MONITORING DYNAMICS OF GRASSLAND VEGETATION IN POYANG LAKE NATIONAL NATURE RESERVE,USING MODIS IMAGERY

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1 MONITORING DYNAMICS OF GRASSLAND VEGETATION IN POYANG LAKE NATIONAL NATURE RESERVE,USING MODIS IMAGERY Guan Yan a, *, Lin Wnjing b, Zhou Filong c, Zng Nanjing c a Scinc Prss,6 Donghuangchnggn North Strt, Bijing, China-(guanyan8228)@gmail.com b Institut of Hydrogology and Environmntal Gology, CAGS, 406 Shigang Strt, Shijiazhuang, China-(lwnjing977)@gmail.com c Poyang Lak National Natur Rsrv, 490 Chunhui Road, Honggutan Xinqu, Nanchang, China-(njzng)@gmail.com Commission VI, ThS-9 KEY WORDS: Satllit rmot snsing, Normalizd Diffrnc Vgtation Indx (NDVI), Spatio-tmporal modling, Ecosystm ABSTRACT: Th particular flood rcssional cosystm in Poyang Lak provids young and high quality grasss in lat autumn and wintrtim, and attracts millions of migratory birds to ovr wintr. Grasslands along th laks within Poyang Lak National Natur Rsrv (NNR) hav a rmarkabl phnology. So far, littl attntion has bn paid to this dynamics of phnology. This thsis aimd to dscrib and invstigat th sasonal pattrns of th rcssional grassland vgtation and how ar ths rlatd to nvironmntal variabls (lvation, watr lvl and air tmpratur). Normalizd Diffrnc Vgtation Indics (NDVI) drivd from tim-sris MODIS was applid to invstigat th phnological pattrns of grassland vgtation. Huisman-Olff-Frsco modl II (HOF modl II) was mployd to dtct th rspons of th grassland vgtation to nvironmnt variabls. Th rsults rvald a strong ngativ rlationship btwn th covr prcntag of Carx and lvation and a positiv rlationship btwn th lngth of Carx and lvation, with R 2 was 7 and 8 rspctivly. Tim sris NDVI showd clar sasonal phnological pattrns of Carx. Th phnology dynamics was attributd to th fluctuation of watr lvl and air tmpratur btwn yars. It rvald that NDVI of Carx has a ngativ rlationship with watr lvl and a positiv rlationship with cumulativ air tmpratur rspctivly.. INTRODUCTION Th particular flood rcssional cosystm in Poyang Lak provids young and high quality grasss in lat autumn and wintrtim, and attracts millions of migratory birds to ovr wintr. As an important national and intrnational wtland cosystm, it has significant cological function in biological divrsity protction. Th grasslands along th laks in Poyang Lak National Natur Rsrv (NNR) hav a rmarkabl phnology (Wu and Ji,2002; Si, 2006; Zng, 2006). Thir spcis composition and pattrn of grning chang with lvation. Grasslands at lowr lvation ar dominatd by short grasss and sdgs (Carx), whil grasslands at highr lvation hav Miscanthus sacchriflorus and Cynodon daxtylon. At highr lvations, vgtation mrging in spring continus to grow ovr summr and snscnc in autumn. Vgtation at lowr lvations which is grn in autumn, wintr and spring submrgs for a shortr or longr priod in summr. In autumn, whn th watr rcds, vgtation mrgs again at th lak dg (Si, 2006). This diffrnc in spcis composition and phnology has bn attributd to diffrncs in flooding. Th phnology of th grasslands is also affctd by tmpratur. Highst and lowst monthly tmpratur of 29. and 4.5 occur in July and January rspctivly in Poyang Lak NNR (Wu and Ji, 2002). In lat autumn, vgtation at highr lvation dis off. Vgtation at low lvation rmains grn but thir growth may b rducd or stoppd bcaus of