\name{dat.curtis1998}
\doctype{data}
\alias{dat.curtis1998}
\title{studies on the effects of elevated co2 levels on woody plant mass}
\description{results from studies examining the effects of elevated co2 levels on woody plant mass.}
\usage{
dat.curtis1998
}
\format{
the data frame contains the following columns:
\tabular{lll}{
\bold{id}       \tab \code{numeric}   \tab observation number \cr
\bold{paper}    \tab \code{numeric}   \tab paper number \cr
\bold{genus}    \tab \code{character} \tab genus name \cr
\bold{species}  \tab \code{character} \tab species name \cr
\bold{fungrp}   \tab \code{character} \tab plant functional group \cr
\bold{co2.ambi} \tab \code{numeric}   \tab ambient co2 level (control group) \cr
\bold{co2.elev} \tab \code{numeric}   \tab elevated co2 level (treatment group) \cr
\bold{units}    \tab \code{character} \tab units for co2 exposure levels \cr
\bold{time}     \tab \code{numeric}   \tab maximum length of time (days) of co2 exposure \cr
\bold{pot}      \tab \code{character} \tab growing method (see \squote{details}) \cr
\bold{method}   \tab \code{character} \tab co2 exposure facility (see \squote{details}) \cr
\bold{stock}    \tab \code{character} \tab planting stock code \cr
\bold{xtrt}     \tab \code{character} \tab interacting treatment code (see \squote{details}) \cr
\bold{level}    \tab \code{character} \tab interacting treatment level codes (see \squote{details}) \cr
\bold{m1i}      \tab \code{numeric}   \tab mean plant mass under elevated co2 level (treatment group) \cr
\bold{sd1i}     \tab \code{numeric}   \tab standard deviation of plant mass underelevated co2 level (treatment group) \cr
\bold{n1i}      \tab \code{numeric}   \tab number of observations under elevated co2 level (treatment group) \cr
\bold{m2i}      \tab \code{numeric}   \tab mean plant mass under ambient co2 level (control group) \cr
\bold{sd2i}     \tab \code{numeric}   \tab standard deviation of plant mass under ambient co2 level (control group) \cr
\bold{n2i}      \tab \code{numeric}   \tab number of observations under ambient co2 level (control group)
}
}
\details{
the studies included in this dataset compared the total above- plus below-ground biomass (in grams) for plants that were either exposed to ambient (around 35 pa) and elevated co2 levels (around twice the ambient level). the \code{co2.ambi} and \code{co2.elev} variables indicate the co2 levels in the control and treatment groups, respectively (with the \code{units} variable specifying the units for the co2 exposure levels). many of the studies also varied one or more additional environmental variables (defined by the \code{xtrt} and \code{level} variables):
\itemize{
\item none = no additional treatment factor
\item fert = soil fertility (either a \code{control}, \code{high}, or \code{low} level)
\item light = light treatment (always a \code{low} light level)
\item fert+l = soil fertility and light (a \code{low} light and soil fertility level)
\item h2o = well watered vs drought (either a \code{ww} or \code{drt} level)
\item temp = temperature treatment (either a \code{high} or \code{low} level)
\item ozone = ozone exposure (either a \code{high} or \code{low} level)
\item uvb = ultraviolet-b radiation exposure (either a \code{high} or \code{low} level)
} in addition, the studies differed with respect to various design variables, including co2 exposure duration (\code{time}), growing method (\code{pot}: number = pot size in liters; \code{grnd} = plants rooted in ground; \code{hydro} = solution or aeroponic culture), co2 exposure facility (\code{method}: \code{gc} = growth chamber; \code{gh} = greenhouse; \code{otc} = field-based open-top chamber), and planting stock (\code{stock}: \code{seed} = plants started from seeds; \code{sap} = plants started from cuttings). the goal of the meta-analysis was to examine the effects of elevated co2 levels on plant physiology and growth and the interacting effects of the environmental (and design) variables.
}
\source{
hedges, l. v., gurevitch, j., & curtis, p. s. (1999). the meta-analysis of response ratios in experimental ecology. \emph{ecology}, \bold{80}(4), 1150--1156. \verb{https://doi.org/10.1890/0012-9658(1999)080[1150:tmaorr]2.0.co;2} (data obtained from \emph{ecological archives}, e080-008-s1, at: \verb{https://doi.org/10.6084/m9.figshare.c.3297278})
}
\references{
curtis, p. s., & wang, x. (1998). a meta-analysis of elevated co2 effects on woody plant mass, form, and physiology. \emph{oecologia}, \bold{113}(3), 299--313. \verb{https://doi.org/10.1007/s004420050381}
}
\author{
wolfgang viechtbauer, \email{wvb@metafor-project.org}, \url{https://www.metafor-project.org}
}
\examples{
### copy data into 'dat' and examine data
dat <- dat.curtis1998
head(dat)
\dontrun{
### load metafor package
library(metafor)
### calculate (log transformed) ratios of means and corresponding sampling variances
dat <- escalc(measure="rom", m1i=m1i, sd1i=sd1i, n1i=n1i,
m2i=m2i, sd2i=sd2i, n2i=n2i, data=dat)
head(dat)
### meta-analysis using a random-effects model
res <- rma(yi, vi, method="dl", data=dat)
res
### average ratio of means with 95\% ci
predict(res, transf=exp, digits=2)
### meta-analysis for plants grown under nutrient stress
res <- rma(yi, vi, method="dl", data=dat, subset=(xtrt=="fert" & level=="low"))
predict(res, transf=exp, digits=2)
### meta-analysis for plants grown under low light conditions
res <- rma(yi, vi, method="dl", data=dat, subset=(xtrt=="light" & level=="low"))
predict(res, transf=exp, digits=2)
}
}
\keyword{datasets}
\concept{ecology}
\concept{ratios of means}
\section{concepts}{
ecology, ratios of means
}