Controls of denitrification in papyrus wetlands in Kenya and Tanzania

Transcription

1 Controls of denitrifiction in ppyrus wetlnds in Keny nd Tnzni Gretchen M. Gettel, Kuenzng Tshering, Hw Nkitende 3 UNESCO-IHE, Institute of Wter Eduction, Delft, The Netherlnds Royl University of Bhutn, Thimphu, Bhutn 3 Ntionl Wter nd Sewerge Corportion, Kmpl, Ugnd

2 Ecosystem Services How do we lnce the competing demnds for ecosystem services? Figure from: clhelth/pges/defult.spx

3 Cyperus ppyrus wetlnds

4 Cyperus ppyrus wetlnds

5 Provisioning, Regulting nd Supporting Services of Ppyrus Wetlnds Ppyrus wetlnds re t the crux of lncing provisioning nd regulting services.

6 Denitrifiction s prt of the Nutrient Retention Requires orgnic cron Requires neroic conditions

7 Are regulting services lost s wetlnds re converted to griculturl lnd uses? Ojectives:. Assess C nd N limittion of denitrifiction in griculturl nd ppyrus vegettion (Proximte controls). Relte potentil denitrifiction in nturl vegettion nd griculturl lnd uses nd relte to soil chrcteristics (Distl controls)

8 Ppyrus Wetlnd Zones (HGMUs) River dischrge Lke Victori Agriculture/ grzing Temporrily flooded Permnently flooded Figure: Edwin Hes Groundwter rechrge

9 Study re: Nyndo wetlnd, Keny Nyndo sin : 3587 km Nyndo wetlnd : ±5 km Kisumu Nyndo river Nykch By (Lke Victori)

10 Smpling loctions: Nyndo River Ogyen Site Dily influx of wter from the Lke, modertely impcted Singid Site Floods with river during the wet seson, lightly impcted Ppyrus Mize Sugrcne Rice

11 Study re: Mr wetlnd, Tnzni

12 Smpling loctions: Mr River Agriculture/ Grzing HGMU Temporrily flooded HGMU Permnently flooded HGMU m m III rd smpling II nd smpling T Smpling site P Smpling site Floting vegettion Min River Chnnel I st smpling Trnsct I: At Mngorey

13 Methods: Field smpling Wter (Permnent Wetlnd) ph, EC, DO, temp. DOC, NO 3, NH 4, SUVA Soil Smple (top 5 cm) ph, % Moisture, AFDM, TOC, NH 4, NO 3 Smpling Frequency: Three times t ech site Decemer Jnury Denitrifiction C vs. N limittion of Denitrifiction Potentil Denitrifiction Dt Anlysis ANOVA, Tukey Post-hoc Multivrite Anlysis

14 Acetylene inhiition method - DEA +C+N Potentil Denitrifiction +N +C - Aneroic conditions with chloremphenicol - Acetylene locks conversion of N O to N - Denitrifiction rte ws clculted from liner regression of N O produced during incution period. - Three replictes for ech tretment

15 Potentil Denitrifiction Rte PDR (ug N-N/g DW/hour) PDR (ug N-N/g DW/hour) Nyndo Ogeny WL Singid WL Mize field S.C Field Rice field Mr Permnent Temporry Agriculture

16 Mr Nyndo Limiting fctors for potentil denitrifiction µg NO/g DW /hour µg NO/g DW /hour µg NO/g DW /hour Ogeny Wetlnd Singid Wetlnd Mize Sugrcne Rice Permnently Flooded Temporrily Flooded Agriculturl

17 Mr Nyndo Nitrte limits PDR in Wetlnd Sites µg NO/g DW /hour µg NO/g DW /hour µg NO/g DW /hour Ogeny Wetlnd Singid Wetlnd Mize Sugrcne Rice Permnently Flooded Temporrily Flooded Agriculturl

18 Mr Nyndo Cron limits PDR in griculturl sites µg NO/g DW /hour µg NO/g DW /hour µg NO/g DW /hour Ogeny Wetlnd Singid Wetlnd Mize Sugrcne Rice Permnently Flooded Temporrily Flooded Agriculturl

