Effects of Microbial Biomass and Activity on Carbon Sequestration in Soils under Different Planted Forests in Chittagong, Bangladesh

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1 Interntionl Journl of Agriulture nd Forestry 216, 6(6): DOI: /j.ijf Effets of Miroil Biomss nd Ativity on Cron Sequestrtion in Soils under Different Plnted Forests in Chittgong, Bngldesh Md. Mmunur Rsid, Nsrin Chowdhury *, Khn Towhid Osmn Deprtment of Soil Siene, University of Chittgong, Chittgong, Bngldesh Astrt Miroil iomss, tivity nd eophysiologil indies together with importnt physil nd hemil properties were studied in soils under four different plnted forests (Ai uriuliformis, Artorpus hplsh, Dipterorpus turintus nd Lgerstroemi speios) in Chittgong, Bngldesh. The prinipl ojetive of the study ws to investigte miroil tivity relted to ron sequestrtion under different tree speies. The men vlues of ph, totl nitrogen, orgni ron, miroil tivity nd miroil iomss ron vried from 4.49 to 4.68,.9 to 1.9 mg kg -1, 6.4 to 1.6 mg kg -1,.6 to.13 mg CO 2 g -1 d -1 nd to µg C g -1 respetively. Plnt iomss s well s orgni ron ontent, miroil iomss nd tivity in soil ws the highest in Artorpus hplsh. There were strong positive orreltions etween plnt iomss nd lmost ll the soil properties whih suggested tht plnt speies ffeted ron trnsformtions in the studied soils. Signifint differene (P <.5) in orgni ron ontent nd miroil tivity ws oserved in soils under Ai uriuliformis from soils under ll other speies. The rtio of miroil iomss ron to soil orgni ron (qmi) ws the highest nd sl respirtion nd miroil iomss ron rtio (qco 2 ) ws the lowest in soils under Ai uriuliformis nd the vrition ws signifint with soils of other speies. Therefore, Artorpus hplsh the indigenous speies of Bngldesh hs greter potentility to sequester ron in soils thn other three speies, nd Ai uriuliformis the exoti speies hs the lest ontriution to sequester ron in these soils. Keywords Soil orgni ron, Biomss ron, Soil respirtion, Forest, Eophysiologil indies 1. Introdution There is strong interest in stilizing the tmospheri undne of ron dioxide (CO 2 ) nd other greenhouse gsses to mitigte the risks of glol wrming [1-4]. CO 2 sequestrtion is n importnt strtegy of lowering CO 2 emissions from point soures through nturl nd engineering tehniques [5]. The glol ron (C) yle is hevily dependent on miroil ommunities tht fix tmospheri C, promote plnt growth nd trnsform orgni mteril in the environment. Most plnt prodution (8-9%) enters the soil s ded wood, leves, exudtes, roots nd exudtes. Soil miroes re the min gents of its rekdown euse they produe enzymes ple of degrding relitrnt plnt-derived ompounds suh s lignin nd ellulose. As result, lrge proportion of soil respirtion is soured from the tivity of heterotrophi miroes. The miroil ontriution to soil ron storge is diretly relted to miroil ommunity dynmis nd the lne * Corresponding uthor: nsrin@u..d (Nsrin Chowdhury) Pulished online t Copyright 216 Sientifi & Ademi Pulishing. All Rights Reserved etween formtion nd degrdtion of miroil y-produts. The mount of sustrte C tht is inorported into miroil iomss nd eventully trnsferred into the miroil derived orgni mtter pool is determined y the size of the miroil iomss nd miroil growth effiieny. Miroil iomss ts s n intermediry ontrolling the type nd quntity of C tht n e tully removed from the tmosphere nd the time sles tht C sty sequestered. Beuse the C yle, espeilly CO 2, plys gret role in glol limte hnge, understnding soil miroil tivity nd iomss will improve understnding