Physical Factors Affecting Plants Physical Factors Affecting

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                                                                                                 Learning Outcomes
                                                                                                 Learning Outcomes
                                                                                      • Soil constraints
            Physical Factors Affecting
            Physical Factors Affecting                                                    – Available water
                      Plants
                      Plants                                                          •   Wind exposure
                                                                                      •   Too much sun
                             Lecture 12                                               •   Too much water
                                                                                      •   Fire




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             Factors Affecting Plant Growth
             Factors Affecting Plant Growth                                                          Serpentinite
                                                                                                     Serpentinite
           • In order to grow                                                         • CA state rock
             plants need…..                                                           • Metamorphic
           • Adequate light                                                           • Transformed
           • Adequate water                                                             seafloor rocks such
           • Adequate Nutrients                                                         as basalt
           • Space                                                                    • Only found near
           • These are limited in                                                       plate boundaries
             supply…..and there are                                                   • Named after green
             other interested                                                           scaly appearance
             parties




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                  Serpentine Outcrops
                  Serpentine Outcrops
                                                                                       Serpentine Soils
                                                                                       Serpentine Soils
                                                                                      • High content of
          • Nearly half of the
                                                                                         – Magnesium
            serpentinite found
                                                                                         – Heavy Metals
            in North America is                                                             • Nickel, Chromium,
            located in                                                                        and Cobalt
            California                                                                • Low content
          • Found in Coast                                                               – Calcium
            Ranges                                                                       – Phosphorus,
                                                                                           Potassium Nitrogen
          • Foothills of Sierra                                                       • Red color due to
            Nevada                     Serpentinite outcrop on                          iron oxide
                                       the coastal bluffs of the
                                       Presidio




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                                                                                         Cation Exchange Capacity
                                                                                         Cation Exchange Capacity
                   Serpentine Endemics
                   Serpentine Endemics
           • May be restricted                                                                                   • Cation = positive charge
                                                                                                                    – Calcium Ca2+
             to serpentine soils
                                                                                                                 • Anion = negative charge
           • Sargent Cypress                                                                                        – Nitrate NO3-
           • Jewelflowers sp                                                                                     • Organic matter and clay
                                                                                                                   negatively charged
           • Or occur on other                                                                                   • Cation exchange
             soils                                                                                                 capacity-
           • Leather Oak                                                                                            – the ability of a soil
                                                                                                                      particle to hold onto
           • Knobcone Pine                                                                                            cations




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                                                                                      • Wind
                    CEC and Soil Fertility
                    CEC and Soil Fertility                                            • Increased rate of
                                                                                                                    Wind Exposure
                                                                                                                    Wind Exposure
                                                                                        evaporation
                                     • Cations retained by the                           – Water loss from soil
                                       negatively charged                             • Increased rate of
                                       particles in the soil                            transpiration
                                        – Clays and humus
                                                                                         – Water loss from leaves
                                     • In equilibrium with
                                       similar cations in the soil                    • Flagging
                                       solution                                       • Prevailing direction of
                                     • Also taken up by plants                          wind chills and kills
                                     • If not retained lost by                          buds
                                       leaching
                                     • Sandy soils low CEC = low                      • Tree islands
                                       fertility                                      • Krummholz
                                     • Acidic Soils exchange
                                       sites occupied by H+ = low
                                       fertility


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           • Leaves absorb light
                                       Coping with
                                       Coping with
             but also absorb heat
                                                                                                   Limiting Factors
                                                                                                   Limiting Factors
           • Reduced leaf area            Heat
                                          Heat
           • Chaparral shrubs
                                                                                      • If water is limiting – deserts
           • cacti
                                                                                      • To survive plants invest in more
           • Leaf orientation                                                           roots and decrease production
                                                                                        of leaves
           • Heat radiated from                                                       • If light is limiting
             leaf to air                                                              • Plants grow more shoots to
           • Increasing surface                                                         increase rate of
             area of leaf increases                                                     photosynthesis
             rate of cooling                                                          • What if nutrients are limiting?
           • Compound leaves




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                       Root:Shoot Ratio
                       Root:Shoot Ratio                                                             Lack of Water
                                                                                                    Lack of Water
           • Roots provide water and nutrients                                        • In arid
           • Do not photosynthesize                                                     environments plant
           • Shoots (stems and leaves)                                                  compete for soil
             photosynthesize                                                            water
           • Require water and nutrients
                                                                                      • Deeper roots
           • Range from 0.2 in rainforests to
                                                                                        access ground          Quercus douglasii – Blue Oak
             1.2 in arid shrublands (SE.
             California) to 4.5 in deserts                                              water
                                                                                      • Shallow spreading
                                                                                        roots soak up rains




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                                                                                          Adaptations to Waterlogged
                                                                                          Adaptations to Waterlogged
                        Too Much Water
                        Too Much Water                                                               Soils
                                                                                                    Soils
           • Root cells need oxygen                                                   • Waterlogging
             to live                                                                    tolerant plants
           • In waterlogged soil air                                                    develop
             replaced by water
                                                                                        aerenchyma
           • Bacteria use up oxygen
                                                                                      • Scirpus californicus
           • anaerobic bacteria
             produce toxic forms                                                        – California Tule
             of nitrogen and
             manganese

                           Scirpus
                           californicus Lotus


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                         Too Much Salt
                         Too Much Salt                                                        Adaptations to Salinity
                                                                                              Adaptations to Salinity
           • Saltmarshes                                                              •   Halophytes
                                                                                      •   Poaceae
           • Desert Soils                                                             •   Chenopodiaceae
                                                                                      •   Salt excreting
                                                                                          glands




                                    Spartina foliosa



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Slide 19                                                                   Slide 20




           • Fire is natural
               – Lightening strikes          Fire
                                             Fire                                               Adaptations to Fire
                                                                                                Adaptations to Fire
           • Native American Fire
             Regime
                                                                                      • Prevent heat from
               – Hunting                                                                damaging growing buds
               – Resource management
                                                                                      • Basal leaf buds
           •   Effects                                                                • Grasses
           •   Kills trees                                                            • Thick bark
           •   Opens space in canopy                                                  • Redwood
           •   Nutrients released                                                     • Crown sprouting
               into soil                                                              • Many chaparral shrubs
                                                                                      • Seeds germinate after
                                                                                        fire
                                                                                      • Fireweed
                                                                                      • Fire Poppy



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Slide 21




                  Fire Cones
                  Fire Cones
           • Coastal Pine trees
           • Bishop Pine
           • Knobcone Pine
           • Pine cones do not open
             until intense heat
             melts pitch
           • Seeds drop a few days
             later
           • Regeneration of
             Bishop Pine decreased
             with Fire Suppression
             Policy




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posted:10/2/2011
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