The relationship of pH to plant distribution in nature

The relationship of pH to plant distribution in nature

Dr Herman KurzThe American Naturalist,

Vol. 64, No. 693. (Jul. - Aug., 1930), pp. 314-341

Overview

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

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 = -log[H+]

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”


Members of the plant kingdom investigatedSeed plants:

- ericads and orchids found in acidic soils- trees and herbaceous flowering plants of forests

tolerate a wide rangeFerns:

- 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


Algae:- Wehrle (1927) 4 classifications of algal habitats1. High constant acidity = ↓ species ↑ individuals2. High constant alkalinity = ↓ species ↑ individuals3. Weakly acidic conditions (pH 5-7) = ↑ species4. Varied alkalinity (without lime) = ↑ species

Some species with narrow ranges and some with wide ranges


- acidity in these habitats changes spatially and temporally (unless strongly buffered) and is due to CO2

- Reaction: CO2 + H2O H⇌ 2CO3 H2CO3 HCO⇌ 3

− + H+

- Stratification is due to:- more photosynthesis occurring in surface layers throughout

the day- more respiration occurring at lower layers (mud organisms)



- Ulehla (1923) performs experiments algae with psychohormia

- 2 treatments for 30 minutes:1. Light exposure: pH changed from 6.9-7.02. 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)


Lichens:- pH is considered a secondary factor in

distribution (found in narrow ranges) to ammonium content


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



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



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)


pH and Species Characters:- Clausen (1922) found 2 species to grow at

intermediate forms in neutral soilspH and Concomitants:- other factors need to be considereda. pH constant but other factors variableb. pH varied and other factors constant


- 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


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)


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

Ecology

Plant EcologyG. 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.“

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.’

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.’

Ecology

Ecology: Theories and Applications 4th EdPeter 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

Ecology

Physical EnvironmentPhysical 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)

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

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?

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 POOL Extinction

?COMMUNITY

Ecology

Centrifugal organization in a salt marsh:

- simple habitats- stressful- display strict zonation

patterns

Salinity

Water-logging

OptimalHabitat

Ecology

Salinity (psu)

25 30 35 40 45 50 55 60

Wat

er C

onte

nt (%

)

15

20

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?

Ecology

Where is the science now?

How Do Communities Come Together? Nicholas J. Gotelli (1999)- 25 years after publication, Diamond’s ideas

on assembly rules are still studied and hotly debated

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)

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.

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.

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;

(2) inability of oligotrophic species to absorb trace elements present in low concentration at high pH;

(3) a toxic effect of relatively high total dissolved ion content associated with high pH;

(4) Coprecipitation of phosphate with calcium, magnesium, and carbonate at high carbonate levels;

(5) a direct toxic effect of carbonate or of hydroxide ions, levels of which increase with increasing pH;

(6) differential availability of different inorganic carbon compounds for photosynthesis.

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

Ecology

Ecology

Implications? Why study at all?

Documents

The relationship of pH to plant distribution in nature