[From the U.S. Government Printing Office, www.gpo.gov]




                                           OF               NA90AA-D-CZ795

                                                               Task 7



                                          (EGE


                   UNIVERSITY OF MARYLAND AT COLLEGE PARK


                                    DEPARTMENT OF AGRONOMY









                                      FINAL REPORT


                                           to


                      THE MARYLAND DEPARTMENT OF NATURAL RESOURCES


                                           from

                             THE SOIL CHEMISTRY LABORATORY
                          UNIVERSITY OF MARYLAND, COLLEGE PARK


                                     Projoct Title:

                         RIPARIAN FOREST YEGETATION MANAGEMENT:
                 CONTROL OF NITROGEN DISOHARGE INTO THE CHESAPEAKE BAY
                                    FROM GROUNDWATER


                                    Perioo of Grant:
                          October 1, 1990 to December 31, 1991


                                 Principa@ Investigator:
                                     Bruce R. James
                                   Agronomy Department
                                 University of Maryland
                                 College Park, MD 20742


                                     April 21, 1992


                 -eparation of this report was made possible through funding
           QK    -ovided by the Coastal Resources Division,          Tidewater
           122.8 Iministration from a Maryland CZM Program Implementation
                 -ant from OCRM/NOAA.
           J36
           .1992





                 H.J. PATTERSON HALL COLLEGE PARK, MAOYLAND20742 (301)405-1349 FAX:(301)314-9049













                                    INTRODUCTION


              In accordance with a Memorandum of Understanding between the
         Maryland Forest, Park, and Wildlife Service and the University of
         Maryland, research was conducted between January 1 and December 31,
         1991 on questions about the efficacy of riparian forest vegetation
         to lower nitrate concentrations in groundwater flowing from
         agricultural land to surface waters of the Chesapeake Bay and its
         tributaries. Specific objectives of the 12-month research project
         were:


              (1)  Ascertain the effects of different types of riparian
                   forest   vegetation   on   nitrate   concentrations     in
                   groundwater, especially regarding differences between
                   non-leguminous and leguminous trees.

              (2)  obtain information on the width of riparian buffer strips
                   that is necessary in order to change the concentration of
                   nitrate in groundwater.

              (3)  Identify seasonal fluctuations in riparian effects on
                   groundwater nitrate concentrations.

              (4)  Relate results for 1991 with other results for
                   groundwater monitoring beneath riparian zones for the
                   period 1987 through 1990.

                                  SITE DESCRIPTION


              The field research was conducted on Wye Island, using riparian
         forests on the shore of the Wye Narrows.      The location of Wye
         Island-makes it ideal for this type of study because it is located
         approximately in the mid-latitudes of the Chesapeake Bay, where
         nitrate may become the limiting nutrient for eutrophication (Fig.
         1).

              Experimental plots of different forest vegetation management
         practices were established in October, 1988 (Fig. 2), and these
         included no cutting (controls) , cutting just trees and leaving
         understory vegetation to grow (cut trees) , and removal of all
         natural riparian vegetation (clear cut) and seeding to tall fescue,
         the grass that was seeded to the 18-ha field around which the
         riparian zones are located. The plots were replicated two to four
         times, depending on the constraints of the site.

              A detailed soil survey (Fig. 3) was made of the site to
         establish how soil drainage class and series designation might
         interact with forest vegetation type and management to affect
         nitrate concentrations in groundwater.      Groundwater depth was
         related to elevation of individual monitoring wells above sea level
         (Fig. 4)   Monitoring wells were drilled in transects of each
         transect from the agricultural field into the riparian zone plot,
         as shown in Figs. 5 to 8). For the 1991 research, two additional









         wells were placed farther downslope toward the shoreline in
         transect 1B (Fig. 5) and two others were placed approximately 30 m
         out into the field from the "field wells" of transects 1C and IF
         (Fig. 5 and 6)   These wells were placed far enough out from the
         riparian-field boundary to prevent riparian tree roots from having
         an effect on groundwater in that region of the field.       A new,
         control plot was established in 1D, between plots 1C and 1 -E. This
         transect was closely-matched to 1B and 1C, but management
         treatments were different among the three (1B was clear cut, IC was
         a cut-trees plot, and 1D was a control).

              Figures 7 and 8 show well positions and soil series for the
         leguminous zone (zone 4) in which black locust trees dominated the
         riparian forest. The  riparian zone here was shorter in length and
         width than was the    non-leguminous zone, so fewer plots were
         established here.     In addition, only two wells composed a
         transects, instead of three to five in the non-leguminous zone.