of limte hnge nd long-term C storge in soils. On the other hnd, miroil iomss n lso t s potentil inditor of C sequestrtion s they n detet tillge nd rop rottion effets on soil erlier thn totl orgni ron or nitrogen mesurements in soil [6]. Forestry ppers to offer reltively low-ost pproh to sequestering C. Plnts ts s medium for trnsfer of tmospheri C into the soil in the form of C-ontining ompounds. The mount of C stored in forest soil is out 124 Pg [7]. C sequestrtion in forest soils depends on the lne etween C inputs through photosynthesis nd outputs through soil miroil respirtion [8]. It is, therefore,

2 198 Md. Mmunur Rsid et l.: Effets of Miroil Biomss nd Ativity on Cron Sequestrtion in Soils under Different Plnted Forests in Chittgong, Bngldesh evident tht forests nd lnd-use plys n importnt role in the glol C yle nd tht ler understnding of this role is vitl omponent of ttempts to understnd nd omt the uses nd onsequenes of limte hnge. Evergreen nd mixed evergreen tropil rin forests one existed in the southern hills of Bngldesh. During pst few dedes, the originl dense nturl over hs lrgely een removed. Currently, there re sq km reserve forest lnd nd 3268 sq km stte forest lnd orresponding to 8.65 nd 2.21 perent respetively of the totl lnd re of Bngldesh [9]. With the fst rtes of deforesttion fterwrds, the need for ringing denuded res under rpid nd effetive over eme more essentil. Chittgong is situted in the hilly region of Bngldesh. Bngldesh Forest Deprtment mintins the fforesttion nd reforesttion progrmme in this re. Afforesttion nd reforesttion should e useful mens y whih C ould e stored in the vrious omponents of forested eosystem [1]. Soil CO 2 flux n e vried with forest produtivity in different eosystems [11] nd silviulturl tretments. Forest mngement tivities hve different effets on soil C sequestrtion [12]. The influenes of forest mngement prties on soil C dynmis were studied elortely [13]. However, little is known out the effets of forest stnd on C sequestrtion on the perspetive of soil miroil proesses. Sine soil miroorgnisms re the primry gents of the soil eosystem responsile for litter deomposition, nutrient yling nd energy trnsfer proesses, reserh progrmme ws designed to investigte the miroil tivity nd iomss in reltion to the potentility of C sequestrtion in soils under Ai uriuliformis, Artorpus hplsh, Dipterorpus turintus nd Lgerstroemi speios forests of Chittgong nd to otin si informtion for long-term monitoring s well s possile short-term effets. This study is ritil to urtely predit effets of forest mngement on the C yle nd to develop pproprite forest mngement strtegies imed t reduing tmospheri CO 2 onentrtions. Figure 1. Lotion of the study re (University of Chittgong, Chittgong, Bngldesh) [15]

3 Interntionl Journl of Agriulture nd Forestry 216, 6(6): Mximum Temperture ( C) Tle 1. Meteorologil dt of the study re (University of Chittgong, Chittgong, Bngldesh) [18] Minimum Temperture ( C) Numer of monthly oservtions Preipittion (mm) Cloud (tenths) Wind speed (km per hr) Humidity (%) Pre Mon Post Pre Mon Post Pre Mon Post Pre Mon Post Pre Mon Post Pre Mon Post [Pre= pre-monsoon, Mon= monsoon nd Post= post-monsoon] 2. Mterils nd Methods 2.1. Study Are The study ws onduted in some forest plnttions on modertely steep slopes (1-12%) of medium (<5 m) hills in the University of Chittgong mpus in Hthzri Upzil of Chtttgong distrit, Bngldesh (Figure 1). The geogrphil position is 22 27'3'' nd 22 29''' North ltitudes nd 91 46'3'' nd 91 47'45'' Est longitudes. These soils elong