Variation in available micronutrients in black soil after 30-year fertilization treatment

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1 Plnt Soil Environ. Vol. 6,, No. 9: 87 9 Vrition in ville mironutrients in lk soil fter -yer fertiliztion tretment Y.G. Zhng,, Y.Y. Zhng, J.P. Ci, P. Zhu, H.J. Go, Y. Jing Stte Key Lortory of Forest nd Soil Eology, Institute of Applied Eology, Chinese Ademy of Sienes, Shenyng, P.R. Chin College of Environmentl Engineering, Shenyng University, Shenyng, P.R. Chin Agriulturl Environment nd Resoures Reserh Center, Jilin Ademy of Agriulturl Sienes, Chnghun, P.R. Chin ABSTRACT To ssess the effets of long-term fertiliztion on soil ville mironutrients in frmlnd, this study exmined diethylenetriminepenteti id (DTPA) extrtle iron (Fe), mngnese (Mn), opper (Cu), nd zin (Zn) in surfe soil with monoulture of orn (Ze mys L.) with -yer filed fertiliztion experiment estlished in Northest Chin. Tretments inluded no fertiliztion (CK); nitrogen only (N); nitrogen nd phosphorus only (NP); NP nd potssium (NPK); NPK plus ornstlk (SNPK), nd NPK plus frmyrd mnure (MNPK). Results showed tht DTPA-Fe nd Mn were signifintly inresed with hemil N pplition, nd DTPA-Cu nd Zn were signifintly inresed with frmyrd mnure mendment, while mironutrients were not signifintly different etween tretment SNPK nd CK. DTPA-Fe nd Mn were out twie to threefold in tretments N, NP, nd NPK s muh s in tretments SNPK, MNPK nd CK. DTPA-Cu nd Zn in tretment MNPK were out.9 nd 6. times s muh s in CK. DTPA-Fe nd Mn deresed with the inresing of soil ph nd tion exhnge pity, while DTPA-Cu nd Zn inresed with the inrese of soil orgni ron nd eletril ondutivity. Keywords: ornstlk; frmyrd mnure; long-term fertiliztion; nutrient yling; soil fertility Mironutrient defiieny is widespred ll over the world euse of the generlly low levels of ville mironutrients in griulturl soils, nd lso euse of inresed nutrient demnds from intensive ropping prties (Allowy 8). Humn tivities suh s tillge, rop residue reyling, fertiliztion, pestiide pplition, nd wste disposl ffet soil physiohemil properties, nd will led to hnges of mironutrients in soils (Jing et l., 9). Orgni mnures re signifint soures of mironutrients in groeosystems (Uprety et l. 9, Xu et l. ). Long-term pplition of pig slurry (Nikoli nd Mtsi ), poultry litter (Pederson et l. ), or ttle mnure (Benke et l. 8, Au-Zhr et l. ) hve een orroorted to inrese Cu nd Zn ontents sustntilly in the upper soil lyer. Mnure mendment inresed soil DTPA-extrtle Cu, Zn, Fe, nd Mn, ut did not signifintly ffet the totl ontents of mironutrients, fter 9 yers of ropping nd fertiliztion in n Aqui Ineptisol in middle Chin (Li et l. ). Mny minerl P fertilizers possess onsiderle mounts of mironutrients, thus they my lso e signifint soures of mironutrients in groeosystems (Uprety et l. 9). Chemil N fertilizer pplition nd lned pplition of NPK ould inrese (Li et l. 7), or derese (Rengel 7), or hve no signifint effet (Beher nd Singh 9) on DTPA-extrtle mironutrients in soils. Inresed yields hieved y minerl Supported y the Ntionl Bsi Reserh Progrm of Chin, Projet No. CB, nd y the Ntionl Key Tehnology R&D Progrm of Chin, Projet No. BADB. 87

