in the Western Ghats, near wet evergreen forest had reached species richness

levels similar to the forest. However, exotics are generally cons~dered less su~table for

reforestation projects as they can turn mvaslve, so the search for su~table local species is

important (Blanc et al. 2002). Restorat~on projects that skip early successional species

and plant only late success~onal species have less understory richness (Arde et a1.1996).

The use of shrubs as nurse plants facilitating later success~onal specles has been

advocated for the Mediterrenean reglons (Castro et al. 2002; Gomez et al. 2004, 2005). A

recent study shows that rotating grazlng land to reduce grazing pressure in dry forest

pastures In N~caragua, recorded a total of 85 forest species found as adults In the pastures,

of wh~ch 60 and 30 specles were able to establ~sh as seedl~ngs and sapl~ngs (Esqu~vel et

al. 2008) So spontaneous succession, wlth a little intervention can help In conservation

of tree specles In the predom~nantly agricultural landscapes In trop~cs.

Rehab~litation of degraded trop~cal landscapes by Identifying stress-tolerant, natlve or

exotic species and appropnate management systems has made s~gn~ficant contributions.

S~nce wood and non-wood products are both Important 'the focus of "wastelands"

reforestat~on programmes for fuelwoodl timber should be broadened to rehabilltation

forestry' (Parona 1998).

I t IS possible to speed up design~ng appropriate resource management programs, by

incorporating trad~ttonal ecological knowledge (TEK), based on local people's

understand~ng of ecolog~cal processes (Berkes et al. 2000). There has been a growing

interest In TEK since 1980s to study specles Identification and classification eg.

enumeration of 48 species of mushrooms in Mex~co (Montaya et al. 2003), study and

proceeded to people understanding of the ecological processes (Alcorn 1989; Gadgil

1993; Huntington 2000).

Local commun~ties have been known to use thew TEK to manage ecosystems and

respond to changes showing a understanding of the complex processes at work in nature

(Berkes et al. 2000) TEK has been useful In savlng specles b~od~vers~ty (Gadgil 1993),

rare specles, recognlzlng and protecting keystone specles and to protect habitats

(Johames 1998; Berkes et al. 2000). In Ind~a, sacred grooves are an example of habitats

protected by cultural beliefs. (Gadgil 1993; Parthasarathy et al. 2008).

But while there are many promoters of TEK, there have been very few cases of synthesis

of TEK and sclence Many promoters have themselves caut~oned agalnst unquestioned

use of TEK (Huntlngton 2000), since it can be wrong as these are knowledge systems that

are usually shared and passed on orally. There IS also inertla to embrace this new

~nterdisc~pl~nary approach to research, but whlch, could be overcome by evidence from

studies documenting and incorporating TEK. Many are reluctant and unwilling, to use

TEK cons~dering It lack~ng In scientific v~gour; and to overcome the obstacle of using

social science methods to document TEK and the reluctance of the TEK holders to share

their knowledge (Huntington 2000, Berkes et al. 2000).

There have only a few instances when sclentlsts and TEK holders have worked together,

a whaling census being one (Huntlngton 2000). The Alaska Esklmo Whaling

Commission, fought against the ban on harvesting bowhead whales in 1977 by the

International whaling Commission. They were allowed a harvesting quota based on the

census of whales. The orignal census of 2000-3000 whales based on visual obsewatlon

was revised by considering visual and acoustic evidences from locations not considered

earher to Increase the census figures to 6000-8000, hased on information from Alaskan

Esktmos.

But there are successful cases of management practices that have been based on local

tradlttonal knowledge and cultural practices, including preservation of remanant forest

pathes of the TDEF In sacred groves (Parthasarathy et al. 2008). mum or shlftlng

cultlvatlon was judged to be harmful In a blodlverslty hotspot In northeastern areas of

Himalayan leading to a regulat~on of shifting cultivat~on in 1947 and promotion of agro-

forestry as the a more su~table and econom~cally susta~nable. But there 1s realization now

that jhum based on years of practlce and refinements, lnvolv~ng use of local cultivars in

fact IS better for conservation of blodlversity and soil and there are now efforts to

promote 11 agaln (Arunachalam et al. 2002)

Since the last twenty years many countnes have handed over management of natural

resources to the local communltles, which have to be monitored. When management

plans and monitonng systems are partlclpatory , incorporating TEK along with scientific

guidelines, they are more acceptable to local stakeholders and llkely to be effective even

afier the donor agencies q u ~ t s the project (Garcia & Lescuyer 2008).

The lrulas arr a hunter-gatherer tribe inhabltlng parts on the Commandel coast since pre-

Dravidian times, whose TEK has been tested and used several times in conservation of

biodiversity and restoration. The~r skills as hunters has been used in modem med~c~ne , to

collect venom of snakes used In producing antl-venom for bites of the four most

polsonous snakes in India and their knowledge of forest plants and their medic~nal value

has been documented and then herbal medicines are be~ng marketed (Methil 2008,

Madras Crocodile Bank 2008).