th low tmpratur. Howvr, th grasslands in Poyang Lak NNR hav shank and thus habitats for wild migrat birds ar in dangr, as a consqunc of lowr and lowr watr lvls in Poyang Lak. This chang in watr lvl has a crtain impact on th dat of up grning and dvlopmnt of rcssional grasslands. Thus monitoring th phnology dynamics of this rcssional grassland vgtation has spcific maning for habitat protction of migratory birds. So far, rsarchs hav bn conductd which focus on monitoring and mapping th grasslands in Poyang Lak (Si, 2006; Zng, 2006). Howvr, littl attntion has bn paid to this dynamics of phnology. Tim sris rmot snsing offrs th possibility to monitor wtland vgtation (Salomonson t al., 989; Zhang t al., 2003; Barbosa t al., 2006) and map phnological pattrns of thm (Davidson and Csillag, 2003; Zng, 2006). Normalizd Diffrnc Vgtation Indics (NDVI) has bn usd for vgtation phnology at global, rgional and local scal (Maslli t al., 998; Chn t al., 200; Choo t al., 2002; Schmidt and Karnili, 2002; Jin and Sadr, 2005; Barbosa t al., 2006; Bck t al., 2006; Si, 2006). This thsis aimd to dscrib and invstigat th sasonal pattrns of th rcssional grassland vgtation using Modrat Rsolution Imaging Spctroradiomtr (MODIS) and how ar ths rlatd to nvironmntal variabls (lvation, watr lvl and air tmpratur). * Corrsponding author. 337

2 2. RESEARCH MATERIALS AND METHODS 2. Study Ara Th rsarch focusd on Dahuchi Lak, which is th cor ara in Poyang Lak NNR. It lis to th south of th Poyang Lak NNR with an ara of 30 km 2 (Wu and Ji, 2002). Th lvation rang of this ara is from 2 to8 mtrs, with only 5 or 6 mtrs diffrnc btwn th minimum and maximum. Although th trrain appars almost flat, vrtical distribution pattrn of vgtation communitis was dvlopd du to watr fluctuation. Th watr lvls in Poyang Lak NNR ar typically high in summr du to th monsoon rains, and low in wintr. In rainy sason, th watr lvl of Dahuchi Lak riss and lak is filld by flooding watr from th Yangtz Rivr and somtims would b mrgd togthr with th larg Poyang Lak. In dry sason, th watr lvls dcras in ths sub laks and vast aras of shallow watr and floodd muddy banks ar xposd. dsignd basd on TM imag of 2005 Octobr 5 th, which wr vrtical to zonal blts of th grassland could b visual intrprtd on th imag. This stratgy insurd th sampl plots that takn along ths lins can includ vgtation at all diffrnt lvation, which was considrd to play a ky rol in modlling (Guisan and Zimmrmann, 2000). In total, 7 sampl plots wr obsrvd. Th lvation of ths sampl plots run from 2.9m to 5.9m. At ach sit, plot of 20 by 20 mtrs was stablishd. Spcis and thir covr wr dscribd and stimatd in this plot. Within ach sit four sub plots of m 2 ach wr stablishd, vnly locatd at th dirction of north, south, ast and wst from cntr of th plot. In ths sub-plots, data on covr prcntag, nams of dominant spcis, lngth of th grass vgtation masurd from ground surfac and othr obsrvation wr collctd. Th final covr prcntag and lngth of th sampl plot was calculatd by th avrag of th four sub plots. 