              Figure 9 shows the dominant types of trees around the field
         before treatments were established. The only softwoods, loblolly
         pine, were found on the north side of the f ield, where a large
         gravel pit made it unwise to establish plots and monitoring wells
         to obtain reliable data.


                   PRELIMINARY RESULTS OF MONITORING GROUNDWATER


              Effects of vegetation treatments on groundwater nitrate
         concentrations are summarized in Figs 10 to 30. These data provide
         background context for evaluation of the 1991 data funded
         specifically by DNR to address the above objectives.

                  RESULTS OF 1991 SAMPLING AND EXPERIMENTAL WORK


                 Effects of Different Types of Riparian Vegetation



              When mean nitrate-N concentrations were calculated for all
         wells in different treatments, two patterns in the 1991 data were
         evident (Table 1) . First, nitrate concentrations decreased 58% and
         89% in the cut-tree and clear-cut plots, respectively, compared to
         @he uncut controls containing the black locust trees. This result
         indicated that the black locust trees are acting as a source of NO 3
         in groundwater, and their removal may be advisable from a
         groundwater protection point-of-view. Second, similar vegetation
         treatments resulted in 57 and 73 %          increases in nitrate
         concentrations in the non-leguminous section.         This result
         indicated that this type of riparian vegetation appeared to lower
         nitrate concentrations, and its removal may be detrimental to water
         quality entering the Bay.

              These results for 1991 were in agreement with those of earlier
         years (Fig. 10-30).










           Observations of buffer width effects on nitrate concentrations


               The most important observation related to the effective width
         of the buffer strips was that the influence of the riparian
         vegetation was measured at least 10 m out into the agricultural
         field from the visible riparian zone-field margin.             This was
         particularly evident in the leguminous zone where cutting the trees
         resulted in decreases in nitrate in the "field wells" positioned
         outside of the riparian zone (Table 2). It was also observed that
         black locust shoots came up and grew rapidly in the field as much
         as 30 m. from the field margin following cutting of the main stems
         in the riparian zone. These were particularly evident in 1991, and
         probably contributed N03 when root nodules were sloughed or when
         leaves were dropped in the fall.

               Effects of buffer strip width in 1991 were not as clear as
         they were in earlier years, perhaps because of high rainfall. The
         cutting treatments in the non-leguminous zone did raise nitrate
         concentrations in the field wells (Table 2), as was evident in the
         riparian wells also. Despite these trends, it was not possible to
         identify a "minimum width" that would be needed- to attenuate
         nitrate in groundwater. The new wells positioned farther out in
         the field had mean concentrations of 5.6 and 2.1 mg NO        3-N/L, not
         far different from those in the field wells closer to the field
         margin.

               There was no riparian effect evident in the leguminous         zone,
         but the nitrate concentrations were lower in the cut treatments
         than in the controls.      Regrowth of black locust trees did raise
         nitrate concentrations, however, as discussed above.


                     Seasonal patterns in nitrate concentrations


               Although fluctuations were small, seasonal patterns showed a
         slightly greater effect of the riparian, non-leguminous vegetation
         during the winter than in the summer. In the treatments in which
         the vegetation was cut, the variation in the nitrate concentrations
         increased, so seasonal patterns were not as clear as in the
         controls. New research is being initiated by injecting nitrate and
         chloride salts into six wells at the site, and the groundwater
         concentrations will be monitored over time to identify seasonal
         effects.


                                        CONCLUSION


               Results of this research funded by DNR in 1991 have
         corroborated earlier patterns in nitrate concentrations in
         groundwater. The most dramatic effect is shown by the black locust
         trees acting a source of nitrate.        Another effect is that when
         these trees are cut, nitrate concentrations decrease.          When non-
         leguminous trees are cut, nitrate concentrations increase.










             More research needs have been identified as a result of this
        year's effort:

             (1)  soil type x vegetation interactions may be central to
                  predicting riparian zone behavior with respect to
                  groundwater

             (2)  buffer width effects remain unclear, especially with
                  respect to tree root influences.

             (3)  effects of re-planting trees in riparian areas has not
                  been investigated, and may be an important area for
                  future management of shoreline ecosystems to protect
                  water quality.

