Abundance - number of individuals of a species in a given space
QUADRATS
FACTORS TO CONSIDER
SIZE OF QUADRAT TO USE
NUMBER OF SAMPLE QUADRATS TO RECORD IN STUDY AREA - LARGER SAMPLE SIZE = MORE RELIABLE
POSITION OF QUADRAT IN STUDY AREA - SHOULD BE RANDOM SAMPLE
RANDOM SAMPLING
AVOID BIAS - ENSURE DATA VALID
IF INVESTIGATING ANIMALS IN SAME TYPE OF HABITAT, CHOOSE TWO CLOSE TOGETHER TO MINIMISE ABIOTIC DIFFERENCES
LAY OUT 2 LONG TAPE MEASURES AT RIGHT ANGLES, ALONG TWO SIDES OF STUDY AREA
OBTAIN SERIES OF COORDINATES, USE RANDOM NUMBERS TAKEN BY RANDOM NUMBER GENERATOR ON COMPUTER
PLATE QUADRAT AT INTERSECTION OF EACH PAIR OF COORDINATES, RECORD SPECIES WITHIN IT.
Point quadrat - HORIZONTAL BAR SUPPORTED BY 2 LEGS, SET INTERVALS ARE HOLES, THROUGH WHICH A PIN CAN BE DROPPED - EACH SPECIES THE PIN TOUCHES IS RECORDED
Frame quadrat - SQUARE FRAME, DIVIDED INTO SMALL EQUAL SUBDIVISIONS, PLACED IN DIFFERENT LOCATIONS, ABUNDANCE OF EACH SPECIES WITHIN EACH QUADRAT RECORDED, E.G ONLY SQUARES CONTAINING OVER 50% COVERAGE COUNTED
Belt transect - TWO PARALLEL STRIPS, SPECIES OCCURRING WITHIN LINES RECORDED
SYSTEMATIC SAMPLING - FOR WHEN THERE IS TRANSITION IN A COMMUNITY, SUCH AS DISTRIBUTION CHANGE AS ALTITUDE INCREASES UP A HILL. STAGES OF ZONATION ESPECIALLY WELL SHOWN USING TRANSECTS
Abundance - number of individuals of a species within a given space
Limitations of frequency measurement - good if a species hard to count, but does not provide info on density and detailed distribution
Percentage cover - data collected rapidly, individual plants don't need to be counted, but less useful when organisms occur in several overlapping layers
MARK, RELEASE,RECAPTURE
KNOWN NUMBER OF ANIMALS CAUGHT AND MARKED IN SOME WAY, AND RELEASED. AFTER A SET TIME, A GIVEN NUMBER OF INDIVIDUALS COLLECTED RANDOMLY, MARKED INDIVUDUALS NUMBER RECORDED.
ESTIMATED POPULATION SIZE = TOTAL NUMBER OF INDIVIDUALS IN FIRST SAMPLE X TOTAL NUMBER OF INDIVIDUALS IN SECOND SAMPLE / NUMBER OF MARKED INDIVIDUALS RECAPTURED
ASSUMPTIONS:
PROPORTION OF MARKED TO UNMARKED INDIVIDUALS IN SECOND SAMPLE SAME PROPORTION OF MARKED TO UNMARKED IN POPULATION AS WHOLE
MARKED INDIVIDUALS RELEASED FROM FIRST SAMPLE DISTRIBUTE EVENLY AND HAVE SUFFICIENT TIME TO DO SO
POPULATION HAS DEFINITE BOUNDARY SO THERE IS NO IMMIGRATION OR EMIGRATION WITHIN POPULATION
FEW DEATHS OR BIRTHS
METHOD OF MARKING NOT TOXIC OR MAKE THE INDIVIDUAL MORE CONSPICUOUS AND LIABLE TO PREDATION
MARK NOT LOST OR RUBBED OFF DURING IVESTIGATION
CORRELATION - WHEN TWO FACTORS VARY IN RELATION TO EACH OTHER
CONSERVATION RULES DURING INVESTIGATIONS
ORGANISMS STUDIED IN SITU - NOT REMOVED - OTHERWISE KEEP NUMBERS TO MINIMUM
RETURN REMOVED ORGANISMS TO SITE, EVEN IF DEAD
SUFFICIENT PERIOD OF TIME SHOULD ELAPSE BEFORE SITE USED FOR FUTURE STUDIES
AVOID DAMAGE AND DISTURBANCE TO SITE
BALANCE BETWEEN DAMAGE DONE AND VALUE OF INFO GAINED