2.4 NDVI NDVI was calculatd for th ach dat for th MOD09GQK datasts (Equation ()) for 200, 2003, 2004, 2005 and 2006 to gt vgtation grnnss. Man NDVI valus of Carx in ach month wr calculatd for Carx for 5 yars, basd on th prcntag of Carx covr. 70% was usd as th thrshold for th calculation, assuming that whn Carx covrs mor than 70% in th sampl plot, it appars to b th ovrwhlming dominant vgtation spcis in this sampl plot. Figur Study ara: Dahuchi Lak (TM imag on 5th Octobr, 2002). Location of Dahuchi Lak in Poyang Lak (lft) Dahuchi Lak (right) 2.2 Data Usd MODIS land surfac rflctanc product was slctd bcaus of its finr spatial and tmporal rsolution (Xiao t al., 2005). This MOD09CQK product has high quality sinc has bn atmosphric and gomtric corrctd. It was usd for calculating NDVI to invstigat th phnological pattrns of grassland vgtation within and btwn yars. Th digital lvation modl (DEM) of Dahuchi Lak was obtaind to driv lvation information. Th spatial rsolution is 20 m and vrtical accuracy is around dcimtr. Th watr lvl data and man daily air tmpratur data masurd in Nanchang Mtrological Station (28 22 N, 5 33) in 200, 2003, 2004, 2005 and 2006 wr usd as nvironmntal variabls for rgrssion analysis. Topographic map of th Poyang Lak NNR was usd to gt gnral ida of th study ara and hlp accssing to sampl plots in th fild. Botanical data from litratur and xprt knowldg from stuff who has workd in th Poyang Lak NNR for mor than 0 yars wr usd to idntify th grasss spcis during fild survy and data analyzing. 2.3 Fild Survy Fild survy was xcutd on 3 th to 6 th Sptmbr 2006 during th summr-blooming growth sason from Sptmbr to Novmbr (Dou t al., 997), whn th watr dpth of Dahuchi Lak was around.2 mtrs. Svral pr-sampl lins wr NDVI whr man NDVIi = n () NDVI man = man NDVI valu in ach month NDVI i = individual NDVI valu of in ach sampl plot with Carx covr mor than 70% (i=, 2, 3 n) n = total numbr of days in ach month. 2.5 Sasonal Pattrn of Watr Lvl and Cumulativ Air Tmpratur Th watr lvl rcords of Dahuchi Lak wr basd on th Wusong hight datum, which is th systm that usd by th govrnmnt for Yangtz in China. It was convrtd to th National Vrtical Datum 985 which is th official and most widly usd hight systm in China, for th sak of calculation with digital lvation modl in Dahuchi Lak. Th lvation of lvlling origin of this hight systm is m (Kong and Mi, 2002; Ning t al., 2004). Man watr lvls for ach month in ths yars wr also calculatd for furthr monthly statistical analysis. H = H.836 (2) 985 wusong whr H 985 = hight in National Vrtical Datum 985 H wusong = hight in Wusong hight datum Cumulativ tmpratur is an fficint way to dscrib tmpratur condition for vgtation growth. Fidanza t al. usd it for prdiction of crop mrgnc (Fidanza t al., 996). Bartholomw and Williams (2005) usd cumulativ tmpratur 338

3 to assss whthr it can b a usful indicator of forag coolsason grass dvlopmnt. Carx is a kind of sdg, which prfrs to grow undr cool nvironmnt and inhabit in msotrophic fns or frquntly watrloggd conditions. In Poyang Lak NNR, thy ar activat undr tmpratur 8-20 (Si, 2006) producing young lavs which utilizd by migratory birds. Schutz s study showd that th sd of Carx may rmain non-dormant undr 0-20 rgim during burial whn watr lvl fluctuats frquntly. This nabls thm to grminat whnvr thy ar xposd to air again during th growing sason, onc inundation has casd (Schutz, 997). Thus, 0 was usd as th standard tmpratur thrshold to calculatd cumulativ tmpratur to driv innr- and intr-annual air tmpratur conditions for th growth of th rcssional grasslands. 