Ecological Archives A021-009-A6

Annika W. Walters and David M. Post. 2011. How low can you go? Impacts of a low-flow disturbance on aquatic insect communities. Ecological Applications 20:163–174.

Appendix F (TABLE F1). Linear model and multiple regression results for insect family biomass.1

  Linear model with flow   Multiple regression: Best model  
  (summer Q) Best single FLOW HABITAT RESOURCES  
  slope R2 P predictor summer Q width %riffles AFDM chloro FPOM R2
Family biomass
Aeshnidae negative -0.04 0.50 % riffles             0.67
Baetidae negative -0.02 0.40 AFDM             0.41
Chironomidae negative 0.14 0.09 width             0.45
Chloroperlidae negative -0.07 0.97 chloro             0.35
Corydalidae negative 0.05 0.21 % riffles             0.74
(adult) negative 0.13 0.10 width             0.11
(larvae) positive 0.23 0.04 width             0.25
Ephemerellidae positive 0.29 0.02 summer Q             0.64
Gomphidae positive 0.18 0.06 width             0.28
Heptageniidae negative 0.58 <0.001 width             0.87
Hydropsychidae negative 0.34 0.01 % riffles             0.82
Leptophlebiidae negative 0.31 0.02 width             0.81
Leuctridae positive -0.07 0.90 FPOM             0.32
Peltoperlidae negative 0.12 0.10 width             0.42
Perlidae negative -0.02 0.42 % riffles             0.30
Philopotamidae negative 0.43 0.003 AFDM             0.52
Polycentropodidae negative 0.02 0.28 chloro             0.49
Psephenidae negative 0.06 0.18 width             0.53
Rhyacophilidae negative -0.02 0.43 % riffles             0.00
Sialidae positive -0.07 0.87 % riffles             0.27
Simuliidae negative 0.39 0.005 summer Q             0.67
Tipulidae negative -0.06 0.60 % riffles             0.35
Veliidae positive -0.06 0.76 FPOM             0.15

1In the linear model a positive slope means that the insect metric or biomass increased at lower flow levels. All August 2005, 2006, and 2007 stream reaches with discharge data are included. In the multiple regression data is from August 2006 and 2007. The flow variable is summer Q value corresponding to mean daily flow (summer Q). Habitat variables are mean stream width (width) and mean percentage of riffle habitat (% riffles). Resource variables are periphyton ash-free dry mass (AFDM), periphyton chlorophyll a (chloro), and fine particulate organic matter (FPOM). The single best predictor is determined using all-subsets regression and the best model is chosen using forward and backwards step-wise selection and is based on AIC criteria. The adjusted R2 for a model is in bold if the fit is significant at P = 0.05.


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