19 NO 3 & NH 4 mong different lnd uses NO 3 -N (mg/g) mg NO3-N/g resin/dy mg NH4-N/g resin/dy NH 4 -N (mg/g ).45.4 N-NO N-NH Nyndo Ogeny WL Singid WL Mize field S.C Field Rice field Ogeny WL Singid WL Mize field S.C Field Rice field Mr Permnent Temporry Agriculture Lnd Uses. Permnent Temporry Agriculture Lnd Uses

20 TN nd TOC mong different lnd uses TN (mg g - DM) mg N/g soil smple TOC (mg/g) g AFDW TN TOC Nyndo c d c c c Mr Permnent Temporry Agriculture Lnd Uses Permnent Temporry Agriculture Lnd Uses

21 Moisture Content % Moisture content % moisture content e Nyndo 4 3 c d Ogenty WL Singid WL Mize field S.C Field Rice field Mr Permnent Temporry Agriculture And Uses

22 Dissolved Oxygen nd SUVA in Wetlnd Sites DO % sturtion DO % Sturtion SUVA (Specific UV Asornce 4 Nyndo Singid Ogeny DO rnged from..8 mg/l Permnently flooded HGMU Temporrily flooded HGMU Mr Permnent Temporry Wetlnd Types

23 Stepwise Multivrite Anlysis: Wetlnd Sites ph, SUVA, DOC, moisture content, AFDW, NO 3 -N, NH 4 -N nd TN were used s predictors of PDR. Nyndo: No significnt reltionships Mr: -SUVA (R =.73, p =.3) nd +DOC (R =.98, p <.) relted to PDR. 3

24 Multivrite Regression Anlysis, Agriculturl Lnd, Mr Moisture content, Ash Free Dry weight/tc, NO 3 -N, NH 4 -N nd TN, used s predictors of PDR Nyndo: +TOC nd +Moisture Content (R =.66, p<.; R =.7, p<.) Mr: +NO 3 concentrtion (R =.99, p =.4) relted to PDR

25 Conclusions: Nyndo nd Mr River dischrge - Denitrifiction ws limited y vilility of cron. - Nitrte concentrtion, TOC, nd MC were relted to potentil denitrifiction rtes. - Lowest potentil denitrifiction rte (.3 µg N O/g DW/hour). Agriculture/ grzing Temporrily flooded Permnently flooded Lke Victori Figure: Edwin Hes Groundwter rechrge

26 Conclusions: Nyndo nd Mr River dischrge - Denitrifiction ws limited y vilility of nitrte. - SUVA nd DOC ws relted to PDR - Permnently flooded re hs the highest potentil denitrifiction rte (3-6 µg N O/g DW/hour). Agriculture/ grzing Temporrily flooded Permnently flooded Lke Victori Figure: Edwin Hes Groundwter rechrge

27 Conclusions Both sites showed similr pttern of NO -limittion of denitrifiction in griculturl sites nd C limittion in wetlnd sites. Potentil denitrifiction is much lower in griculturl sites thn wetlnd sites. Environmentl controls of denitrifiction re vrile, ut re relted to cron nd moisture content. Cron qulity my e importnt in understnding vrition in denitrifiction.

28 Ecosystem Services How do we lnce the competing demnds for ecosystem services? (Are regulting services lost in griculturl lnd uses?) Figure from: clhelth/pges/defult.spx

29 Thnk you Dr. Julius Kipkemoi, Dr. Anne vn Dm, Edwin Hes, Prisch Rongoei, Wende Kem, Sddiki Liser, Do Phuong Hien, Field nd Logistics Support: Egerton University: Chemistry Deprtment, Lortory of Biologicl Sciences Deprtment VIRED Interntionl (Dr. J.B. Okeyo-Owuor) World Wildlife Fund (Dr. Willim Ksng, Mr. Oscr Dimosso ) Ministry of Wter nd Irrigtion, Musom (Mr. Mthyo Athumn) Lke Victori Environmentl Mngement Progrm (Mr. Omri Mynz) UNESCO-IHE Lortory (Fred Kruis, Lyzette Roemot, Peter Heerings, Frnk Wiegmn) Funding: ECOLIVE UNESCO-IHE Prtnership Reserch Fund Mr Flows Project US AID, UNESCO-IHE Prtnership Reserch Fund NFP Netherlnds Fellowship Progrm, ADA Austrin Development Agency