2.6 Rgrssion Analysis Thr dominant vgtation spcis wr suggstd by arlir rsarchs in Poyang Lak NNR (Si, 2006; Zng, 2006). Th variation in th abundanc of spcis in spac and tim wr supposd to b rlatd to nvironmntal factors (Dou t al., 997; Cui t al., 2000). Howvr, vry fw studis hav xamind ths rlationships through statistical analysis in Poyang Lak NNR. Simpl mathmatical modls thn wr rquird to dscrib ths obsrvd rlationships. Huisman-Olff-Frsco modl II (HOF modl II) was mployd to dtct th rspons of th grassland vgtation to ths nvironmnt variabls. HOF modl is a hirarchical st of fiv modls for spcis rspons analysis, which is particularly suitd for dscription of rsponss in tim or ovr major nvironmntal gradints (Huisman t al., 993; Guisan and Zimmrmann, 2000) Rgrssion for lngth of Carx and Elvation: In arly spring, as air tmpratur incrasing, Carx grn up and start to grow. At diffrnt lvation, th way that Carx grow is diffrnt. At lowr lvation, Carx ar floodd in Jun or arly July (dpnding on hydrological conditions of th yar), with avrag lngth around 7cm (Dou t al., 997). During rainy sason, Carx along th dg of th lak would b floodd as watr lvl rising. By th tim thy ar totally submrgd, Carx would stop growing. At highr lvation, Carx, which ar submrgd by flooding latr than thos at lowr lvation, would continu to grow and thir lngth would b longr. For th yar that watr lvl is low during summr, Carx at highr lvation vn would not b submrgd and kp growing through summr tim. Usually, matur Carx (Carx cinrascns, Carx argi and Carx unisxualis) has lngth from 30 to 70 cm (DEELECTIS FLORAE REIPUBLICAE POPULARIS SINICAE AGENDEE ACADEMIAE SINICAE EDITA, 2000). Fild obsrvation found th maximum lngth in Dahuchi Lak was around 0 cm and no mor than 20 cm, hnc 20 cm was usd as th uppr thrshold in this analysis. Thus th M was qual to as th uppr bound in HOF modl II aftr log 0 transformd Rgrssion for lngth of Carx and Exposd Days: Th numbr of xposd days to air for ach sampl plot is dtrmind by two factors. On is th lvation of th sampl plot. Th othr on is watr lvls along tim gradint. Firstly, th diffrnc btwn th hight of watr lvl and lvation was calculatd by using daily watr lvl minus th valu of lvation of ach sampl plot. Th formula was list blow: α = H ELE (3) Whr 985 H 985 = hight of daily watr lvl of sampl plots masurd in National Vrtical Datum 985 ELE = lvation of sampl plots; α = valu of diffrnc btwn daily watr lvl and lvation of sampl plots. Whn watr lvl was highr than th lvation of th sampl plots, lablld α as 0; whn watr lvl was lowr than th lvation of th sampl plots, lablld α as. Thn sum function was conductd to calculat th total numbr of days at ach sampl plot in 2006 from January to Sptmbr. N = α (4) i Whr α i = diffrnc btwn daily watr lvl and lvation of ach sampl plot on ach dat (i =, 2, 3,, 365 or 366 ) N = total numbr of xposd days to air of ach sampl plot Rgrssion for NDVI and Tim Sris Sasonal Watr Fluctuation: Watr lvls triggr up grning of Carx in autumn. If watr lvl in Sptmbr or Octobr casd arlir, Carx would grn up at th dg of th lak arlir. Consquntly, th arlir th Carx startd to grow again, th highr th NDVI valu would b obtaind from satllit imags. Thus, if th watr lvl was high in Sptmbr or Octobr, th man NDVI valu of Carx would b low. HOF modl II was mployd to dtct how watr lvl in Sptmbr or Octobr dtrmind th NDVI valu of Carx. Th uppr bound M in th modl was st as sinc th NDVI rangd from - to Rgrssion for NDVI and Tim Sris Cumulativ Air Tmpratur: In Dahuchi Lak, Carx grn up as arly as in Fbruary if th air tmpratur was warm nough for thir growth. In som yars, whn wintr was cold and air tmpratur was low in arly spring, Carx would grn up latr and grow slowly. Thus th NDVI valus on satllit imags would appar diffrntly in ths months btwn yars. Th man monthly NDVI valus in spring (Fbruary and March) during which vgtation would grn up wr calculatd for ach yar. Cumulativ tmpraturs abov a thrshold of 0 at th nd of Fbruary and March wr usd. HOF modl II was applid to dtct how th cumulativ tmpratur affctd th up grning of Carx in spring. 339

4 3. RESULTS AND DISCUSSIONS 3. Spatial Composition of Grassland Vgtation Young rcssional vgtation was locatd at th dg of th lak or spring out in th wt land with an avrag lngth no mor than 5 cm. Th ground was wt muddy ground mixd with opn watr. Thr wr two spcis found in ths aras. In most of th cass, young Carx dominat with a proportion mor than 95% of th vgtation. Along lvation gradints, a littl bit far away from th dg of th lak, Carx covr dominatd mor than 70%. Th lngths of th plant masurd from ground surfac wr from 20 to 40 cm. A grat lot of dad Carx with lngth around 40 cm wr found laying ovr th muddy ground surfac. It rvald that in spring Carx dvlopd in ths aras and did off during submrgd whn th watr lvl ros in summr. At highr lvation, Carx and Miscanthus grw mixd with ach othr. At highr lvation far away from th dg of th lak, Miscanthus was th dominant spcis which tak up mor than 70% land covr. Its hight varis from undr 0cm to mor than 300 cm along th gradints from lowr to highr lvation. 3.2 Rlation btwn Carx and Environmntal Variabls 3.2. Rlation btwn Elvation and Carx Covr: Carx prfrs to inhabit in msotrophic fns or frquntly watrloggd conditions. In Dahuchi Lak, thy usually mrgd at th dg of th lak bank at lowr lvation. At highr lvation, fw Carx grw mixd with Miscanthus and Cynodon. At lvation around 5 m, Carx was hardly found. Th rgrssion modl was list in Equation (5). Th R 2 was 7. Th significant lvl was 99%. It indicatd that as th lvation incras, th covr prcntag of Carx dcrasd, whil Miscanthus incrasd. It also rvald that Carx dominatd lvation at around 3 to 3.5 m, whil Miscanthus appard at highr lvation around 4 m. Within th rang of lvation from 3 to 3.5 m, most of sampl plots covrd by Carx mor than 50%. Byond 4 m, Carx covrd lss than 30% in th plots and almost non was found at 6 m. = (5) + y x Rlation btwn Lngth of Carx and Elvation: A zonal pattrn of grassland had dvlopd sinc th watr lvl dclind gradually in autumn. In th fild, th lngth of Carx varid from 8 cm to mor than 0 cm. At th dg of th lak, th lngth of Carx was around 0cm, whil at highr lvation th lngth of Carx was much longr. In addition, th longr th Carx, th colour of it was darkr. In th wst and north part of th lak, most of Carx had lngth mor than 40 cm. Thy wr old and appard yllow at th top of th plant, which indicatd that thy had bn snscnc. Th Figur 2 showd a positiv rlationship btwn lngth of Carx and lvation using HOF modl II. Th R 2 is 8. Th significant lvl was 99%. It rvald that Carx wr longr at highr lvation than thos at lowr lvation. Figur 2 Rlation btwn lngth of Carx and lvation Rlation btwn Lngth of Carx and Exposd Days: Carx mrgd whn thy xposd again to