2 Vol. 6,, No. 9: 87 9 Plnt Soil Environ. NPK pplition my elerte mironutrient removl from groeosystems, using imlne in nutrient yling, nd hene, the vrition in soil ville mironutrient with different fertiliztion regimes ws dependent on fertilizer vrieties, soil physiohemil properties, rop sorptions, nd reyling rtes (Cliskn et l. 8). Mny reserhes involving long-term fertiliztion foused on soil produtivity, ron nd mronutrients, reltive to mironutrients (Edmedes, Yn nd Gong ). From the erly 98 s, mny long-term fertiliztion experiments were estlished in Chin s frmlnds, ut little informtion is ville relting to long-term fertiliztion on plnt ville soil mironutrients. Blk soils in Northest Chin (' N, '7 E) re fertile nd produtive, ounting for one-third of Chin s totl orn yield, thus, mesures nd studies relted to the mintinility of soil fertility re of ritil importne. It is silly ler tht soil orgni C, mronutrients, soil ph nd oxidtion-redution onditions, wter-holding pity, soil fun, miroes nd enzyme hnge lot under different fertiliztion regimes (Zhu et l. 7, Li et l. 9), nd our hypothesis ws tht, with different fertilizer pplition, soil extrtle mironutrients would hnge long with soil physiohemil nd iologil properties mentioned ove, nd hene, the ojetives were to exmine the vrition in soil DTPA-extrtle mironutrients under hemil fertilizer pplition, ornstlk ddition nd frmyrd mnure mendment in long-term field experiment with monoulture of orn, nd to identify ftors ontriuting to the vrition in soil mironutrients. MATERIAL AND METHODS Site desription. The study ws onduted t n ongoing Ntionl Long-term Experimentl Sttion for Soil Fertility Monitoring in Blk Soil, loted t Gongzhuling, Chin ( 'N, 8'E). It is loted in ontinentl temperte monsoon zone. The nnul temperture rnges.. C, nnul preipittion rnges 6 mm, nd nnul non-frost period rnges dys. The soil is lssified s Hlpi Pheozem (FAO 988). A long-term fertiliztion experiment with monoulture orn ws estlished in 98, inluding six tretments: () CK no fertilizer; () N only; () NP only; () NPK; () NPK plus ornstlk (SNPK), nd (6) NPK plus frmyrd mnure (MNPK). Nutrient input ws 6 kg N/h, 6 kg P/h, nd 68. kg K/h, with ure, (NH ) HPO, nd KCl, nd 7 kg/h/yer ir-dried ornstlk in SNPK, nd t/h/yer frmyrd mnure ( mixture of swine mnure, plnt residue nd soil) in MNPK, respetively. The totl mount of N, P nd K input in the lst three tretments ws the sme. The tretments were lloted in m plots, replited thrie. Before the experiment ws estlished, the soil properties in m soil lyer were s follows, soil orgni mtter. g/kg, totl N. g/kg, totl P.9 g/kg, totl K. g/kg; soil ph 7.; the soil texture is lomy ly with prtile size distriution.. mm.%;.. mm.8%;.. mm 9.87%, nd <. mm.%; the ulk density ws.9 g/m, the totl porosity ws.9%. Exept for the SNPK tretment, ll the oveground rop residues were removed fter hrvest. All plots were ploughed to depth of m in utumn, nd the field ws disked nd ridged in spring efore sowing. The verge orn yield during to ws out 9 nd 6 kg/h for CK nd MNPK tretments, respetively, while the other four tretments hrvested out 8 98 kg/h orn per yer. Smpling nd soil nlyses. In Otoer, fter hrvesting, mixed soil smples were olleted from the tretment plots t the depth of m. Soil smples were ir-dried nd ground to pss through -mm nd.9-mm sieves. Soil mironutrients were extrted with. mol/l DTPA,. mol/l CCl, nd. mol/l TEA t ph 7., the totl ontents were digested with 8% HF nd onentrted HNO. Both totl nd DTPA-Fe, Mn, Cu, nd Zn were nlyzed y tomi sorption spetrophotometer (AAS, Shimdzu, Jpn). Soil ph nd eletril ondutivity (EC) were mesured with eletrodes in :. soil:wter suspension. Exhngele C, Mg, K nd N were determined y AAS. Soil orgni C nd totl N were determined y using Vrio ELIII elementl nlyzer (Elementr, Germny). Soil totl P ws determined with spetrophotometer t -nm wvelength, nd K ws mesured y using flme photometer; mmoni N nd NO -N were extrted with mol/l KCl nd determined using mgnesium oxide-devrd lloy method (Pge 98). Chin s ntionl stndrd soil referene mterils for lk soil (GBW7 nd GBW78) were dopted through the digestion, extrtion nd nlysis proedures s prt of the QA/QC protool. 88