to Brown Hill Soils ording to the Generl soil type whih re equivlent to Dystri Eutrohrepts ording to USDA Soil Txonomy [14] nd were formed from tertiry unonsolidted sediments. Aording to Köppen limte lssifition, the limte is tropil monsoon [16]. The verge mximum temperture is 32.3 C during My, nd the minimum, 13.9 C in Jnury. The verge mximum reltive humidity rehes 97% during Septemer, nd the minimum, 38% in Mrh [17]. Meteorologil dt of the study re re shown in Tle 1 [18] Smpling Plots nd Smpling Design Some of the dt were olleted through physil mesurement in the field nd from plnttion reords of the Institute of Forestry nd Environmentl Siene of University of Chittgong. These plnttions were 3 yers old. Cnopy overge of the sites ws lmost 9% nd undergrowth onsisted of different kinds of hers nd shrus. Nine smple plots (1 m x 1 m) were distriuted over the entire plnted re of eh speies nd soil smples were olleted from eh plot in April, 214. Girth dimeter of ll the trees in plot ws mesured y using dimeter tpe. Totl height ws mesured using Spiegel Relskope. Complete Rndomized Blok Design (CRBD) ws followed for tking smples from the smple plots Proessing of Soil Smples Soil smples were tken from surfe -15 m in polythene gs nd rought into the lortory. Eh soil smple ws divided into two su-smples, one for physil nd hemil nlysis, nd the other ws used for soil miroil nlysis. The soil smples for hemil nd physil nlysis were ir dried, pssed through 2 mm sieve nd were preserved in plsti pots efore nlysis Anlysis of Physil nd Chemil Properties of Soil The prtile size nlysis of soils ws rried out y the hydrometer method s desried in [19]. Bulk density ws estimted y ore method [2]. Mximum wter holding pity (WHC) of the soils ws mesured volumetrilly. Soil ph ws determined with stndrdized ph meter in suspension hving soil: wter rtio of 1:2.5 [21]. Ction exhnge pity (CEC) of soils ws determined with IN NH 4 OAC uffered t ph 7. ording to the method of Jkson [22]. Totl nitrogen (TN) ontent of soils ws determined y miro-kjeldhl digestion nd distilltion method s desried in [23]. Orgni C ontent in soils ws determined y the wet oxidtion method (hromi id digestion) of Wlkley nd Blk [24] s desried y Jkson [22] Anlysis of Soil Miroiologil Properties Vile eroi teri nd fungl ell numers in fresh soils were ounted using the dilution plte method s desried in [25]. Nutrient gr medium ws used for teri nd potto dextrose gr medium for fungi. Three pltes were used for eh soil. The pltes were inuted t 28 C for 72 h to 12 h nd ounting were mde for forming olonies. Miroil tivity ws determined y soil respirtion, trpping the CO 2 in sodium hydroxide (NOH) whih ws evolved from the soil during inution in losed system [26]. The trpped CO 2 ws determined y mesuring eletril ondutivity [27]. For this purpose, 5 g soil (oven dry sis), moistened to 5% of wter holding pity, ws pled in 1 liter pity inution jrs. A 1 ml liquot of.5 M NOH solution in 5 ml flon tues were pled in eh jr s the CO 2 trp. A flon tue with wter ws dded into the jr to mintin the soil moisture. Jrs were mde ir tight immeditely. Two jrs with.5 M NOH ut without soil were used s ontrols. All jrs were inuted t 25 C. The CO 2 sored in trps were nlyzed t eh dys of NOH plement. Eh time fresh NOH solution (1 ml) ws repled to trp CO 2 for the next dys. In this method, CO 2 evolved from eh smple ws lulted s the differene etween the initil nd the CO 2 onentrtion fter eh mesurement period. Bsl respirtion rte ws lulted sed on umultive CO 2 evolution over the 11 dy period.