             (4)  seasonal patterns are still unclear, but the data does
                  show that winter may be the most important season for
                  nitrate attenuation in groundwater. This is especially
                  important for Bay water quality because this is also the
                  season when groundwater recharge below agricultural land
                  may leach nitrate downward and toward surface waters.









        Table 1. Effects of Non-Leguminous and Leguminous Riparian
                   Vegetation    Management     on    Groundwater    Nitrate
                   Concentrations in 1991



                                                  Type of Tree

                                        Non-Leguminous            Legume



        Cutting Treatment    ---------------- mg N03-N/L -----------------
                                       (mean        standard error)

        No cutting                      3.0 ï¿½ 0.3                 3.8 ï¿½ 0.6


        Cut-trees only                  4.7 ï¿½ 0.8                 1.6 ï¿½ 0.9


        Clear cut/plant fescue          5.2 ï¿½ 0.6                 0.4 ï¿½ 0.1









          Table 2.   Groundwater nitrate concentrations in field wells (FW: 10
                     m into field from margin) and in first (RZ1: 5 m. from
                     field margin into riparian zone) and second riparian
                     wells (RZ2: 5 m closer to shoreline from first riparian
                     well)    of non-leguminous and leguminous sections of
                     riparian zones. Values are means ï¿½ standard errors.


                                                Type of Vegetation

                                      Non-Leguminous                   Leguminous


                                                Well  Position


                                FW. RZ1     RZ2                  FW    RZ1 RZ2



                          -------------------------   mg N03-NIL  ----------------


          Cutting Treatment

               No cutting       3.0 2.8 2.9                      2.9 4.8
                                0.2 0.7 1.0                      0.4 0.6



               Cut trees        4.6   4.4  5.8                   0.1   0.1
                             +  1.7   1.6  1.0                   0.0   0.0



               Clear cut        6.3   5.3  4.8                   0.4   0.4
                                1.8   1.2  2.4                   0.2   0.3







          no wells at this position




















                                                                        q
                       CHESAPEAKE BAY                                                                 19
                                                                                                      N




                                20 30 40 B a I
                            KILOMETERS






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                                                      JA:1 n'
                                           on                                       s     d
                                                                               y



                                                              h

                                                              IS
                                                              a
                                                              P
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                                                                                                      38*
                                                                                                      30'


                                                                   y

                                           Potorn

                                                -1



                  7. ,@l             77*00'                76030'             76000'






                    rigure 1. Location of the Wye Island Research Site
                    within the Chesapeake Bay watershed of Maryland.
                               Wa












                                                                                                N


                                                 Ole




                                                                                   10
                                                        4Z

                                                      4
                                                    4
                                                   4B
                                                                                      20
                                            %q'   4A


                                                                      $B
                                                                             M

                                                                                B


                                                                                     IE
                                                                                  I MIX
                                                                                           IB

                                                                                                        Control
                                           One Troalmast Wldlh     25 Molars                            Cut Tree
                                                                                                        clear     Cut
                                                                                                        Unused Area
                           Figure             2.             Location of riparian vegetation
                           management treatments (control, clear-cut, 'cut-
                           tree) for both Non-Leguminous Zones.






     Legend for Soil Maps, Closeups.of Soil and
     w
        ell Location, and Well Transect Profiles.

         S.ojI Type

               D.owner sandy loam                Fallingston Sandy loam




               Sassafras sandy loam           "-N Bibb silt loam



               Woodstown sandy loam               Ti4dal Marsh



               Unnamed   sandyloam'                Unmapped Land Area




          Labels
                                               5
                                                   Ele
                                                     ,ykjon
                                                   Inter
          A   Well Location                            vbl - 5 ft.)
          0   Soil Pit                        FE   Field , Edge

                                              SS   Sol I Surface
              Soil Boring

                                              WT   Watertable
                Gravel Pit

                                              SL   Sea leve I
              Stream
                                           Ltl' 't' iI-l.,



















                                            @Xv


                                           "VA


                                                          Ot

                                                   M M*










                                  Al z@ - -
                                             M
                                  14 t OT





















              Figure 3. Soil map of the Wye@ Island Research site
              illustrating the diverse soil types present within
              the riparian and agricultural area. Scale: 1cm
              12 M.

















                                      W 11 Elevatlon vs. Depth to Water
                                                   Wye Island Research Site

                                    epth to Groundweiter from Surface(cm)
                              Goo



                              400



                              300



                              200



                              100

                                 0                                                J1
                                  0                       2            3           4
                                              Elevation above Sealevel (meters)

                                                           Regresslon Unt


                           A-sqaursd 0.28 y-iolAx-82.2








                       Figure 4               Regression line f or groundwater depth
                        from the soil surface in relation to elevation
                        changes in respect to sea level.






