3 Plnt Soil Environ. Vol. 6,, No. 9: 87 9 Sttistil nlysis. The otined dt were nlyzed with the SPSS (SPSS In., Chigo, USA) Version. for Windows, using one-wy ANOVA nd the Dunn s pirwise omprison for mens seprtion, nd signifine level of P <. ws hosen for deteting signifint differenes. RESULTS AND DISCUSSION Chemil N pplition signifintly inresed DTPA-extrtle Fe nd Mn in soils. Between groups ANOVA showed tht DTPA-Fe ws signifintly greter in tretments NP nd NPK thn in the other tretments, nd it ws greter in N tretment thn in SNPK tretment nd CK. DTPA-Mn ws signifintly greter in tretments NP, NPK, nd N thn in the other three tretments (Figure ). The vrition in DTPA-Fe nd Mn mong different fertiliztion tretments ws highly dependent on soil ph (Figure ). The verge soil ph vlues in tretments N, NP, nd NPK were 6.7, 6.6, nd 6., respetively, whih were lower reltive to those in tretments SNPK, MNPK nd CK (7.9, 6.8 nd 7., respetively). The initil soil ph t the eginning of the experiment ws 7. in 98, while it ws 7. in the CK while smpling in, nd this redution my e due to the tmospheri deposition of N in this region. For one unit derese of soil ph, DTPA-Fe or Mn ws oserved to inrese out threefold. As tion exhnge pity (CEC) ws inresed long with inresing soil ph, it ws negtively orrelted (P <.) with DTPA-Fe or Mn ould lso e expressed with liner regression equtions (Figure ). For eh soil ph unit inrese, Fe +, Fe +, nd Mn + derese hundred to thousnd fold. Thus, Fe nd/or Mn defiieny is most often oserved on high-ph nd lreous soils in rid regions (Hvlin et l. ), nd lso in north Chin s frmlnds (Allowy 8). Iron nd Mn re solule in the redued stte ut redily oxidized in high ph soils, nd so rendered highly unville in suh soils (Allowy 8). It ws well doumented tht plnt ville Fe nd Mn in soils derese with inresing ph (Shrm et l. ). Drusmn et l. (99) reported tht N fertiliztion for yers used signifint inrese in ville Fe nd Mn, nd derese in soil ph (. vs. 6.) in surfe soil. Thus, hemil N fertilizer indued ph redution ws onsidered s the leding ftor tht inreses DTPA-Fe nd Mn in soils. Most niml wste nd rop residues ontin smll quntity of plnt ville Fe nd Mn (Hvlin DTPA-Fe (mg/kg) DTPA-Cu (mg/kg) DTPA-Zn (mg/kg) Figure. DTPA-extrtle mironutrient onentrtions under different fertiliztion tretments. CK no fertiliztion; N, P nd K 6 kg N/h, 6 kg P/h nd 68. kg K/h input; S 7 kg/h ornstlk input; M t/h frmyrd mnure input. Vlues ove the olumn of single figure followed y different letters re signifintly different t P <. ording to the Dunn s multiple rnge test 89

4 Vol. 6,, No. 9: 87 9 Plnt Soil Environ. R =.86; P <. R =.; P <. DTPA-Fe (mg/kg) DTPA-Fe (mg/kg) R = 6.9.7; P 7.<.7. 8 R =.7; P < Soil ph Ction exhnge pity (mol + /kg) Figure. Liner regression of DTPA-Fe nd Mn with soil ph nd tion exhnge pity et l. ). Although frmyrd mnure mendment nd ornstlk ddition my inrese Fe nd Mn soluility through heltion retions, the inresed soil ph in tretments SNPK nd MNPK deresed onentrtions of DTPA-Fe nd Mn in soil, reltive to hemil N fertiliztion tretments (Figure ). However, 9-yer experiment in middle Chin showed tht ornstlk inorported with minerl NPK (ph 8.) did not signifintly ffet DTPA-Fe nd Mn, s ompred with