4 2 Md. Mmunur Rsid et l.: Effets of Miroil Biomss nd Ativity on Cron Sequestrtion in Soils under Different Plnted Forests in Chittgong, Bngldesh The sustrte indued respirtion (SIR) llows the estimtion of the mount of C held in non-resting, living miroorgnisms in soil smple. The initil respirtory response to dded gluose, reorded efore ny development in existing soil miroflor ould e viewed s n index of the existing soil miroflor [28]. Soil respirtion ws ssessed s stted ove. The sustrte indued respirtion vlues were trnsformed to iomss C using the formul s desried y West nd Sprling [29] s follows: µg miroil iomss C/g soil 2.6. Eo-physiologil Indies = 433 (log1 µl CO 2 g -1 soil h -1 ) (1) The minerliztion quotient (qm) inditing the frtion of totl orgni C minerlized lulted from sl respirtion nd soil orgni C rtio (μg CO 2 -C/C org d -1 ) nd ws expressed s perent (%) to desrie the perent of orgni C evolved s CO 2 d -1. qm = μg CO 2 -C umultive μg totl orgni C -1 [3] (2) The miroil quotient (qm) representing the rtio of miroil iomss C (MBC) to orgni C expressed s perent (%) to explore the perent of orgni C present s miroil iomss C. qmi = μg of MBC μg totl orgni C -1 [31] (3) The metoli quotient (qco 2 ) expressing the sl respirtion nd MBC rtio (µg CO 2 -C/mg MBC h -1 ) ws lulted ording to proedures desried y Anderson nd Domsh [32], s rtio of sl soil respirtion y C mi s follows: qco 2 = μg CO 2 -C sl mg MBC h -1 [32] (4) Sttistil Anlyses Correltions etween the seleted prmeters, level of signifine nd stndrd devition were determined using sttistil pkges in Offie 27 Progrm. All mesurements of physil, hemil nd miroiologil properties were done in triplite for eh soil smple. The effets of different forest plnttions were determined y one-wy nlysis of vrine (ANOVA) with three replites nd signifine of the prmeters ws tested using the lest signifint differene multiple rnge test t P.5 fter one-wy ANOVA. Person s orreltion oeffiients nlyses were rried out with IBM SPSS (version 2., Chigo, USA) to study reltionships etween miroil properties nd physil properties, miroil properties nd hemil properties nd within miroiologil properties themselves. 3. Results 3.1. Tree Speies The men dt for folir men density of tree numers, height, dimeter t girth, ove ground iomss nd elow ground iomss in four tree speies is summrized in Tle 2. The mximum tree height ws found in A. hplsh (17 m) followed y A. uriuliformis (15.67 m), D. turintus (14. m) nd L. speios (13.67 m). Men dimeter t girth of exoti tree speies (A. uriuliformis) showed lower volumetri growth (72 m) thn indigenous forest tree speies. Biomss of trees per unit hetre of the indigenous forest tree speies ws lso higher thn exoti tree speies. The highest iomss ontent ws found in A. hplsh ( t h -1 ) followed y L. speios (284 t h -1 ) nd D. turintus (279 t h -1 ) ll of whih re pure indigenous speies for Bngldesh Soil Chemil nd Physil Properties The studied soils were slightly to strongly id soils. Soil ph, CEC nd TN ontent vried from 4.49 to 4.68, 4.31 to 6.5 mol kg -1 nd.9 to 2.3 mg kg -1 respetively (Figure 2). The CEC ws signifintly low in soils under A. uriuliformis thn soils under indigenous speies (Figure 2). There were signifint (P<.5) differenes etween soils under tree speies for onentrtions of orgni C. Orgni C ontent in soils under A. uriuliformis vried from 6.4 to 8.7 mg kg -1 nd the men vlue ws 7.5 mg kg -1 (Figure 2d). Men orgni C ontent ws the highest in soils under A. hplsh (1.8 mg kg -1 ) thn the soils under other plnt speies (Figure 2d). Soil texture ws sndy lom everywhere. The ulk density nd wter holding pity rnged from 1.52 to 1.54 g m -3 nd to 34.75% respetively. Correltion nlysis reveled signifint reltionship of different plnt growth prmeters on hemil nd physil properties. Totl iomss of tree speies strongly ffeted orgni ron (r=.74, p<.1), totl nitrogen(r=.66, p<.1) nd tion exhnge pity (r=.62, p<.1) in soils under four plnted forests (Tle 3) Soil Miroil Properties Soil miroil properties under ll the plnt speies differed signifintly with eh other (Tle 3). Miroil prmeters were found higher in indigenous tree speies thn the exoti speies A. uriuliformis. Within the indigenous tree speies A. hplsh ontined higher numer of ultivle teri nd fungi thn L. speios nd D. turintus (Figure 3,). Miroil C ontent ws lso high in soil under A. hplsh ( µg C g -1 ). The rte of sl respirtion vried from.6 to.7 mg CO 2 g -1 dy -1,.11 to.13 mg CO 2 g -1 dy 1,.1 to.14 mg CO 2 g -1 dy -1 nd.11 to.13 mg CO 2 g -1 dy -1 with men vlue of.6,.12,.13 nd.12 mg CO 2 g -1 dy -1 in soils under A.uriuliformis, A. hplsh, D. turintus nd L. speios respetively (Figure 3). Fungi in forest floor were more signifintly ffeted thn teri y ll the plnt growth prmeters. Totl iomss of plnttions strongly ffeted numer of teri (r=.62, p<.1), numer of fungi (r=.72, p<.1), miroil iomss C (r=.695, p<.1) nd miroil tivity (r=.669, p<.1) (Tle 3).