air sinc th flood rcdd in autumn. As watr lvl falling, nw blts of Carx dvlopd down-shor. Manwhil, th Carx which mrgd arlir up-shor had bn growing tallr and oldr. This continud as th watr lvl fll, rsulting in a zonal pattrn of short young Carx down-shor and tallr and oldr Carx up-shor. Thus, th longr th priod that Carx xposd to air, th tallr thy wr. Th Equation (7) showd a positiv rlationship btwn th lngth of Carx and th numbr of xposd days. It rvald that Carx grw tallr whn th priod of inundation was shortr. Th R 2 is 4. Th significant lvl was 99%. y = (7) x Tim Sris Sasonal NDVI Pattrn of Carx Sasonal phnological NDVI pattrns of Carx wr obtaind in Figur 3. In most of yars, NDVI valus incrasd sharply from Fbruary in arly spring and yild a pak in April or May with a valu around. In 200, it was xtrmly high around. NDVI dcrasd gradually during summr tim and rachd its lowst point in July or August at around, with small fluctuation somtims. As arly as in lat August or Sptmbr, NDVI of Carx incrasd again through autumn and thn dcrasd in wintr tim. Howvr, in diffrnt yars, th maximum and minimum NDVI valus of Carx appard in diffrnt month at diffrnt valus. Man NDVI (200) Man NDVI (2003) y = (6) x + 340

5 Man NDVI (2004) Man NDVI (2006) Man NDVI (2005) Figur 3 Tim sris sasonal NDVI pattrns of Carx 3.4 Rlation btwn NDVI of Carx and Watr Lvl From th tim sris sasonal NDVI pattrns of Carx and watr lvl, it rvald a ngativ rlationship btwn thm. Also, th dat of NDVI incrasd again aftr rainy sason was diffrnt btwn yars. It was attributd to th variation in th dat that watr lvl dclind. Th HOF rgrssion modl II (Equation (8)) showd a ngativ rlationship btwn NDVI valus of Carx and watr lvls in Sptmbr and Octobr through rgrssion analysis. Th R 2 was 79. Th significant lvl was 95%. It rvald that if watr lvl had dclind as arlir as in Sptmbr or Octobr, th NDVI valu of Carx was highr. Thus, it licitd that in autumn th dat of up grning of Carx was ngativ rlatd to th dat of watr lvl dclind. = (8) + y x Abov it was suggstd that watr lvl influncs up grning of Carx in autumn. Howvr, in 2004 and 2006, although thr was a similar fluctuation pattrn with th maximum valu of watr lvl around 5.0 m, th NDVI in 2004 was quit highr than in 2006 sinc up grning. W attributd this to th variation in th dat of watr lvl incrasd. It is possibl bcaus Carx had bn tall nough whn watr lvl incrasd and was not totally submrgd during rainy sason. And NDVI valus of th pixl somwhat influncd by mixd opn watr might b anothr rason. Howvr, this situation confirmd that th sasonal dynamics of watr lvl has crtain impact on th sasonal phnology of Carx. 3.5 Rlation btwn NDVI of Carx and Cumulativ Air Tmpratur In arly spring in Fbruary and March whn th air tmpratur was warm nough (abov 0 ) for grn up, Carx startd to grow. Consquntly, th NDVI valu incrasd. Rgrssion analysis using HOF modl II rvald a positiv rlationship btwn cumulativ tmpratur and NDVI valu of Carx through. It indicatd that whn cumulativ tmpratur was highr in spring, th NDVI valu of Carx was also rlativ highr. Th HOF rgrssion modl was in Equation (9). Th R 2 was 48. Th significant lvl was 95%. y = x + (9) 4. CONCLUSIONS Th rcssional grasslands in Dahuchi Lak hav a spatial pattrn of spcis composition. And it changs along lvation gradint. Grasslands at lowr lvation ar dominatd by