minerl fertiliztion (ph ) nd no fertilizer (ph 8.8) tretments (Li et l. ). Our results my e different due to the different soil ph nd other physiohemil onditions in the two regions. Frmyrd mnure mendment signifintly inresed DTPA-extrtle Cu nd Zn in soils. DTPA-Cu nd Zn were signifintly inresed in MNPK tretment, while NPK tretment hd more DTPA-Cu thn in SNPK tretment nd CK. Conentrtions of DTPA-Cu were out times higher in MNPK tretment thn in CK or SNPK tretment, while DTPA-Zn ws out.8 6. times higher in MNPK tretment thn in the other tretments (Figure ). The vritions of DTPA-Cu nd Zn minly ourred s frmyrd mnure mendment indued hnges in hemil properties, suh s soil orgni ron (SOC), exhngele tions nd EC in soils. DTPA-Cu nd Zn were signifintly nd positively orrelted with SOC nd EC (Figure ). A se study with 98 soil smples in Indi lso showed tht DTPA-Cu nd Zn were positively orrelted with soil SOC nd EC (Vijynkumr et l. ). Orgni mendments re often used for orgni mtter replenishment nd to void pplition of high levels of hemil fertilizers. Although most niml wstes ontin smll quntity of plnt ville Cu nd Zn, nimls require metls s prt of their diet, so mironutrients like Cu nd Zn re dded to feedstuffs s growth promoters or dirrhe preventers (Crlson et l. 8). Thus, long-term frmyrd mnure mendment tended to inrese Cu nd Zn in soils. A six yer study showed tht ompost mendment resulted in n inrese in ll extrtle mironutrients, s ompred with soil with minerl fertiliztion (Hereni et l. 8). Reltive to minerl fertilizer inputs, frmyrd mnure pplied t t/h signifintly inresed soil levels of Cu nd Zn, using the dt from the Rothmsted experiments (Johnston 997). Consequently, long-term pplition of frmyrd mnure signifintly inresed DTPA-Cu nd Zn in soil in this study. Cornstlk inorported with minerl NPK did not signifintly ffet DTPA-Cu nd Zn, s ompred with CK, whih ws in ordne with similr 9

5 Plnt Soil Environ. Vol. 6,, No. 9: 87 9 R =.6; P <. R =.67; P <. DTPA-Cu (mg/kg) DTPA-Cu (mg/kg) DTPA-Zn (mg/kg) R = 7.77; P 9 <. DTPA-Zn (mg/kg) Soil orgni ron (g/kg) 8 6 R =.88; P < Soil eletril ondutivity (ds/m) Soil orgni ron (g/kg) Figure. Liner regression of DTPA-Cu nd Zn with soil orgni ron nd eletril ondutivity study onduted in n Aqui Ineptisol for 9 yers in middle Chin (Li et l. ). The min resons for lower DTPA-Cu nd Zn in SNPK tretment were dedued s follows, (i) omprtively Totl Fe (g/kg) ns NS Totl Mn (mg/kg) lower totl Cu nd Zn in soil euse of the smll quntity of mironutrients in ornstlk (Figure ), nd (ii) omprtively higher soil ph (7.9) deresed the vilility of soil mironutrients. Totl Mn (mg/kg) 8 6 Totl Cu (mg/kg) Totl Zn (mg/kg) 8 6 CK N NP NPK SNPK MNPK Figure. Totl mironutrient onentrtions under different fertiliztion tretments. CK no fertiliztion; N, P nd K 6 kg N/h, 6 kg P/h nd 68. kg K/h input; S 7 kg/h ornstlk input; M t/h frmyrd mnure input. Vlues ove the olumn of single figure followed y different letters re signifintly different t P <. ording to the Dunn s multiple rnge test 9

