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Landscape Patterns in Plant and Soil Micro- and - Micro- and macro

VIEWS: 69 PAGES: 16

									Micro- and macro- nutrient profiles of soils and plants across
         KNP- implications for herbivore dynamics



        Jayashree Ratnam, Mahesh Sankaran, Niall Hanan,
                    Rina Grant, Nick Zambatis
Sampling locations in KNP (N=108)
                                    N




                                    Decreasing rainfall
    Granitic soils

   Basalt soils
                               Methods


Data Collection
Soil and plant samples collected from each of 101 sites across KNP
in the dry (2003) and wet seasons (2004).

    Soil samples from each site are averages of 2- 5 cores
    (Depth15 cm).

    Plant samples at each site were from two-three dominant tree
    species at the site and all grasses for a generic value for “grass”.

Lab Analyses
Soils analyzed for texture, total C,N, P, trace nutrients, and assayed for
anaerobic Nitrogen mineralization potential. Plants dried and analyzed
for total C,N,P and trace nutrients.
                           Methods (continued)
Statistical Analyses
Discriminant analyses of the macro- and micro- nutrient profiles (19 nutrients) to
see if it was possible to distinguish between
1) Soils- granites, basalts, sodic sites
2) Different plant functional groups- fine and broad leaved trees, grasses
3) Plants of a functional group on different soil substrates
    Root 2




                                 Root 1
                                      Discriminant plots of soil nutrient profiles by geology
                                                6

                                                5

          Iron (Fe), Manganese (Mn)             4

                                                3

                                                2
                                       Root 2

                                                                                                          Granite
                                                1                                                         Basalt
                                                                                                          Sodic
                                                0

                                                -1

                                                -2

                                                -3

                                                -4
                                                  -7   -6   -5   -4   -3   -2   -1   0   1    2   3   4
                                                                            Root 1

                                                                 Sodium (Na), Selenium (Se)


• Sodic soils differed from granitic and basaltic soils in soil micro & macro
  nutrient profiles.
• Granitic and basaltic soils could not be discriminated from each other.
            Discriminant plots of grass leaf nutrient profiles by geology

                          5

                          4

                          3
                                                                         Granite
                          2
                 Root 2                                                  Basalt
                          1                                              Sodic
                          0

                          -1

                          -2

                          -3

                          -4
                            -8   -6     -4     -2      0      2      4
                                              Root 1

                                   Sodium (Na), Selenium (Se),
                                 Iron (Fe), Sulphur (S), Boron (B)

• Grasses from sodic sites were significantly elevated in Sodium, Selenium,
  Iron, Sulphur and Boron relative to those from non-sodic sites.
• There were no discernible differences between grasses from granites versus
  basalts.
                      Broad-leaf tree nutrient profiles by geology
                 6

                 5

                 4

                 3

                 2
                                                                           Granite
                 1
                                                                           Basalt
                                                                           Sodic
                 0

                 -1

                 -2

                 -3

                 -4
                   -4    -3   -2   -1   0      1   2       3   4   5   6
                                            Nitrogen (N)
                                            Sodium (Na)

• Broadleaf trees from sodic sites had high sodium and low nitrogen relative
  to trees from non-sodic sites.
• There were no discernible differences in broadleaf trees from granites
  versus basalts
So,

What are other sources of variation in plant nutrient
landscapes across KNP?
         Discriminant Plot: Nutrient profiles of plant functional groups
                                         6

                                         5

                                         4
           Cobalt (Co), Magnesium (Mg)
                                         3

                                         2
                   Nitrogen (N)

                                                                                                 Grasses
                                         1                                                       Broad-leaf trees
                                         0                                                       Fine-leaf trees

                                         -1

                                         -2

                                         -3

                                         -4

                                         -5
                                           -10   -8   -6     -4    -2    0    2      4   6   8


                                                           Calcium (Ca), Boron (B)
                                                                 Sodium (Na)