                                  ALI


                                       4@
                                     io


                                          gy


                                     q
                                                 MI.    01





                                                           WO












             Figure 5.  Closeup of riparian well transects IB,
             IC, and IE,   indicating well location, soil type,
             and elevation (ft). Scale: 1cm    12m.








                                    V@W'jk                11-@.







                                                                          MR,


                                                                           INN
                                            @Rsl
                                                                                IN
                                                                                       kU
                                                                    R A


                                                              NO


                                         N'-@z    V
                                                                                        @ @ mm
                                        RS
                                       ,N' RNIKNI




                 Figure 6. Closeup               of   riparian well transects IF,
                 IM,, IIB, and Ilm,             indicating well location, soil
                 type, and elevation (ft). Scale: 1cm = 12m.



























                                                                                                            J"
                                                                                                            IV





                                                                                                                          Ir    -r
                                                                                      etj,
                                                                                                            -.rj,
                                                                                                            60
                                                                                                  Ize 0,6 0



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                                                                                                                    O-Q.
                                                                           09

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                                                                                                                                       @3      *-'

                                                                          '0
                                                                                         MY=

                                                                                                                                         CS
                                                                               b-                                                        TN
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                                                                                                                           .00   .0.
                                                                                                                          %. -P-tr
                                                                                                0%
                                                                                                                       . V.                         R
                                                                                                                     R1                                -0
                                                                                 -Q        r Rt.,.        'N.
                                                                                                                                                (-.A-V
                                                            do                                                                            130


                                                                                                                                                    r4
                                                                           04
                                                                                                                                    Oz



                              Figure          7.        Closeup of               riparian well transects                                    I11B
                              IIIH, IIIPI IVA, and IVB, indicating well location,
                              soil type, and elevation (ft). Scale: 1cm                                                                     12m.




















                                            tPO











                                                            -n,


                                         31"





               Figure 8 - Close up of riparian well transects IVXP
               1VPj IVQj and IVZ,  indicating well location, soil
               type, and elevation (ft). Scale: 1cm    12M.
























                                           B k he
                                           L
                                              01  Pkne
                                            ob



                                 Lo  st




                               Blac  herry
                                      a s
                                  a kS
                                        s-Ifrat
                                       Black  erry'
                                        Oak/Sassafras
                                          Wa I nij
                                               t



                                             Ma
                                               p.le/Black
                                                  Cherr


                                                  Ma
                                           0











                rigure 9.   Types of vegetation present before the
                establishment of riparian vegetation management
                transect in October, 1898.









 'A




















                        Riparian Effects on N03 vs Landscape Position
                                Non-Leguminous  Controls
            10



            8




            6

         z


            4

         z


            2




            0
                        LA                Ilm              Him
                                    Landscape Position
                                 Field       Riparian


                Figure 10. Mean NO,  concentration in Non-Leguminous
                control transect, IM, IIM, and IIIH as a function
                of   management    treatment   and   well    landscape
                position.





















                       Riparian Seasonal Effects on N03 vs Time
                           Non-Leguminous Control IM
           15





           10


       Z   5

       z    0





            S/87 F/87 W/83 S188 S/88 F/88 WM S/89 S/89 FW W/90 S/90 S/90 F190
                         Seasonal Time (Summer/87-FaHNO)
                             Field     Riparian


               Figure 11.  mean seasonal riparian effects on N03
               concentration in Non-Leguminous, control transect
               IX from summer/87 to Fall/90.



















                           Riparian Seasonal Effects on N03 vs Time
                               Non -Leguminous Control IIM
            15





            10




        Z




        z
             0





               S/87 F/87 W/88 S138 S133 F/88 NV\89 S/89 S/89 FM W/90 S/90 S/90 F/90
                             Seasonal Time (Summer/87-Fall/90)
                                 Field       Riparian




                 Figure 12.     Mean seasonal riparian effect on N03
                 concentration in Non-Leguminous, control transect
                 IIIM from Summer/87 to Fall/90.



















