[R-sig-ME] mixed model for nested factor?

[Jinsong Zhao]

Hi there,

We have conducted an experiments for five years. The experiment is a 
completed block design with repeated measures. In detail, there is only 
one factor, i.e., temperature, and the experiments is performed in four 
blocks. In each block, the plot was split into two subplots. One subplot 
received two degree warming in Spring, and one degree warming in Fall, 
the other subplot didn't received any changes in Spring and Fall. We 
measured SOC every Spring and Fall. So we have got data something like:

SOC, Temp, Season, Year, block
2.032, 2, Spring, 2007, 1
1.988, 0, Spring, 2007, 1
1.977, 1, Fall, 2007, 1
1.881, 0, Fall, 2007, 1
....
....
It seems that mixed model might be the right way to analyze the data. 
However, we have encountered the difficulties that Temp seems to be 
nested with Season, and don't know how to code a formula for lme() in 
nlme package.

Any suggestions or comments will be really appreciated. Thanks in advance.

Best regards,
Jinsong