• Grass leaves are high in Sodium, low in Calcium and Boron relative to trees.
• Leaves of fine-leaved trees are high in nitrogen, and low in Magnesium
  and Cobalt relative to broad-leaved trees.
      Discriminant Plot: Nutrient profiles of grasses by catenal position
              5

              4

              3

              2

              1
                                                                  Crest
                                                                  Midslope
              0                                                   Footslope
             -1

             -2

             -3

             -4

             -5
               -5   -4   -3   -2    -1    0       1   2   3   4

                                   S, P, Na, Se


• Grass leaves from footslopes at the bottom of soil catenas are high
  in S, P, Na, and Se relative to grasses from mid-slopes and crests
        Nutrient profiles of broad and fine leaved trees by catenal position


       Broad-leaf trees                               Fine-leaved trees                     Footslope
                                                                                            Midslope
5
                                               4                                            Crest
4
                                               3
3

                                               2
2

1                                              1

0
                                               0
-1
                                               -1
-2
                                               -2
-3

-4                                             -3

-5                                             -4
  -5     -4   -3   -2     -1   0   1   2   3     -5      -4   -3   -2     -1    0   1   2   3    4

                          P                                                    Na
                        Mn, Co                                                 Sr
   Landscape scale patterns in soil and plant nutrient
                   Profiles in KNP

 Granites and basalts do NOT differ from each other either in the nutrient
 profiles of their soils (top 15 cm) or in the nutrient profiles of plant
 functional groups (grasses and trees).

IMPLICATION: The high abundances of mammalian herbivores reported
  on basalts cannot be attributed to high nutritional quality of forage


Sodic and non-sodic sites differ from each other in the nutrient profiles of
both soils and different plant functional groups.

Importantly, sodic soils, grasses and trees have elevated levels of Sodium
and Selenium relative to the rest of the landscape

IMPLICATION: Sodic sites dotted across the landscape provide essential
 nutrients Na and Se for herbivores and may be important determinants
                   of herbivore spatial distribution.
    Patch scale patterns in plant nutrient landscapes
                         in KNP


     Most of the variation in plant macro-nutrient and micro-nutrient
     landscapes in KNP occurs at small “patch” spatial scales of a few
     to a 100 meters and stems from

     •Variation between the major plant functional groups

     •Variation within functional groups
              - across soil catenas
              - across sodic and non-sodic sites

IMPLICATION: Nutrient quality variation more likely to drive herbivore
movements at smaller rather than larger spatial scales in this landscape.
       Site scale correlations of plant nutrients to grazer biomass

                                                     Grazer biomass as a function of grass leaf P


                                          3500

                                          3000            R2 = 0.0804

                 Grazer biomass (kg/km2
                                          2500

                                          2000

                                          1500

                                          1000

                                          500

                                            0
                                                 0        1000     2000      3000     4000      5000   6000
                                                                        Leaf P (mg/g)




There was a similar weak but significant correlation of grazer biomass
                              to Leaf Zn
Site scale correlations of plant nutrients to mixed-feeder biomass



                                              Mixed feeder biomass as a function of tree leaf N



           Browser + mixed feeder biomas
                                           2000
                                           1800
                                                       2
                                           1600       R = 0.065
                                           1400
                                           1200
                                           1000
                                            800
                                            600
                                            400
                                            200
                                              0
                                                  1         1.5     2             2.5     3       3.5
                                                                        Leaf %N




There were also weak but significant correlations of mixed-feeder
                 biomass to leaf Na and leaf Fe.
Acknowledgements

Jenna Rettenmayer        Harry Biggs                Corli Coetsee
Joyce Dickens            Thembi Khosa               Louise Rademan
Eric Peterson            Angela Gaylard             Navashni Govender
Dan Reuss                Holger Eckhardt            Glynn Alard
                         Guin Zambatis              Walter Kubheka
Bob Scholes
Mary Scholes
Joe Craine                                 Johan Baloyi




                    Funded by
                    National Science Foundation

								
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