short grasss and sdgs (Carx), whil grasslands at highr lvation hav Miscanthus sacchriflorus and Cynodon daxtylon. This rsarch showd that th covr by Carx incrasd towards lowr lvations. W also dmonstratd that th lngth of Carx dclind towards lowr lvation. This is attributd to th fact that Carx plants at lowr lvation ar youngr, as thy hav xprincd a shortr priod sinc mrgnc. Rgrssion analysis by HOF modl II provd that th lngth of Carx incrasd as thy wr arlir xposd again to air sinc watr dclind. Carx which is th dominant spcis at lowr lvation has rmarkabl sasonal phnology. Th tim sris NDVI showd th sasonal pattrns of Carx. Usually, it is grn in autumn, wintr and spring. During rainy sason in summr Carx is submrgd by flooding for a shortr or longr priod and whn th watr rcds in autumn, it mrgs again at th lak dg. It rvald that th dat of up grning of Carx in spring and autumn was diffrnt btwn yars. Th tim sris NDVI rvald that th dat of mrgnc in autumn diffrd btwn yars. This yar to yar dfrnc of up grning of Carx in autumn had a strong ngativ rlationship with watr lvl. Whn watr lvl rcdd arlir in autumn, highr NDVI was yild sinc Carx mrgd arlir. In contrast, if watr lvl was still high in Sptmbr and Octobr, th NDVI was lowr. Th tim sris NDVI also rvald that th dat of up grning in spring diffrd btwn yars. Our rsarch indicatd that this yar to yar variation was positiv rlatd to variation btwn yars in cumulativ tmpratur. Whn cumulativ air tmpratur in Fbruary or March was highr, th NDVI of Carx incrasd sharply arlir. In contrast, whn cumulativ air tmpratur was xtrmly low in som yars, th tim of NDVI incrasd dlayd to April. MODIS imagry has rlativ lowr spatial, but highr tmporal rsolution, compard with TM. MODIS providing daily imagry is idal for monitoring phnology of th grasslands vgtation. Som rsarchs hav alrady showd MODIS could dtct vgtation phnology wll using vgtation indics at rgional scal. Our rsarch rvald that, at local scal, NDVI drivd from MODIS succssfully prformd to monitor th dynamics of rcssional grassland vgtation (Carx). REFERENCES Barbosa, H. A., A. R. Hut, and W. E. Bathgn A 20- yar study of NDVI variability ovr th Northast Rgion of Brazil. Journal of Arid Environmnts, 67(2), pp

6 Bartholomw, P. W., and R. D. Williams Cool-Sason Grass Dvlopmnt Rspons to Accumulatd Tmpratur undr a Rang of Tmpratur Rgims. Crop Scinc Socity of Amrican, 45, pp Bck, P. S. A., C. Atzbrgr, K. A. Hogda, B. Johansn, and A. K. Skidmor Improvd monitoring of vgtation dynamics at vry high latituds: A nw mthod using MODIS NDVI. Rmot Snsing of Environmnt, 00(3), pp Chn, X., C. Xu, and Z. Tan An analysis of rlationships among plant community phnology and sasonal mtrics of Normalizd Diffrnc Vgtation Indx in th northrn part of th monsoon rgion of China. Intrnational Journal of Biomtorology, 45(4), pp Choo, Y.-S., C.-B. L, and R. Albrt Effcts of nitrogn nutrition on th pattrn of ions and organic soluts in fiv sdgs (Carx spp.). Flora - Morphology, Distribution, Functional Ecology of Plants, 97(), pp Cui, X., Y. Zhong, and J. Chn Influnc of a catastrophic flood on dnsitis and biomasss of thr plant spcis in Poyang Lak, China. Journal of Frshwatr Ecology, 5(44), pp Davidson, A., and F. Csillag A comparison of thr approachs for prdicting C4 spcis covr of northrn mixd grass prairi. Rmot Snsing of Environmnt, 86(), pp