6 Vol. 6,, No. 9: 87 9 Plnt Soil Environ. Tle. Person orreltion oeffiients of DTPA-extrtle mironutrients with relted soil hemil properties (n = 8) DTPA-Fe DTPA-Mn DTPA-Cu DTPA-Zn Totl Cu.89** Eletril ondutivity.*.78**.66**.767** Soil ph.99**.868**.67. Soil orgni ron..79*.77**.86** Totl nitrogen **.9** Totl phosphorus Totl potssium.6... Ammoni nitrogen (NH + -N).6** Nitrte nitrogen (NO -N).6..6**.6** Exhngele lium.7**.786**.8. Exhngele mgnesium.6**.98.8**.67** Exhngele potssium..6**.68**.77** Exhngele sodium...897**.9** Ction exhnge pity.6**.7**.68.8 *P <.; **P <. It ws well reported tht soil ville Cu nd Zn would e inresed with pplition of minerl P fertilizers (e.g. Li et l. 7), ut se study showed tht ontinuous pplition of inorgni NPK fertilizers in ssv prodution resulted in derese of ville Zn nd Cu in soil (Rengel 7). However, no signifint differene ws oserved in DTPA-Cu nd Zn mong hemil fertiliztion tretments, nd SNPK (Figure ). Reltionships of DTPA-extrtle mironutrients with other soil hemil properties. The onentrtion of DTPA-Cu ws highly orrelted with totl Cu (Tle ), while DTPA-extrtle Fe, Mn or Zn were not signifintly orrelted with their totl ontents. No signifint differene ws oserved for totl Fe mong tretments, while totl Mn ws only signifintly greter in N tretment thn in MNPK tretment. Totl Cu ontents in tretments were sequened from high to low s MNPK, NPK, NP, SNPK, N, nd CK. Totl Zn ontent ws signifintly lower in tretments NP nd SNPK thn in the other tretments (Figure ). Soil EC ws positively orrelted with DTPA-Fe nd Mn, s opposed to negtively with Cu nd Zn. Soil ph ws only signifintly nd negtively orrelted with Fe nd Mn. Soil orgni C nd totl N were positively orrelted with Cu nd Zn, ut nitrite N tht orrelted negtively with them; neither totl P nor totl K ws signifintly orrelted with ny of the mironutrients. Ammoni N ws the only one to orrelte with Fe, exhngele C nd CEC orrelted negtively with Fe nd Mn, while exhngele Mg, K nd N positively with Cu nd Zn (Tle ). In onlusion, long-term hemil N pplition signifintly inresed DTPA-extrtle Fe nd Mn in soils, while the frmyrd mnure mendment signifintly inresed DTPA-extrtle Cu nd Zn in soils. DTPA-Fe nd Mn inresed signifintly with the derese of soil ph nd CEC, while DTPA-Cu nd Zn inresed signifintly with inresing SOC nd EC. Although ornstlk ddition signifintly inresed SOC, low ontents of totl mironutrients in ornstlk nd the omprtively higher soil ph deresed the vilility of soil mironutrients. The reserh implites tht frmyrd mnure mendment is for enefiil enhning of soil Cu nd Zn fertility, while mironutrients should e dded to meet rop requirements in ornstlk ddition prties in the lk soil frmlnds of Northest Chin. REFERENCES Au-Zhr T.R., Auker S.M., Thou A.B., Al-Adi A.A. (): Effet of orgni mtter soures on mironutrients nd hevy metls umultion in soil. Food, Agriulture nd Environment, 8: 99. Allowy B.J. (8): Mironutrient Defiienies in Glol Crop Prodution. Springer-Verlg, Berlin, Heidelerg. Beher S.K., Singh D. (9): Effet of yers of ontinuous ropping nd fertilizer use on soil properties nd uptke of 9

7 Plnt Soil Environ. Vol. 6,, No. 9: 87 9 mironutrients y mize (Ze mys)-whet (Tritium estivum) system. Indin Journl of Agriulturl Sienes, 79: Benke M.B., Indrrtne S.P., Ho X.Y., Chng C., Goh T.B. (8): Tre element hnges in soil fter long-term ttle mnure pplitions. Journl of Environmentl Qulity, 7: Cliskn S., Ozky I., Cliskn M.E., Arsln M. (8): The effets of nitrogen nd iron fertiliztion on growth, yield nd fertilizer use effiieny of soyen in Mediterrnen-type soil. Field Crops Reserh, 8: 6. Crlson D., Sehested J., Feng Z., Poulsen H.D. (8): Serosl zin ttenute serotonin nd vsotive intestinl peptide indued seretion in piglet smll intestinl epithelium in vitro. Comprtive Biohemistry nd Physiology. Prt A, Moleulr nd Integrtive Physiology, 9: 8. Drusmn, Stone L.R., Whitney D.A., Jnssen K.A., Long J.H. (99): Soil properties fter twenty yers of fertiliztion with different nitrogen soures. Soil Siene Soiety of Ameri Journl, : 97. Edmedes D.C. (): The long-term effets of mnures nd fertilisers on soil produtivity nd qulity: A review. Nutrient Cyling in Agroeosystems, 66: 6 8. FAO (988): FAO-UNESCO Soil Mps of the World, Revised Legend. World Soil Resoures Reports 6, FAO, Rome. Hvlin J.H., Tisdle S.L., Nelson W.L., Beton J.D. (): Soil Fertility nd Fertilizers: An Introdution to Nutrient Mngement. 