Table 2.

Generalized linear models show significant relationships between invaded areas and fire occurrence and frequency

Grass	Fire-Occurrence Model	Fire-Size Model	Fire-Frequency Model
B. tectorum	Invaded***, Road***, BPS***, Ecorg***, Dev***	BPS^, Ecorg***	Invaded***, Road^, BPS***, Ecorg***, Dev***
Dev. Explain, %	7.1 (0.58)	12	9.3 (0.59)
ΔAIC	20		81
I. cylindrica	Invaded**, Road***, BPS**, Ecorg***	BPS***, Ecorg***, Dev***	Invaded^, Road***, BPS**, Ecorg***
Dev. Explain, %	5.9 (0.20)	21.3	7 (0.08)
ΔAIC	8.1		1.3
M. sinensis	Invaded*, Road**	Ecorg***	n/a
Dev. Explain, %	10 (3.0)	39.2	n/a
ΔAIC	2.3
M. vimineum	Invaded*, Road**, Ecorg***	n/a	Invaded*, Road***, Ecorg***
Dev. Explain, %	2.3 (0.19)	n/a	3.9 (0.27)
ΔAIC	2.5		3.6
N. reynaudiana	Invaded***, Dev***	n/a	Invaded***, BPS***
Dev. Explain, %	13.8 (5.93)	n/a	11.3 (5.91)
ΔAIC	44.9		40.8
P. ciliare	Invaded***, Road***, BPS*, Ecorg**, Dev**	Dev*	Invaded***, Road***, Ecorg***, Dev*
Dev. Explain, %	7.4 (2.56)†	10.0	10.8 (2.18)‡,†
ΔAIC	60.9		30.0
P. australis	Road**, BPS***, Ecorg***, Dev^	n/a	n/a
Dev. Explain, %	9.8	n/a	n/a
ΔAIC
S. barbatus	Invaded*, Road**, BPS*	n/a	n/a
Dev. Explain, %	11 (2.03)	n/a	n/a
ΔAIC	4.6
T. caput-medusae	Invaded***, Ecorg***, Dev	Ecorg***, Dev**	Invaded***, Ecorg***, Dev^
Dev. Explain, %	10.1 (2.66)	15.8	14.8 (3.44)
ΔAIC	20.3		20.6

Percent deviance explained refers to the top-ranked model, with the percent explained by grass invasion in parentheses. ΔAIC is reported for the model if “Invaded” is dropped. Road, distance to road; BPS, biophysical setting; Ecorg, EPA level III ecoregion; Dev, percent development; Invaded, grass-invaded pixel; Dev. Explain, %, percent deviance explained. ^ P < 0.1 *P < 0.05 **P < 0.01 ***P < 0.001.

^†Spatial autocorrelation was present in the full model.

^‡A negative binomial model was used because of overdispersion in the Poisson model.