These data were collected by biologist Mike Anderson in a study of nitrogen fixation by bacteria growing on the root nodules of alder bushes.
data(Alder)
A data frame Alder with 196 rows and 24 variables:
LAND. landscape, floodplain vs. upland.
SAMPPER. sampling period: early, mid, late
SPECIES. host species, Alnus tenuifolia (AT) vs. A. crispa (AC)
STAGE. successional stage, early vs. late in floodplain and upland landscapes. This is not equivalent across landscapes.
JULDAY. Julian day
PERNODN. nodule percent nitrogen by mass
RF. bacterial genotype
SNF. nitrogen fixation rate of nodule tissue, umol N2/gram of nodule dry weight/hr
SLA. specific leaf weight, grams of leaf weight/square-meter, dry
ONECM. soil temperature at 1 cm depth
FIVECM. soil temperature at 5 cm depth
PERH2O. soil moisture, percent H2O by mass
DEL. del15N of leaf tissue
DELNOD. del15N of nodule tissue
NPERAREA. leaf nitrogen content per unit leaf area
NDiff. nitrogen content difference between leaf and nodule of the same plant
delDiff. del15N difference between leaf and nodule of the same plant
SITE. Site designations: 1A,B,C for replicate early succession floodplain sites, 4A,B,C for late succession floodplain, UP1A,B,C for early succession upland and UP3A,B,C for late succession upland
HABSPEC. habitat+species, concatenated LAND, STAGE, SPECIES
SITESPEC. concatenated SITE, SPECIES
REP. replicate site within a given level of HABSPEC
PLNO. plant number, unique for individuals of each species (AT1-180, AC1-270)
Michael Anderson
Two questions that Anderson wanted to answer are:
(1) Can any variation in nitrogen fixation (variable SNF)
be attributed to genotype (variable RF)? (2) What are
the major sources of variation in SNF and
PERLEAFN? Variables of biological interest are
seasonality (SAMPPER or JULDAY),
soil temperature and moisture, and habitat differences (STAGE for
host species AT andSTAGE and LAND for host species AC).
Three replicate sites were sampled for each landscape/stage combination in three sampling periods across the growing season. Site sampling was arranged in a Latin Square design in order to systematize any effects of seasonality on N2-fixation rates.
Anderson MD, Ruess RW, Myrold DD, Taylor DL. ``Host species and habitat affect modulation by specific Frankia genotypes in interior Alaska'' Oecologia (2009) 160:619-630.
mod <- lm(logSNF ~ RF + SITESPEC, data = Alder)