How pine trees re­stored na­tive veg­e­ta­tion in a Sri Lankan for­est

Pine trees have helped re­store na­tive veg­e­ta­tion in Sri Lanka’s Sin­haraja For­est Re­serve

Down to Earth - - CONTENTS - SAND­HYA SEKAR

EF­FORTS to re­store rain­for­est tree species in Sri Lanka’s Sin­haraja For­est Re­serve have ul­ti­mately borne fruit. It has been found that pine trees are very ef­fec­tive in pro­vid­ing favourable con­di­tions for growth un­der­neath. Till now there have been no eco­log­i­cal pro­cesses that could fully re­store wet forests.

Over the past 25 years, re­searchers have been try­ing to re­store na­tive tree species in for­est re­serves across South Asia. Fast-grow­ing species such as Pi­nus carib­aea, Aca­cia mangium and Eu­ca­lyp­tus spp were planted in large tracts of aban­doned agri­cul­tural land and de­graded forests in south­west Sri Lanka and in the Western Ghats of In­dia un­der re­for­esta­tion pro­grammes in the 1970s and 1980s. Such plan­ta­tions make the en­vi­ron­ment more hos­pitable. They at­tract birds and bats which help in seed dis­per­sal. They also im­prove soil fer­til­ity by in­creas­ing or­ganic mat­ter and by re­tain­ing mois­ture. These fac­tors make the area con­ducive for na­tive species.

“In south­west Sri Lanka, pine plan­ta­tions have proven to be very ef­fec­tive at shad­ing fire- de­pen­dent grasses and ferns. The pine them­selves are fire- and drought- tol­er­ant, mak­ing them hardy pi­o­neers that can be planted in open lands that were once agri­cul­tural lands but have been aban­doned be­cause the soils have eroded or be­come nutrient poor,” says Mark Ashton, first au­thor of the paper pub­lished on­line on April 8 in For­est Ecol­ogy and Man­age­ment.

Ashton also said he would rec­om­mend plant­ing pine plan­ta­tions in aban­doned agri­cul­tural ar­eas. The only prob­lem, he says, is that pine can nat­u­ralise— it can spread widely if unchecked, even be­com­ing an in­va­sive species that out­com­petes na­tives.

Priya Davi­dar, pro­fes­sor of ecol­ogy at Pondicherry Univer­sity, agrees. “The plan­ta­tion tree cho­sen to act as a ‘nurse’ species should not be in­va­sive. I also doubt that re­gen­er­a­tion takes place un­der young plan­ta­tions; there is prob­a­bly re­gen­er­a­tion only when the plan­ta­tion trees are old and there is less com­pe­ti­tion and al­lelopa­thy (the process of se­cre­tion of chem­i­cals by some species to de­ter growth of other plants in the vicin­ity). I would rec­om­mend na­tive tree species for nurse trees, rather than an ex­otic like pine,” she says. How­ever, use of other na­tive species as nurse trees needs fur­ther re­search.

“Na­tive species like Al­sto­nia macro­phylla or Perese re­an­thes fal­cataria are some can­di­dates [for nurse trees] which we have tried here. Fire pro­tec­tion and soil con­ser­va­tion dur­ing early days may be needed [ for them]. [ Na­tive species such as] Dipte­ro­car­pus spp and Miche­lia cham­paca can then be planted,” said Ni­mal Gu­natilleke from the Univer­sity of Per­adeniya, Sri Lanka. Gu­natilleke was one of the au­thors of the study.

Other species that were used for plan­ta­tions ( Aca­cia spp and Eu­ca­lyp­tus spp) also need to be stud­ied. How­ever, there is now an op­por­tu­nity to bet­ter man­age the ex­ten­sive pine plan­ta­tion across South Asia.

Pine trees at­tract birds and bats which dis­perse seeds. They also im­prove soil fer­til­ity by re­tain­ing mois­ture

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