NOTES ON Ian F. Spellerberg's Monitoring Ecological Change

Part B:A biological and ecological basis for monitoring

Chapter 4  Elements of Ecology and Ecological Methods

Population Size
    Changes in size are partly due to externma factors and partly due to inherent population characteristics.
    pg. 64 "This lack of detailed and continuous data from long-term population studies poses not insignificant problems in monitoring because, in the face of a multifactorial source of variability it is difficult to distinguish trends to to pollution from those which are inherent long-term cycles."

Population distribution and limits of tolerance
    organisms with narrow tolerances (or species taht are sensitive to small changes in their environment)  may be useful indicator species because changes in distribution and abundance in these species may indicate environmental perturbations like chemical pollution

Distribution Patterns
    spacial distribution can theoretically be either uniform, random or aggregated - meaning most often found sigma^2 > x bar

Population Structure
    age-class distributions of size-class distributions provide a summary of the populations status and so give a useful basis for monitoring changes in populations, mean life expectancy can be calculated

Communities and Ecosystems
    ecological community:  assemblage of interacting populatiosn of different species ina  particular area or habitat
    ecosystem:  consists of the ecological community and the abiotic environment with which it interacts in a dynamic and complex way
    study ecosystems via nutrient cycle and energy flow

Niche and Resource Partitioning
    biotic factors as well as abiotic factors are important in determinng species composition and community structure
    way to look at species interactions:
        examine how different resources such as food, space or roosting sites, etc. are divided or partitioned between different species
            first we look at the niche of each species
                niche - defined as the sum of all the relationships between the species and the environment
                                can alternatively be defined as teh activity range of each species along every dimension of the abiotic and biotic environment
    in isolation plants and animals are able to exist in a wide range of environmental conditions and that range of conditions defines it's fundamental niche
    outside the fundamental niche, the plant or animal will not survive
    in natural communties a species has a realized nice, that is in the presence of competition and predators, not all resources may be used to the extent at which it would be, if the species were in isolation - the extent to which resources are used in this situation is called the 'realized niche'

Some formulas to describe this:
        B(Breadth of niche) = 1/[(sum from i=1 to s) (P sub i) ^2] -> simpler in formula form
        Where P sub i is the frequency of utilization of each category
                    Ex.  A lizard's diet consists of 10% lizards, 40% ants and 50% spiders.
                        Using this information plug in for P sub i : .1, .4 then .5 - after squaring each, taking the inverse and summing, you end up with a measure of the breadth of the niche of
                                species of lizard.

        When species interact you can calculate the niche overlap, or how much of the resources are needed by both:
        O sub j,k (Overlap) = [(sum from i=1 to s) P sub ij * P sub ik]/[square root of ((sum from i=1 to s P sub ij ^2)*(sum from i=1 to s Psubik ^2))]   -> a lot simpler in formula form

Abundance and Rarity
    natural and unnatrual rarity exist
    commonness and rareness of a species is an important and interesting phenomenon which is basic to our understanding of the use of species richness, species diversity and other variables used in monitoring

Ecological Succession
    development of a community over time, or the process of change is called ecological succession
    although succession is a process of continual change, it can be described as a series of phases (seral stages) through which the community develops
    succession can be viewed as the development of a community from it's inception (pioneer stage) which is then replaced by a whole series of communities
    whole sequence is called a sere and each stage can be considered a community in its own right
    final, mature community is called the climax community
    in general, species richness increases as the climax community is approached
    primary succession -> establishment and development of communities in newly formed habitats
    secondary succession -> recolonizations where natural communties have been destroyed
    terrestial habitats -> climax stage usually dominated by long-lived plants
    process of natural change may be arrested by man's activites such as by burning or cutting
    ex.  Europe's heathlands are managed communities where the natural change to woodland has been arrested resulting in a plagioclimax community

Chapter 5  Ecological Methods

Qualitative and Quantitative Surveys
    what species are there?  where are they?  how many are there?  finding out what species are present in order to build a picture of species composition requires less rigorous sampling than does estimating species abundance
    to find out which species are present a useful method is to keep a cumulative record of the number of species recorded (along transects or in quadrants)
    eventually the probability fo finding a new species will diminish, which indicates a thorough sample has been made
    random stratified sampling is the most common type used
    sampling is divided on the basis of a subjective classification, and the plots are randomized
    number of sample replicates are required, and statistical analysis of these replicates gives some amount of precision

Frequency of Sampling and Location of Sampling
    monitoring requires that information is collected at intervals throughout time and the frequency of data collection is cruicial to success
    ex. sampling frequency can be twice the highest frequency of the event being monitored
    for thorough sampling of an area random selection of location is necessary, but for consistant data within an area constancy of location in necessary

Population Size
    when counting individuals, or finding an estimate of population size is hard, the population index is used:
        regular census of small sample populations
        changes in the index may reflect changes in the total population
    capture-recapture method is a popular what to estimate the size of a population
        # of marked in sample/total caught in sample   =   # marked in population/total population size
        alternatively written as   P  =  an/r
                        P is the population size
                        a is the total number of animals marked
                        n is the number of individuals caught again (marked) in a subsequent sample and
                        r is the total caught in the sample

Species Associations
   species composition, relative abundance, dominance and species associations are all important characteristics
    size of sampling quadrants has a great impact on the data recorded