[R-sig-ME] Combining two sets of subplots obtained with different protocols

[Baldwin, Jim -FS]

I might not be understanding the selection process for the oak subplots.  If those are centered on an oak seedling and you use oak seedling density as the dependent variable, would you not have to account for those oak subplots having at least one oak seedling?

Jim

Jim Baldwin
Station Statistician
Pacific Southwest Research Station
USDA Forest Service

-----Original Message-----
From: r-sig-mixed-models-bounces at r-project.org [mailto:r-sig-mixed-models-bounces at r-project.org] On Behalf Of Diaci, Jurij
Sent: Sunday, February 02, 2014 9:33 AM
To: r-sig-mixed-models at r-project.org
Subject: [R-sig-ME] Combining two sets of subplots obtained with different protocols

Dear all,
we study oak natural regeneration in black pine plantations. Since oak seedlings are rare, we made two sets of smaller subplots (1,5 x 1,5 m) within each larger stand plot (20 x 20 m). One set was with subplots cantered at oak seedling (Oak subplot), while the second one was located independently of tree seedlings (Herb subplot; sensu Maguire & Forman, 1983). We measured several ecological variables (soil moisture, light climate...) and estimated coverage of ground vegetation per species.
We wonder, if are allowed to analyse this two data sets together in one mixed negative binomial model, with oak seedling density as dependent variable, ecological factors as fixed factors, large plots as random factor and take into account affiliation to each set of subplots as a fixed factor.
Maguire, D.A., Forman, R.T.T., 1983. Herb cover effects on tree seedling patterns in a mature Hemlock-Hardwood forest. Ecology 64, 1367-1380.

Many thanks in advance for your help.

Best regards,
Jurij
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