The relationship of pH to plant distribution in nature

1
The relationship of pH to plant distribution
in nature

• Dr Herman Kurz
• The American Naturalist,
• Vol. 64, No. 693.
• (Jul. - Aug., 1930), pp. 314-341

2
Overview

• Part A pH and Plant Distribution
• Part B Ecology
• Part C Plant Distribution in General

3
pH

• Sörenson (1909) was involved in work testing the
  acidity of beer and the pH symbol rooted in the
  French "pouvoir hydrogene" (power of hydrogen)
• pH -logH

4
pH and Plant Distribution

• pH as a factor in plant distribution?
• Wherry (1916) was first to consider pH as an
  explanation for plant distribution
• Scientists divided (as of 1930)between
  considering pH the factor a factor or
  unimportant in their species

5
pH and Plant Distribution

• Members of the plant kingdom investigated
• Seed plants
• - ericads and orchids found in acidic soils
• - trees and herbaceous flowering plants of
  forests tolerate a wide range
• Ferns
• - tolerate wide range of acidity
• - there is a relationship between soil acidity
  and geographic range but there are also
  other factors at work (Wherry and Steagall)
• Mosses and liverworts
• - are not sensitive to reactions and general
  conclusions not warranted

6
pH and Plant Distribution

• Algae
• Wehrle (1927) 4 classifications of algal habitats
• High constant acidity ? species ? individuals
• High constant alkalinity ? species ?
  individuals
• Weakly acidic conditions (pH 5-7) ? species
• Varied alkalinity (without lime) ? species
• Some species with narrow ranges and some with
  wide ranges

7
pH and Plant Distribution

• acidity in these habitats changes spatially and
  temporally (unless strongly buffered) and is due
  to CO2
• Reaction CO2 H2O ? H2CO3
• H2CO3 ? HCO3- H
• Stratification is due to
• more photosynthesis occurring in surface layers
  throughout the day
• more respiration occurring at lower layers (mud
  organisms)

8
pH and Plant Distribution
9
pH and Plant Distribution

• Ulehla (1923) performs experiments algae with
  psychohormia
• 2 treatments for 30 minutes
• 1. Light exposure pH changed from 6.9-7.0
• 2. Dark pH changed from 5.85-6.18
• after algae was kept in the dark for 48 hrs they
  died
• In nature algae are often found on shell animals
  (where their calcareous shells keep the
  environment locally neutralized)

10
pH and Plant Distribution

• Lichens
• pH is considered a secondary factor in
  distribution (found in narrow ranges) to ammonium
  content

11
pH and Plant Distribution

• Special pH correlations
• pH, leaching and successions
• Salisbury (1921) showed that leeching and removal
  of carbonates results in increased acidity
• Seen in oak forest invading hill tops as humus
  and acidity develop
• Leeched soil may be deposited at slope base
  (encouraging acid loving vegetation)
• In general he saw forests advancing downward
  progressive downward leeching

12
pH and Plant Distribution
13
pH and Plant Distribution

• pH and soil profiles
• Braun-Blanquet and Jenny (1926) showed 4 stages
  of humus development along with successional
  vegetation
• Geisler (1926) saw no relationship between pH and
  plant successions and found that climax
  communities had a wider range of acidity than the
  pioneer

14
pH and Plant Distribution
15
pH and Plant Distribution

• Influence of plants on pH
• plants alter the soil they are in
• Arrhenius (1926) thought that plants change their
  environment to what is most suitable for them
• Chodat (1924) thought that each plant alters its
  environment by making it more favorable for
  successors (agrees with other successional
  theories)

16
pH and Plant Distribution

• pH and Species Characters
• Clausen (1922) found 2 species to grow at
  intermediate forms in neutral soils
• pH and Concomitants
• other factors need to be considered
• pH constant but other factors variable
• pH varied and other factors constant

17
pH and Plant Distribution

• Kotilainen (1927) found good correlation between
  pH and plant distribution but still considers pH
  and secondary or unimportant
• although certain vegetation occurs within narrow
  ranges, acidity itself is an indicator of other
  edaphic conditions
• critical of other studies that alter acidity, as
  this changes other factors as well

18
pH and Plant Distribution

• Kotilainen (1927) continued
• Sphagnum can stand alkaline soil water if its low
  in nutrient salts
• Water level, electrolyte concentration, calcium
  ions and oxygen content are more direct factors
  (are often the producers of acidity)

19
pH and Plant Distribution

• Salt and water and pH
• Montfort and Brandrup (1927) looked at the
  distribution of salt marsh plants
• other factors (salinity and flooding) outweigh
  and pH is not important

20
Ecology

• Plant Ecology
• G. E. Nichols.
• Ecology, Vol. 9, No. 3. (Jul., 1928), pp.
  267-270.
• Ecology was 1st introduced in 1885 (by zoologist
  Reiter)
• clearly defined the following year (by zoologist
  Haeckel)
• " the science treating of the reciprocal
  relations of organisms and the external world."
• " If the botanists persist in appropriating the
  term ecology as synonymous with plant ecology,"
  we are warned, " we shall be forced to
  domesticate the new term bio-ecology to take its
  place as referring to the whole field.

