Dear All,

I was wondering if anyone knows a way to reliably extract parameter
estimates from a LMEM where VarIdent and corAR1 are necessary.

Here is the full model I am currently working with:

model1<-lme(asin(max_cover/100)~1+provenance*lifeform*year_trt*N*P*K,method="ML",random=~1|site/plot,weights=varIdent(form=~1|lifeform),
na.action=na.exclude,
correlation=corAR1(form=~as.numeric(year_trt)|site/plot), data=dat1)

The two lifeforms I am working with are graminoids and forbs, and the
experiment is a full factorial fertilization experiment that has been
conducted at 26 sites. Max_cover represents 16 species and their response to
fertilization. Because I am hypotheses testing, I have simplified the model
using LRT and I have found a significant four-way interaction and these
trends follow the results shown in the raw data. I used REML and LRT to
test  VarIdent and the autocorrelation with treatment year and both are
necessary.

Is there a method for calculating parameter estimates from such a complex
model for a designed experiment? If there isn't, does anyone have any
suggestions on methods or approaches I could use to get around this issue?

Thank you very much for any help or advice in advance.

Best wishes,

Karen

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