5 Interntionl Journl of Agriulture nd Forestry 216, 6(6): Eo-physiologil Indies Men minerliztion quotient ws the lowest in soils of A. uriuliformis (.27%) nd the highest in soil of D. turintus (.39%) (Figure 4). Men miroil quotient ws the highest in soils of A. uriuliformis (11.47%) nd the lowest in soils of L. speios (7.22%). The qmi in soils of A. uriuliformis hd signifint differene with the soils of other sites (Figure 4). The vrition of qmi in soils of D. turintus nd L. speios ws lso signifint. Vlues of metoli quotient (qco 2 ) in soils of A. uriuliformis, A. hplsh, D. turintus nd L. speios vried from.9 to 1.9, 1.56 to 1.72, 1.45 to 1.98 nd 1.56 to 2.3 (µg CO 2 -C mg -1 C mi h -1 ) with men vlue of.98, 1.61, 1.8 nd 1.87 (µg CO 2 -C mg -1 C mi h -1 ) respetively. Men vlue of qco 2 ws the highest in soils of L. speios nd the lowest in soils of A. uriuliformis (Figure 4). Totl iomss of plnttions strongly ffeted qmi (r= -.648, p<.1 (Tle 5). Speies Tle 2. Volume of tree speies in unit re, ove ground, elow ground nd totl iomss of tree speies in study re Men Girth dimeter (m) Men Height (m) Density of tree numers (n/h) Men sl re (m 3 h -1 ) Aove Ground Biomss (t h -1 ) Below ground iomss (t h -1 ) Totl iomss (t h -1 ) Ai uriuliformis 72.± ± ± ± ± ± ±11.93 Artorpus hplsh 9.67± ± ± ± ± ± ±13.61 Dipterorpus turintus Lgerstroemi speios 86.33± ± ± ± ± ± ± ± ± ± ± ± ± ±1.58 ph CEC (mol kg -1 ) TN (mg kg -1 ) OC (mg kg -1 ) d 4 Plnttion Plnttion. Plnttion. Plnttion () () () (d) Cly (%) Bulk density (g -1 ) WHC (ml) Plnttion 1.4 Plnttion Plnttion (e) (f) (g) Figure 2. Reltionship of () ph, () CEC, () TN, (d) OC, (e) Cly ontent, (f) Bulk density nd (g) WHC with plnttion in the forest soils. Brs with the sme letters within the different plnttions re not signifintly different from eh other t p <.5. [CEC= Ction exhnge pity, TN= Totl nitrogen, OC= Orgni ron, WHC= Wter holding pity, AA= Ai uriuliformis, AC= Artorpus hplsh, DT= Dipterorpus turintus nd LS= Lgerstroemi speios] Numer of Bteri log 1 (CFU g -1 soil) Plnttion Numer of Fungi log 1 (CFU g -1 soil) Plnttion Miroil tivity (mg CO 2 g -1 d -1 ) Plnttion Miroil iomss ron (µg C g-1) Plnttion () () () (d) Figure 3. Reltionship of () numer of ultivle teri, () numer of ultivle fungi, () miroil tivity, nd (d) miroil iomss ron with plnttion in the forest soils. Brs with the sme letters within the different plnttions re not signifintly different from eh other t p <.5. [CFU= Colony forming unit, AA= Ai uriuliformis, AC= Artorpus hplsh, DT= Dipterorpus turintus nd LS= Lgerstroemi speios]

6 22 Md. Mmunur Rsid et l.: Effets of Miroil Biomss nd Ativity on Cron Sequestrtion in Soils under Different Plnted Forests in Chittgong, Bngldesh Tle 3. Person s orreltion oeffiients etween soil hemil, physil nd miroiologil properties ph OC TN Bteri Fungi MA MBC qm qmi qco 2 ph ** -.25** -.41** -.11**.7** -.25**.37**.6**.14** OC 1..87**.89**.86**.87**.52**.32** -.97**.82** TN 1..72**.6** ns.23** Bteri 1..89**.73**.52**.2** ns.6** Fungi 1..87**.64**.53** -.82**.79** MA 1..47**.75** -.88**.97** MBC 1..23** -.34**.24** qm **.74** qmi ** qco 2 1. [OC= Orgni ron, TN= Totl nitrogen, Bteri= Numer of ultivle teri, Fungi= Numer of ultivle fungi, MA= Miroil tivity, MBC= Miroil iomss ron, qm= Minerliztion quotient, qmi= Miroil quotient, qco 2 = Metoli quotient] Tle 4. Person s orreltion oeffiients etween different plnt growth prmeters of tree speies in the study re in unit re nd soil properties Plnt growth prmeters ph Bulk Density OC TN CEC Numer of ultivle teri Numer of ultivle fungi Miroil tivity Miroil iomss C DBH -.6** -.52**.67**.31**.55**.6**.83**.717**.897** MH -.35** -.22**.35**.18**.1**.49**.54** -.56**.521** MBA.63** ns.31**.18**.56**.6**.3**.68**.67** Totl Biomss -.1** -.39**.74**.66**.62**.62**.72**.669**.695** Tree density.2** -.19**.51**.46**.4** ns.26**.471** -.58** Correltion is signifint t the.1 level. OC= Orgni ron, TN= Totl nitrogen, CEC= Ction exhnge pity. qm (%) d Plnttion qmi (%) d Plnttion qco 2 (ug CO2-C mg -1 MBC h -1 ) Plnttion () () () Figure 4. Reltionship of eophysiologil indies ()qm, () qmi nd () qco 2 with plnttion in the forest soils. Brs with the sme letters within the different plnttions re not signifintly different from eh other t p <.5. [qm= Minerliztion quotient, qmi= Miroil quotient nd qco 2 = Metoli quotient, AA= Ai uriuliformis, AC= Artorpus hplsh, DT= Dipterorpus turintus nd LS= Lgerstroemi speios] Tle 5. Person s orreltion oeffiients etween plnt growth prmeters tree speies in the study re in unit re nd eo-physiologil indies Plnt growth prmeters qm qmi qco 2 DBH.512** -.566**.544** MH -.114**.112** -.212** MBA.883** -.414**.721** Totl Biomss.325** -.648**.554** Tree density.157** -.585**.535** Correltion is signifint t the.1 level. qm= Minerliztion quotient, qmi= Miroil quotient nd qco 2 = Metoli quotient. 4. Disussion 4.1. Plnt Speies Results show tht indigenous speies n sequester more orgni C thn exoti speies. Among the indigenous speies A. hplsh hd the highest iomss ontent (299 t h -1 ). Therefore, it hs the ility to store more C nd t s sink thn exoti speies in plnttions. Akter et l. [33] nd Almgir nd Al-Amin [34] found tht men orgni C ws the highest for indigenous speies thn exoti speies in Chittgong University mpus. Higher mounts of plnt residue inputs in soil might either elerte deomposition nd redue C storge through deresed metoli effiieny or enhne deomposition of existing soil C. Alterntively or in prllel, higher mounts of plnt residue inputs ould enhne C storge through inresed mss of ded plnt mteril umultion over time. The oserved inrese in C storge with plnt speies therefore either reflets higher primry prodution or longer persistene of plnt-derived orgni mterils due to slower deomposition. Inresed plnt residue inputs n lso

7 Interntionl Journl of Agriulture nd Forestry 216, 6(6): provide more sustrte for soil miroorgnisms, resulting in more tive nd more undnt miroil ommunity in study re Soil Chemil nd Physil Properties The C storge in forest soils is ffeted y forest type, nd site qulity [35] nd mngement prties, suh s fire, ler felling et. There were signifint differenes etween soil hemil nd physil properties under the four different tree speies (Tle 3). A. uriuliformis ontriutes the lowest ontent of orgni C in soils whih is 1.5 times less s ompred with A. hplsh nd L. speios (Figure 2d). Men orgni C ontent ws the highest in soils under A. hplsh due to return of gretest quntity of litter to the soil. Deiduous tree speies usully hve higher-qulity (low C:N) folir litter thn do evergreen tree speies [36]. Litter from different tree speies deomposes t different rtes [37, 38, 39], therey influening soil C umultion rtes [4] Soil Miroiologil Properties Individul plnt speies re known to influene soil miroil tivity nd nutrient yling through the qulity nd quntity of orgni mtter return to the soil [41]. Bsl respirtion represented the minerliztion of ntive orgni sustnes in the soil smples. Men respirtion rte inditing the miroil tivity nd Miroil iomss C s well s numer of ultivle teri nd fungi were the highest in soil under A. hplsh. On the other hnd, these prmeters were the lowest in soils of A. uriuliformis. The levels of miroil iomss C differed etween