7 th Edition. Person Edution, Prentie Hll. Hereni J.F., Ruiz J.C., Morillo E., Melero S., Villverde J., Mqued C. (8): The effet of orgni nd minerl fertiliztion on mironutrient vilility in soil. Soil Siene, 7: Jing Y., Ling W.J., Wen D.Z., Zhng Y.G., Chen W.B. (): Sptil heterogeneity of DTPA-extrtle zin in ultivted soils indued y ity pollution nd lnd use. Siene in Chin Series C Life Sienes, 8: 8 9. Jing Y., Zhng Y.G., Zhou D., Qin Y., Ling W.J. (9): Profile distriution of mironutrients in n qui rown soil s ffeted y lnd use. Plnt, Soil nd Environment, : Johnston A.E. (997): The vlue of long-term field experiments in griulturl, eologil, nd environmentl reserh. Advnes in Agronomy, 9: 9. Li B.Y., Zhou D.M., Cng L., Zhng H.L., Fn X.H., Qin S.W. (7): Soil mironutrient vilility to rops s ffeted y long-term inorgni nd orgni fertilizer pplitions. Soil nd Tillge Reserh, 96: Li B.Y., Hung S.M., Wei M.B., Zhng H.L., Shen A.L., Xu J.M., Run X.L. (): Dynmis of soil nd grin mironutrients s ffeted y long-term fertiliztion in n Aqui Ineptisol. Pedosphere, : 7 7. Li Q., Jing Y., Ling W.J., Wng H., Jing S.W. (9): Nemtode diversity in pheozem groeosystems of Northest Chin. Pedosphere, 9: Nikoli T., Mtsi T. (): Influene of liquid ttle mnure on mironutrients ontent nd uptke y orn nd their vilility in lreous soil. Agronomy Journl, : 8. Pge A.L. (98): Methods of Soil Anlysis. Agronomy Monogrph 9, Prt : Chemil nd Minerlogil Properties. nd Edition. Amerin Soiety of Agronomy, Mdison. Pederson G.A., Brink G.E., Firrother T.E. (): Nutrient uptke in plnt prts of sixteen forges fertilized with poultry litter: Nitrogen, phosphorus, potssium, opper, nd zin. Agronomy Journl, 9: Rengel Z. (7): Cyling of mironutrients in terrestril eosystems. In: Mrshner P., Rengel Z. (eds.): Nutrient Cyling in Terrestril Eosystems. Springer-Verlg, Berlin, Heidelerg, 9. Shrm B.D., Mukhopdhyy S.S., Sidhu P.S., Ktyl J.C. (): Pedospheri ttriutes in distriution of totl nd DTPAextrtle Zn, Cu, Mn nd Fe in Indo-Gngeti plins. Geoderm, 96:. Uprety D., Hejmn M., Száková J., Kunzová E., Tlustoš P. (9): Conentrtion of tre elements in rle soil fter long-term pplition of orgni nd inorgni fertilizers. Nutrient Cyling in Agroeosystems, 8:. Vijynkumr R., Arokirj A., Prsth M.D.P. (): Mronutrient nd mironutrient sttus nd their reltionship with soil properties of nturl disster prone ostl soils. Reserh Journl of Chemistry nd Environment, : 8. Yn X., Gong W. (): The role of hemil nd orgni fertilizers on yield, yield vriility nd ron sequestrtion results of 9-yer experiment. Plnt nd Soil, : 7 8. Xu Y., Yu W., M Q., Zhou H. (): Aumultion of opper nd zin in soil nd plnt within ten-yer pplition of different pig mnure rtes. Plnt, Soil nd Environment, 9: Zhu P., Ren J., Wng L.C., Zhng X.P., Yng X.M., Don MTvish (7): Long-term fertiliztion impts on orn yields nd soil orgni mtter on ly-lom soil in Northest Chin. Journl of Plnt Nutrition nd Soil Siene, 7: 9. Reeived on Jnury, Aepted on July, Corresponding uthor: Prof. Dr. Yong Jing, Chinese Ademy of Sienes, Institute of Applied Eology, Stte Key Lortory of Forest nd Soil Eology, Shenyng 6, P.R. Chin phone: , fx: , e-mil: jingyong@ie..n 9