DEELECTIS FLORAE REIPUBLICAE POPULARIS SINICAE AGENDEE ACADEMIAE SINICAE EDITA FLORA REIPUBLICAE POPULARIS SINICAE. Scinc Prss, Bijing. Dou, H., S. Zhang, Y. Liu, and H. Zhu Poyang Lak typical wtland bio-sction monitoring, rsourc xploration and habitat protction. In: Thr gorgs, wtland along th Yangtz Rivr and pickld land in stuary, Scinc Prss, Bijing, pp Fidanza, M. A., P. H. Drnodn, and M. Zhang Dgrdays for prdicting smooth crabgrass mrgnc in cool-sason turfgrasss. Crop Scinc, 36, pp Guisan, A., and N. E. Zimmrmann Prdictiv habitat distribution modls in cology. Ecological Modlling, 35(2-3), pp Huisman, J., H. Olff, and L. F. M. Frsco A Hirarchical St of Modls for Spcis Rspons Analysis. Journal of Vgtation Scinc, 4(), pp Jin, S., and S. A. Sadr MODIS tim-sris imagry for forst disturbanc dtction and quantification of patch siz ffcts. Rmot Snsing of Environmnt, 99(4), pp Kong, X., and S. Mi Control Survying. Wuhan Univrsity Prss, Wuhan. Ning, J., J. Chn, D. Li, J. Liu, and Z. Zhang Introduction to Gomatics, First dition. Wuhan Univrsity Prss,Wuhan. Salomonson, V. V., W. L. Barns, P. W. Maymon, H. E. Montgomry, and H. Ostrow MODIS: advancd facility instrumnt for studis of th Earth as a systm. Goscinc and Rmot Snsing, IEEE Transactions on 27(2): pp Schmidt, H., and A. Karnili Analysis of th tmporal and spatial vgtation pattrns in a smi-arid nvironmnt obsrvd by NOAA AVHRR imagry and spctral ground masurmnts. Intrnational Journal of Rmot Snsing, 23(9), pp Schutz, W Primary dormancy and annual dormancy cycls in sds of six tmprat wtland sdgs. Aquatic Botany, 59(-2), pp Si, Y Mapping flood rcssional grasslands grazd by ovrwintring gs : an application of multi-tmporal rmot snsing. ITC, Enschd, Th Nthrland. Wu, Y., and W. Ji Study on Jiangxi Poyang Lak National Natru Rsrv. Scinc Prss, Bijing Xiao, X., S. Bols, J. Liu, Z. Dafang, S. Frolking, C. Li, W. Salas, and B. M. III Mapping paddy ric agricultur in southrn China using multi-tmporal MODIS imags. Rmot Snsing of Environmnt, 95(4), pp Zng, Y Monitoring grassland in Poyang natural rsrv, China. ITC, Enschd, Th Nthrland. Zhang, X., M. A. Fridl, C. B. Schaaf, A. H. Strahlr, J. C. F. Hodgs, F. Gao, B. C. Rd, and A. Hut Monitoring vgtation phnology using MODIS. Rmot Snsing of Environmnt, 84(3), pp ACKNOWLEDGEMENTS I would lik to giv my spcial thanks to Mr. Zhou Filong and othr staff of Poyang Lak National Natur Rsrv. Without thir coopration and willingnss to shar data I could not achiv this. Thanks to Zhuo Luo for assisting m during fildwork. I wish to xprss my dp gratitud to Dr. Jan D Luw, for guiding m through this rsarch. I want to xprss my gratitud to Dr. David Rossitr for your prsonal hlp and your frindship. Your scintific and critical attitud for rsarch imprssd m so much. Prof. A. d Gir, thank you so much for your commnts and lctur about statistics. I ow spcial thanks to Mr. G. Rinink and Mr. V. Vnus for acquiring and procssing RS imags. My spcial thanks to Dr. Wu Guofng and Dr. Wang Tijun for your numrous usful data, advics, commnts and insights in this subjct. Spcial thanks go to Sisi, Fi Tng, Zng Yuandi, Zhou Yuhong and Shi Jusong for your hlp and ncouragmnt. Maslli, F., M. A. Gilabrt, and C. Cons Intgration of High and Low Rsolution NDVI Data for Monitoring Vgtation in Mditrranan Environmnts. Rmot Snsing of Environmnt, 63(3), pp