soils under indigenous nd exoti speies (Figure 3). This indites tht the mintenne of ntive vegettion ensures the est onditions (plnt iomss nd N level), with positive influene on the development nd estlishment of the soil miroiot [42] (Tle 4). Though miroil popultion ws higher in soils of L. speios thn D. turintus, miroil iomss C ws higher in soils under D. turintus s the fungi to teri rtio ws higher in soils of D. turintus (.81) thn L. speios (.8). Menyilo et l. [43] nd Sinh et l. [44] reported tht the seondry rodleved forest hd higher soil miroil iomss C nd N thn the Cunninghmi lneolt plnttions inditing tht tree speies ffeted soil miroil proesses Eo-physiologil Indies Miroiologil prmeters were orrelted in mny studies s n index [45]. The minerliztion quotient (qm), miroil quotient (qmi) nd metoli quotient (qco 2 ) re hve often een used for evluting the miroil eophysiology implying n interlinkge etween ell-physiologil funtioning under the influene of environmentl ftors [46]. In this study the responses of different plnt speies to eophysiologil indies found to e strongly ffeted (Tle 4). Signifint hnges in qm, or the potentil C minerliztion mens tht ll the plnt speies ffeted the pity of the soils to store C. Miroil metoli quotient is sensitive inditor of the iologil tivity nd sustrte qulity [31, 47]. The low qmi nd the high qco 2 reflet less effiient use of orgni sustrtes y miroil iomss [46, 3]. Men miroil quotient rnged form % nd ws in the order of A. uriuliformis> D. turintus> A. hplsh> L. speios whih denotes perentge of metolilly tive C is highest in soil under A. uriuliformis nd lowest in soil under L. speios. Even though the soil under A. uriuliformis hd lower orgni C nd miroil tivity, it hs higher miroil quotient s ompred to the soils under other speies. Higher vlue of qmi in soil under A. uriuliformis lso represents ssimiltion of C y miroes. In ddition, lower rte of deomposition my filitte higher rte of C ssimiltion. When the miroil iomss eomes more effiient in the use of the eosystem resoures, less CO 2 (per unit of miroil iomss C) is lost through respirtion nd higher mount of the C is inorported into miroil iomss, resulting derese in qco 2 [48]. The men vlue of metoli quotient vried from (µg CO 2 -C mg -1 C mi h -1 ) in the studied soils nd ws in the sequene of L. speios> D. turintus> A. hplsh to A. uriuliformis. This indites tht soil miroes under L. speios hd lest C use effiieny where s soil miroes under A. uriuliformis were utilizing C t pek level. We n therefore suggest tht, the C ville for miroes hs een used to uild up more miroil iomss s the signifint inrese of miroil quotient under A. uriuliformis. A. uriuliformis provided C for miroil growth, ut numer of ultivle teri nd fungi, miroil tivity nd iomss were lower thn other plnt speies in its soil. On the other hnd lower rte of minerliztion in soils under A. hplsh (.31%) thn L. speios (.32%) nd D. turintus (.39%) long with higher orgni C, miroil popultion indite tht sequestered C ws higher in this site. Bsed on physio-hemil nd miroil properties s well s sttistil nlyses for investigting the potentility of C sequestrtion, it n e sum up tht ron dynmis ws higher in A. hplsh thn ll other speies nd therefore hs greter potentility to sequester C in soils. ACKNOWLEDGEMENTS The finnil support from the University of Chittgong, Bngldesh, is grtefully knowledged. REFERRENCES [1] Kerr, R. A., 27, Sientists tell poliymkers we re ll wrming the world., Siene., 315, [2] Kintish, E., 27, New ongress my e wrming up to plns for pping emissions. Siene., 315, 444.

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