21
Ecology

• The student of plant ecology and the student of
  animal ecology have many points of interest in
  common. They consider their material from
  essentially the same points of view. Up to a
  certain point, they may work with the same
  materials. Each, in his own field, may contribute
  much to supplement the work of the other. But,
  after all is said and done, with rare exceptions,
  the modern ecologist, both by training and
  experience, is either a botanist or a zoologist.
  In other words, just as the general biologist of
  the past generation has given way to the plant
  scientist and the animal scientist, so the modern
  ecologist almost inevitably is either a plant
  ecologist or an animal ecologist.

22
Ecology

• Plant ecology has made great progress during the
  past twenty-five years. Formerly looked upon as a
  helpless infant, and later as the playful child
  (in the opinion of some, the bad boy) among the
  plant sciences, it has grown to be an
  active-minded, healthy youth. It has even
  acquired a certain amount of dignity and
  self-respect, although it is still far from
  mature.

23
Ecology

• Ecology Theories and Applications 4th Ed
• Peter Stiling, 2002
• Life is not evenly distributed on Earth and
  ecology seeks to explain this phenomenon
• Ecology is the study of interactions among
  organisms and their environment, including the
  study of individuals, populations, communities
  and ecosystems
• 4 broad areas behavioral, population, community
  and ecosystems

24
Ecology

• Physical Environment
• Physical variables commonly limit the abundance
  of plants and animals and are divided into 2
  groups
• those used as resources (nutrients, CO2, H2O)
• Those which are not used but are critical to
  survival (temperature, wind, pH)

25
Ecology

• Robert Whittaker, 1967 (plant ecologist)
  formalized the concept that community is governed
  by physical variables (physical factors affect
  distribution patterns, species abundance and
  species richness)
• considered an environmental gradient

26
Ecology

• Examined vegetation along an elevation gradient
  in mountain ranges (western US), along with
  various abiotic factors
• Whittaker observations agreed with the principle
  of species individuality (asserted by Gleason in
  1926)
• Concluded that composition of species at any one
  point in the environment was determined largely
  by physical factors
• What about biotic factors?

27
Ecology

• Assembly rules were first introduced by Diamond
  (1975)
• How are communities assembled from species
  pools?
• looked at bird species on islands (niche space
  and competition)
• physical environment did not change (but
  resources did due to changes in island size)

Speciation
Extinction
POOL
?
COMMUNITY
28
Ecology

• Centrifugal organization in a salt marsh
• simple habitats
• stressful
• display strict zonation patterns

29
Ecology
30
Ecology

• Pennings, Grant and Bertness (2005) showed that
  stress tolerant species survived when moved into
  a less stressful zone ONLY if neighbors were not
  present
• species in less stressful zones could not survive
  when moved to stressful zones
• Do trade-offs between competitive ability and
  stress tolerance exist within the plant species
  of a salt marsh community?

31
Ecology

• Where is the science now?
• How Do Communities Come Together?
• Nicholas J. Gotelli (1999)
• - 25 years after publication, Diamonds ideas on
  assembly rules are still studied and hotly debated

32
Ecology

• The Influence of Environmental Factors on the
  Distribution of Freshwater Algae An Experimental
  Study II. The Role of pH and the Carbon
  Dioxide-Bicarbonate System
• Brian Moss (1973)
• Contrasted levels of several common ions present
  in different freshwaters could help to explain
  the differential distribution of eutrophic and
  oligotrophic algae noted in Part I (Moss 1972)

33
Ecology

• Bicarbonate levels increase markedly from those
  in the softest oligotrophic waters to those in
  the eutrophic waters of soft rock areas, and pH
  tends to increase with bicarbonate level.
• The availability of free CO2 decreases, at
  constant bicarbonate level, with increasing pH
  and increases, at constant pH, with increasing
  bicarbonate
• The combined effect is usually an overall
  decrease in availability of free CO2, with
  increasing hardness of natural waters.

34
Ecology

• Looked at growth rates of species in relation to
  pH
• No pattern was found in the minimum pH tolerated.
• Most would not grow at pH values lower than
  4.5-5.1, though the exact minima lay somewhere
  above pH 3.8
• Distinct differences were found in the maximum pH
  tolerated by the eutrophic and oligotrophic
  groups
• Most oligotrophic species would not grow at pH
  values above 8.85, and the actual maxima recorded
  were 8.6 or less.
• This contrasts with growth of
• typical eutrophic algae where very high rates
  were maintained between pH 8.4 and 9.3 or above.

35
Ecology

• There are several ways in which high pH might
  exclude oligotrophic algae from eutrophic waters
  
• (1) an intrinsic effect of pH on enzymes, in the
  cell wall or membrane,
• responsible for uptake of one or more essential
  nutrients
• inability of oligotrophic species to absorb trace
  elements present in low concentration at high pH
  
• a toxic effect of relatively high total dissolved
  ion content associated with high pH
• Coprecipitation of phosphate with calcium,
  magnesium, and carbonate at high carbonate
  levels
• a direct toxic effect of carbonate or of
  hydroxide ions, levels of which increase with
  increasing pH
• differential availability of different inorganic
  carbon compounds for photosynthesis.

36
Ecology

• Current work on pH in ecology
• Local plant diversity patterns and evolutionary
  history at a regional scale
• Meelis Partel 2002
• Used published studies
• positive relationships between species richness
  and pH were significantly more probable when
  evolutionary centers were on high pH soils
• negative relationships between species richness
  and pH were significantly more probable when
  evolutionary centers were on low pH soils
• soil pH increases with latitude, so there is also
  a positive relationship between richness and pH
  at high latitudes and negative at low latitudes

37
Ecology
38
Ecology

• Implications? Why study at all?