Changes between Version 1 and Version 2 of EwEugBasicEstimates


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Timestamp:
2010-02-05 17:09:39 (9 years ago)
Author:
varunr
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  • EwEugBasicEstimates

    v1 v2  
    11== 7.3 Basic estimates == 
    2  
    32Once you have entered sufficient input parameters you can proceed to estimate the parameters of Ecopath by selecting Basic estimates under the Parameterization node in the Navigator window. The missing parameters will be estimated so that mass balance is achieved. Both input (black font) and calculated (blue font) parameters are displayed on the Basic estimates form. 
    43 
     
    98Notes on most of the parameters below have already been provided in the notes on [[Basic input.htm|Basic parameters]], but we repeat them here as a reminder. 
    109 
    11 ==== Trophic level ==== 
     10'''Trophic level''' 
    1211 
    1312Lindeman (1942) introduced the concept of trophic levels. In Ecopath, the trophic levels are not necessarily integers (1, 2, 3...) as proposed by Lindeman, but can be fractional (e.g., 1.3, 2.7, etc.) as suggested by Odum and Heald (1975). A routine assigns definitional trophic levels (TL) of 1 to producers and detritus and a trophic level of 1 + [the weighted average of the preys' trophic level] to consumers. 
     
    1716The trophic level is a dimensionless index. 
    1817 
    19 ==== Habitat area (fraction) ==== 
     18'''Habitat area (fraction)''' 
    2019 
    2120The fraction of the total area in which the group occurs, that is, the fraction of the total area to which the biomass in habitat area pertains. Default is that the habitat area is 1, i.e. that the group occurs in the total area. 
    2221 
    23 ==== Biomass in habitat area ==== 
     22'''Biomass in habitat area''' 
    2423 
    2524The average biomass per unit area in the habitat area where the group occurs. It is assumed that an average value can be used to represent the biomass of each group. Appropriate units should be used, (e.g., t/km²) for the biomasses. Entry of biomasses is optional for living groups but biomass(es) should be entered for the detritus group(s). However, if biomasses are unknown for all living groups and there are no exports from any of the groups, it is necessary to enter at least one biomass estimate, preferably of a top predator. 
     
    2726Biomasses should be entered relative to the habitat area where the group occurs. An example: assume a species for instance has a biomass of 1 t/km² in its habitat area, and the habitat area is 100 km², while the total area in your model is 1000 km². You should then enter a habitat area of 0.1 and a biomass in habitat area of 1 t/km² as the biomass for the group in your model. 
    2827 
    29 ==== Biomass ==== 
     28'''Biomass''' 
    3029 
    3130This is the Biomass in habitat area x Habitat area. 
    3231 
    33 ==== Production/biomass ==== 
     32'''Production/biomass''' 
    3433 
    3534Enter the Production/Biomass (''P/B'') ratio for each group using consistent units, e.g., per year. The ''P/B'' ratio is equivalent to the instantaneous rate of total mortality (Z) used by fisheries biologists (Allen 1971). Entry of ''P/B'' ratios is optional. 
     
    3938''P/B'' = Z = F + M2 + NM + BA + M0. 
    4039 
    41 For more details, see [[Production.htm|Production]]. 
     40For more details, see [wiki:EwEugProduction Production]. 
    4241 
    43 ==== Consumption/biomass ==== 
     42'''Consumption/biomass''' 
    4443 
    45 Consumption/biomass (''Q/B'') ratios are entered using the same units as for ''''P/B''''. Entry of consumption/biomass ratios is optional. For more details, see [[Consumption.htm|Consumption]]. 
     44Consumption/biomass (''Q/B'') ratios are entered using the same units as for 'P/B'. Entry of consumption/biomass ratios is optional. For more details, see [wiki:EwEugConsumption Consumption]. 
    4645 
    4746The ''Q/B'' input box will be blocked (blue colour) for primary producers. If your model unit is carbon, you can however, click the blue input box, and enter a Q/B value, which will be used to calculate respiration for the group. 
    4847 
    49 ==== Ecotrophic efficiency ==== 
     48'''Ecotrophic efficiency''' 
    5049 
    5150The ecotrophic efficiency (''EE'') is the fraction of the production that is used in the system, i.e. either passed up the food web, used for biomass accumulation, migration or export. Ecotrophic efficiency is difficult to measure directly. It varies between 0 and 1 and can be expected to approach 1 for groups with considerable predation pressure. The part of the production that is not included in the ''EE'' is often called ‘[[Other mortality.htm|other mortality]]’. ''EE'' is dimensionless, and the entry of'' EE'' values is optional.