enaR (version 2.9.1)

enaMTI: Mixed Trophic Impacts (MTI) Analysis

Description

Calculates the Mixed Trophic Impacts of one species on another in the given ecosystem model following the algorithm of Ulanowicz and Puccia (1990). This considers both the direct and indirect trophic impacts.

Usage

enaMTI(x,eigen.check=TRUE,zero.na=TRUE, balance.override=FALSE)

Arguments

x

a network object. This includes all weighte dflows into and out of each node. It must also include the "Living" vector that identifies the living (TRUE/FALSE) status of each node.

zero.na

A logical parameter that specifies if NAs generated in the analysis should be reset to zero. The default is TRUE.

balance.override

Mixed Trophic Impacts analysis builds on flow analysis and thus assumes the network model is at steady-state (inputs = outputs). Setting balance.override = TRUE allows the function to be run on unbalanced models, though this is unadvised.

eigen.check

LOGICAL: should the dominant eigen value be checked? By default, the function will not return utility values if the eigenvalue is larger than one; however, if eigen.check is set to FALSE, then the function will be applied regardless of the mathematic concern.

Value

G

output-oriented direct flow intensity matrix as in enaFlow, except oriented from row to column.

FP

input-oriented direct flow intensity matrix similar to enaFlow; however, the calculation exclude respiration losses from the throughflow in the denominator to focus on NET production. Also, if the receiver compartment is not living, the flux intensity is set to zero.

Q

direct net trophic impacts (G-t(FP)).

M

Total (direct and indirect) tropic impacts of compartment i on j.

References

Ulanowicz, R.E. and C.J. Puccia. 1990. Mixed trophic impacts in ecosystems. Coenoses 5, 7--16.

See Also

enaFlow,enaUtility

Examples

data(troModels)
mti <- enaMTI(troModels[[6]])
attributes(mti)