                       Riparian Seasonal Effects on N03 vs Time
                           Non-Leguminous Control HIM
           1.5



           10
       t

       Z    5

       z
            0





             S/87 F/87 W/88 S133 S/88 F/88 WO S189 S/89 FN89 W/90 S/90 S/90 F190
                          Seasonal Time (Summer/87 -Fall/90)
                             Field      Riparian




                Figure 13.  Mean seasonal riparian effects on N03
                concentration in Non-Leguminous, control transect.
                IIIM from Summer/87 to Fall/90.



















                    Ripatian Effecls on N03 vs Landscape Position
                          Nou-Legujiihious /Clear Cut
         lu








         6

      z
      @ F
      4-J
         4

      z


         2




         0
                  IB          IF           1113        RIC
                               Landscape Position
                            Field      Riparian



              Figure 14. Mean NO 3concentration in Non-Leguminous
              clear cut transect, IB, IF, IIB, and IIIC as a
              function of managements treatments and well
              landscape position.






















                            Riparian Seasonal Effects on. N03 vs Time
                                Non-Leguininous Clear Cut/ IB




             10




         Z




         z
              0





               W\89     S/89    S/89    FW     W/90     S/90    S/90    F190
                               Seasonal'I'ime (Winter/89-Fall/90)
                                 -Field       Riparian


                 Figure 15.    Mean seasonal riparian effects on No     3
                 concentration in Non-Leguminous, clear cut transect
                 IB from Winter/89 to Fall/90.










                            Riparian Seasonal Effects on N03 vs Time
                                Non -Leguminous  Clear Cut/ IF
             is





             10
          t
          Z

          z





                W\89    S/89    S/89    F\89    W/90    S/90    S/90    F/90
                               Seasonal Time (Winter/89-FaWO)
                                   Field       Riparian


                   Figure  16.   Mean seasonal riparian ef f ect on No3
                   concentration in Non-Leguminous, clear-cut transect
                   IF from Winter/89 to Fall/90.





















                        Riparian Seasonal Effects on N03 vs Time
                           Non -Leguminous  Clear Cut IIB
         is




         10








      z
          0







                                                       ----------L--------- J__j
            W\89    S/39    S/89    F\89   W/90    S/90   -S/90    F/90
                           Seasonal Time (Winter/89-FalOO)
                               Field      Riparian

               Figure 17.    Xean seasonal riparian effects on N03
               concentration      in    Non-Leguminous,      clear-cut
               transects IIB from winter/89 to Fall/90.




















                           -RIpailan Seasonal Effects on N03 vs Thne
                              Non-Leguminous  Clear Cut IRC




             10



         Z    5


         z
              0





               W9      S189    S189    F@$9   W/90:   S/90    S/90   F/90
                              Seasonal Time (Winter/89-Fall/90)
                                  Field      Riparian


                  rigure is     Mean seasonal riparian ettecr- on nu3
                  concentration     in    Non-Leguminous,      clear-cut
                  transects iiic from winter/89 to Fall/90.










                       Riparian Effects on N03 vs Landscape PositIon
                              Non -Leguminous / CutTree
             10




             8

          tt,
          Fi 6
          z


          4-J
             4

          z



             01-
                     IC           IE         11M          HIP
                                  Landscape Position'
                             OField       Riparian


              rigure 19. Mean wo 3 concentration in Non-Leguminous
              cut tree transects, 1c,
              function  of   managementlE, IIIB,, and IIIP as a
                                         treatments   and well
              landscape position.




















                        Riparian Seasonal Effects on N03,vs Time
                            Non-Leguminous I Cui Tree IC
            15





            10



        Z    5



        z
             0





              W\39   S/89   5/89   F\89   W/90   S/90   S190   F/90
                           Seasonal Time (Winter/49-Fall/90)
                              Field      Riparian


               Figure 20.   Mean seasonal riparian effects on N03
                concentration in Non-Leguminous, out tree transect
                IC from Winter/89 to Fall/90.










  A














                           Riparian Seasona( Effects on N03 vs Time
                               Non -Leguminous I Cut Tree IE
             15





             10



         Z    5

         4-4


         z
              0





               W9      S/89    S/89    R89    W190    S/90    S/90   FJ90
                              Seasonat'rime (Winter/89-FalOO)
                                 Field       Riparian


                  Figure 21. Mean seasonal riparian effects on        H03
                  concentration in Non-Leguminous, cut tree transect.
                  IE from Winter/89 to Fall/go.


















