I have a model:
$y=a+bx+\varepsilon_1$ for each observation (tree)
$b=c+dz+\varepsilon_2$ for each forest (group of trees)
$y$, $x$, $z$ are continuous variables. $a$, $b$, $c$, $d$ are coefficients. $z$ is a property of forests (not individual trees). Error $\varepsilon_1$ is normally distributed and varies by tree. Error $\varepsilon_2$ varies by forest and not much is known about its distribution.
Is this lme4 model specification correct?
I will greatly appreciate your help!