                            Riparian Seasonal Effects on N03 vs Time
                               Non -Leguminous CutFree  IHB




             10
          ib

          Z




          z
              0





                W9      S/89    S/89    F\89   W/90    S/90    S/90    F/90
                               Seasonal Time (Winter/89-FalOO)
                                   Field      Riparian




                 Figure 22.    mean seasonal   riparian effects on N03
                 concentration in   14on-Leguminoust cut tree transect
                  IIIB from winter/89 to Fall/90.



















                       Riparian Seasonal Effects on N03 vs Time
                          Non-Leguminous /Cut Tree /111P




         10




          5



      z
          0





            W\89   S/89   S/89   F\@9   W190   SNO     S/90  F190
                         Seasonal Time (Winter/89-:-Fall/90)
                             Field     Riparian



              Figure 23.   mean seasonal r iparian  effect on No3
              concentration in lion-Leguminous, cut tree transect
              IIIP from Winter/s9 to Fall/go.











                       Ripadan Effects on N03 vs Landscape Position
                                1,egunlillotis /Treatments
             10


          t   6
          z
          I



          z


              2




              0
                   IVA     IVB     IVM      IVP     IVQ     IVz
                                  Landscape Position
                                Field  0 Riparian
                 Figure 24,  Mean N03 concentration in Leguminous
                 vegetation treatments transect IVA, IVB, IVM, IVPr
                 IVQ, and IVZ as a function of management treatment
                 and well landscape position.












                                  Ripailan Seasonal Efrects on N03 vs The
                                         Leguininotis Control IVA




                    10



                Z   5

                 Qj


                z
                    0





                      S/87 F/87 W/88 S/88 S/88 F/83 W\89 S/89 S/89 FW W/90 S190 SM F190
                                     Seasonal Time (Summer/87-Fall/90)
                                         Field       Riparian



                          Figure 25.    mean seasonal   riparian effects,on N03
                          concentration in Leguminous, central transect at
                          IVA from Summer/87 to Fail/90.


















                      Riparian Seasonal Effects on N03 vs The
                           Leguminous CutTree IVZ
           15




           10



       Z    5



       z
            0





             S/87 F/87 W/83 S183 S183 F/88 W\89 S189 S/89 FW W190 S/90 S/90 F/90
                        SeasonalTime (Sammer/97.-Fall/90)
                           F ield    Riparian


               1!'IgUZe 25. mean seasonai ripartan ef f ects on N03
               concentration in Leguminous, central transect. IVZ
               from Summer/87 to Fall/88, and clear cut from
               winter/89 to Fall/90.



















                        Riparian Seasonal Effects on N03 vs, Time
                             Leguminous ConLrol /.IVM
            15





            10



        Z    5


        z
             0





              S/87 F/87 W/88 S188 S/88 F/88 W\89 S189 S/89 17\89 W/90 S/90 S/90 F/90
                          Seasonal Time (Summer/87-Fall/90)
                              Field     Riparian

                Figure 270  Mean s' easonal riparian effects on NO3
                concentration in Leguminous, central transect of
                JVH from Summer/87 to Fall/90.














                               Riparian Seasonal Effects on N03 vs Time
                                   Leguminous /Clear Cut/ lVB




                 10




              Z




              z
                  0





                    W\39   S/89   S/89   F\89   W/90   S/90   SNO    F/90
                                 Seasonal Time (Winter/89-FaIWO)
                                    Field      Mparian


                     Figure 28.  Mean seasonal riparian effects on N03
                     concentration in Leguminous, cut tree transect IVB
                     from Winter/89 to Fall/go.





















                       Riparian Seasonal Effects on N03 vs Time
        15                  Lcgunihious Clear Cut IVQ


        .10
     t

     Z   5

     4-J


     z






                            L
            W\89   S/89    S/89   FW     W/90    S/90    S/90   F/90
                          Seasonal Time ffinter/89@-Fall/90)
                             Field       Riparian
                                               al

               Figure 29.    Mean seasonal riparian effects on No3
               concentration in Leguminous, cut tree transect IVQ
               from Winter/89 to Fall/90.




















                            Riparian Seasonal Effects on N03 vs Time
                                  Leguminous /Cutrree/IVP
              15





              10





               5



          z
               0





                NV\39   S/89    S/39    F\89   W/90    S/90    S/90    F/90
                               Seasonal Time (Winter/89-Fall/90)
                                   Field      Riparian


                 Figure 30. Mean seasonal riparian effects on No3
                 concentration in Leguminous, clear cut transect IVP
                 from Winter/89 to Fall/90.








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